Soft X-ray observation of the Rho Ophiuchus dark cloud region

NASA Technical Reports Server (NTRS)

Apparao, K. M. V.; Hayakawa, S.; Hearn, D. R.

1979-01-01

Soft X-rays (0.1-0.8 keV) from the region including the Rho Oph dark cloud were observed with the SAS-3 low-energy X-ray telescope. No X-ray absorption by the cloud was observed. This indicates that the diffuse component of soft X-rays in this region is mostly from the foreground of the Rho Oph cloud which is located at a distance of 160-200 pc.

Chemical abundances in cold, dark interstellar clouds

NASA Technical Reports Server (NTRS)

Irvine, William M.; Kaifu, Norio; Ohishi, Masatoshi

1991-01-01

Current tabulations are presented of the entire range of known interstellar molecules, giving attention to that subset which has been identified in the cold, dark interstellar clouds out of which the sun has been suggested to have formed. The molecular abundances of two such clouds, Taurus Molecular Cloud 1 and Lynd's 134N, exhibit prepossessing chemical differences despite considerable physical similarities. This discrepancy may be accounted for by the two clouds' differing evolutionary stages. Two novel classes of interstellar molecules are noted: sulfur-terminated carbon chains and silicon-terminated ones.

Cosmic ray processing of N2-containing interstellar ice analogues at dark cloud conditions

NASA Astrophysics Data System (ADS)

Fedoseev, G.; Scirè, C.; Baratta, G. A.; Palumbo, M. E.

2018-04-01

N2 is believed to lock considerable part of nitrogen elemental budget and, therefore, to be one of the most abundant ice constituent in cold dark clouds. This laboratory-based research utilizes high energetic processing of N2 containing interstellar ice analogues using 200 keV H+ and He+ ions that mimics cosmic ray processing of the interstellar icy grains. It aims to investigate the formation of (iso)cyanates and cyanides in the ice mantles at the conditions typical for cold dark clouds and prestellar cores. Investigation of cosmic ray processing as a chemical trigger mechanism is explained by the high stability of N2 molecules that are chemically inert in most of the atom- and radical-addition reactions and cannot be efficiently dissociated by cosmic ray induced UV-field. Two sets of experiments are performed to closer address solid-state chemistry occurring in two distinct layers of the ice formed at different stages of dark cloud evolution, i.e. `H2O-rich' and `CO-rich' ice layers. Formation of HNCO and OCN- is discussed in all of the performed experiments. Corresponding kinetic curves for HNCO and OCN- are obtained. Furthermore, a feature around 2092 cm-1 assigned to the contributions of 13CO, CN-, and HCN is analysed. The kinetic curves for the combined HCN/CN- abundance are derived. In turn, normalized formation yields are evaluated by interpolation of the obtained results to the low irradiation doses relevant to dark cloud stage. The obtained values can be used to interpret future observations towards cold dark clouds using James Webb Space Telescope.

Detection of nitric oxide in the dark cloud L134N

NASA Technical Reports Server (NTRS)

Mcgonagle, D.; Irvine, W. M.; Minh, Y. C.; Ziurys, L. M.

1990-01-01

The first detection of interstellar nitric oxide (NO) in a cold dark cloud, L134N is reported. Nitric oxide was observed by means of its two 2 Pi 1/2, J = 3/2 - 1/2, rotational transitions at 150.2 and 150.5 GHz, which occur because of Lambda-doubling. The inferred column density for L134N is about 5 x 10 to the 14th/sq cm toward the SO peak in that cloud. This value corresponds to a fractional abundance relative to molecular hydrogen of about 6 x 10 to the -8th and is in good agreement with predictions of quiescent cloud ion-molecule chemistry. NO was not detected toward the dark cloud TMC-1 at an upper limit of 3 x 10 to the -8th or less.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wenlong; Kevrekidis, P. G.

We have performed a systematic study quantifying the variation of solitary wave behavior from that of an ordered cloud resembling a “crystalline” configuration to that of a disordered state that can be characterized as a soliton “gas.” As our illustrative examples, we use both one-component, as well as two-component, one-dimensional atomic gases very close to zero temperature, where in the presence of repulsive interatomic interactions and of a parabolic trap, a cloud of dark (dark-bright) solitons can form in the one- (two-) component system. We corroborate our findings through three distinct types of approaches, namely a Gross-Pitaevskii type of partialmore » differential equation, particle-based ordinary differential equations describing the soliton dynamical system, and Monte Carlo simulations for the particle system. In addition, we define an “empirical” order parameter to characterize the order of the soliton lattices and study how this changes as a function of the strength of the “thermally” (i.e., kinetically) induced perturbations. As may be anticipated by the one-dimensional nature of our system, the transition from order to disorder is gradual without, apparently, a genuine phase transition ensuing in the intermediate regime.« less

Dark Spot and Jovian Galaxy

NASA Image and Video Library

2017-03-24

This enhanced-color image of a mysterious dark spot on Jupiter seems to reveal a Jovian "galaxy" of swirling storms. Juno acquired this JunoCam image on Feb. 2, 2017, at 5:13 a.m. PDT (8:13 a.m. EDT), at an altitude of 9,000 miles (14,500 kilometers) above the giant planet's cloud tops. This publicly selected target was simply titled "Dark Spot." In ground-based images it was difficult to tell that it is a dark storm. Citizen scientist Roman Tkachenko enhanced the color to bring out the rich detail in the storm and surrounding clouds. Just south of the dark storm is a bright, oval-shaped storm with high, bright, white clouds, reminiscent of a swirling galaxy. As a final touch, he rotated the image 90 degrees, turning the picture into a work of art. http://photojournal.jpl.nasa.gov/catalog/PIA21386

The spectral energy distribution of the scattered light from dark clouds

NASA Technical Reports Server (NTRS)

Mattila, Kalevi; Schnur, G. F. O.

1989-01-01

A dark cloud is exposed to the ambient radiation field of integrated starlight in the Galaxy. Scattering of starlight by the dust particles gives rise to a diffuse surface brightness of the dark nebula. The intensity and the spectrum of this diffuse radiation can be used to investigate, e.g., the scattering parameters of the dust, the optical thickness of the cloud, and as a probe of the ambient radiation field at the location of the cloud. An understanding of the scattering process is also a prerequisite for the isolation of broad spectral features due to fluorescence or to any other non-scattering origin of the diffuse light. Model calculations are presented for multiple scattering in a spherical cloud. These calculations show that the different spectral shapes of the observed diffuse light can be reproduced with standard dust parameters. The possibility to use the observed spectrum as a diagnostic tool for analyzing the thickness of the cloud and the dust particle is discussed.

A New Dark Vortex

NASA Astrophysics Data System (ADS)

Wong, Michael

2015-10-01

A bright, unusually long-lived outburst of cloud activity on Neptune was observed in 2015. This led to speculation about whether the clouds were convective in nature, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2). HST OPAL images at blue wavelengths finally answered this question by discovering a new dark vortex at 45 deg S. We call this feature SDS-2015, for southern dark spot discovered in 2015.Dark vortices on Neptune are rare; SDS-2015 is only the fifth ever seen. All five were diverse in terms of size and shape, the distribution of bright companion clouds, and horizontal motions (oscillations and drifts). The drift of these vortices is highly sensitive to horizontal and vertical wind shear, making them valuable probes into the structure of Neptune's atmospheric jets. We have traced oscillations in the longitudinal positions of bright companion clouds of SDS-2015, but a second epoch of HST imaging is needed to measure latitudinal motion of the dark vortex itself.Only HST can image dark vortices on Neptune. Ground-based facilities lack the resolution to detect these low-contrast features at blue optical wavelengths, while infrared observations don't detect the dark spots themselves, only their bright companion features. We propose observations of SDS-2015, in order to measure its size, drift rate, and aerosol structure, and to trace its temporal evolution. The observations will improve our understanding of the life cycle of neptunian vortices, of their influence on the surrounding atmosphere, and of the structure of planetary jets.

Discovery of interstellar ketenyl (HCCO), a surprisingly abundant radical

NASA Astrophysics Data System (ADS)

Agúndez, Marcelino; Cernicharo, José; Guélin, Michel

2015-05-01

We conducted radioastronomical observations of 9 dark clouds with the IRAM 30 m telescope. We present the first identification in space of the ketenyl radical (HCCO) toward the starless core Lupus-1A and the molecular cloud L483 and the detection of the related molecules ketene (H2CCO) and acetaldehyde (CH3CHO) in these two sources and 3 additional dark clouds. We also report the detection of the formyl radical (HCO) in the 9 targeted sources and of propylene (CH2CHCH3) in 4 of the observed sources, which significantly extends the number of dark clouds where these molecules are known to be present. We have derived a beam-averaged column density of HCCO of ~5 × 1011 cm-2 in both Lupus-1A and L483, which means that the ketenyl radical is just ~10 times less abundant than ketene in these sources. The non-negligible abundance of HCCO found implies that there must be a powerful formation mechanism able to counterbalance the efficient destruction of this radical through reactions with neutral atoms. The column densities derived for HCO, (0.5-2.7) ×1012 cm-2, and CH2CHCH3, (1.9-4-2) ×1013 cm-2, are remarkably uniform across the sources where these species are detected, confirming their ubiquity in dark clouds. Gas phase chemical models of cold dark clouds can reproduce the observed abundances of HCO, but cannot explain the presence of HCCO in Lupus-1A and L483 and the high abundances derived for propylene. The chemistry of cold dark clouds needs to be revised in light of these new observational results. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).Tables 3-6 are available in electronic form at http://www.aanda.org

Recent observations of organic molecules in nearby cold, dark interstellar clouds

NASA Technical Reports Server (NTRS)

Suzuki, H.; Ohishi, M.; Morimoto, M.; Kaifu, N.; Friberg, P.

1985-01-01

Recent investigations of the organic chemistry of relatively nearby cold, dark interstellar clouds are reported. Specifically, the presence of interstellar tricarbon monoxide (C3O) in Taurus Molecular Cloud 1 (TMC-1) is confirmed. The first detection in such regions of acetaldehyde (CH3CHO), the most complex oxygen-containing organic molecule yet found in dark clouds is reported, as well as the first astronomical detection of several molecular rotational transitions, including the J = 18-17 and 14-13 transitions of cyanodiacetylene (HC5N), the 1(01)-0(00) transition of acetaldehyde, and the J = 5-4 transition of C3O. A significant upper limit is set on the abundance of cyanocarbene (HCCN) as a result of the first reported interstellar search for this molecule.

How to Become a Star

NASA Astrophysics Data System (ADS)

2001-01-01

ESO Telescopes Provide Most Detailed View Ever Into a Dark Cloud Summary How do stars like our Sun come into being? Which fundamental processes are responsible for transforming a dark and diffuse interstellar cloud of gas and dust into a much denser, shining object? Astronomers have just taken an important step towards answering this fundamental question. Based on the most detailed study ever made of the internal structure of a small interstellar cloud, three scientists from ESO and the USA [1] have found that it is apparently on the verge of becoming unstable - and thus in the stage immediately preceding a dramatic collapse into a dense and hot, low-mass star. Interestingly, the current structure of this cloud, a "Bok globule" known as Barnard 68 (B68) [2], is governed by the same basic physics as is that of a star. The cloud is obviously in a temporary state of near-equilibrium, where the inward force of gravity caused by its mass more or less balances that of the outward pressure due to its temperature. But this situation may not last long. The astronomers believe that this particular cloud, together with some others in the same galactic neighbourhood, constitute the few resistent remains of a much larger cloud that has disappeared due to the influence of strong stellar winds and ultraviolet radiation from young and heavy stars as well as supernova explosions. The new and unique insight into the pre-collapse phase of the complicated process of stellar birth is based on observations made with ESO telescopes at the La Silla and Paranal observatories in Chile. PR Photo 02a/01 : The Bok Globule B68 , as seen in visual light. PR Photo 02b/01 : Looking through the Bok Globule B68 . PR Photo 02c/01 : A comparison of the visual and infrared views of the Bok Globule B68 . From Dark Clouds to Stars Astronomers have known for some time that stars like our Sun are formed from interstellar clouds of gas and dust. When they contract, the interior temperature rises. If the cloud is sufficiently heavy, it will become so hot at the centre that energy-producing nuclear processes ignite. After a while, the central regions of the cloud reach equilibrium and a new star is born. Planets are formed from condensations in the surrounding material as this collects in a circumstellar disk. A good understanding of the origin of stars and planetary systems, like our own solar system, is therefore intimately connected to a detailed knowledge about the conditions in the cold interiors of dark clouds in interstellar space. However, such clouds are highly opaque and their physical structure has remained a mystery for as long as we have known about their existence. The following phases of stellar evolution are much better known and some scientists therefore refer to these very earliest stages as the "missing link" in our current picture of star formation. Finely balanced equilibrium The present results are changing this situation. By means of a new and straightforward observational technique, it has now been possible to explore the detailed structure of a nearby cloud. It is found to be quite simple, with the mean density steadily increasing towards the centre. In fact, the way this happens (referred to as the cloud's "density profile") is exactly as expected in an isolated gas sphere at a certain temperature in which the inward force of gravity is finely balanced against the internal thermal pressure. With this clear physical description it is now possible to determine with unprecedented precision (approx. 3%) the fundamental parameters of the cloud, such as its distance and gas-to-dust ratio. ESO astronomer João Alves from the team is content: "These measurements constitute a major breakthrough in the understanding of dark clouds. For the first time, the internal structure of a dark cloud has been specified with a detail approaching that which characterizes our knowledge of stellar interiors". Seeing light through the dark The observational technique that has led to the new result is straightforward but rather difficult to apply to dark clouds. It is based on measurements of the light from stars that are located behind the cloud. When this light passes through the cloud, it is absorbed and scattered by the dust inside. The effect depends on the colour (wavelength) and the background stars will appear redder than they really are . It is also proportional to the amount of obscuring material and is therefore largest for stars that are situated behind the cloud's centre. By measuring the degree of this "reddening" experienced by stars seen through different areas of the cloud, it is thus possible to chart the distribution of dust in the cloud . The finer the net of background stars is, the more detailed this map will be and the better the information about the internal structure of the cloud. And that is exactly the problem. Even small clouds are so opaque that very few background stars can be seen through them. Only large telescopes and extremely sensitive instruments are able to observe a sufficient number of stars in order to produce significant results. In particular, until now it has never been possible to map the densest, central areas of a dark cloud. The structure of Barnard 68 ESO PR Photo 02a/01 ESO PR Photo 02a/01 [Preview - JPEG:400 x 482 pix - 92k] [Normal - JPEG: 800 x 964 pix - 560k] [Hires - JPEG: 2296 x 2768 pix - 7.9M] ESO PR Photo 02b/01 ESO PR Photo 02b/01 [Preview - JPEG: 400 x 480 pix - 89k] [Normal - JPEG: 800 x 960 pix - 432k] [Hires - JPEG: 2301 x 2762 pix - 7.3M] ESO PR Photo 02c/01 ESO PR Photo 02c/01 [Preview - JPEG: 624 x 400 pix - 88k] [Normal - JPEG: 1247 x 800 pix - 496k] [Hires - JPEG: 2828 x 1814 pix - 5.6M] Caption : PR Photo 02a/01 shows a colour composite of visible and near-infrared images of the dark cloud Barnard 68 . It was obtained with the 8.2-m VLT ANTU telescope and the multimode FORS1 instrument in March 1999. At these wavelengths, the small cloud is completely opaque because of the obscuring effect of dust particles in its interior. PR Photo 02b/01 is a false-colour composite based on a visible (here rendered as blue), a near-infrared (green) and an infrared (red) image. Since the light from stars behind the cloud is only visible at the longest (infrared) wavelengths, they appear red. In PR Photo 02c/01 , the central area of these two photos may be directly compared. Technical information about these photos is available below. At a distance of only 410 light-years, Barnard 68 is one of the nearest dark clouds. Its size is about 12,500 AU (= 2 million million km; 1 Astronomical Unit [AU] = 150 million km), or just about the same as the so-called "Oort Cloud" of long-period comets that surrounds the solar system. The temperature of Barnard 68 is 16 Kelvin (-257 °C) and the pressure at its boundary is 0.0025 nPa, or about 10 times higher than in the interstellar medium (but still 40,000 million million times less than the atmospheric pressure at the Earth's surface!). The total mass of the cloud is about twice that of the Sun. A new investigation of Barnard 68 was carried out by means of instruments at the 3.58-m New Technology Telescope (NTT) at La Silla and the Very Large Telescope (VLT) at Paranal. Long exposures revealed a total of about 3700 background stars (of which over 1000 can only be seen at infrared wavelengths), cf. PR Photos 02a-c/01 . Careful measurements of the colours of these stars and hence, the degree of obscuration, allowed the most finely sampled (in more than 1000 individual areas) and most accurate mapping of the dust distribution inside a dark cloud ever performed. In order to further increase the accuracy, the mean dust density was measured in concentric circles around the centre - this resulted in a very accurate determination of the change in dust density with the distance from the centre. It was found that this dependance is almost exactly as that predicted for a sphere in which the opposite forces of gravity and internal pressure closely balance each other. Nevertheless, it is also evident that Barnard 68 is only marginally stable and is on the verge of collapse. The origin of Barnard 68 This first-ever, detailed characterization of a dark interstellar cloud that is currently in the stage immediately preceding collapse and subsequent star formation constitutes a very important step towards a better understanding of earliest phases of the stellar life cycle. The astronomers suggest that Barnard 68 (and its neighbouring brethren, the dark clouds Barnard 69, 70 and 72) may be the precursors of an isolated and sparsely populated association of low-mass solar-like stars. However, where did these clouds come from? João Alves thinks he and his colleagues know the answer: "It is most likely that they are the remnant cores of particularly resistent parts of a larger cloud. By now, most of it has been 'eaten away' because of strong attrition caused by ultraviolet radiation and stellar winds from hot massive stars or 'storms' from exploding supernovae". He adds: "Our new observations show that objects with just the right mass like Barnard 68 can reach a temporary equilibrium and survive for some time before they begin to collapse." The team is now eager to continue this type of investigation on other dark clouds. More information The research described in this Press Release is reported in a research article ("Seeing Light Through the Dark: Measuring the Internal Structure of a Cold Dark Cloud"), that appears in the international research jounal Nature on Thursday, January 11, 2001. Notes [1]: The team consists of João F. Alves (ESO-Garching, Germany), Charles J. Lada (Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass. USA) and Elizabeth A. Lada (University of Florida, Gainsville, Fl., USA). [2]: The Dutch astronomer Bart Bok (1906-1983) studied the dark clouds in the Milky Way and described the small, compact ones as "globules". The early stages of the present investigation of Barnard 68 were presented in ESO PR Photos 29a-c/99 , with more background information about this cloud. Technical information about the photos PR Photo 02a/01 of the sky area of Barnard 68 is based on three frames through B- (440 nm = 0.44 µm - here rendered as blue), V- (0.55 µm - green) and I-band 0.90 µm - red) optical filters, as obtained with FORS1 instrument at the VLT ANTU telescope on March 27, 1999. The field measures 6.8 x 6.8 arcmin 2 (2048 x 2048 pix 2 a 0.20 arcsec. PR Photo 02b/01 is a false-colour composite based on B- (wavelength 0.44 µm - 1.5 min; here rendered as blue), I- (wavelength 0.85 µm - 1.5 min; green), and Ks-filters (2.16 µm - 30 min; red), respectively. The B and I images were obtained on March 1999, with the FORS1 instrument at the 8.2-m VLT ANTU. The Ks image was obtained in March 1999 with the SOFI instrument at the ESO 3.58-m New Technology Telescope (NTT) at La Silla. The sky field measures about 4.9 x 4.9 arcmin 2 (1024 x 1024 pixels 2 a 0.29 arcsec). North is up and East is left. PR Photo 02c/01 allows a direct comparison between the two views.

Dark matter annihilations in the Large Magellanic Cloud

NASA Astrophysics Data System (ADS)

Gondolo, Paolo

1994-05-01

I examine the possibility of detecting high energy γ-rays from non-baryonic dark matter annihilations in the central region of the Large Magellanic Cloud. Present address: LPTHE, Université Paris VII, Tour 24-14, 5 étage, 2 Place Jussieu, 75251 Paris Cédex 05, France;

Catching the Drift: Simulating Dark Spots and Bright Companions on the Ice Giants

NASA Astrophysics Data System (ADS)

LeBeau, R. P., Jr.; Koutas, N.; Palotai, C. J.; Bhure, S.; Hadland, N.; Sankar, R.

2017-12-01

Starting with the original Great Dark Spot (GDS-89) observed by Voyager 2, roughly a half-dozen large geophysical vortices have been observed on the Ice Giants, the most recent in 2015 on Neptune (Wong et al., 2016). While the presumption is that these Dark Spots are similar in structure to the large vortices on Jupiter, in some cases the Dark Spots exhibit dynamical motions such as the shape oscillations and latitudinal drift of GDS-89 (Smith et al., 1989) or the possible vortex drift underlying the "Berg" cloud feature on Uranus (de Pater et al., 2011). Others, like NGDS-1998, have remained largely stable across years of observation (Sromovsky et al., 2002). In addition, several of the vortices are linked with Bright Companion clouds which are presumed to be orographic features formed as the atmosphere rises over the vortex. The numerical simulation of these features has evolved with each new observation. Prior simulations have captured the forms if not all the specifics of observed Dark Spot dynamics (LeBeau and Dowling, 1998; LeBeau and Deng, 2006); likewise, numerical models have demonstrated the potential for orographic companion clouds (Stratman et al., 2001). However, as more knowledge of the Ice Giant atmospheres has been obtained, it has proven challenging to generate consistent dynamical models that capture the details of the Dark Spot variations and are physically consistent with known observations. In particular, current simulations indicate that the addition of a companion cloud can alter the vortex dynamics, both in terms of drift and oscillations. Given the impact of these clouds, a new parametric simulation study uses an updated microphysics model, implemented in the Explicit Planetary Isentropic Coordinate (EPIC) general circulation model (Dowling et al., 1998, 2006), to account for the condensation of methane and hydrogen sulfide (Palotai et al., 2016). Simulations of dark spots with varying sizes, strengths, and locations are conducted with different microphysical parameters such as the deep abundance and ambient supersaturation. Simulations are evaluated in terms of vortex stability and drift rate along with companion cloud formation with the goal of improving our understanding of the underlying physics driving the varying behaviors of the observed Dark Spots.

Measuring the Internal Structure and Physical Conditions in Star and Planet Forming Clouds Core: Toward a Quantitative Description of Cloud Evolution

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2005-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular cloud cores and investigate the physical conditions which give rise to star and planet formation. The goals of this program are to acquire, reduce and analyze deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds in order to internal structure of starless cloud cores and to quantitatively investigate the evolution of such structure through the star and planet formation process. During the second year of this grant, progress toward these goals is discussed.

Measuring the Internal Structure and Physical Conditions in Star and Planet Forming Clouds Cores: Towards a Quantitative Description of Cloud Evolution

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2004-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular cloud cores and investigate the physical conditions which give rise to star and planet formation. The goals of this program are to acquire, reduce and analyze deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds in order to determine the detailed initial conditions for star formation from quantitative measurements of the internal structure of starless cloud cores and to quantitatively investigate the evolution of such structure through the star and planet formation process.

Embedded Outflows from Herbig-Haro 46/47

NASA Technical Reports Server (NTRS)

2003-01-01

[figure removed for brevity, see original site] Click on image for larger view of insert

This image from NASA's Spitzer Space Telescope transforms a dark cloud into a silky translucent veil, revealing the molecular outflow from an otherwise hidden newborn star. Using near-infrared light, Spitzer pierces through the dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic stars, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared.

The Spitzer image was obtained with the infrared array camera and is a three-color mosaic. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red.

HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1,140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity.

The 8-micron channel of the infrared array camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron emission corresponds to the lower right edge of the dark cloud in the visible-light picture.

Outflows are fascinating objects, since they characterize one of the most energetic phases of the formation of low-mass stars (like our Sun). The jets arising from these protostars can reach sizes of trillions of miles and velocities of hundreds of thousands miles per hour. Outflows are clear evidence of the presence of a process that creates supersonic beams of gas. This mechanism is tightly bound to the presence of circumstellar discs which surround the young stars. Such discs are likely to contain the materials from which planetary systems form. Our Sun probably underwent a similar process some 4.5 billion years ago. Hence the interest in understanding how quickly and efficiently this mass accretion and loss process takes place in protostars.

Studies of Dark Spots and Their Companion Clouds on the Ice Giant Planets

NASA Astrophysics Data System (ADS)

Bhure, Sakhee; Sankar, Ramanakumar; Hadland, Nathan; Palotai, Csaba J.; Le Beau, Raymond P.; Koutas, Nikko

2017-10-01

Observations of ice giant planets in our Solar System have shown several large-scale dark spots with varying lifespans. Some of these features were directly observed, others were diagnosed from their orographic companion clouds. Historically, numerical simulations have been able to model certain characteristics of these storms such as the shape variability of the Neptune Great Dark Spot (GDS-89) (Deng and Le Beau, 2006), but have not been able to match observed drift rates and lifespans using the standard zonal wind profiles (Hammel et al. 2009). Common amongst these studies has been the lack of condensable species in the atmosphere and an explicit treatment of cloud microphysics. Yet, observations show that dark spots can affect neighboring cloud features, such as in the case of bright companion clouds or the “Berg” on Uranus. An analysis of the cloud structure is therefore required to gain a better understanding of the underlying atmospheric physics and dynamics of these vortices.For our simulations, we use the Explicit Planetary Isentropic Coordinate (EPIC) general circulation model (Dowling et al. 1998, 2006) and adapt its jovian cloud microphysics module which successfully reproduced the cloud structure of jovian storms, such as the Great Red Spot and the Oval BA (Palotai and Dowling 2008, Palotai et al. 2014). EPIC was recently updated to account for the condensation of methane and hydrogen sulfide (Palotai et al. 2016), which allows us to account for both the high-altitude methane ice-cloud and the deep atmosphere hydrogen sulfide ice-cloud layers.In this work, we simulate large-scale vortices on Uranus and Neptune with varying cloud microphysical parameters such as the deep abundance and the ambient supersaturation. We examine the effect of cloud formation on their lifespan and drift rates to better understand the underlying processes which drive these storms.

Ultra-High Spectral Resolution Observations of Fragmentation in Dark Cloud Cores

NASA Technical Reports Server (NTRS)

Velusamy, T.; Langer, W.; Kuiper, T; Levin, S.; Olsen, E.

1993-01-01

This paper presents new evidence of the fragmentary structure of dense cores in dark clouds using the high resolution spectra of the carbon chain molecule CCS transition (J subscript N = 2 subscript 1 - 1 subscript o) at 22.344033 GHz with 0.008 km s superscript -1 resolution.

Tharsis Limb Cloud

NASA Technical Reports Server (NTRS)

2005-01-01

[figure removed for brevity, see original site] Annotated image of Tharsis Limb Cloud

7 September 2005 This composite of red and blue Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) daily global images acquired on 6 July 2005 shows an isolated water ice cloud extending more than 30 kilometers (more than 18 miles) above the martian surface. Clouds such as this are common in late spring over the terrain located southwest of the Arsia Mons volcano. Arsia Mons is the dark, oval feature near the limb, just to the left of the 'T' in the 'Tharsis Montes' label. The dark, nearly circular feature above the 'S' in 'Tharsis' is the volcano, Pavonis Mons, and the other dark circular feature, above and to the right of 's' in 'Montes,' is Ascraeus Mons. Illumination is from the left/lower left.

Season: Northern Autumn/Southern Spring

Storm clouds on Saturn: Lightning-induced chemistry and associated materials consistent with Cassini/VIMS spectra

USGS Publications Warehouse

Baines, K.H.; Delitsky, M.L.; Momary, T.W.; Brown, R.H.; Buratti, B.J.; Clark, R.N.; Nicholson, P.D.

2009-01-01

Thunderstorm activity on Saturn is associated with optically detectable clouds that are atypically dark throughout the near-infrared. As observed by Cassini/VIMS, these clouds are ~20% less reflective than typical neighboring clouds throughout the spectral range from 0.8 ??m to at least 4.1 ??m. We propose that active thunderstorms originating in the 10-20 bar water-condensation region vertically transport dark materials at depth to the ~1 bar level where they can be observed. These materials in part may be produced by chemical processes associated with lightning, likely within the water clouds near the ~10 bar freezing level of water, as detected by the electrostatic discharge of lightning flashes observed by Cassini/RPWS (e.g., Fischer et al. 2008, Space Sci. Rev., 137, 271-285). We review lightning-induced pyrolytic chemistry involving a variety of Saturnian constituents, including hydrogen, methane, ammonia, hydrogen sulfide, phosphine, and water. We find that the lack of absorption in the 1-2 ??m spectral region by lightning-generated sulfuric and phosphorous condensates renders these constituents as minor players in determining the color of the dark storm clouds. Relatively small particulates of elemental carbon, formed by lightning-induced dissociation of methane and subsequently upwelled from depth - perhaps embedded within and on the surface of spectrally bright condensates such as ammonium hydrosulfide or ammonia - may be a dominant optical material within the dark thunderstorm-related clouds of Saturn. ?? 2009 Elsevier Ltd. All rights reserved.

Red and nebulous objects in dark clouds - A survey

NASA Technical Reports Server (NTRS)

Cohen, M.

1980-01-01

A search on the NGS-PO Sky Survey photographs has revealed 150 interesting nebulous and/or red objects, mostly lying in dark clouds and not previously catalogued. Spectral classifications are presented for 55 objects. These indicate a small number of new members of the class of Herbig-Haro objects, a significant number of new T Tauri stars, and a few emission-line hot stars. It is argued that hot, high-mass stars form preferentially in the dense cores of dark clouds. The possible symbiosis of high and low mass stars is considered. A new morphology class is defined for cometary nebulae, in which a star lies on the periphery of a nebulous ring.

Ices in the Taurus dark cloud environment

NASA Technical Reports Server (NTRS)

Chiar, J. E.; Whittet, D. C. B.; Adamson, A. J.; Kerr, T. H.

1995-01-01

Field stars provide an important means for probing undisturbed regions of molecular clouds where icy mantles are most likely to form. Combining observation of field stars with those of protostars provides a comparison of the extent of grain processing in photostellar environments. The Taurus dark cloud provides an ideal environment for the formation of icy mantles as it is free from shocks and bright internal sources of ultraviolet (UV) radiation. Earlier low-resolution observations of the Taurus cloud done by Whittet et al. (1989) showed that about 30 percent of the available CO is depleted on to the grains.

School Consolidation: A Silver Lining in a Dark Cloud

ERIC Educational Resources Information Center

Waldfogel, Dean

2011-01-01

Everyone--board members, parents, and staff--loves small schools, bur it's no secret that small schools cost more to operate, particularly if administrative and teaching staff cannot be assigned efficiently. If there is a silver lining in this dark contextual cloud, it's that political support for consolidating schools has rarely been better. The…

[CII] observations of H2 molecular layers in transition clouds

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Pineda, J. L.; Goldsmith, P. F.; Li, D.; Yorke, H. W.

2010-10-01

We present the first results on the diffuse transition clouds observed in [CII] line emission at 158 μm (1.9 THz) towards Galactic longitudes near 340° (5 LOSs) & 20° (11 LOSs) as part of the HIFI tests and GOT C+ survey. Out of the total 146 [CII] velocity components detected by profile fitting we identify 53 as diffuse molecular clouds with associated 12CO emission but without 13CO emission and characterized by AV < 5 mag. We estimate the fraction of the [CII] emission in the diffuse HI layer in each cloud and then determine the [CII] emitted from the molecular layers in the cloud. We show that the excess [CII] intensities detected in a few clouds is indicative of a thick H2 layer around the CO core. The wide range of clouds in our sample with thin to thick H2 layers suggests that these are at various evolutionary states characterized by the formation of H2 and CO layers from HI and C+, respectively. In about 30% of the clouds the H2 column densities (“dark gas”) traced by the [CII] is 50% or more than that traced by 12CO emission. On the average ~25% of the total H2 in these clouds is in an H2 layer which is not traced by CO. We use the HI, [CII], and 12CO intensities in each cloud along with simple chemical models to obtain constraints on the FUV fields and cosmic ray ionization rates. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

The CO Transition from Diffuse Molecular Gas to Dense Clouds

NASA Astrophysics Data System (ADS)

Rice, Johnathan S.; Federman, Steven

2017-06-01

The atomic to molecular transitions occurring in diffuse interstellar gas surrounding molecular clouds are affected by the local physical conditions (density and temperature) and the radiation field penetrating the material. Our optical observations of CH, CH^{+}, and CN absorption from McDonald Observatory and the European Southern Observatory are useful tracers of this gas and provide the velocity structure needed for analyzing lower resolution ultraviolet observations of CO and H_{2} absorption from Far Ultraviolet Spectroscopic Explorer. We explore the changing environment between diffuse and dense gas by using the column densities and excitation temperatures from CO and H_{2} to determine the gas density. The resulting gas densities from this method are compared to densities inferred from other methods such as C_{2} and CN chemistry. The densities allow us to interpret the trends from the combined set of tracers. Groupings of sight lines, such as those toward h and χ Persei or Chameleon provide a chance for further characterization of the environment. The Chameleon region in particular helps illuminate CO-dark gas, which is not associated with emission from H I at 21 cm or from CO at 2.6 mm. Expanding this analysis to include emission data from the GOT C+ survey allows the further characterization of neutral diffuse gas, including CO-dark gas.

Dark Matter Reality Check: Chandra Casts Cloud On Alternative Theory

NASA Astrophysics Data System (ADS)

2002-10-01

New evidence from NASA's Chandra X-ray Observatory challenges an alternative theory of gravity that eliminates the need for dark matter. The observation also narrows the field for competing forms of dark matter, the elusive material thought to be the dominant form of matter in the universe. An observation of the galaxy NGC 720 shows it is enveloped in a slightly flattened, or ellipsoidal cloud of hot gas that has an orientation different from that of the optical image of the galaxy. The flattening is too large to be explained by theories in which stars and gas are assumed to contain most of the mass in the galaxy. "The shape and orientation of the hot gas cloud require it to be confined by an egg-shaped dark matter halo," said David Buote of the University of California, Irvine, and lead author of a report on this research in the 2002 September 20 issue of The Astrophysical Journal. "This means that dark matter is not just an illusion due to a shortcoming of the standard theory of gravity - it is real." According to the generally accepted standard theory of gravity, the hot X-ray cloud would need an additional source of gravity - a halo of dark matter - to keep the hot gas from expanding away. The mass of dark matter required would be about five to ten times the mass of the stars in the galaxy. If the dark matter tracked the optical light from the stars in the galaxy, the hot X-ray cloud would be more round than it is. The flattened shape of the hot gas cloud requires a flattened dark matter halo. An alternative theory of gravity called MOND, for Modified Newtonian Dynamics, was proposed in 1983 by Mordecai Milgrom of the Weizmann Institute in Israel, and has remained viable over the years. MOND does away with the need for dark matter by modifying the theory where the acceleration produced by gravity is very small, such as the outskirts of galaxies. However, MOND cannot explain the Chandra observation of NGC 720. This is apparently the first dynamical evidence that has successfully distinguished dark matter from MOND. The researchers also found that the Chandra data fit predictions of the cold dark matter theories, according to which dark matter consists of slowly moving particles, which interact with each other and "normal" matter only through gravity. Other forms of dark matter, such as self-interacting dark matter, and cold molecular dark matter, are not consistent with the observation in that they require a dark matter halo that is too round or too flat, respectively. "Chandra's ability to precisely identify and locate the point-like sources contaminating the diffuse emission in the X-ray image was absolutely essential," said Buote. "Only then could we make accurate measurements of the shape and orientation of the X-ray image contours." The conclusion from the Chandra data that NGC 720 possesses a dark matter halo assumes that the hot gas cloud has not been unduly disturbed by collisions or mergers with other galaxies in the last 100 million years. The lack of evidence of such activity indicates that this assumption is valid. Chandra observed NGC 720, which is about 80 million light years from Earth, for 11 hours with the Advanced CCD Imaging Spectrometer (ACIS). Other members of the team include Tesla Jeltema and Claude Canizares of Massachusetts Institute of Technology (MIT) in Cambridge, and Gordon Garmire of Pennsylvania State University in University Park. Penn State and MIT developed the instrument for NASA. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program, and TRW, Inc., Redondo Beach, Calif., is the prime contractor for the spacecraft. The Smithsonian's Chandra X-ray Center controls science and flight operations from Cambridge, Mass.

Models of bright storm clouds and related dark ovals in Saturn's Storm Alley as constrained by 2008 Cassini/VIMS spectra

NASA Astrophysics Data System (ADS)

Sromovsky, L. A.; Baines, K. H.; Fry, P. M.

2018-03-01

A 5° latitude band on Saturn centered near planetocentric latitude 36°S is known as "Storm Alley" because it has been for several extended periods a site of frequent lightning activity and associated thunderstorms, first identified by Porco et al. (2005). The thunderstorms appeared as bright clouds at short and long continuum wavelengths, and over a period of a week or so transformed into dark ovals (Dyudina et al., 2007). The ovals were found to be dark over a wide spectral range, which led Baines et al. (2009) to suggest the possibility that a broadband absorber such as soot produced by lightning could play a significant role in darkening the clouds relative to their surroundings. Here we show that an alternative explanation, which is that the clouds are less reflective because of reduced optical depth, provides an excellent fit to near infrared spectra of similar features obtained by the Cassini Visual and Infrared Mapping Spectrometer (VIMS) in 2008, and leads to a plausible scenario for cloud evolution. We find that the background clouds and the oval clouds are both dominated by the optical properties of a ubiquitous upper cloud layer, which has the same particle size in both regions, but about half the optical depth and physical thickness in the dark oval regions. The dark oval regions are also marked by enhanced emissions in the 5-μm window region, a result of lower optical depth of the deep cloud layer near 3.1-3.8 bar, presumably composed of ammonium hydrosulfide (NH4SH). The bright storm clouds completely block this deep thermal emission with a thick layer of ammonia (NH3) clouds extending from the middle of the main visible cloud layer probably as deep as the 1.7-bar NH3 condensation level. Other condensates might also be present at higher pressures, but are obscured by the NH3 cloud. The strong 3-μm spectral absorption that was displayed by Saturn's Great Storm of 2010-2011 (Sromovsky et al., 2013) is weaker in these storms because the contrast is muted by the overlying cloud deck that these less intense storms do not fully penetrate. Our speculated evolutionary scenario that seems consistent with these results is that deep convection produces lightning and bright clouds of large ammonia particles that rise up into the mid level of the overlying visible deck, pushing out the particles in that layer with the outflow at the top of the convective towers. When the convective pulse subsides, these large particles fall out of the column within a week or so, leaving behind less optical depth than background clouds, making them appear darker because they are less reflective. However, this simple picture does not explain all details of the phenomenon, e.g. the irregular morphology of the bright convective regions and the stable regular shapes of the dark ovals that are formed in their wake.

HUBBLE FINDS NEW DARK SPOT ON NEPTUNE

NASA Technical Reports Server (NTRS)

2002-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet. The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared. Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere. Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere. The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops. Credit: H. Hammel (Massachusetts Institute of Technology) and NASA

Infrared Extinction and the Initial Conditions For Star and Planet Formation

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2003-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program are to: 1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds, 2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds, 3) prepare results, where appropriate, for publication.

Infrared Extinction and the Initial Conditions for Star and Planet Formation

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2002-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program are to: (1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds; (2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds; and (3) prepare results, where appropriate, for publication.

A simple model for the cloud adjacency effect and the apparent bluing of aerosols near clouds

NASA Astrophysics Data System (ADS)

Marshak, Alexander; Wen, Guoyong; Coakley, James A.; Remer, Lorraine A.; Loeb, Norman G.; Cahalan, Robert F.

2008-07-01

In determining aerosol-cloud interactions, the properties of aerosols must be characterized in the vicinity of clouds. Numerous studies based on satellite observations have reported that aerosol optical depths increase with increasing cloud cover. Part of the increase comes from the humidification and consequent growth of aerosol particles in the moist cloud environment, but part comes from 3-D cloud-radiative transfer effects on the retrieved aerosol properties. Often, discerning whether the observed increases in aerosol optical depths are artifacts or real proves difficult. The paper only addresses the cloud-clear sky radiative transfer interaction part. It provides a simple model that quantifies the enhanced illumination of cloud-free columns in the vicinity of clouds that are used in the aerosol retrievals. This model is based on the assumption that the enhancement in the cloud-free column radiance comes from enhanced Rayleigh scattering that results from the presence of the nearby clouds. This assumption leads to a larger increase of AOT for shorter wavelengths, or to a "bluing" of aerosols near clouds. The assumption that contribution from molecular scattering dominates over aerosol scattering and surface reflection is justified for the case of shorter wavelengths, dark surfaces, and an aerosol layer below the cloud tops. The enhancement in Rayleigh scattering is estimated using a stochastic cloud model to obtain the radiative flux reflected by broken clouds and comparing this flux with that obtained with the molecules in the atmosphere causing extinction, but no scattering.

Neptune's New Dark Vortex: Imaging with HST/WFC3

NASA Astrophysics Data System (ADS)

Wong, M. H.; Tollefson, J.; De Pater, I.; de Kleer, K.; Hammel, H. B.; Luszcz-Cook, S.; Hueso, R.; Sanchez-Lavega, A.; Simon, A. A.; Delcroix, M.; Sromovsky, L. A.; Fry, P. M.; Orton, G. S.; Baranec, C.

2016-12-01

A bright, unusually long-lived outburst of cloud activity on Neptune was observed in 2015 (Hueso et al. 2015, DPS 400.02). This led to speculation about whether the clouds were convective in nature, or bright companions to an unseen dark vortex (similar to the Great Dark Spot studied in detail by Voyager 2: Smith et al. 1989, Science 246, 1422). HST OPAL images at blue wavelengths finally answered this question by discovering a new dark vortex at 45 deg S. We call this feature SDS-2015, for "southern dark spot discovered in 2015" (Wong et al. 2016, CBET 4278). Dark vortices on Neptune are rare; SDS-2015 is only the fifth ever seen. All five were diverse in terms of size and shape, the distribution of bright companion clouds, and horizontal motions (oscillations and drifts). The drift of these vortices is highly sensitive to horizontal and vertical wind shear, making them valuable probes into the structure of Neptune's atmospheric jets. We will present imaging observations of SDS-2015 obtained with the WFC3/UVIS camera on the Hubble Space Telescope, covering the discovery of the vortex in September 2015 and follow-up observations in May 2016. No significant latitudinal drift was seen over this time span. We will compare size estimates, which are complicated by the continual presence of companion clouds, and by the low contrast between the vortex and its surroundings. The 2015 observations included 7 filters spanning 467-845 nm, weighted toward longer wavelengths to study general cloud motions and vertical distributions. The 2016 observations included 7 filters spanning 336-763 nm, weighted toward shorter wavelengths where the dark spot itself can be detected. A companion abstract (Tollefson et al., this meeting) will present results from radiative transfer modeling of the multispectral data. [This conference abstract is based on observations made with the NASA/ESA Hubble Space Telescope, associated with programs GO-13937 ("OPAL") and GO-14492.

Search for gamma-ray emission from dark matter annihilation in the Small Magellanic Cloud with the Fermi Large Area Telescope

DOE PAGES

Caputo, Regina; Buckley, Matthew R.; Martin, Pierrick; ...

2016-03-22

The Small Magellanic Cloud (SMC) is the second-largest satellite galaxy of the Milky Way and is only 60 kpc away. As a nearby, massive, and dense object with relatively low astrophysical backgrounds, it is a natural target for dark matter indirect detection searches. In this work, we use six years of Pass 8 data from the Fermi Large Area Telescope to search for gamma-ray signals of dark matter annihilation in the SMC. Using data-driven fits to the gamma-ray backgrounds, and a combination of N-body simulations and direct measurements of rotation curves to estimate the SMC DM density profile, we found that themore » SMC was well described by standard astrophysical sources, and no signal from dark matter annihilation was detected. We set conservative upper limits on the dark matter annihilation cross section. Furthermore, these constraints are in agreement with stronger constraints set by searches in the Large Magellanic Cloud and approach the canonical thermal relic cross section at dark matter masses lower than 10 GeV in the bb¯ and τ +τ - channels.« less

Infrared Extinction and the Initial Conditions for Star and Planet Formation

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2005-01-01

This grant funded a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program were to: 1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds, 2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds, 3) use the results to measure and quantitatively describe the physical conditions of the dense gas and dust that produce stars and their accompanying planetary systems in molecular clouds. The goals of this project were met and exceeded as described below. 1) The infrared data for the project were obtained in a number of observing runs using the 3.5-meter NTT and 8-meter VLT telescopes of the European Southern Observatory in Chile and the 1.2-meter telescope of the Smithsonian Astrophysical Observatory in Arizona, the 1 0-meter Keck telescope in Hawaii, the 6.5-meter MMT of the Smithsonian Astrophysical Observatory in Arizona, and the NASA Hubble Space Telescope. The molecular-line data was obtained in three runs using the IRAM 30-meter telescope in Spain and one run with the ESO-15 meter millimeter-wave telescope in Chile. Millimeter-wave continuum measurements were obtained with the 15-meter JCMT in Hawaii. 2) Considerable effort was expended to reduce the infrared imaging observations including the development of custom software to produce high quality photometry and source astrometry. All the millimeter-line data was reduced using standard reduction routines. The highlights of the infrared analysis were the production of detailed extinction maps and the construction of profiles of the density structure of the B68, Coalsack, B335 and Lupus clouds. 3) The principal scientific accomplishments of this research program include the following: We were able to use our infrared observations to determine the density structure of the B68 cloud to an unprecedented level of precision. This lead to a major breakthrough in the study of molecular cloud structure. For the first time we have been able to characterize the structure of a dark cloud in a detail only exceeded by that known for a star. We determined that the cloud's structure is exquisitely well described by the equations of a Bonner-Ebert sphere (a pressure confined isothermal sphere). We were able to show that the cloud is very nearly in equilibrium with the internal thermal pressure of the cloud balancing gravity and the external pressure of the surrounding interstellar medium. We were able to determine for the first time the gas-to-dust ratio in a dense cloud core. We also demonstrated a new method to determine extremely precise distances to such clouds by combining knowledge of the properties of Bonner-Ebert Spheres with our infrared and millimeter-wave observations.

ScienceCast 88: Dark Lightning

NASA Image and Video Library

2013-01-07

Researchers studying thunderstorms have made a surprising discovery: The lightning we see with our eyes has a dark competitor that discharges storm clouds and flings antimatter into space. Scientists are scrambling to understand "dark lightning."

Clouds at CTIO and the Dark Energy Survey

DOE Office of Scientific and Technical Information (OSTI.GOV)

Neilsen, Jr., Eric

An understanding of the weather patters at Cerro-Tololo Inter-American (CTIO) Observatory, the observing site for the Dark Energy Survey (DES), is important for assessing the efciency of DES operations in using observing time and for planning future operations. CTIO has maintained records of cloud-cover by quarters of nights since 1975. A comparison between these cloud records in the 2013-2014 DES observing season (DES year 1) and achieved observing efciency and exposure quality allows the DES collaboration to make better use of the historical records in survey planning. Plots and tables here relate human recorded cloud-cover to collection of good DESmore » data, show the variation of typical cloud-cover by month, and evaluate the relationship between the El Niño weather pattern and cloud-cover at CTIO.« less

Peering into the heart of galactic star formation: A detailed characterization of infrared-dark clouds

NASA Astrophysics Data System (ADS)

Ragan, Sarah E.

2009-09-01

Everything we know about other galaxies is based on light from massive stars, yet, in our own Galaxy, it's the formation of massive stars that is the least understood. Star formation studies to date have focused on nearby, low-mass regions, but the bulk of star formation takes place in massive clusters, which takes place primarily in the inner-Galaxy, where the bulk of the molecular gas resides. To learn about the conditions under which massive clusters form, we seek out their precursors, called infrared-dark clouds (IRDCs). We present the results of a high-resolution multi-wavelength observational study of IRDCs, which vastly improves our knowledge of the initial conditions of cluster formation. Beginning with IRDC candidates identified with Midcourse Science Experiment (MSX) survey data, we map 41 IRDCs in the N 2 H + 1 [arrow right] 0, CS 2 [arrow right] 1 and C 18 O 1 [arrow right] 0 molecular transitions using the Five College Radio Astronomy Observatory. We examine the stellar content and absorption structure with Spitzer Space Telescope observations of eleven IRDCs, and we use Very Large Array NH 3 observations to probe the kinematics and chemistry of six IRDCs. Our comprehensive high-resolution study of IRDCs confirms that these objects are cold and dense precursors to massive stars and clusters. For the first time. we quantify IRDC sub-structure on sub-parsec scales and show the kinematic structure of IRDCs is diverse and depends on associated local star- formation activity. Overall, IRDCs exhibit non-thermal dynamics, suggesting that turbulence and systematic motions dominate. IRDC temperatures are between 8 and 16 K and are mostly flat with hints of a rise near the edges due to external heating. This study shows that IRDCs are a unique star-forming environment, one that dominates the star formation in the Milky Way. Using high-resolution observations, we have quantified the structure, star formation, kinematics, and chemistry of infrared-dark clouds. Our study of sub- structure in particular shows that IRDCs are undergoing fragmentation and are the precursors to star clusters, and thus we have placed IRDCs in context with Galactic star formation. The characterization presented here offers new constraints on theories of molecular cloud fragmentation and clustered star formation.

DISTANCES TO DARK CLOUDS: COMPARING EXTINCTION DISTANCES TO MASER PARALLAX DISTANCES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Foster, Jonathan B.; Jackson, James M.; Stead, Joseph J.

We test two different methods of using near-infrared extinction to estimate distances to dark clouds in the first quadrant of the Galaxy using large near-infrared (Two Micron All Sky Survey and UKIRT Infrared Deep Sky Survey) surveys. Very long baseline interferometry parallax measurements of masers around massive young stars provide the most direct and bias-free measurement of the distance to these dark clouds. We compare the extinction distance estimates to these maser parallax distances. We also compare these distances to kinematic distances, including recent re-calibrations of the Galactic rotation curve. The extinction distance methods agree with the maser parallax distancesmore » (within the errors) between 66% and 100% of the time (depending on method and input survey) and between 85% and 100% of the time outside of the crowded Galactic center. Although the sample size is small, extinction distance methods reproduce maser parallax distances better than kinematic distances; furthermore, extinction distance methods do not suffer from the kinematic distance ambiguity. This validation gives us confidence that these extinction methods may be extended to additional dark clouds where maser parallaxes are not available.« less

Infrared Extinction and the Initial Conditions for Star and Planet Formation

NASA Technical Reports Server (NTRS)

Lada, Charles J.

2004-01-01

This grant funds a research program to use infrared extinction measurements to probe the detailed structure of dark molecular clouds and investigate the physical conditions which give rise to star and planet formation. The goals of the this program are to: 1) acquire deep infrared and molecular-line observations of a carefully selected sample of nearby dark clouds, 2) reduce and analyze the data obtained in order to produce detailed extinction maps of the clouds, 3) prepare results, where appropriate, for publication. A description of how these goals were met are included.

IRAS observations of dust heating and energy balance in the Rho Ophiuchi dark cloud

NASA Technical Reports Server (NTRS)

Greene, Thomas P.; Young, Erick T.

1989-01-01

The equilibrium process dust emission in the Rho Ophiuchi dark cloud is studied. The luminosity of the cloud is found to closely match the luminosity of the clouds's known embedded and external radiation sources. There is no evidence for a large population of undetected low-luminosity sources within the cloud and unknown external heating is also only a minor source of energy. Most of the cloud's luminosity is emitted in the mid-to-far-IR. Dust temperature maps indicate that the dust is not hot enough to heat the gas to observed temperatures. A simple cloud model with a radiation field composed of flux HD 147889, S1, and Sco OB2 associations predicts the observed IRAS 60 to 100 micron in-band flux ratios for a mean cloud density n(H2) = 1400. Flattened 12 and 25 micron observations show much extended emission in these bands, suggesting stochastic heating of very small grains or large molecules.

CCD Photometry of the Open Cluster Tombaugh 5 in the Vilnius System

DTIC Science & Technology

2011-01-01

Collinder 428 (Laugalys et ai. 2007) and IC 361 (Zdanavicius et al. 2010), and four areas in the dark cloud LDN 935 at the North America and Pelican nebulae ...based on the Dobashi et a!. (2005) atlas of dark clouds (TGU numbers) and shows the positions of the nebulae Sh2-202, Sh2-205, vdB 14 and vdB 15, the

GOT C+ Survey of [CII] 158 Micrometer Emission: Atomic to Molecular Cloud Transitions in the Inner Galaxy

NASA Technical Reports Server (NTRS)

Velusamy, T.; Langer, W. D.; Willacy, K.; Pineda, J. L.; Goldsmith, P. F.

2012-01-01

We present the results of the distribution of CO-dark H2 gas in a sample of 2200 interstellar clouds in the inner Galaxy (l = 90 deg to +57 deg) detected in the velocity resolved [CII] spectra observed in the GOT C+ survey using the Herschel HIFI. We analyze the [CII] intensities along with the ancillary HI, (12)CO and (13)CO data for each cloud to determine their evolutionary state and to derive the H2 column densities in the C(+) and C(+)/CO transition layers in the cloud. We discuss the overall Galactic distribution of the [CII] clouds and their properties as a function Galactic radius. GOT C+ results on the global distribution of [CII] clouds and CO-dark H2 gas traces the FUV and star formation rates in the Galactic disk.

GOT C+ Survey of [CII] 158 μm Emission: Atomic to Molecular Cloud Transitions in the Inner Galaxy

NASA Astrophysics Data System (ADS)

Velusamy, T.; Langer, W. D.; Willacy, K.; Pineda, J. L.; Goldsmith, P. F.

2013-03-01

We present the results of the distribution of CO-dark H2 gas in a sample of 2223 interstellar clouds in the inner Galaxy (l=-90° to +57°) detected in the velocity resolved [CII] spectra observed in the GOT C+ survey using the Herschel HIFI. We analyze the [CII] intensities along with the ancillary HI, 12CO and 13CO data for each cloud to determine their evolutionary state and to derive the H2 column densities in the C+ and C+/CO transition layers in the cloud. We discuss the overall Galactic distribution of the [CII] clouds and their properties as a function Galactic radius. GOT C+ results on the global distribution of [CII] clouds and CO-dark H2 gas traces the FUV intensity and star formation rate in the Galactic disk.

The CN/C15N isotopic ratio towards dark clouds

NASA Astrophysics Data System (ADS)

Hily-Blant, P.; Pineau des Forêts, G.; Faure, A.; Le Gal, R.; Padovani, M.

2013-09-01

Understanding the origin of the composition of solar system cosmomaterials is a central question, not only in the cosmochemistry and astrochemistry fields, and requires various approaches to be combined. Measurements of isotopic ratios in cometary materials provide strong constraints on the content of the protosolar nebula. Their relation with the composition of the parental dark clouds is, however, still very elusive. In this paper, we bring new constraints based on the isotopic composition of nitrogen in dark clouds, with the aim of understanding the chemical processes that are responsible for the observed isotopic ratios. We have observed and detected the fundamental rotational transition of C15N towards two starless dark clouds, L1544 and L1498. We were able to derive the column density ratio of C15N over 13CN towards the same clouds and obtain the CN/C15N isotopic ratios, which were found to be 500 ± 75 for both L1544 and L1498. These values are therefore marginally consistent with the protosolar value of 441. Moreover, this ratio is larger than the isotopic ratio of nitrogen measured in HCN. In addition, we present model calculations of the chemical fractionation of nitrogen in dark clouds, which make it possible to understand how CN can be deprived of 15N and HCN can simultaneously be enriched in heavy nitrogen. The non-fractionation of N2H+, however, remains an open issue, and we propose some chemical way of alleviating the discrepancy between model predictions and the observed ratios. Appendices are available in electronic form at http://www.aanda.orgThe reduced spectra (in FITS format) are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/557/A65

Search for gamma-ray emission from dark matter annihilation in the large magellanic cloud with the fermi large area telescope

DOE PAGES

Buckley, Matthew R.; Charles, Eric; Gaskins, Jennifer M.; ...

2015-05-05

At a distance of 50 kpc and with a dark matter mass of ~10 10 M ⊙, the large magellanic cloud (LMC) is a natural target for indirect dark matter searches. We use five years of data from the Fermi Large Area Telescope (LAT) and updated models of the gamma-ray emission from standard astrophysical components to search for a dark matter annihilation signal from the LMC. We perform a rotation curve analysis to determine the dark matter distribution, setting a robust minimum on the amount of dark matter in the LMC, which we use to set conservative bounds on the annihilationmore » cross section. The LMC emission is generally very well described by the standard astrophysical sources, with at most a 1–2σ excess identified near the kinematic center of the LMC once systematic uncertainties are taken into account. As a result, we place competitive bounds on the dark matter annihilation cross section as a function of dark matter particle mass and annihilation channel.« less

Factor analysis as a tool for spectral line component separation 21cm emission in the direction of L1780

NASA Technical Reports Server (NTRS)

Toth, L. V.; Mattila, K.; Haikala, L.; Balazs, L. G.

1992-01-01

The spectra of the 21cm HI radiation from the direction of L1780, a small high-galactic latitude dark/molecular cloud, were analyzed by multivariate methods. Factor analysis was performed on HI (21cm) spectra in order to separate the different components responsible for the spectral features. The rotated, orthogonal factors explain the spectra as a sum of radiation from the background (an extended HI emission layer), and from the L1780 dark cloud. The coefficients of the cloud-indicator factors were used to locate the HI 'halo' of the molecular cloud. Our statistically derived 'background' and 'cloud' spectral profiles, as well as the spatial distribution of the HI halo emission distribution were compared to the results of a previous study which used conventional methods analyzing nearly the same data set.

A study of the stellar population in the Chamaeleon dark clouds

NASA Technical Reports Server (NTRS)

Gauvin, Lisa S.; Strom, Karen M.

1992-01-01

The properties of the stellar population in the Chamaeleon dark clouds are discussed. Spectral energy distributions, based on the extant photometric and spectroscopic data base and IRAS fluxes measured from coadded data taken at the position of each star, and spectral types allow placement of the stars in an H-R diagram. The age and mass distributions and the luminosity function for the Chamaeleon stars are compared to those in the Taurus-Auriga dark clouds and are found to be similar. A small subsample (eight of 36) of the Chamaeleon stars show unusual spectral energy distributions which seem best interpreted as arising from circumstellar disks whose inner regions (R(in)) is less than 30-50 stellar radii) area devoid of material. The X-ray properties of this sample of premain-sequence objects are compared to those of other premain-sequence samples, as well as to the Hyades and the Pleiades main-sequence stars.

Wide-Field Infrared Survey Explorer Observations of Young Stellar Objects in the Lynds 1509 Dark Cloud in Auriga

NASA Technical Reports Server (NTRS)

Liu, Wilson M.; Padgett, Deborah L.; Terebey, Susan; Angione, John; Rebull, Luisa M.; McCollum, Bruce; Fajardo-Acosta, Sergio; Leisawitz, David

2015-01-01

The Wide-Field Infrared Survey Explorer (WISE) has uncovered a striking cluster of young stellar object (YSO) candidates associated with the L1509 dark cloud in Auriga. The WISE observations, at 3.4, 4.6, 12, and 22 microns, show a number of objects with colors consistent with YSOs, and their spectral energy distributions suggest the presence of circumstellar dust emission, including numerous Class I, flat spectrum, and Class II objects. In general, the YSOs in L1509 are much more tightly clustered than YSOs in other dark clouds in the Taurus-Auriga star forming region, with Class I and flat spectrum objects confined to the densest aggregates, and Class II objects more sparsely distributed. We estimate a most probable distance of 485-700 pc, and possibly as far as the previously estimated distance of 2 kpc.

ARC-1989-A89-7006

NASA Image and Video Library

1989-08-21

Range : 12 million km (7.5 million miles) Resolution 110 km (68 miles) per pixel. These 2 images of Neptune were taken by Voyager 2's narrow-angle camera. During the 17.6 hours between the left and right images, the Great Dark Spot, at 22 degrees south latitude (left of center), has completed a little less than one rotation of Neptune. The smaller dark spot, at 54 south, completed a little more than one rotation, as can be seen by comparing its relative positions in the two pictures. The Great Dark Spot and the smaller spot have a relative velocity of 100 meters per second (220 miles an hour). The light and dark bands circling Neptune indicate predominantly zonal (east-west) motion. The diffuse white feature north of the Great Dark Spot is near Neptune's equator, and rotates with about the same period as the Great Dark Spot. Streak of bright clouds at the south edge, and just east of the Great Dark Spot, are its constatnt companions, and change the details of their appearance, often within a few hours. Changing brightness of the cloud streaks could be a result of vertical mortions.

Precombination Cloud Collapse and Baryonic Dark Matter

NASA Technical Reports Server (NTRS)

Hogan, Craig J.

1993-01-01

A simple spherical model of dense baryon clouds in the hot big bang 'strongly nonlinear primordial isocurvature baryon fluctuations' is reviewed and used to describe the dependence of cloud behavior on the model parameters, baryon mass, and initial over-density. Gravitational collapse of clouds before and during recombination is considered including radiation diffusion and trapping, remnant type and mass, and effects on linear large-scale fluctuation modes. Sufficiently dense clouds collapse early into black holes with a minimum mass of approx. 1 solar mass, which behave dynamically like collisionless cold dark matter. Clouds below a critical over-density, however, delay collapse until recombination, remaining until then dynamically coupled to the radiation like ordinary diffuse baryons, and possibly producing remnants of other kinds and lower mass. The mean density in either type of baryonic remnant is unconstrained by observed element abundances. However, mixed or unmixed spatial variations in abundance may survive in the diffuse baryon and produce observable departures from standard predictions.

X-Ray Shadowing Experiments Toward Infrared Dark Clouds

NASA Technical Reports Server (NTRS)

Anderson, L. E.; Snowden, S.; Bania, T. M.

2009-01-01

We searched for X-ray shadowing toward two infrared dark clouds (IRDCs) using the MOS detectors on XMM-Newton to learn about the Galactic distribution of X-ray emitting plasma. IRDCs make ideal X-ray shadowing targets of 3/4 keY photons due to their high column densities, relatively large angular sizes, and known kinematic distances. Here we focus on two clouds near 30 deg Galactic longitude at distances of 2 and 5 kpc from the Sun. We derive the foreground and background column densities of molecular and atomic gas in the direction of the clouds. We find that the 3/4 ke V emission must be distributed throughout the Galactic disk. It is therefore linked to the structure of the cooler material of the ISM, and to the birth of stars.

ARC-1990-AC91-2014

NASA Image and Video Library

1990-02-14

Range : 1.7 million miles This photo of Venus was taken by the Galileo spacecraft's Solid State Imaging System. A high-pass spatial filter has been applied in order to emphasize the smaller-scale cloud features, and the rendition has been colorized to a bluish hue in order to emphasize the subtle contrasts in the cloud markings and to indicate how it was taken through a violet filter. The sulfuric acid clouds indicate considerable convective activity, in the equatorial regions of the planet to the left and downwind of the subsolar point (afternoon on Venus), They are analogous to 'fair weather clouds' on Earth. The filamentary dark features visible in the colorized image are here revealed to be composed of several dark nodules, like strings on a bead, each about 60 miles across.

Neptune Blue-green Atmosphere

NASA Image and Video Library

2000-02-16

Neptune's blue-green atmosphere is shown in greater detail than ever before by the Voyager 2 spacecraft as it rapidly approaches its encounter with the giant planet. This color image, produced from a distance of about 16 million kilometers, shows several complex and puzzling atmospheric features. The Great Dark Spot (GDS) seen at the center is about 13,000 km by 6,600 km in size -- as large along its longer dimension as the Earth. The bright, wispy "cirrus-type" clouds seen hovering in the vicinity of the GDS are higher in altitude than the dark material of unknown origin which defines its boundaries. A thin veil often fills part of the GDS interior, as seen on the image. The bright cloud at the southern (lower) edge of the GDS measures about 1,000 km in its north-south extent. The small, bright cloud below the GDS, dubbed the "scooter," rotates faster than the GDS, gaining about 30 degrees eastward (toward the right) in longitude every rotation. Bright streaks of cloud at the latitude of the GDS, the small clouds overlying it, and a dimly visible dark protrusion at its western end are examples of dynamic weather patterns on Neptune, which can change significantly on time scales of one rotation (about 18 hours). https://photojournal.jpl.nasa.gov/catalog/PIA02245

Neptune's blue-green atmosphere

NASA Technical Reports Server (NTRS)

1989-01-01

Neptune's blue-green atmosphere is shown in greater detail than ever before by the Voyager 2 spacecraft as it rapidly approaches its encounter with the giant planet. This color image, produced from a distance of about 16 million kilometers, shows several complex and puzzling atmospheric features. The Great Dark Spot (GDS) seen at the center is about 13,000 km by 6,600 km in size -- as large along its longer dimension as the Earth. The bright, wispy 'cirrus-type' clouds seen hovering in the vicinity of the GDS are higher in altitude than the dark material of unknown origin which defines its boundaries. A thin veil often fills part of the GDS interior, as seen on the image. The bright cloud at the southern (lower) edge of the GDS measures about 1,000 km in its north-south extent. The small, bright cloud below the GDS, dubbed the 'scooter,' rotates faster than the GDS, gaining about 30 degrees eastward (toward the right) in longitude every rotation. Bright streaks of cloud at the latitude of the GDS, the small clouds overlying it, and a dimly visible dark protrusion at its western end are examples of dynamic weather patterns on Neptune, which can change significantly on time scales of one rotation (about 18 hours).

Earth observations taken from orbiter Discovery during STS-91 mission

NASA Image and Video Library

2016-08-24

STS091-708-077 (2-12 June 1998) -- The cloud shadows grew long as the STS-91 astronauts aboard the Space Shuttle Discovery approached the dark side of the Earth during "sunset" over Poland. The taller building cumulus clouds cast shadows over the lower clouds.

Islands in the Sky: Ecophysiological Cloud-Vegetation Linkages in Southern Appalachian Mountain Cloud Forests

NASA Astrophysics Data System (ADS)

Reinhardt, K.; Emanuel, R. E.; Johnson, D. M.

2013-12-01

Mountain cloud forest (MCF) ecosystems are characterized by a high frequency of cloud fog, with vegetation enshrouded in fog. The altitudinal boundaries of cloud-fog zones co-occur with conspicuous, sharp vegetation ecotones between MCF- and non-MCF-vegetation. This suggests linkages between cloud-fog and vegetation physiology and ecosystem functioning. However, very few studies have provided a mechanistic explanation for the sharp changes in vegetation communities, or how (if) cloud-fog and vegetation are linked. We investigated ecophysiological linkages between clouds and trees in Southern Appalachian spruce-fir MCF. These refugial forests occur in only six mountain-top, sky-island populations, and are immersed in clouds on up to 80% of all growing season days. Our fundamental research questions was: How are cloud-fog and cloud-forest trees linked? We measured microclimate and physiology of canopy tree species across a range of sky conditions (cloud immersed, partly cloudy, sunny). Measurements included: 1) sunlight intensity and spectral quality; 2) carbon gain and photosynthetic capacity at leaf (gas exchange) and ecosystem (eddy covariance) scales; and 3) relative limitations to carbon gain (biochemical, stomatal, hydraulic). RESULTS: 1) Midday sunlight intensity ranged from very dark (<30 μmol m-2 s-1, under cloud-immersed conditions) to very bright (>2500 μmol m-2 s-1), and was highly variable on minute-to-minute timescales whenever clouds were present in the sky. Clouds and cloud-fog increased the proportion of blue-light wavelengths 5-15% compared to sunny conditions, and altered blue:red and red:far red ratios, both of which have been shown to strongly affect stomatal functioning. 2) Cloud-fog resulted in ~50% decreased carbon gain at leaf and ecosystem scales, due to sunlight levels below photosynthetic light-saturation-points. However, greenhouse studies and light-response-curve analyses demonstrated that MCF tree species have low light-compensation points (can photosynthesize even at low light levels), and maximum photosynthesis occurs during high-light, diffuse-light conditions such as occurs during diffuse 'sunflecks' inside the cloud fog. Additionally, the capacity to respond to brief, intermittent sunflecks ('photosynthetic induction', e.g., time to maximum photosynthesis) was high in our MCF species. 3) Data quantifying limitations to photosynthesis were contradictory, underscoring complex relationships among photosynthesis, light, carbon and water relations. While stomatal response to atmospheric moisture demand was sensitive (e.g., 80% drop in stomatal conductance in a <1 kPa drop in vapor-pressure-deficit in conifer species), stem xylem hydraulic conductivity suggested strong drought tolerance capabilities. CONCLUSIONS: Clouds and cloud-fog exert strong influence on canopy-tree and ecosystem carbon relations. MCF are dynamic light environments. In these highly variable but ultimately light-limited ecosystems, vegetation must be able to both fix carbon when cloudy and dark but also be able to capitalize on saturating sunlight when possible.

Thoughts About Advancement of the Discipline: Dark Clouds and Bright Lights.

PubMed

Turkel, Marian; Fawcett, Jacqueline; Chinn, Peggy L; Eustace, Rosemary; Hansell, Phyllis Shanley; Smith, Marlaine C; Watson, Jean; Zahourek, Rothlyn

2018-01-01

In this essay, several nurse scholars who are particularly concerned about the contemporary state of nursing science present their specific concerns (dark clouds) about the advancement of our discipline and the ways in which the concerns have been addressed (bright lights). This essay is the first of two essays that were catalyzed by Barrett's paper, "Again, What Is Nursing Science?" The second essay will be published in the next issue Nursing Science Quarterly.

Neptune's New Dark Vortex: Aerosol Properties from Optical Data

NASA Astrophysics Data System (ADS)

Tollefson, J.; Luszcz-Cook, S.; Wong, M. H.; De Pater, I.

2016-12-01

Over the past year, amateur and professional astronomers alike have monitored the appearance of a new dark vortex on Neptune, dubbed SDS-2015 for "southern dark spot discovered in 2015" (Wong et al. 2016; CBET 4278). The discovery of SDS-2015 is fortuitous, being one of only five dark spots observed on Neptune since Voyager 2 imaged the Great Dark Spot (Smith et al. 1989, Science 246, 1422). A companion abstract (Wong et al., this meeting) will present Hubble Space Telescope images of SDS-2015, showcasing the discovery of the vortex in September 2015 and subsequent observations in May 2016. These observations span the optical regime. Longer wavelengths track bright companion clouds thought to form as air is diverted around SDS-2015. Shorter wavelengths reveal the dark spot itself. Combined, these data probe the vertical extent of the dark spot and Neptune's surrounding upper atmosphere. We present preliminary radiative transfer analyses of SDS-2015 using our multispectral data. Our model is the same as that in Luszcz-Cook et al. (2016, Icarus 276, 52) but extended to optical wavelengths. Prior to this work, little was known about the composition and vertical extent of Neptune's dark spots. Only data at optical wavelengths reveal these vortices, suggesting they consist of clearings in the background of fine, evenly-distributed haze particle. Alternatively, the spots may consist of low-albedo aerosols, causing their apparent darkness. Radiative transfer modeling is also one way to determine the vortex top altitude. Simulations of the Great Dark Spot by Stratman et al. (2001, Icarus 151, 275) found that the vortex top altitude is coupled to the brightness of companion clouds, where cloud opacity weakened as the top of the vortex reached higher into the tropopause region. The modeling presented here will compare these hypotheses and provide the first glimpses into the vertical structure of SDS-2015.

Discovery of a Bright Equatorial Storm on Neptune

NASA Astrophysics Data System (ADS)

Molter, E. M.; De Pater, I.; Alvarez, C.; Tollefson, J.; Luszcz-Cook, S.

2017-12-01

Images of Neptune, taken with the NIRC2 instrument during testing of the new Twilight Zone observing program at Keck Observatory, revealed an extremely large bright storm system near Neptune's equator. The storm complex is ≈9,000 km across and brightened considerably between June 26 and July 2. Historically, very bright clouds have occasionally been seen on Neptune, but always in the midlatitude regions between ≈15° and ≈60° North or South. Voyager and HST observations have shown that cloud features large enough to dominate near-IR photometry are often "companion" clouds of dark anti-cyclonic vortices similar to Jupiter's Great Red Spot, interpreted as orographic clouds. In the past such clouds and their coincident dark vortices often persisted for one up to several years. However, the cloud complex we detect is unique: never before has a bright cloud been seen at, or so close to, the equator. The discovery points to a drastic departure in the dynamics of Neptune's atmosphere from what has been observed for the past several decades. Detections of the complex in multiple NIRC2 filters allows radiative transfer modeling to constrain the cloud's altitude and vertical extent.

Neptune Great Dark Spot in High Resolution

NASA Image and Video Library

1999-08-30

This photograph shows the last face on view of the Great Dark Spot that Voyager will make with the narrow angle camera. The image was shuttered 45 hours before closest approach at a distance of 2.8 million kilometers (1.7 million miles). The smallest structures that can be seen are of an order of 50 kilometers (31 miles). The image shows feathery white clouds that overlie the boundary of the dark and light blue regions. The pinwheel (spiral) structure of both the dark boundary and the white cirrus suggest a storm system rotating counterclockwise. Periodic small scale patterns in the white cloud, possibly waves, are short lived and do not persist from one Neptunian rotation to the next. This color composite was made from the clear and green filters of the narrow-angle camera. http://photojournal.jpl.nasa.gov/catalog/PIA00052

Size-density relations in dark clouds: Non-LTE effects

NASA Technical Reports Server (NTRS)

Maloney, P.

1986-01-01

One of the major goals of molecular astronomy has been to understand the physics and dynamics of dense interstellar clouds. Because the interpretation of observations of giant molecular clouds is complicated by their very complex structure and the dynamical effects of star formation, a number of studies have concentrated on dark clouds. Leung, Kutner and Mead (1982) (hereafter LKM) and Myers (1983), in studies of CO and NH3 emission, concluded that dark clouds exhibit significant correlations between linewidth and cloud radius of the form delta v varies as R(0.5) and between mean density and radius of the form n varies as R(-1), as originally suggested by Larson (1981). This result suggests that these objects are in virial equilibrium. However, the mean densities inferred from the CO data of LKM are based on an local thermodynamic equilibrium (LTE) analysis of their 13CO data. At the very low mean densities inferred by LKM for the larger clouds in their samples, the assumption of LTE becomes very questionable. As most of the range in R in the density-size correlation comes from the clouds observed in CO, it seems worthwhile to examine how non-LTE effects will influence the derived densities. One way to assess the validity of LTE-derived densities is to construct cloud models and then to interpret them in the same way as the observed data. Microturbulent models of inhomogeneous clouds of varying central concentration with the linewidth-size and mean density-size relations found by Myers show sub-thermal excitation of the 13CO line in the larger clouds, with the result that LTE analysis considerbly underestimates the actual column density. A more general approach which doesn't require detailed modeling of the clouds is to consider whether the observed T sub R*(13CO)/T sub R*(12CO) ratios in the clouds studied by LKM are in the range where the LTE-derived optical depths (and hence column densities) can be seriously in error due to sub-thermal excitation of the 13CO molecule.

Jovian Dark Spot

NASA Technical Reports Server (NTRS)

1998-01-01

A recently discovered black spot in Jupiter's clouds is darker than any feature ever before observed on the giant planet. The spot may be the result of a downward spiraling wind that blows away high clouds and reveals deeper, very dark cloud layers. These three panels depict the same area of Jupiter's atmosphere. A map of Jovian temperatures near 250 millibar pressure (top) panel is derived from the photopolarimeter-radiometer instrument on NASA's Galileo Jupiter orbiter. This map is compared with maps derived from images of the same area in visible light (middle panel)and thermal radiation sensitive to cloud-top temperatures (bottom panel).

The single downward-pointing arrow in the top panel indicates the location of a warm area that corresponds to the position of a so-called 'black spot'(shown in the middle panel), a feature that is about a year old. Features this dark are rare on Jupiter. The bottom panel, sensitive to temperatures at Jupiter's cloud tops, shows this feature as a bright object, meaning that upper-level cold clouds are missing - allowing us to see deeper into Jupiter's warmer interior. The dark visible appearance of the feature than most likely represents the color of very deep clouds. The warm temperatures and cloud-free conditions imply that this feature is a region where dry upper-atmospheric gas is being forced to converge, is warmed up and then forced to descend, clearing out clouds. It is the opposite of wet, upwelling gas in areas such as Jupiter's Great Red Spot or white ovals. On the other hand, it is unlike the dry and relatively cloudless feature into which the Galileo probe descended in 1995, because that region had the same temperatures as its surroundings and did not appear nearly as dark as this new spot.

The temperatures sampled by the photopolarimeter radiometer are near the top of Jupiter's troposphere, where wind motions control the atmosphere. The top row of arrows shows the location of temperature waves in a warm region of the atmosphere. These types of waves have never been seen before. What is interesting about these waves is both that they are 'channeled' within the warm band at the top of the panel, and that they appear to have no counterpart in the visible cloud structure. Thermal waves have already been seen in Jupiter that are independent of the cloud structure, but those waves were much larger in size. This is the first time Jupiter's temperatures have been mapped at a spatial resolution better than 2,000 kilometers (1,243 miles), allowing these waves to be detected.

These maps include an area on Jupiter between approximately the equator and 40 degrees south latitude, covering about 60 degrees of longitude. They were taken in late September during the spacecraft's 17th orbit.

The Jet Propulsion Laboratory, Pasadena, CA manages the Galileo mission for NASA's Office of Space Science, Washington, DC.

Star counts and visual extinctions in dark nebulae

NASA Technical Reports Server (NTRS)

Dickman, R. L.

1978-01-01

Application of star count techniques to the determination of visual extinctions in compact, fairly high-extinction dark nebulae is discussed. Particular attention is devoted to the determination of visual extinctions for a cloud having a possibly anomalous ratio of total to selective extinction. The techniques discussed are illustrated in application at two colors to four well-known compact dust clouds or Bok globules: Barnard 92, B 133, B 134, and B 335. Minimum masses and lower limits to the central extinction of these objects are presented.

Thoughts About Nursing Curricula: Dark Clouds and Bright Lights.

PubMed

Turkel, Marian C; Fawcett, Jacqueline; Amankwaa, Linda; Clarke, Pamela N; Dee, Vivien; Eustace, Rosemary; Hansell, Phyllis Shanley; Jones, Dorothy A; Smith, Marlaine C; Zahourek, Rothlyn

2018-04-01

In this essay, several nurse scholars who are particularly concerned about the contemporary state of nursing science present their concerns about the inclusion of nursing conceptual models and theories in the curricula of nursing programs (dark clouds) and ways in which the concerns have been addressed (bright lights). This essay is the second of two essays that were catalyzed by Barrett's paper, "Again, What Is Nursing Science?" The first essay was published in the previous issue of Nursing Science Quarterly.

Dark Murky Clouds in the Bright Milky Way

NASA Image and Video Library

2011-08-24

This infrared image from NASA Wide-field Infrared Survey Explorer shows exceptionally cold, dense cloud cores seen in silhouette against the bright diffuse infrared glow of the plane of the Milky Way galaxy.

Hubble Finds New Dark Spot on Neptune

NASA Technical Reports Server (NTRS)

1995-01-01

NASA's Hubble Space Telescope has discovered a new great dark spot, located in the northern hemisphere of the planet Neptune. Because the planet's northern hemisphere is now tilted away from Earth, the new feature appears near the limb of the planet.

The spot is a near mirror-image to a similar southern hemisphere dark spot that was discovered in 1989 by the Voyager 2 probe. In 1994, Hubble showed that the southern dark spot had disappeared.

Like its predecessor, the new spot has high altitude clouds along its edge, caused by gasses that have been pushed to higher altitudes where they cool to form methane ice crystal clouds. The dark spot may be a zone of clear gas that is a window to a cloud deck lower in the atmosphere.

Planetary scientists don t know how long lived this new feature might be. Hubble's high resolution will allow astronomers to follow the spot's evolution and other unexpected changes in Neptune's dynamic atmosphere.

The image was taken on November 2, 1994 with Hubble's Wide Field Planetary Camera 2, when Neptune was 2.8 billion miles (4.5 billion kilometers) from Earth. Hubble can resolve features as small as 625 miles (1,000 kilometers) across in Neptune's cloud tops.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

A survey of carbon monoxide emission in dark clouds. [cosmic dust

NASA Technical Reports Server (NTRS)

Dickman, R. L.

1975-01-01

Results are reported of a CO and (C-13)O survey of 68 dark clouds from the Lynds catalog. CO was detected in 63 of the 64 sources in which it was searched for, and the (C-13)O line was seen in 52 of 55 clouds. There is a rather narrow distribution of CO peak line radiation temperatures about a mean of 6 K; this may reflect the presence of a roughly uniform kinetic temperature of 9.5 K in the sources. Despite the probably subthermal excitation temperature of the (C-13)O transition observed, derived (C-13)O column densities are most likely good to within a factor of 2. Typical CO column densities for the clouds surveyed are 5 x 10 to the 17-th power per sq cm, assuming a terrestrial carbon isotope ratio. All 68 clouds have previously been studied by Dieter in 6-cm H2CO absorption; a comparison of line widths shows the (C-13)O lines to generally be wider than their formaldehyde counterparts. Possible explanations of this fact in terms of internal cloud motions are discussed.

New T Tauri stars in Chamaeleon I and Chamaeleon II

NASA Technical Reports Server (NTRS)

Hartigan, Patrick

1993-01-01

A new objective prism survey of the entire Chamaeleon I dark cloud and 2/3 of the Chamaeleon II cloud has uncovered 26 new H-alpha emission line objects that were missed by previous H-alpha plate surveys. The new H-alpha emission line objects have similar IR colors and spatial distributions to the known T Tauri stars in these dark clouds, and could represent the very low mass end of the stellar population in these clouds or an older, less active component to the usual classical T Tauri star population. The new H-alpha survey identified 70 percent of the total known Young Stellar Objects (YSOs) in Cha I, compared with 35 percent for IRAS, and 25 percent from the Einstein X-ray survey. Ten of the new objects are weak-lined stars, with H-alpha equivalent widths less than 10 A. Weak-lined T Tauri stars make up about half of the total population of young stars in the Chamaeleon I cloud, a proportion similar to the Taurus-Auriga cloud. Presented are coordinates, finding charts, and optical and IR photometry of the new emission-line objects.

Modeling the chemistry of the dense interstellar clouds. I - Observational constraints for the chemistry

NASA Technical Reports Server (NTRS)

Federman, S. R.; Huntress, W. T., Jr.; Prasad, S. S.

1990-01-01

A search for correlations arising from molecular line data is made in order to place constraints on the chemical models of interstellar clouds. At 10 to the 21st H2/sq cm, N(CO) for dark clouds is a factor of six greater than the value for diffuse clouds. This implies that the strength of the UV radiation field where CO shields itself from dissociation is about one-half the strength of the average Galactic field. The dark cloud data indicate that the abundance of CO continues to increase with A(V) for directions with A(V) of 4 mag or less, although less steeply with N(H2) than for diffuse clouds. For H2CO, a quadratic relationship is obtained in plots versus H2 column density. The data suggest a possible turnover at the highest values for A(V). NH3 shows no correlation with H2, C(O-18), HC3N, or HC5N; a strong correlation is found between HC5N and HC3N, indicating a chemical link between the cyanopolyynes.

Simulating glories and cloudbows in color.

PubMed

Gedzelman, Stanley D

2003-01-20

Glories and cloudbows are simulated in color by use of the Mie scattering theory of light upwelling from small-droplet clouds of finite optical thickness embedded in a Rayleigh scattering atmosphere. Glories are generally more distinct for clouds of droplets of as much as approximately 10 microm in radius. As droplet radius increases, the glory shrinks and becomes less prominent, whereas the cloudbow becomes more distinct and eventually colorful. Cloudbows typically consist of a broad, almost white band with a slightly orange outer edge and a dark inner band. Multiple light and dark bands that are related to supernumerary rainbows first appear inside the cloudbow as droplet radius increases above approximately 10 microm and gradually become more prominent when all droplets are the same size. Bright glories with multiple rings and high color purity are simulated when all droplets are the same size and every light beam is scattered just once. Color purity decreases and outer rings fade as the range of droplet sizes widens and when skylight, reflected light from the ground or background, and multiply scattered light from the cloud are included. Consequently, the brightest and most colorful glories and bows are seen when the observer is near a cloud or a rain swath with optical thickness of approximately 0.25 that consists of uniform-sized drops and when a dark or shaded background lies a short distance behind the cloud.

Angular momentum of the N2H+ cores in the Orion A cloud

NASA Astrophysics Data System (ADS)

Tatematsu, Ken'ichi; Ohashi, Satoshi; Sanhueza, Patricio; Nguyen Luong, Quang; Umemoto, Tomofumi; Mizuno, Norikazu

2016-04-01

We have analyzed the angular momentum of the molecular cloud cores in the Orion A giant molecular cloud observed in the N2H+ J = 1-0 line with the Nobeyama 45 m radio telescope. We have measured the velocity gradient using position-velocity diagrams passing through core centers, and made sinusoidal fits against the position angle. Twenty-seven out of 34 N2H+ cores allowed us to measure the velocity gradient without serious confusion. The derived velocity gradient ranges from 0.5 to 7.8 km s-1 pc-1. We marginally found that the specific angular momentum J/M (against the core radius R) of the Orion N2H+ cores tends to be systematically larger than that of molecular cloud cores in cold dark clouds obtained by Goodman et al., in the J/M-R relation. The ratio β of rotational to gravitational energy is derived to be β = 10-2.3±0.7, and is similar to that obtained for cold dark cloud cores in a consistent definition. The large-scale rotation of the ∫-shaped filament of the Orion A giant molecular cloud does not likely govern the core rotation at smaller scales.

A systematic search for dwarf counterparts to ultra compact high velocity clouds

NASA Astrophysics Data System (ADS)

Bennet, Paul; Sand, David J.; Crnojevic, Denija; Strader, Jay

2015-01-01

Observations of the Universe on scales smaller than typical, massive galaxies challenge the standard Lambda Cold Dark Matter paradigm for structure formation. It is thus imperative to discover and characterize the faintest dwarf galaxy systems, not just within the Local Group, but in relatively isolated environments as well in order to properly connect them with models of structure formation. Here we report on a systematic search of public ultraviolet and optical archives for dwarf galaxy counterparts to so-called Ultra Compact High Velocity Clouds (UCHVCs), which are compact, isolated HI sources recently found in the Galactic Arecibo L-band Feed Array-HI (GALFA-HI) and Arecibo Legacy Fast ALFA (ALFALFA-HI) surveys. Our search has uncovered at least three strong dwarf galaxy candidates, and we present their inferred star formation rate and structural properties here.

Peering Deep into Jupiter Atmosphere

NASA Image and Video Library

2013-03-14

The dark hot spot in this false-color image from NASA Cassini spacecraft is a window deep into Jupiter atmosphere. All around it are layers of higher clouds, with colors indicating which layer of the atmosphere the clouds are in.

Jupiter

NASA Image and Video Library

1998-06-04

This processed color image of Jupiter was produced in 1990 by the U.S. Geological Survey from a Voyager image captured in 1979. Zones of light-colored, ascending clouds alternate with bands of dark, descending clouds. http://photojournal.jpl.nasa.gov/catalog/PIA00343

The clouds and winds of Neptune

NASA Astrophysics Data System (ADS)

Beebe, R.

1992-04-01

The atmospheric features of Neptune are described based on the images from Voyager 2 with comparisons made to the atmosphere of Uranus. Specific attention is given to the clear atmosphere's methane content and lack of the smog associated with Uranus. Neptune absorbs only a small amount of energy from sunlight and radiates about 2.7 times as much as it absorbs. The mechanisms that keep Neptune's atmosphere free of smog are thought to be upwelling enhanced by an outward heat flow and melting ice. The Voyager photographs show streaks of white clouds indicating strong winds and probably white ice in the upper atmosphere. The Great Dark Spot and a small triangular cloud are described in terms of their periods of rotation, and the wind speed is discussed in terms of cloud variations. The Great Dark Spot drifted equatorward during the observational period, and the drift yields some important clues regarding the nature of the Neptunian atmosphere and climate.

Cosmic-rays, gas, and dust in nearby anticentre clouds. II. Interstellar phase transitions and the dark neutral medium

NASA Astrophysics Data System (ADS)

Remy, Q.; Grenier, I. A.; Marshall, D. J.; Casandjian, J. M.

2018-03-01

Aim. H I 21-cm and 12CO 2.6-mm line emissions trace the atomic and molecular gas phases, respectively, but they miss most of the opaque H I and diffuse H2 present in the dark neutral medium (DNM) at the transition between the H I-bright and CO-bright regions. Jointly probing H I, CO, and DNM gas, we aim to constrain the threshold of the H I-H2 transition in visual extinction, AV, and in total hydrogen column densities, NHtot. We also aim to measure gas mass fractions in the different phases and to test their relation to cloud properties. Methods: We have used dust optical depth measurements at 353 GHz, γ-ray maps at GeV energies, and H I and CO line data to trace the gas column densities and map the DNM in nearby clouds toward the Galactic anticentre and Chamaeleon regions. We have selected a subset of 15 individual clouds, from diffuse to star-forming structures, in order to study the different phases across each cloud and to probe changes from cloud to cloud. Results: The atomic fraction of the total hydrogen column density is observed to decrease in the (0.6-1) × 1021 cm-2 range in NHtot (AV ≈ 0.4 mag) because of the formation of H2 molecules. The onset of detectable CO intensities varies by only a factor of 4 from cloud to cloud, between 0.6 × 1021 cm-2 and 2.5 × 1021 cm-2 in total gas column density. We observe larger H2 column densities than linearly inferred from the CO intensities at AV > 3 mag because of the large CO optical thickness; the additional H2 mass in this regime represents on average 20% of the CO-inferred molecular mass. In the DNM envelopes, we find that the fraction of diffuse CO-dark H2 in the molecular column densities decreases with increasing AV in a cloud. For a half molecular DNM, the fraction decreases from more than 80% at 0.4 mag to less than 20% beyond 2 mag. In mass, the DNM fraction varies with the cloud properties. Clouds with low peak CO intensities exhibit large CO-dark H2 fractions in molecular mass, in particular the diffuse clouds lying at high altitude above the Galactic plane. The mass present in the DNM envelopes appears to scale with the molecular mass seen in CO as MHDNM = 62 ± 7 MH2CO0.51 ± 0.02 across two decades in mass. Conclusions: The phase transitions in these clouds show both common trends and environmental differences. These findings will help support the theoretical modelling of H2 formation and the precise tracing of H2 in the interstellar medium.

What is the Uncertainty in MODIS Aerosol Optical Depth in the Vicinity of Clouds?

NASA Technical Reports Server (NTRS)

Patadia, Falguni; Levy, Rob; Mattoo, Shana

2017-01-01

MODIS dark-target (DT) algorithm retrieves aerosol optical depth (AOD) using a Look Up Table (LUT) approach. Global comparison of AOD (Collection 6 ) with ground-based sun photometer gives an Estimated Error (EE) of +/-(0.04 + 10%) over ocean. However, EE does not represent per-retrieval uncertainty. For retrievals that are biased high compared to AERONET, here we aim to closely examine the contribution of biases due to presence of clouds and per-pixel retrieval uncertainty. We have characterized AOD uncertainty at 550 nm, due to standard deviation of reflectance in 10 km retrieval region, uncertainty related to gas (H2O, O3) absorption, surface albedo, and aerosol models. The uncertainty in retrieved AOD seems to lie within the estimated over ocean error envelope of +/-(0.03+10%). Regions between broken clouds tend to have higher uncertainty. Compared to C6 AOD, a retrieval omitting observations in the vicinity of clouds (< or = 1 km) is biased by about +/- 0.05. For homogeneous aerosol distribution, clear sky retrievals show near zero bias. Close look at per-pixel reflectance histograms suggests retrieval possibility using median reflectance values.

Photometry and Classification of Stars in the Direction of the Dark Cloud Tgu 619 IN Cepheus. I. a Catalog of Magnitudes, Color Indices and Spectral Types of 1304 Stars

NASA Astrophysics Data System (ADS)

Zdanavičius, K.; Zdanavičius, J.; Straižys, V.; Maskoliūnas, M.

The catalog contains magnitudes and color indices of 1304 stars down to ˜ 16.6 mag in V measured in the seven-color Vilnius photometric system in the area of 1.5 square degrees with the center at Galactic coordinates 102.4°, +15.5°, containing the dark cloud TGU 619 in the Cepheus Flare. For most of the stars spectral and luminosity classes determined from the photometric data are given.

The Invisible Dragon

NASA Image and Video Library

2010-07-07

A dragon-shaped cloud of dust seems to fly out from a bright explosion in this infrared light image from NASA Spitzer Space Telescope. These views have revealed that this dark cloud, called M17 SWex, is forming stars at a furious rate.

Water and complex organic chemistry in the cold dark cloud Barnard 5: Observations and Models

NASA Astrophysics Data System (ADS)

Wirström, Eva; Charnley, Steven B.; Taquet, Vianney; Persson, Carina M.

2015-08-01

Studies of complex organic molecule (COM) formation have traditionally been focused on hot cores in regions of massive star formation, where chemistry is driven by the elevated temperatures - evaporating ices and allowing for endothermic reactions in the gas-phase. As more sensitive instruments have become available, the types of objects known to harbour COMs like acetaldehyde (CH3CHO), dimethyl ether (CH3OCH3), methyl formate (CH3OCHO), and ketene (CH2CO) have expanded to include low mass protostars and, recently, even pre-stellar cores. We here report on the first in a new category of objects harbouring COMs: the cold dark cloud Barnard 5 where non-thermal ice desorption induce complex organic chemistry entirely unrelated to local star-formation.Methanol, which only forms efficiently on the surfaces of dust grains, provide evidence of efficient non-thermal desorption of ices in the form of prominent emission peaks offset from protostellar activity and high density tracers in cold molecular clouds. A study with Herschel targeting such methanol emission peaks resulted in the first ever detection of gas-phase water offset from protostellar activity in a dark cloud, at the so called methanol hotspot in Barnard 5.To model the effect a transient injection of ices into the gas-phase has on the chemistry of a cold, dark cloud we have included gas-grain interactions in an existing gas-phase chemical model and connected it to a chemical reaction network updated and expanded to include the formation and destruction paths of the most common COMs. Results from this model will be presented.Ground-based follow-up studies toward the methanol hotspot in B5 have resulted in the detection of a number of COMs, including CH2CO, CH3CHO, CH3OCH3, and CH3OCHO, as well as deuterated methanol (CH2DOH). Observations have also confirmed that COM emission is extended and not localised to a core structure. The implications of these observational and theoretical studies of B5 will be discussed in the context of the gas-grain interaction in dark clouds and its relation to the chemistry of the earliest phases of low-mass star formation.

The Dark Heart of the King

NASA Image and Video Library

2010-09-29

NASA Wide-field Infrared Survey Explorer captured this image of a hidden star-forming cloud of dust and gas located in the constellation of Cepheus. What appears to the naked eye as the blackness of space is in fact a dark nebula.

Twomey Effect in Subtropical Stratocumulus Clouds from UV Depolarization LIDAR

NASA Astrophysics Data System (ADS)

de Graaf, Martin; Brown, Jessica; Donovan, David

2018-04-01

Marine stratocumulus clouds are important climate regulators, reflecting sunlight over a dark ocean background. A UV-depolarization lidar on Ascension, a small remote island in the south Atlantic, measured cloud droplet sizes and number concentration using an inversion method based on Monte Carlo (MC) modelling of multiple scattering in idealised semiadiabatic clouds. The droplet size and number concentration weremodulated due to smoke from the African continent, measured by the same instrument.

Mid-J CO Shock Tracing Observations of Infrared Dark Clouds. III. SLED Fitting

NASA Astrophysics Data System (ADS)

Pon, A.; Kaufman, M. J.; Johnstone, D.; Caselli, P.; Fontani, F.; Butler, M. J.; Jiménez-Serra, I.; Palau, A.; Tan, J. C.

2016-08-01

Giant molecular clouds contain supersonic turbulence that can locally heat small fractions of gas to over 100 K. We run shock models for low-velocity, C-type shocks propagating into gas with densities between 103 and 105 cm-3 and find that CO lines are the most important cooling lines. Comparison to photodissociation region (PDR) models indicates that mid-J CO lines (J = 8 \\to 7 and higher) should be dominated by emission from shocked gas. In Papers I and II we presented CO J = 3 \\to 2, 8 \\to 7, and 9 \\to 8 observations toward four primarily quiescent clumps within infrared dark clouds. Here we fit PDR models to the combined spectral line energy distributions and show that the PDR models that best fit the low-J CO emission underpredict the mid-J CO emission by orders of magnitude, strongly hinting at a hot gas component within these clumps. The low-J CO data clearly show that the integrated intensities of both the CO J = 8 \\to 7 and 9 \\to 8 lines are anomalously high, such that the line ratio can be used to characterize the hot gas component. Shock models are reasonably consistent with the observed mid-J CO emission, with models with densities near {10}4.5 cm-3 providing the best agreement. Where this mid-J CO is detected, the mean volume filling factor of the hot gas is 0.1%. Much of the observed mid-J CO emission, however, is also associated with known protostars and may be due to protostellar feedback.

Physical properties of Southern infrared dark clouds

NASA Astrophysics Data System (ADS)

Vasyunina, T.; Linz, H.; Henning, Th.; Stecklum, B.; Klose, S.; Nyman, L.-Å.

2009-05-01

Context: What are the mechanisms by which massive stars form? What are the initial conditions for these processes? It is commonly assumed that cold and dense Infrared Dark Clouds (IRDCs) represent the birth-sites of massive stars. Therefore, these clouds have been receiving an increasing amount of attention, and their analysis offers the opportunity to tackle the afore mentioned questions. Aims: To enlarge the sample of well-characterised IRDCs in the southern hemisphere, where ALMA will play a major role in the near future, we have developed a program to study the gas and dust of southern infrared dark clouds. The present paper attempts to characterize the continuum properties of this sample of IRDCs. Methods: We cross-correlated 1.2 mm continuum data from SIMBA bolometer array mounted on SEST telescope with Spitzer/GLIMPSE images to establish the connection between emission sources at millimeter wavelengths and the IRDCs that we observe at 8 μm in absorption against the bright PAH background. Analysing the dust emission and extinction enables us to determine the masses and column densities, which are important quantities in characterizing the initial conditions of massive star formation. We also evaluated the limitations of the emission and extinction methods. Results: The morphology of the 1.2 mm continuum emission is in all cases in close agreement with the mid-infrared extinction. The total masses of the IRDCs were found to range from 150 to 1150 M_⊙ (emission data) and from 300 to 1750 M_⊙ (extinction data). We derived peak column densities of between 0.9 and 4.6 × 1022 cm-2 (emission data) and 2.1 and 5.4 × 1022 cm-2 (extinction data). We demonstrate that the extinction method is unreliable at very high extinction values (and column densities) beyond AV values of roughly 75 mag according to the Weingartner & Draine (2001) extinction relation RV = 5.5 model B (around 200 mag when following the common Mathis (1990, ApJ, 548, 296) extinction calibration). By taking the spatial resolution effects into account and restoring the column densities derived from the dust emission to a linear resolution of 0.01 pc, peak column densities of 3-19 × 1023 cm-2 are obtained, which are much higher than typical values for low-mass cores. Conclusions: Taking into account the spatial resolution effects, the derived column densities are beyond the column density threshold of 3.0 × 1023 cm-2 required by theoretical considerations for massive star formation. We conclude that the values of column densities derived for the selected IRDC sample imply that these objects are excellent candidates for objects in the earliest stages of massive star formation.

A study of the large-scale infrared emission from a selected dark cloud

NASA Technical Reports Server (NTRS)

Young, Erick T.

1993-01-01

An investigation of the infrared emission energetics and embedded population in the rho Ophiuchi dark cloud is summarized. With a distance of approximately 140 pc, the rho Ophiuchi cloud is one of the closest regions of recent star formation. It is also one of the best studied such regions with numerous observations at all wavelengths. The Infrared Astronomy Satellite (IRAS) data of the cloud provided a new glimpse of the overall structure of the cloud. In particular, the interaction of radiation from the Sco-Oph OB Association on the external heating of the cloud was very evident on Skyflux and Survey CO-Add images produced by IRAS. The infrared survey also revealed a number of new embedded sources in the cloud which have subsequently been observed from the ground. In earlier study, the overall energies of the cloud using the IRAS data was explored. The main conclusions of that work were: (1) the overall luminosity of the cloud is well explained by the emission of the known B-stars, HD 147889, SR-3, and S1, along with a 15 percent contribution from the external radiation field; (2) the dust physical temperatures were significantly lower than the observed CO gas temperatures; and (3) dust grains are heated to only 10 percent to 20 percent of the total depth into the cloud. This analysis was extended by drawing on data from large-scale CO maps of Loren (1989) and from near-infrared surveys of the embedded population.

Neptune's small dark spot (D2)

NASA Technical Reports Server (NTRS)

1999-01-01

This bulls-eye view of Neptune's small dark spot (D2) was obtained by Voyager 2's narrow-angle camera. Banding surrounding the feature indicates unseen strong winds, while structures within the bright spot suggest both active upwelling of clouds and rotation about the center. A rotation rate has not yet been measured, but the V-shaped structure near the right edge of the bright area indicates that the spot rotates clockwise. Unlike the Great Red Spot on Jupiter, which rotates counterclockwise, if the D2 spot on Neptune rotates clockwise, the material will be descending in the dark oval region. The fact that infrared data will yield temperature information about the region above the clouds makes this observation especially valuable. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications.

Four Views of Mars in Northern Summer

NASA Technical Reports Server (NTRS)

1997-01-01

Four faces of Mars as seen on March 30, 1997 are presented in this montage of NASA Hubble Space Telescope images. Proceeding in the order upper-left, upper-right, lower-left, lower-right, Mars has rotated about ninety degrees between each successive time step. For example the Tharsis volcanoes, which are seen (between 7:30 and 9 o'clock positions) in mid-morning in the UPPER-RIGHT view, are seen near the late afternoon edge of the planet (about 3 o'clock position) in the lower-left image. All of these color images are composed of individual red (673 nanometers), green (502 nm), and blue (410 nm) Planetary Camera exposures.

Upper left: This view is centered on Ares Valles, where Pathfinder will land on July 4, 1997; the Valles Marineris canyon system stretches to the west across the lower left portion of the planet, while the bright, orangish desert of Arabia Planitia is to the east. The bright polar water-ice cap, surrounded by a dark ring of sand dunes, is obvious in the north; since it is northern summer and the pole is tilted toward us, the residual north polar cap is seen in its entirety in all four images. Acidalia Planitia, the prominent dark area fanning southward from the polar region, is thought to have a surface covered with dark sand. Numerous 'dark wind streaks' are visible to the south of Acidalia, resulting from wind-blown sand streaming out of the interiors of craters.

Upper right: The Tharsis volcanos and associated clouds are prominent in the western half of this view. Olympus Mons, spanning 340 miles (550 km) across its base and reaching an elevation of 16 miles (25 km), extends through the cloud deck near the western limb, while (from the south) Arsia Mons, Pavonis Mons, and Ascraeus Mons are to the west of center. Valles Marineris stretches to the east, and the Pathfinder landing site is shrouded in clouds near the afternoon limb.

Lower left: This relatively featureless sector of Mars stretches from the Elysium volcanic region in the west to the Tharsis volcanoes (shrouded by the bright clouds near the afternoon limb) in the east. The group of three dark specks just left of center are all that remain of Cerberus, a very prominent dark region during the Viking and Mariner 9 missions. This is an example of the remarkable large scale changes which can occur on Mars due to windblown dust: the former dark area has now been covered by a layer of bright dust, masking the underlying material.

Lower right: The dark Syrtis Major region dominates this image. Syrtis Major is one of the most prominent dark features on Mars, and has been visible since ground-based observers first peered at Mars through telescopes. The bright cloud at 3 o'clock is associated with Elysium Mons. The bright bluish-white feature near the southern limb of the planet is Hellas, a 1,200 mile (2,000 km) diameter impact basin formed by the collision of a large body with Mars long ago. Hellas is covered with dry ice frost and clouds during this season (winter in the south).

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Non-destructive Faraday imaging of dynamically controlled ultracold atoms

NASA Astrophysics Data System (ADS)

Gajdacz, Miroslav; Pedersen, Poul; Mørch, Troels; Hilliard, Andrew; Arlt, Jan; Sherson, Jacob

2013-05-01

We investigate non-destructive measurements of ultra-cold atomic clouds based on dark field imaging of spatially resolved Faraday rotation. In particular, we pursue applications to dynamically controlled ultracold atoms. The dependence of the Faraday signal on laser detuning, atomic density and temperature is characterized in a detailed comparison with theory. In particular the destructivity per measurement is extremely low and we illustrate this by imaging the same cloud up to 2000 times. The technique is applied to avoid the effect of shot-to-shot fluctuations in atom number calibration. Adding dynamic changes to system parameters, we demonstrate single-run vector magnetic field imaging and single-run spatial imaging of the system's dynamic behavior. The method can be implemented particularly easily in standard imaging systems by the insertion of an extra polarizing beam splitter. These results are steps towards quantum state engineering using feedback control of ultracold atoms.

Extragalactic background light: a measurement at 400 nm using dark cloud shadow*†- I. Low surface brightness spectrophotometry in the area of Lynds 1642

NASA Astrophysics Data System (ADS)

Mattila, K.; Lehtinen, K.; Väisänen, P.; von Appen-Schnur, G.; Leinert, Ch.

2017-09-01

We present the method and observations for the measurement of the Extragalactic Background Light (EBL) utilizing the shadowing effect of a dark cloud. We measure the surface brightness difference between the opaque cloud core and its unobscured surroundings. In the difference the large atmospheric and Zodiacal light components are eliminated and the only remaining foreground component is the scattered starlight from the cloud itself. Although much smaller, its separation is the key problem in the method. For its separation we use spectroscopy. While the scattered starlight has the characteristic Fraunhofer lines and 400 nm discontinuity, the EBL spectrum is smooth and without these features. Medium resolution spectrophotometry at λ = 380-580 nm was performed with VLT/FORS at ESO of the surface brightness in and around the high-galactic-latitude dark cloud Lynds 1642. Besides the spectrum for the core with AV ≳ 15 mag, further spectra were obtained for intermediate-opacity cloud positions. They are used as proxy for the spectrum of the impinging starlight spectrum and to facilitate the separation of the scattered starlight (cf. Paper II; Mattila et al.). Our spectra reach a precision of ≲ 0.5 × 10-9 erg cm-2 s-1 sr-1 Å-1 as required to measure an EBL intensity in range of ˜1 to a few times 10-9 erg cm-2 s-1 sr-1 Å-1. Because all surface brightness components are measured using the same equipment, the method does not require unusually high absolute calibration accuracy, a condition that has been a problem for some previous EBL projects.

A new species of Lactarius (subgenus Gerardii) from two relict Fagus grandifolia var. mexicana populations in Mexican montane cloud forests.

PubMed

Montoya, Leticia; Bandala, Victor Manuel; Haug, Ingeborg; Stubbe, Dirk

2012-01-01

A new milkcap species, Lactarius fuscomarginatus, was found in the subtropical region of central Veracruz (eastern Mexico) associated with two relict populations of Fagus grandifolia var. mexicana. The species is characterized macroscopically by its dark pileus and stipe and by its distant and whitish lamellae with blackish to blackish brown edges. A molecular phylogenetic analyses based on ITS and LSU nucDNA sequences confirms the delimitation of this new taxon and places L. fuscomarginatus in subgenus Gerardii. A detailed morphological comparison is given with similar species.

ARC-1989-AC89-7019

NASA Image and Video Library

1989-08-23

P-34666 This false color photograph of Neptune was reconstructed from two images taken by Voyager 2's wide angle camera, through the orange and two different methane filters. Objects that deep in the atmosphere are blue, while those at higher altitudes are white. Light at methane wavelengths is mostly absorbed in the deeper atmosphere. The bright, white feature is a high altitude cloud just south of the Great dark Spot. The hard, sharp inner boundary within the bright cloud is an artifact of computer processing on Earth. Other, smaller clouds associated with the Great Dark Spot are white or pink, and are also at high altitudes. Neptune's limb looks reddish because Voyager 2 is viewing it tangentially, and the sunlight is scattered back to space before it can be absorbed by methane. A long, narrow band of high-altitude clouds near the top of the image is located at 25 degrees north latitude, and faint hazes mark the equator and polor regions

MEST- avoid next extinction by a space-time effect

NASA Astrophysics Data System (ADS)

Cao, Dayong

2013-03-01

Sun's companion-dark hole seasonal took its dark comets belt and much dark matter to impact near our earth. And some of them probability hit on our earth. So this model kept and triggered periodic mass extinctions on our earth every 25 to 27 million years. After every impaction, many dark comets with very special tilted orbits were arrested and lurked in solar system. When the dark hole-Tyche goes near the solar system again, they will impact near planets. The Tyche, dark comet and Oort Cloud have their space-time center. Because the space-time are frequency and amplitude square of wave. Because the wave (space-time) can make a field, and gas has more wave and fluctuate. So they like dense gas ball and a dark dense field. They can absorb the space-time and wave. So they are ``dark'' like the dark matter which can break genetic codes of our lives by a dark space-time effect. So the upcoming next impaction will cause current ``biodiversity loss.'' The dark matter can change dead plants and animals to coal, oil and natural gas which are used as energy, but break our living environment. According to our experiments, which consciousness can use thought waves remotely to change their systemic model between Electron Clouds and electron holes of P-N Junction and can change output voltages of solar cells by a life information technology and a space-time effect, we hope to find a new method to the orbit of the Tyche to avoid next extinction. (see Dayong Cao, BAPS.2011.APR.K1.17 and BAPS.2012.MAR.P33.14) Support by AEEA

Bands of Clouds and Lace

NASA Image and Video Library

2004-05-13

As Cassini nears its rendezvous with Saturn, new detail in the banded clouds of the planet's atmosphere are becoming visible. Cassini began the journey to the ringed world of Saturn nearly seven years ago and is now less than two months away from orbit insertion on June 30. Cassini’s narrow-angle camera took this image on April 16, 2004, when the spacecraft was 38.5 million kilometers (23.9 million miles) from Saturn. Dark regions are generally areas free of high clouds, and bright areas are places with high, thick clouds which shield the view of the darker areas below. A dark spot is visible at the south pole, which is remarkable to scientists because it is so small and centered. The spot could be affected by Saturn's magnetic field, which is nearly aligned with the planet's rotation axis, unlike the magnetic fields of Jupiter and Earth. From south to north, other notable features are the two white spots just above the dark spot toward the right, and the large dark oblong-shaped feature that extends across the middle. The darker band beneath the oblong-shaped feature has begun to show a lacy pattern of lighter-colored, high altitude clouds, indicative of turbulent atmospheric conditions. The cloud bands move at different speeds, and their irregularities may be due to either the different motions between them or to disturbances below the visible cloud layer. Such disturbances might be powered by the planet's internal heat; Saturn radiates more energy than it receives from the Sun. The moon Mimas (396 kilometers, 245 miles across) is visible to the left of the south pole. Saturn currently has 31 known moons. Since launch, 13 new moons have been discovered by ground-based telescopes. Cassini will get a closer look and may discover new moons, perhaps embedded within the planet’s magnificent rings. This image was taken using a filter sensitive to light near 727 nanometers, one of the near-infrared absorption bands of methane gas, which is one of the ingredients in Saturn's atmosphere. The image scale is approximately 231 kilometers (144 miles) per pixel. Contrast has been enhanced to aid visibility of features in the atmosphere. http://photojournal.jpl.nasa.gov/catalog/PIA05391

Jovian cloud structure from 5-mu M images

NASA Astrophysics Data System (ADS)

Ortiz, J. L.; Moreno, F.; Molina, A.; Roos-Serote, M.; Orton, G. S.

1999-09-01

Most radiative transfer studies place the cloud clearings responsible for the 5-mu m bright areas at pressure levels greater than 1.5 bar whereas the low-albedo clouds are placed at lower pressure levels, in the so-called ammonia cloud. If this picture is correct, and assuming that the strong vertical shear of the zonal wind detected by the Galileo Entry Probe exists at all latitudes in Jupiter, the bright areas at 5 mu m should drift faster than the dark clouds, which is not observed. At the Galileo Probe Entry latitude this can be explained by a wave, but this is not a likely explanation for all regions where the anticorrelation between 5-mu m brightness and red-nIR reflectivity is observed. Therefore, either the vertical zonal wind shears are not global or cloud clearings and dark clouds are located at the same pressure level. We have developed a multiple scattering radiative transfer code to model the limb-darkening at several jovian features derived from IRTF 4.8-mu m images, in order to retrieve information on the cloud levels. The limb darkening coefficients range from 1.4 at hot spots to 0.58 at the Equatorial Region. We also find that reflected light is dominant over thermal emission in the Equatorial Region, as already pointed out by other investigators. Preliminary results from our code tend to favor the idea that the ammonia cloud is a very high-albedo cloud with little influence on the contrast seen in the red and nIR and that a deeper cloud at P >1.5 bar can be responsible for the cloud clearings and for the low-albedo features simultaneously. This research was supported by the Comision Interministerial de Ciencia y Tecnologia under contract ESP96-0623.

Properties of Cold HI Emission Clouds in the Inner-Galaxy ALFA Survey

NASA Astrophysics Data System (ADS)

Hughes, James Marcus; Gibson, Steven J.; Noriega-Crespo, Alberto; Newton, Jonathan; Koo, Bon-Chul; Douglas, Kevin A.; Peek, Joshua Eli Goldston; Park, Geumsook; Kang, Ji-hyun; Korpela, Eric J.; Heiles, Carl E.; Dame, Thomas M.

2017-01-01

Star formation, a critical process within galaxies, occurs in the coldest, densest interstellar clouds, whose gas and dust content are observed primarily at radio and infrared wavelengths. The formation of molecular hydrogen (H2) from neutral atomic hydrogen (HI) is an essential early step in the condensation of these clouds from the ambient interstellar medium, but it is not yet completely understood, e.g., what is the predominant trigger? Even more troubling, the abundance of H2 may be severely underestimated by standard tracers like CO, implying significant "dark" H2, and the quantity of HI may also be in error if opacity effects are neglected. We have developed an automated method to account for both HI and H2 in cold, diffuse clouds traced by narrow-line HI 21-cm emission in the Arecibo Inner-Galaxy ALFA (I-GALFA) survey. Our algorithm fits narrow (2-5 km/s), isolated HI line profiles to determine their spin temperature, optical depth, and true column density. We then estimate the "visible" H2 column in the same clouds with CfA and Planck CO data and the total gas column from dust emission measured by Planck, IRAS, and other surveys. Together, these provide constraints on the dark H2 abundance, which we examine in relation to other cloud properties and stages of development. Our aim is to build a database of H2-forming regions with significant dark gas to aid future analyses of coalescing interstellar clouds. We acknowledge support from NSF, NASA, Western Kentucky University, and Williams College. I-GALFA is a GALFA-HI survey observed with the 7-beam ALFA receiver on the 305-meter William E. Gordon Telescope. The Arecibo Observatory is a U.S. National Science Foundation facility operated under sequential cooperative agreements with Cornell University and SRI International, the latter in alliance with the Ana G. Mendez-Universidad Metropolitana and the Universities Space Research Association.

Jupiter's Bands of Clouds

NASA Image and Video Library

2017-06-22

This enhanced-color image of Jupiter's bands of light and dark clouds was created by citizen scientists Gerald Eichstädt and Seán Doran using data from the JunoCam imager on NASA's Juno spacecraft. Three of the white oval storms known as the "String of Pearls" are visible near the top of the image. Each of the alternating light and dark atmospheric bands in this image is wider than Earth, and each rages around Jupiter at hundreds of miles (kilometers) per hour. The lighter areas are regions where gas is rising, and the darker bands are regions where gas is sinking. Juno acquired the image on May 19, 2017, at 11:30 a.m. PST (2:30 p.m. EST) from an altitude of about 20,800 miles (33,400 kilometers) above Jupiter's cloud tops. https://photojournal.jpl.nasa.gov/catalog/PIA21393

A search for the 13175 A infrared diffuse band in dense environments

NASA Technical Reports Server (NTRS)

Adamson, A. J.; Kerr, Tom H.; Whittet, D. C. B.; Duley, Walter W.

1994-01-01

Models of ionized interstellar C60 predict a strong transition in the 1.2 micrometer region, and two candidate bands have recently been detected in reddened stars. We have searched for the stronger of these bands (at 13175 A) in the Taurus dark cloud complex, to determine its response to the dark-cloud environment. None of the three lines of sight studied (two near the cloud surface, one reaching A(sub V) greater than 20(sup m)) give rise to a detectable band; in one case the equivalent width is a factor of order three below that predicted. Since such behaviour is also shown by the optical Diffuse Interstellar Bands, we suggest that the 13175 A band is a genuine DIB, but we caution against an automatic interpretation in terms of an ionic carrier.

Stars Take Longer to Form, Need a 'Kick' to Get Started, Astronomers Say

NASA Astrophysics Data System (ADS)

2002-01-01

Star formation is a longer process than previously thought, and is heavily dependent on outside events, such as supernova explosions, to trigger it, a team of astronomers has concluded. The scientists reached their conclusions after making a detailed study of a number of the dark gas clouds in which new stars are formed. Optical and mm-wave overlay of dark cloud Optical image of the dark cloud L57, with white contours indicating submillimeter-wave emission from dust within the dark cloud. "Our observations indicate that we need to drastically revise our ideas about the very early stages of star formation," said Claire Chandler, an astronomer at the National Radio Astronomy Observatory (NRAO) in Socorro, New Mexico. Chandler, who worked with John Richer and Anja Visser at the Mullard Radio Astronomy Observatory in the United Kingdom, presented the results at the American Astronomical Society's meeting in Washington, D.C. The astronomers observed the gas clouds with the SCUBA camera on the James Clerk Maxwell Telescope on Mauna Kea, Hawaii. This instrument is sensitive to submillimeter-wavelength radiation, which lies between radio waves and infrared waves in the electromagnetic spectrum. They studied clouds that previously had been observed with optical and infrared telescopes. The SCUBA images allowed them to see aspects of the clouds not visible at other wavelengths. Some young "protostars" are so deeply embedded in their parent gas clouds that they are invisible to infrared telescopes, while others have become visible by consuming and blowing away much of their surrounding clouds. Earlier studies had indicated that the "invisible" stars are only about one-tenth as common as those visible to infrared telescopes. "What we see in our study, however, is equal numbers of both types," said Chandler, who added, "This means that both stages probably have about the same lifetime -- roughly 200,000 years each." Another conclusion coming from the study is that star formation is heavily dependent on a triggering event to get it started. Such a triggering event might be the shock wave from a supernova explosion that causes gas clouds to begin the gravitational collapse that ultimately results in a new star. Another challenge to traditional wisdom about the early stages of star formation came in the team's analysis of data on starless cores -- gas clouds that have not yet begun their collapse into stars. The astronomers found that the starless cores in their study are on the verge of collapsing, and probably have shorter lifetimes than previously thought. "This means that, contrary to what we thought before, you don't need strong magnetic fields to hold these things up against gravitational collapse, because they don't last that long," Chandler said. Much theoretical work on early star formation that focuses on the role of magnetic fields may need revision, the study indicates. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Detection of interstellar HCS and its metastable isomer HSC: new pieces in the puzzle of sulfur chemistry

NASA Astrophysics Data System (ADS)

Agúndez, M.; Marcelino, N.; Cernicharo, J.; Tafalla, M.

2018-03-01

We present the first identification in interstellar space of the thioformyl radical (HCS) and its metastable isomer HSC. These species were detected toward the molecular cloud L483 through observations carried out with the IRAM 30 m telescope in the λ3 mm band. We derive beam-averaged column densities of 7 × 1012 cm-2 for HCS and 1.8 × 1011 cm-2 for HSC, which translate into fractional abundances relative to H2 of 2 × 10-10 and 6 × 10-12, respectively. Although the amount of sulfur locked by these radicals is low, their detection allows placing interesting constraints on the chemistry of sulfur in dark clouds. Interestingly, the H2CS/HCS abundance ratio is found to be quite low, 1, in contrast with the oxygen analog case, in which the H2CO/HCO abundance ratio is around 10 in dark clouds. Moreover, the radical HCS is found to be more abundant than its oxygen analog, HCO. The metastable species HOC, the oxygen analog of HSC, has not yet been observed in space. These observational constraints are compared with the outcome of a recent model of the chemistry of sulfur in dark clouds. The model underestimates the fractional abundance of HCS by at least one order of magnitude, overestimates the H2CS/HCS abundance ratio, and does not provide an abundance prediction for the metastable isomer HSC. These observations should prompt a revision of the chemistry of sulfur in interstellar clouds.

ARC-1989-AC89-0114-324

NASA Image and Video Library

1989-02-28

Arctic Ozone Expedition Stavanger Norway These clouds in the polar regions north of Stravanger, Norway are representative of what are called 'Type 1' and Type 2' polar stratospheric clouds. Type 1 are seen in the lower portion and consist of cloud particles comprised of nitrogen trihydrates. Seen edge-on as in this view, they appear as a thin dark orange or brown layer. Multiple layering can be seen. The Type 2 clouds are above and consist mostly of water molecules frozen as ice. The size of the particles in Type 2 clouds, the water-ice clouds, are much larger than the particle size of the Type 1 clouds - which are on the order of the wavelength of light.

KSC-2011-2640

NASA Image and Video Library

2011-03-31

CAPE CANAVERAL, Fla. – At NASA's Kennedy Space Center in Florida, dark clouds hover over the Vehicle Assembly Building in the Launch Complex 39 area. Severe storms associated with a frontal system are moving through Central Florida, producing strong winds, heavy rain, frequent lightning and even funnel clouds. Photo credit: NASA/Jack Pfaller

KSC-2011-2641

NASA Image and Video Library

2011-03-31

CAPE CANAVERAL, Fla. – At NASA's Kennedy Space Center in Florida, dark clouds hover over the Vehicle Assembly Building in the Launch Complex 39 area. Severe storms associated with a frontal system are moving through Central Florida, producing strong winds, heavy rain, frequent lightning and even funnel clouds. Photo credit: NASA/Jack Pfaller

CO Column Density and Extinction in the Chamaeleon II--III Dark-Cloud Complex

NASA Astrophysics Data System (ADS)

Hayakawa, Takahiro; Cambrésy, Laurent; Onishi, Toshikazu; Mizuno, Akira; Fukui, Yasuo

2001-12-01

We carried out 13CO (J = 1 -- 0) and C18O (J = 1 -- 0) observations of the Chamaeleon II--III dark-cloud complex with the NANTEN radio telescope. The column densities of both molecular isotopes were derived assuming LTE. The AV values were obtained by scaling the AV values that were derived using an adaptive-grid star-count method applied to the DENIS J-band data. We established the AV--CO isotope column-density relations in Cha II and III, and compared them with those in Cha I. The slopes of the AV--13CO relations for Cha II and III are steeper than that for Cha I. Those of the AV -- C18O relations are similar among the three clouds. The total column density ratio, N(13O) / N(C18O, in Cha I tends to be small compared with those in Cha II or Cha III; the ratios range from ~ 5 to ~ 25 at low extinction in Cha II and III, but at most ~ 10 in Cha I. We suggest that the increase of N(13CO) due to the 13CO formation process causes cloud-to-cloud variations in the AV -- N(13CO) correlation.

Longitudinal Variation and Waves in Jupiter's South Equatorial Wind Jet

NASA Technical Reports Server (NTRS)

Simon-Miller, A. A.; Rogers, John H.; Gierasch, Peter J.; Choi, David; Allison, Michael; Adamoli, Gianluigi; Mettig, Hans-Joerg

2012-01-01

We have conducted a detailed study of the cloud features in the strong southern equatorial wind jet near 7.5 S planetographic latitude. To understand the apparent variations in average zonal wind jet velocity at this latitude [e.g.. 1,2,3], we have searched for variations iIi both feature latitude and velocity with longitude and time. In particular, we focused on the repetitive chevron-shaped dark spots visible on most dates and the more transient large anticyclonic system known as the South Equatorial Disturbance (SED). These small dark spots are interpreted as cloud holes, and are often used as material tracers of the wind field.

Simulating the evolution of optically dark HI clouds in the Virgo cluster : will no-one rid me of this turbulent sphere ?

NASA Astrophysics Data System (ADS)

Taylor, R.; Wünsch, R.; Palouš, J.

2018-05-01

Most detected neutral atomic hydrogen (HI) at low redshift is associated with optically bright galaxies. However, a handful of HI clouds are known which appear to be optically dark and have no nearby potential progenitor galaxies, making tidal debris an unlikely explanation. In particular, 6 clouds identified by the Arecibo Galaxy Environment Survey are interesting due to the combination of their small size, isolation, and especially their broad line widths atypical of other such clouds. A recent suggestion is that these clouds exist in pressure equilibrium with the intracluster medium, with the line width arising from turbulent internal motions. Here we explore that possibility by using the FLASH code to perform a series of 3D hydro simulations. Our clouds are modelled using spherical Gaussian density profiles, embedded in a hot, low-density gas representing the intracluster medium. The simulations account for heating and cooling of the gas, and we vary the structure and strength of their internal motions. We create synthetic HI spectra, and find that none of our simulations reproduce the observed cloud parameters for longer than ˜100 Myr : the clouds either collapse, disperse, or experience rapid heating which would cause ionisation and render them undetectable to HI surveys. While the turbulent motions required to explain the high line widths generate structures which appear to be inherently unstable, making this an unlikely explanation for the observed clouds, these simulations demonstrate the importance of including the intracluster medium in any model seeking to explain the existence of these objects.

The physics and chemistry of the L134N molecular core

NASA Technical Reports Server (NTRS)

Swade, Daryl A.

1989-01-01

The dark cloud L134N is studied in detail via millimeter- and centimeter-wavelength emission-line spectra. A high-density core of molecular gas exists in L134N which has a kinetic temperature of about 12 K, a peak molecular hydrogen density of about 10 exp 4.5/cu cm, and a mass of about 23 solar. The core may be the site of future star formation. Maps of emission from (C-18)O, CS, H(C-13)O(+), SO, NH3, and C3H2 reveal morphologically different distributions resulting in part from both varying physical conditions within the cloud and optical depth effects. Significant differences also exist which are probably due to chemical abundance variations. A consistent set of LTE chemical abundances has been estimated at as many as seven positions, which can be used to constrain chemical models of dark clouds.

Newly detected molecules in dense interstellar clouds

NASA Astrophysics Data System (ADS)

Irvine, William M.; Avery, L. W.; Friberg, P.; Matthews, H. E.; Ziurys, L. M.

Several new interstellar molecules have been identified including C2S, C3S, C5H, C6H and (probably) HC2CHO in the cold, dark cloud TMC-1; and the discovery of the first interstellar phosphorus-containing molecule, PN, in the Orion "plateau" source. Further results include the observations of 13C3H2 and C3HD, and the first detection of HCOOH (formic acid) in a cold cloud.

Nanolensed Fast Radio Bursts

NASA Astrophysics Data System (ADS)

Eichler, David

2017-12-01

It is suggested that fast radio bursts can probe gravitational lensing by clumpy dark matter objects that range in mass from 10-3 M ⊙-102 M ⊙. They may provide a more sensitive probe than observations of lensings of objects in the Magellanic Clouds, and could find or rule out clumpy dark matter with an extended mass spectrum.

Similar complex kinematics within two massive, filamentary infrared dark clouds

NASA Astrophysics Data System (ADS)

Barnes, A. T.; Henshaw, J. D.; Caselli, P.; Jiménez-Serra, I.; Tan, J. C.; Fontani, F.; Pon, A.; Ragan, S.

2018-04-01

Infrared dark clouds (IRDCs) are thought to be potential hosts of the elusive early phases of high-mass star formation. Here, we conduct an in-depth kinematic analysis of one such IRDC, G034.43+00.24 (Cloud F), using high sensitivity and high spectral resolution IRAM-30m N2H+ (1-0) and C18O (1-0) observations. To disentangle the complex velocity structure within this cloud, we use Gaussian decomposition and hierarchical clustering algorithms. We find that four distinct coherent velocity components are present within Cloud F. The properties of these components are compared to those found in a similar IRDC, G035.39-00.33 (Cloud H). We find that the components in both clouds have high densities (inferred by their identification in N2H+), trans-to-supersonic non-thermal velocity dispersions with Mach numbers of ˜1.5-4, a separation in velocity of ˜3 km s-1, and a mean red-shift of ˜0.3 km s-1 between the N2H+ (dense gas) and C18O emission (envelope gas). The latter of these could suggest that these clouds share a common formation scenario. We investigate the kinematics of the larger-scale Cloud F structures, using lower-density-tracing 13CO(1-0) observations. A good correspondence is found between the components identified in the IRAM-30m observations and the most prominent component in the 13CO data. We find that the IRDC Cloud F is only a small part of a much larger structure, which appears to be an inter-arm filament of the Milky Way.

PREDICTED SIZES OF PRESSURE-SUPPORTED HI CLOUDS IN THE OUTSKIRTS OF THE VIRGO CLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burkhart, Blakesley; Loeb, Abraham

Using data from the ALFALFA AGES Arecibo HI survey of galaxies and the Virgo cluster X-ray pressure profiles from XMM-Newton , we investigate the possibility that starless dark HI clumps, also known as “dark galaxies,” are supported by external pressure in the surrounding intercluster medium. We find that the starless HI clump masses, velocity dispersions, and positions allow these clumps to be in pressure equilibrium with the X-ray gas near the virial radius of the Virgo cluster. We predict the sizes of these clumps to range from 1 to 10 kpc, in agreement with the range of sizes found formore » spatially resolved HI starless clumps outside of Virgo. Based on the predicted HI surface density of the Virgo sources, as well as a sample of other similar resolved ALFALFA HI dark clumps with follow-up optical/radio observations, we predict that most of the HI dark clumps are on the cusp of forming stars. These HI sources therefore mark the transition between starless HI clouds and dwarf galaxies with stars.« less

Hydroxyl as a Tracer of Dark Gas in a Diffuse Molecular Cloud

NASA Astrophysics Data System (ADS)

White, Josh; Donate, Emmanuel; Magnani, Loris A.

2017-06-01

In an attempt to determine the extent of dark molecular gas at high Galactic latitudes, we have conducted a survey of OH at 18 cm in a region containing the diffuse molecular cloud MBM 53. Dark molecular gas is a term that refers to molecular hydrogen that is either difficult or impossible to detect by conventional spectroscopic means. While models of photo-dissociation regions predict that some molecular hydrogen is found under conditions where other species are too low in abundance to be detected by radio spectroscopy, recent estimates have predicted that as much dark molecular gas exists as that normally detected by CO(1-0) surveys. However, more sensitive surveys either in the CO(1-0) line or other tracers should detect some of this gas. We observed 44 lines of sight at 18 cm to see if very sensitive OH observations could detect some of the dark molecular gas in the Pegasus-Pisces region. Our data were taken with the 305 m Arecibo radiotelescope and have typical rms values of 6-7 mK. We compared our OH observations with the Georgia/Harvard-Smithsonian CfA high-latitude CO(1-0) survey. Of 8 OH detections at 1667 MHz, 5 were not detected by the CO survey and indicate that at least some of the dark molecular gas may be traced by sensitive OH observations.

Hubble Space Telescope Wide Field Planetary Camera 2 Observations of Neptune

NASA Technical Reports Server (NTRS)

1995-01-01

Two groups have recently used the Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC 2) to acquire new high-resolution images of the planet Neptune. Members of the WFPC-2 Science Team, lead by John Trauger, acquired the first series of images on 27 through 29 June 1994. These were the highest resolution images of Neptune taken since the Voyager-2 flyby in August of 1989. A more comprehensive program is currently being conducted by Heidi Hammel and Wes Lockwood. These two sets of observations are providing a wealth of new information about the structure, composition, and meteorology of this distant planet's atmosphere.

Neptune is currently the most distant planet from the sun, with an orbital radius of 4.5 billion kilometers (2.8 billion miles, or 30 Astronomical Units). Even though its diameter is about four times that of the Earth (49,420 vs. 12,742 km), ground-based telescopes reveal a tiny blue disk that subtends less than 1/1200 of a degree (2.3 arc-seconds). Neptune has therefore been a particularly challenging object to study from the ground because its disk is badly blurred by the Earth's atmosphere. In spite of this, ground-based astronomers had learned a great deal about this planet since its position was first predicted by John C. Adams and Urbain Leverrier in 1845. For example, they had determined that Neptune was composed primarily of hydrogen and helium gas, and that its blue color caused by the presence of trace amounts of the gas methane, which absorbs red light. They had also detected bright cloud features whose brightness changed with time, and tracked these clouds to infer a rotation period between 17 and 22 hours.

When the Voyager-2 spacecraft flew past the Neptune in 1989, its instruments revealed a surprising array of meteorological phenomena, including strong winds, bright, high-altitude clouds, and two large dark spots attributed to long-lived giant storm systems. These bright clouds and dark spots were tracked as they moved across the planet's disk, revealing wind speeds as large as 325 meters per second (730 miles per hour). The largest of the giant, dark storm systems, called the 'Great Dark Spot', received special attention because it resembled Jupiter's Great Red Spot, a storm that has persisted for more than three centuries. The lifetime of Neptune's Great Dark Spot could not be determined from the Voyager data alone, however, because the encounter was too brief. Its evolution was impossible to monitor with ground-based telescopes, because it could not be resolved on Neptune's tiny disk, and its contribution to the disk-integrated brightness of Neptune confused by the presence of a rapidly-varying bright cloud feature, called the 'Bright Companion' that usually accompanied the Great Dark spot.

The repaired Hubble Space Telescope provides new opportunities to monitor these and other phenomena in the atmosphere of the most distant planet. Images taken with WFPC-2's Planetary Camera (PC) can resolve Neptune's disk as well as most ground-based telescopes can resolve the disk of Jupiter. The spatial resolution of the HST WFPC-2 images is not as high as that obtained by the Voyager-2 Narrow-Angle Camera during that spacecraft's closest approach to Neptune, but they have a number of other assets that enhance their scientific value, including improved ultra-violet and infrared sensitivity, better signal-to-noise, and, and greater photometric accuracy.

The images of Neptune acquired by the WFPC-2 Science team in late June clearly demonstrate these capabilities. The side of the planet facing the Earth at the start of the program (11:36 Universal Time on July 27) was imaged in color filters spanning the ultraviolet (255 and 300-nm), visible (467, 588, 620, and 673- nm), and near-infrared (890-nm) parts of the spectrum. The planet then rotated 180 degrees in longitude, and the opposite hemisphere was imaged in a subset of these colors (300, 467, 588, 620, and 673-nm). The HST/WFPC-2 program more recently conducted by Hammel and Lockwood provides better longitude coverage, and a wider range of observing times, but uses a more restricted set of colors.

The ultraviolet pictures show an almost featureless disk that is slightly darker near the edge. The observed contrast increases in the blue, green, red, and near-infrared images, which reveal many of the features seen by Voyager 2, including the dark band near 60 S latitude and several distinct bright cloud features. The bright cloud features are most obvious in the red and infrared parts of the spectrum where methane gas absorbs most strongly (619 and 890 nm). These bright clouds thought to be high above the main cloud deck, and above much of the absorbing methane gas. The edge of the planet's disk also appears somewhat bright in these colors, indicating the presence of a ubiquitous, high-altitude haze layer.

The northern hemisphere is occupied by a single prominent cloud band centered near 30 N latitude. This planet-encircling feature may be the same bright cloud discovered last fall by ground-based observers. Northern hemisphere clouds were much less obvious at the time of the Voyager-2 encounter. The tropics are about 20 % darker than the disk average in the 890-nm images, and one of these images reveals a discrete bright cloud on the equator, near the edge of the disk. The southern hemisphere includes two broken bright bands. The largest and brightest is centered at 30 S latitude, and extends for least 40 degrees of longitude, like the Bright Companion to the Great Dark Spot. There is also a thin cloud band at 45 S latitude, which almost encircles the planet.

One feature that is conspicuous by its absence is the storm system known as the Great Dark Spot. The second smaller dark spot, DS2, that was seen during the Voyager-2 encounter was also missing. The absence of these dark spots was one of the biggest surprises of this program. The WFPC-2 Science team initially assumed that the two storm systems might be near the edge of the planet's disk, where they would not be particularly obvious. An analysis of their longitude coverage revealed that less than 20 degrees of longitude had been missed in the colors where these spots had their greatest contrast (467 and 588 nm). The Great Dark Spot covered almost 40 degrees of longitude at the time of the Voyager-2 fly-by. Even if it were on the edge of the disk, it would appear as a 'bite' out of the limb. Because no such feature was detected, we concluded that these features had vanished. This conclusion was reinforced by the more recent observations by Hammel and Lockwood, which also show no evidence of discrete dark spots.

These dramatic changes in the large-scale storm systems and planet-encircling clouds bands on Neptune are not yet completely understood, but they emphasize the dynamic nature of this planet's atmosphere, and the need for further monitoring. Additional HST WFPC-2 observations are planned for next summer. These two teams are continuing their analysis of these data sets to place improved constraints on these and other phenomena in Neptune's atmosphere.

Figure Captions:

These almost true-color pictures of Neptune were constructed from HST/WFPC2 images taken in blue (467-nm), green (588- nm), and red (673-nm) spectral filters. There is a bright cloud feature at the south pole, near the bottom right of the image. Bright cloud bands can be seen at 30S and 60S latitude. The northern hemisphere also includes a bright cloud band centered near 30N latitude. The second picture was compiled from images taken after the planet had rotated about 180 degrees of longitude (about 9 hours later) to show the opposite hemisphere.

The Wide Field/Planetary Camera 2 was developed by the Jet Propulsion Laboratory and managed by the Goddard Spaced Flight Center for NASA's Office of Space Science.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

KSC-01pp1163

NASA Image and Video Library

2001-06-15

KENNEDY SPACE CENTER, Fla. -- Dark clouds and strong winds seem almost to touch the ground near the tow-way leading from the Shuttle Landing Facility (SLF). In the background (right) can be seen the new hangar at the SLF and the mate/demate device. The cloud formation is proceeding across the SLF towards the Vehicle Assembly Building

La Freccia Rossa: An IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate

NASA Astrophysics Data System (ADS)

Ravi, Vikram; Vedantham, Harish; Phinney, E. Sterl

2018-05-01

The dynamics of the high-velocity compact molecular cloud CO-0.40-0.22 have been interpreted as evidence for a ˜105M⊙ black hole within 60 pc of Sgr A*. Recently, Oka et al. have identified a compact millimetre-continuum source, CO-0.40-0.22*, with this candidate black hole. Here we present a collation of radio and infrared data at this location. ATCA constraints on the radio spectrum, and the detection of a mid-infrared counterpart, are in tension with an Sgr A*-like model for CO-0.40-0.22* despite the comparable bolometric to Eddington luminosity ratios under the IMBH interpretation. A protostellar-disk scenario is, however, tenable. CO-0.40-0.22(*) is positionally coincident with an arrowhead-shaped infrared-dark cloud (which we call the Freccia Rossa). If the VLSR ≈ 70 km s-1 systemic velocity of CO-0.40-0.22 is common to the entire Freccia Rossa system, we hypothesise that it is the remnant of a high-velocity cloud that has plunged into the Milky Way from the Galactic halo.

Far-infrared observations of young clusters embedded in the R Coronae Australis and Rho Ophiuchi dark clouds

NASA Technical Reports Server (NTRS)

Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

1985-01-01

Multicolor far-infrared maps in two nearby dark clouds, R Coronae Australis and Rho Ophiuchi, have been made in order to investigate the individual contribution of low-mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low-mass stars has been detected in CrA and four in Rho Oph; their far-infrared luminosities range from 2 solar luminosities to 40 solar luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50 percent of the star's energy was radiated longward of 20 microns. Meaningful limits to the far-infrared luminosities of an additional 11 association members in CrA and two in Rho Oph were also obtained. The dust optical depth surrounding the star R CrA appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of these results for the cloud energetics and star formation efficiency in these two clouds are discussed.

Far-infrared observations of young clusters embedded in the R Coronae Austrinae and RHO Ophiuchi dark clouds

NASA Technical Reports Server (NTRS)

Wilking, B. A.; Harvey, P. M.; Joy, M.; Hyland, A. R.; Jones, T. J.

1985-01-01

Multicolor far infrared maps in two nearby dark clouds, R Coronae Austrinae and rho Ophiuchi, were made in order to investigate the individual contribution of low mass stars to the energetics and dynamics of the surrounding gas and dust. Emission from cool dust associated with five low mass stars in Cr A and four in rho Oph was detected; their far infrared luminosities range from 2 far infrared luminosities L. up to 40 far infrared luminosities. When an estimate of the bolometric luminosity was possible, it was found that typically more than 50% of the star's energy was radiated longward of 20 micrometers. meaningful limits to the far infrared luminosities of an additional eleven association members in Cr A and two in rho Oph were also obtained. The dust optical depth surrounding the star R Cr A appears to be asymmetric and may control the dynamics of the surrounding molecular gas. The implications of the results for the cloud energetics and star formation efficiency in these two clouds are discussed.

The 15 273 Å diffuse interstellar band in the dark cloud Barnard 68

NASA Astrophysics Data System (ADS)

Elyajouri, Meriem; Cox, Nick L. J.; Lallement, Rosine

2017-09-01

High obscuration of background stars behind dark clouds precludes the detection of optical diffuse interstellar bands (DIBs) and hence our knowledge of DIB carriers in these environments. Taking advantage of the reduced obscuration of starlight in the near-infrared (NIR) we used one of the strongest NIR DIBs at 15 273 Å to probe the presence and properties of its carrier throughout the nearby interstellar dark cloud Barnard 68. We measured equivalent widths (EW) for different ranges of visual extinction AV, using VLT/KMOS H-band (1.46-1.85 μm) moderate-resolution (R 4000) spectra of 43 stars situated behind the cloud. To do so, we fitted the data with synthetic stellar spectra from the APOGEE project and TAPAS synthetic telluric transmissions appropriate for the observing site and time period. The results show an increase of DIB EW with increasing AV. However, the rate of increase is much flatter than expected from the EW-AV quasi-proportionality established for this DIB in the Galactic diffuse interstellar medium. Based on a simplified inversion assuming sphericity, it is found that the volume density of the DIB carrier is 2.7 and 7.9 times lower than this expected average value in the external and central regions of the cloud, which have nH≃ 0.4 and 3.5 × 105 cm-3, respectively. Further measurements with multiplex NIR spectrographs should allow detailed modeling of such an edge effect of this DIB and other bands and help clarify its actual origin. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere under ESO programme 096.C-0931(A).

Meteorology of Jupiter's Equatorial Hot Spots and Plumes from Cassini

NASA Technical Reports Server (NTRS)

Choi, David Sanghun; Showman, Adam P.; Vasavada, Ashwin R.; Simon-Miller, Amy A.

2013-01-01

We present an updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the Imaging Science Subsystem (ISS) onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial hot spots and their interactions with adjacent latitudes. Hot spots are relatively cloud-free regions that emit strongly at 5 lm; improved knowledge of these features is crucial for fully understanding Galileo probe measurements taken during its descent through one. Hot spots are quasistable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but diffuse western edges serving as nebulous boundaries with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-like 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. These clouds travel at 150-200 m/s, much faster than the 100 m/s hot spot and plume drift speed. This raises the possibility that the scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. Most previously published zonal wind profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby wave controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed.

New Observations and Studies of Saturn's Long-Lived North Polar SPOT

NASA Astrophysics Data System (ADS)

Sanchez-Lavega, Agustin; Rojas, Jose Félix; Acarreta, Juan Ramón; Lecacheux, Jean; Colas, François; Sada, Pedro V.

1997-08-01

We report on a new series of ground-based CCD observations at visual wavelengths, covering a period of 1255 days between May 1992 and November 1995, of the longest-lived asymmetric feature known in Saturn's atmosphere: the north polar spot (NPS). This completes our previous analysis of this feature during the period 1990-1991 (A. Sanchez-Lavega, J. Lecacheux, F. Colas, and P. Lagues, 1993,Science260,329-332). Longitude measurements of the NPS indicate an averaged longitudinal drift of -0.030 deg/day for the whole period 1990-1995 corresponding to a zonal velocity of 0.11 msec-1. These data, when combined with previous and new measurements of the NPS position on Voyager 1 and 2 images obtained in 1980 and 1981, indicate a long-term drift in longitude of the NPS with a constant angular acceleration of 1.1 × 10-5deg/(day)2. High-resolution Voyager 2 violet, blue, green, and orange images were used to measure the size and reflectivity of the NPS. Its structure is characterized by a bright elliptical core surrounded by a dark ring and a large uniform area. The contrast between all these features changes appreciably from violet to orange: the spot is dark in violet but bright in orange relative to its surroundings. The spot is embedded within a region seeded by a “field of bright clouds” with characteristic size 1000 km reminiscent of a cellular convection pattern. The NPS's east-west apparent size is shorter at violet-blue (about 7000 km as limited by a dark ring at these wavelengths) than at green-orange (about 11,000 km corresponding to the large uniform area). Green processed images show apparent spiral patterns within the NPS consistent with anticyclonic vorticity. The results of ground-based photometry of the north polar region (NPR) and the NPS in the red methane absorption bands and their adjacent continuum are consistent with a radiative transfer model of the cloud vertical structure consisting of a clear gas layer, a haze layer, and a semi-infinite cloud. In the context of this model the NPS cloud tops are slightly higher than neighboring clouds reaching a pressure level of 45 mbar. Calculations of the seasonal insolation at the north pole, together with a simple linear radiative response of the atmosphere to this heating at different altitudes, suggest temperature changes at the level of the NPS cloud tops which should influence the NPS dynamics. Because of the long lifetime of the NPS, and because its motions did not vary appreciably during the long observing period, we suggest that the main properties and dynamics of the NPS are insensitive to the external solar forcing.

The Relationship Between Infrared Dark Cloud and Stellar Properties

NASA Astrophysics Data System (ADS)

Calahan, Jenny; Hora, Joseph L.

2018-01-01

Massive stars are known to form within infrared dark clouds (IRDCs), but many details about how molecular clouds collapse and form stars remain poorly understood.We determine the relationship between the dark cloud mass and the population of young stellar objects (YSOs) associated with the cloud to shed light on the physical processes occurring within these star forming regions. We chose to use a sample of IRDCs and YSOs within the Cygnus-X region, a close-by giant star formation complex that has every stage of star formation represented. Using observations from IRAC, MIPS, PACS, and SPIRE on Spitzer and Herschel we identified a sample of 30,903 YSOs and 167 IRDCs. We derived the class of each YSO as well as the mass of YSO and IRDCs from the flux information. Using these parameters, as well as their locations in the cloud, we were sorted IRDC fragments into larger filaments and associate a set of YSOs with each IRDC. By measuring and comparing parameters such as YSO total mass, number of YSOs, Class 0, Class I, and Class II populations, distance from host filament, and filament mass we tested for correlations between the YSO and IRDC parameters. Using this treasure trove of information, we find that Class 0 and I objects are located more closely to their host IRDC than their Class II counterparts. We also find that high-density IRDCs are better environments for star formation than low-density IRDCs. However, we find no correlation between the total mass of the IRDC and the largest YSO mass in the IRDC, suggesting that IRDCs of any mass can have massive YSOs associated with them.The SAO REU program is funded by the National Science Foundation REU and Department of Defense ASSURE programs under NSF Grant AST-1659473, and by the Smithsonian Institution.

The 2010-2011 Revival of Jupiter's South Equatorial Belt: Perturbations of Temperatures, Clouds and Composition from Infrared Observations

NASA Technical Reports Server (NTRS)

Orton, G.; Fletcher, L.; Yanamandra-Fisher, P.; Sanchez-Lavega, A.; Perez-Hoyos, S.; Baines, K.; de Pater, I.; Wong, M.; Goetz, R.; Valkov, S.;

PIA01492

NASA Image and Video Library

1998-10-30

This picture of Neptune was produced from the last whole planet images taken through the green and orange filters on NASA's Voyager 2 narrow angle camera. The images were taken at a range of 4.4 million miles from the planet, 4 days and 20 hours before closest approach. The picture shows the Great Dark Spot and its companion bright smudge; on the west limb the fast moving bright feature called Scooter and the little dark spot are visible. These clouds were seen to persist for as long as Voyager's cameras could resolve them. North of these, a bright cloud band similar to the south polar streak may be seen. http://photojournal.jpl.nasa.gov/catalog/PIA01492

Shuttle Atlantis enters Earth's Atmosphere

NASA Image and Video Library

2011-07-21

ISS028-E-018216 (21 July 2011) --- This unprecedented view of the space shuttle Atlantis, appearing like a bean sprout against the darkness of space, a faint line of airglow over a dark cloud-covered Earth, on its way home, was photographed by the crew of the International Space Station. Airglow over Earth can be seen in the background.

Anthropogenic disruption of the night sky darkness in urban and rural areas.

PubMed

Bará, Salvador

2016-10-01

The growing emissions of artificial light to the atmosphere are producing, among other effects, a significant increase of the night sky brightness (NSB) above its expected natural values. A permanent sensor network has been deployed in Galicia (northwest of Iberian peninsula) to monitor the anthropogenic disruption of the night sky darkness in a countrywide area. The network is composed of 14 detectors integrated in automated weather stations of MeteoGalicia, the Galician public meteorological agency. Zenithal NSB readings are taken every minute and the results are openly available in real time for researchers, interested stakeholders and the public at large through a dedicated website. The measurements allow one to assess the extent of the loss of the natural night in urban, periurban, transition and dark rural sites, as well as its daily and monthly time courses. Two metrics are introduced here to characterize the disruption of the night darkness across the year: the significant magnitude ( m 1/3 ) and the moonlight modulation factor ( γ ). The significant magnitude shows that in clear and moonless nights the zenithal night sky in the analysed urban settings is typically 14-23 times brighter than expected from a nominal natural dark sky. This factor lies in the range 7-8 in periurban sites, 1.6-2.5 in transition regions and 0.8-1.6 in rural and mountain dark sky places. The presence of clouds in urban areas strongly enhances the amount of scattered light, easily reaching amplification factors in excess of 25, in comparison with the light scattered in the same places under clear sky conditions. The periodic NSB modulation due to the Moon, still clearly visible in transition and rural places, is barely notable at periurban locations and is practically lost at urban sites.

Anthropogenic disruption of the night sky darkness in urban and rural areas

PubMed Central

2016-01-01

The growing emissions of artificial light to the atmosphere are producing, among other effects, a significant increase of the night sky brightness (NSB) above its expected natural values. A permanent sensor network has been deployed in Galicia (northwest of Iberian peninsula) to monitor the anthropogenic disruption of the night sky darkness in a countrywide area. The network is composed of 14 detectors integrated in automated weather stations of MeteoGalicia, the Galician public meteorological agency. Zenithal NSB readings are taken every minute and the results are openly available in real time for researchers, interested stakeholders and the public at large through a dedicated website. The measurements allow one to assess the extent of the loss of the natural night in urban, periurban, transition and dark rural sites, as well as its daily and monthly time courses. Two metrics are introduced here to characterize the disruption of the night darkness across the year: the significant magnitude (m1/3) and the moonlight modulation factor (γ). The significant magnitude shows that in clear and moonless nights the zenithal night sky in the analysed urban settings is typically 14–23 times brighter than expected from a nominal natural dark sky. This factor lies in the range 7–8 in periurban sites, 1.6–2.5 in transition regions and 0.8–1.6 in rural and mountain dark sky places. The presence of clouds in urban areas strongly enhances the amount of scattered light, easily reaching amplification factors in excess of 25, in comparison with the light scattered in the same places under clear sky conditions. The periodic NSB modulation due to the Moon, still clearly visible in transition and rural places, is barely notable at periurban locations and is practically lost at urban sites. PMID:27853572

Gas-grain chemical models of star-forming molecular clouds as constrained by ISO and SWAS observations

NASA Astrophysics Data System (ADS)

Charnley, S. B.; Rodgers, S. D.; Ehrenfreund, P.

2001-11-01

We have investigated the gaseous and solid state molecular composition of dense interstellar material that periodically experiences processing in the shock waves associated with ongoing star formation. Our motivation is to confront these models with the stringent abundance constraints on CO2, H2O and O2, in both gas and solid phases, that have been set by ISO and SWAS. We also compare our results with the chemical composition of dark molecular clouds as determined by ground-based telescopes. Beginning with the simplest possible model needed to study molecular cloud gas-grain chemistry, we only include additional processes where they are clearly required to satisfy one or more of the ISO-SWAS constraints. When CO, N2 and atoms of N, C and S are efficiently desorbed from grains, a chemical quasi-steady-state develops after about one million years. We find that accretion of CO2 and H2O cannot explain the [CO2/H2O]ice ISO observations; as with previous models, accretion and reaction of oxygen atoms are necessary although a high O atom abundance can still be derived from the CO that remains in the gas. The observational constraints on solid and gaseous molecular oxygen are both met in this model. However, we find that we cannot explain the lowest H2O abundances seen by SWAS or the highest atomic carbon abundances found in molecular clouds; additional chemical processes are required and possible candidates are given. One prediction of models of this type is that there should be some regions of molecular clouds which contain high gas phase abundances of H2O, O2 and NO. A further consequence, we find, is that interstellar grain mantles could be rich in NH2OH and NO2. The search for these regions, as well as NH2OH and NO2 in ices and in hot cores, is an important further test of this scenario. The model can give good agreement with observations of simple molecules in dark molecular clouds such as TMC-1 and L134N. Despite the fact that S atoms are assumed to be continously desorbed from grain surfaces, we find that the sulphur chemistry independently experiences an ``accretion catastrophe''. The S-bearing molecular abundances cease to lie within the observed range after about 3 x 106 years and this indicates that there may be at least two efficient surface desorption mechanisms operating in dark clouds - one quasi-continous and the other operating more sporadically on this time-scale. We suggest that mantle removal on short time-scales is mediated by clump dynamics, and by the effects of star formation on longer time-scales. The applicability of this type of dynamical-chemical model for molecular cloud evolution is discussed and comparison is made with other models of dark cloud chemistry.

Observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

NASA Astrophysics Data System (ADS)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-01-01

Based on airborne spectral imaging observations three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and ice floes have been identified and quantified. A method is presented to discriminate sea ice and open water in case of clouds from imaging radiance measurements. This separation simultaneously reveals that in case of clouds the transition of radiance between open water and sea ice is not instantaneously but horizontally smoothed. In general, clouds reduce the nadir radiance above bright surfaces in the vicinity of sea ice - open water boundaries, while the nadir radiance above dark surfaces is enhanced compared to situations with clouds located above horizontal homogeneous surfaces. With help of the observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge. This affected distance Δ L was found to depend on both, cloud and sea ice properties. For a ground overlaying cloud in 0-200 m altitude, increasing the cloud optical thickness from τ = 1 to τ = 10 decreases Δ L from 600 to 250 m, while increasing cloud base altitude or cloud geometrical thickness can increase Δ L; Δ L(τ = 1/10) = 2200 m/1250 m for 500-1000 m cloud altitude. To quantify the effect for different shapes and sizes of the ice floes, various albedo fields (infinite straight ice edge, circles, squares, realistic ice floe field) were modelled. Simulations show that Δ L increases by the radius of the ice floe and for sizes larger than 6 km (500-1000 m cloud altitude) asymptotically reaches maximum values, which corresponds to an infinite straight ice edge. Furthermore, the impact of these 3-D-radiative effects on retrieval of cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30% in retrievals of cloud optical thickness and effective radius reff, respectively. With help of Δ L quantified here, an estimate of the distance to the ice edge for which the retrieval errors are negligible is given.

Cloudy Earth

NASA Image and Video Library

2015-05-08

Decades of satellite observations and astronaut photographs show that clouds dominate space-based views of Earth. One study based on nearly a decade of satellite data estimated that about 67 percent of Earth’s surface is typically covered by clouds. This is especially the case over the oceans, where other research shows less than 10 percent of the sky is completely clear of clouds at any one time. Over land, 30 percent of skies are completely cloud free. Earth’s cloudy nature is unmistakable in this global cloud fraction map, based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. While MODIS collects enough data to make a new global map of cloudiness every day, this version of the map shows an average of all of the satellite’s cloud observations between July 2002 and April 2015. Colors range from dark blue (no clouds) to light blue (some clouds) to white (frequent clouds).

The OGLE view of microlensing towards the Magellanic Clouds - II. OGLE-II Small Magellanic Cloud data

NASA Astrophysics Data System (ADS)

Wyrzykowski, Ł.; Kozłowski, S.; Skowron, J.; Belokurov, V.; Smith, M. C.; Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Szewczyk, O.

2010-09-01

The primary goal of this paper is to provide evidence that can prove true or false the hypothesis that dark matter in the Galactic halo can clump into stellar-mass compact objects. If such objects exist, they would act as lenses to external sources in the Magellanic Clouds, giving rise to an observable effect of microlensing. We present the results of our search for such events, based on data from the second phase of the OGLE survey (1996-2000) towards the Small Magellanic Cloud (SMC). The data set we used comprises 2.1 million monitored sources distributed over an area of 2.4deg2. We found only one microlensing event candidate, however its poor-quality light curve limited our discussion of the exact distance to the lensing object. Given a single event, taking blending (crowding of stars) into account for the detection-efficiency simulations and deriving the Hubble Space Telescope (HST)-corrected number of monitored stars, the microlensing optical depth is τ = (1.55 +/- 1.55) × 10-7. This result is consistent with the expected SMC self-lensing signal, with no need to introduce dark matter microlenses. Rejecting the unconvincing event leads to an upper limit on the fraction of dark matter in the form of massive compact halo objects (MACHOs) of f < 20 per cent for deflector masses around 0.4Msolar and f < 11 per cent for masses between 0.003 and 0.2Msolar (95 per cent confidence limit). Our result indicates that the Milky Way's dark matter is unlikely to be clumpy and to form compact objects in the subsolar-mass range. Based on observations obtained with the 1.3-m Warsaw Telescope at the Las Campanas Observatory of the Carnegie Institution of Washington. E-mail: wyrzykow@ast.cam.ac.uk ‡ Name pronunciation: Woocash Vizhikovsky

Neptune - Changes in Great Dark Spot

NASA Technical Reports Server (NTRS)

1989-01-01

These images show changes in the clouds around Neptune's Great Dark Spot (GDS) over a four and one-half-day period. From top to bottom the images show successive rotations of the planet an interval of about 18 hours. The GDS is at a mean latitude of 20 degrees south, and covers about 30 degrees of longitude. The violet filter of the Voyager narrow angle camera was used to produce these images at distances ranging from 17 million kilometers (10.5 million miles) at the top, to 10 million kilometers (6.2 million miles) at bottom. The images have been mapped on to a rectangular latitude longitude grid to remove the effects of changing viewing geometry and the changing distance to Neptune. The sequence shows a large change in the western end (left side) of the GDS, where a dark extension apparent in the earlier images converges into an extended string of small dark spots over the next five rotations. This 'string of beads' extends from the GDS at a surprisingly large angle relative to horizontal lines of constant latitude. The large bright cloud at the southern (bottom) border of the GDS is a more or less permanent companion of the GDS. The apparent motion of smaller clouds at the periphery of the GDS suggests a counterclockwise rotation of the GDS reminiscent of flow around the Great Red Spot in Jupiter's atmosphere. This activity of the GDS is surprising because the total energy flux from the sun and from Neptune's interior is only 5 percent as large as the total energy flux on Jupiter.

Lidar and radar measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study: observations of dark and bright band phenomena

NASA Astrophysics Data System (ADS)

di Girolamo, P.; Summa, D.; Bhawar, R.; di Iorio, T.; Norton, E. G.; Peters, G.; Dufournet, Y.

2011-11-01

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark and bright bands were observed by the University of BASILicata Raman lidar system (BASIL) during several intensive (IOPs) and special (SOPs) observation periods (among others, 23 July, 15 August, and 17 August 2007). Lidar data were supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Results from BASIL and the radars for 23 July 2007 are illustrated and discussed to support the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar and radar dark and bright bands. Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE.

Characterization of Cloud Water-Content Distribution

NASA Technical Reports Server (NTRS)

Lee, Seungwon

2010-01-01

The development of realistic cloud parameterizations for climate models requires accurate characterizations of subgrid distributions of thermodynamic variables. To this end, a software tool was developed to characterize cloud water-content distributions in climate-model sub-grid scales. This software characterizes distributions of cloud water content with respect to cloud phase, cloud type, precipitation occurrence, and geo-location using CloudSat radar measurements. It uses a statistical method called maximum likelihood estimation to estimate the probability density function of the cloud water content.

Search for the CO-dark Mass in the Central Molecular Zone by using the ASTE 10-m Telescope

NASA Astrophysics Data System (ADS)

Tanaka, Kunihiko

2017-01-01

Atomic carbon (C0) is one of the most abundant carbon-bearing species in the interstellar molecular gas, and its submillimeter lines are good tracers of low-density molecular clouds which are often dark in CO rotational lines. We present a new map of the central 150 pc region of the Milky Way in the 500 GHz [CI] line, which has been recently obtained with the ASTE 10-m telescope. The [CI] emission is brightest toward the central 5-pc region, where massive GMCs are absent. This [CI]-bright region is approximately centered toward Sgr A*, covering the entire circum-nuclear ring (CND) and the western part of the 50-km/s cloud. The C0/CO abundance ratio is 0.5-2 there, and the highest ratio is observed toward the CND but just outside of the 2-pc ring of dense gas. This discovery may suggest that the CO-dark component occupies a significant fraction of the molecular gas in the circumnuclear region.

Featured Image: A New Dark Vortex on Neptune

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2018-03-01

This remarkable series of images by the Hubble Space Telescope (click for the full view) track a dark vortex only the fifth ever observed on Neptune as it evolves in Neptunes atmosphere. These Hubble images, presented in a recent study led by Michael Wong (University of California, Berkeley), were taken in 2015 September, 2016 May, 2016 October, and 2017 October; the observations have monitored the evolution of the vortex as it has gradually weakened and drifted polewards. Confirmation of the vortex solved a puzzle that arose in 2015, when astronomers spotted an unexplained outburst of cloud activity on Neptune. This outburst was likely a group of bright companion clouds that form as air flows over high-pressure dark vortices, causing gases to freeze into methane ice crystals. To learn more about what the authors have since learned by studying this vortex, check out the paper below.CitationMichael H. Wong et al 2018 AJ 155 117. doi:10.3847/1538-3881/aaa6d6

Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)★

PubMed Central

Agúndez, M.; Cernicharo, J.; de Vicente, P.; Marcelino, N.; Roueff, E.; Fuente, A.; Gerin, M.; Guélin, M.; Albo, C.; Barcia, A.; Barbas, L.; Bolaño, R.; Colomer, F.; Diez, M. C.; Gallego, J. D.; Gómez-González, J.; López-Fernández, I.; López-Fernández, J. A.; López-Pérez, J. A.; Malo, I.; Serna, J. M.; Tercero, F.

2015-01-01

Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5 – 4 and J = 10 – 9 rotational transitions using the 40m radiotelescope of Yebes and the IRAM 30m telescope. We derive beam averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm−2 in TMC-1 and (3.9 ± 1.8) × 1010 cm−2 in L483, which translate to fairly low fractional abundances relative to H2, in the range (1-10) × 10−12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~ 10−4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10−8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N. PMID:26543239

Thermal infrared and optical photometry of Asteroidal Comet C/2002 CE10

NASA Astrophysics Data System (ADS)

Sekiguchi, Tomohiko; Miyasaka, Seidai; Dermawan, Budi; Mueller, Thomas; Takato, Naruhisa; Watanabe, Junichi; Boehnhardt, Hermann

2018-04-01

C/2002 CE10 is an object in a retrograde elliptical orbit with Tisserand parameter - 0.853 indicating a likely origin in the Oort Cloud. It appears to be a rather inactive comet since no coma and only a very weak tail was detected during the past perihelion passage. We present multi-color optical photometry, lightcurve and thermal mid-IR observations of the asteroidal comet. With the photometric analysis in BVRI, the surface color is found to be redder than asteroids, corresponding to cometary nuclei and TNOs/Centaurs. The time-resolved differential photometry supports a rotation period of 8.19 ± 0.05 h. The effective diameter and the geometric albedo are 17.9 ± 0.9 km and 0.03 ± 0.01, respectively, indicating a very dark reflectance of the surface. The dark and redder surface color of C/2002 CE10 may be attribute to devolatilized material by surface aging suffered from the irradiation by cosmic rays or from impact by dust particles in the Oort Cloud. Alternatively, C/2002 CE10 was formed of very dark refractory material originally like a rocky planetesimal. In both cases, this object lacks ices (on the surface at least). The dynamical and known physical characteristics of C/2002 CE10 are best compatible with those of the Damocloids population in the Solar System, that appear to be exhaust cometary nucleus in Halley-type orbits. The study of physical properties of rocky Oort cloud objects may give us a key for the formation of the Oort cloud and the solar system.

Far-infrared Extinction Mapping of Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Lim, Wanggi; Tan, Jonathan C.

2014-01-01

Progress in understanding star formation requires detailed observational constraints on the initial conditions, i.e., dense clumps and cores in giant molecular clouds that are on the verge of gravitational instability. Such structures have been studied by their extinction of near-infrared and, more recently, mid-infrared (MIR) background light. It has been somewhat more of a surprise to find that there are regions that appear as dark shadows at far-infrared (FIR) wavelengths as long as ~100 μm! Here we develop analysis methods of FIR images from Spitzer-MIPS and Herschel-PACS that allow quantitative measurements of cloud mass surface density, Σ. The method builds on that developed for MIR extinction mapping by Butler & Tan, in particular involving a search for independently saturated, i.e., very opaque, regions that allow measurement of the foreground intensity. We focus on three massive starless core/clumps in the Infrared Dark Cloud (IRDC) G028.37+00.07, deriving mass surface density maps from 3.5 to 70 μm. A by-product of this analysis is the measurement of the spectral energy distribution of the diffuse foreground emission. The lower opacity at 70 μm allows us to probe to higher Σ values, up to ~1 g cm-2 in the densest parts of the core/clumps. Comparison of the Σ maps at different wavelengths constrains the shape of the MIR-FIR dust opacity law in IRDCs. We find that it is most consistent with the thick ice mantle models of Ossenkopf & Henning. There is tentative evidence for grain ice mantle growth as one goes from lower to higher Σ regions.

Widespread SiO and CH3OH emission in filamentary infrared dark clouds

NASA Astrophysics Data System (ADS)

Cosentino, G.; Jiménez-Serra, I.; Henshaw, J. D.; Caselli, P.; Viti, S.; Barnes, A. T.; Fontani, F.; Tan, J. C.; Pon, A.

2018-03-01

Infrared dark clouds (IRDCs) are cold, dense regions of high (optical and infrared) extinction, believed to be the birthplace of high-mass stars and stellar clusters. The physical mechanisms leading to the formation of these IRDCs are not completely understood and it is thus important to study their molecular gas kinematics and chemical content to search for any signature of the IRDCs formation process. Using the 30-m-diameter antenna at the Instituto de Radioastronomía Milimétrica (IRAM), we have obtained emission maps of dense gas tracers (H13CO+ and HN13C) and typical shock tracers (SiO and CH3OH) towards three IRDCs, G028.37+00.07, G034.43+00.24, and G034.77-00.55 (clouds C, F, and G, respectively). We have studied the molecular gas kinematics in these clouds and, consistent with previous works towards other IRDCs, the clouds show complex gas kinematics with several velocity-coherent substructures separated in velocity space by a few km s-1. Correlated with these complex kinematic structures, widespread (parsec-scale) emission of SiO and CH3OH is present in all the three clouds. For clouds C and F, known to be actively forming stars, widespread SiO and CH3OH is likely associated with on-going star formation activity. However, for cloud G, which lacks either 8 or 24 μm sources and 4.5 μm H2 shock-excited emission, the detected widespread SiO and CH3OH emission may have originated in a large-scale shock interaction, although a scenario involving a population of low-mass stars driving molecular outflows cannot be fully ruled out.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Walmsley, C.M.; Churchwell, E.; Nash, A.

We report observations of the J = 1..-->..0 line of HCN measured toward six positions in nearby low-temperature dark clouds. The measured relative intensities of the hyperfine components of the J = 1..-->..0 line are anomalous in that the F = 0..-->..1 transition is stronger than would be expected if all three components (F = 2..-->..1, F = 1..-->..1, F = 0..-->..1) had equal excitation temperatures. Differences of approximately 20% in the populations per sublevel of J = 1 could account for the observations. The results are in contrast to the situation observed in warmer molecular clouds associated with Hmore » II regions where the F = 1..-->..1 line is anomalously weak. The apparent overpopulation of J = 1, F = 0 in dark clouds may be related to the phenomenon observed in the J = 1..-->..0 transitions of HCO/sup +/ and HNC in the same objects where /sup 13/C substituted version of these species is found to be stronger than the /sup 12/C species.« less

The stellar population of the Lupus clouds

NASA Technical Reports Server (NTRS)

Hughes, Joanne; Hartigan, Patrick; Krautter, Joachim; Kelemen, Janos

1994-01-01

We present photometric and spectroscopic observations of the H alpha emission stars in the Lupus dark cloud complex. We estimate the effective temperatures of the stars from their spectral types and calculate the reddening towards each object from the (R-I) colors. From these data, we derive mass and age distributions for the Lupus stars using a new set of pre-main sequence evolutionar tracks. We compare the results for the Lupus stars with those for a similar population of young stellar objects in Taurus-Auriga and Chamaeleon and with the initial mass function for field stars in the solar neighborhood. From the H-R diagrams, Lupus appears to contain older stars than Taurus. The Lupus dark clouds form a greater proportion of low mass stars than the Taurus complex. Also, the proportion of low mass stars in Lupus is higher than that predicted by the Miller-Scalo initial mass function, and the lowest mass stars in Lupus are less active than similar T Tauri stars in other regions.

Star formation in Bok globules.

NASA Astrophysics Data System (ADS)

Reipurth, B.

1981-12-01

Among the many dark clouds seen projected against the luminous band of the Milky Way are a number of small, isolated compact clouds, which often exhibit a large degree of regularity. These objects are today known as Bok globules, after the Dutch-American astronomer Bart Bok, who more than 30 years aga singled out the globules as a group of special interest among the dark clouds. Bok globules usually have angular sizes of from a few arcminutes to about 20 arcminutes, with real sizes of typically 0.15 to 0.8 parsecs. It is generally not so easy to estimate the distance, and thus the dimensions, of a given globule. Most known globules are closer than 500 pc, since they normally are found by their obscuring effects, and more distant globules become less conspicuous because of foreground stars. A nearby, compact Bok globule is indeed a spectacular sight; when William Herschel for the first time saw a globule in his telescape, he exclaimed: ' Mein Gott, da ist ein Loch im Himmel.'

Measurements of the H2(13)CO ortho/para ratio in cold dark molecular clouds

NASA Technical Reports Server (NTRS)

Minh, Y. C.; Dickens, J. E.; Irvine, W. M.; McGonagle, D.

1995-01-01

H2(13)CO has been detected for the first time toward cold dark molecular clouds using the NRAO 12 m telescope. The H2(13)CO ortho/para abundance ratio R for B335, which we report as R approximately 1.7, suggests equilibrium at the local kinetic temperature and appears to be distinctly different from that for both TMC-1 and L134N, where R is close to or higher than the statistical value 3. Since only B335 among the observed positions includes an imbedded IR source, this difference may result from heating of the grain surfaces, providing the energy necessary for desorption of formaldehyde formed on the grains.

VizieR Online Data Catalog: Mass Distribution of Infrared Dark Clouds (Gomez+, 2014)

NASA Astrophysics Data System (ADS)

Gomez, L.; Wyrowski, F.; Shculler, F.; Menten, K. M.; Ballesteros-Paredes, J.

2014-01-01

Six southern hemisphere clouds with high extinction were observed on 2007-08-25/28 with the LABOCA (Large APEX BOlometer CAmera) instrument on the APEX 12m telescope, at a frequency of 345GHz and a bandwidth of 610GHz (for the instrument, see Siringo et al. 2009A&A...497..945S). (2 data files).

Refrigeration of the 18.3 GHz C_3H_2 Transition in Dark Clouds G1.6-0.25

NASA Technical Reports Server (NTRS)

Kuiper, T. B. H.; Whiteoak, J. B.; Peng, R. -S.; Peters, W. L., III; Reynolds, J. E.

1993-01-01

We have observed the 1_(10)-1_(01) (18.3 GHz) transition of orthocyclopropenylidene, C_(-3)H_(-2), at 24 positions in the unusual dense cloud G1.6- 0.025. Except for one position, the transition is refrigerated, a phenomenon which has not been seen in this transition before.

La Freccia Rossa: an IR-dark cloud hosting the Milky Way intermediate-mass black hole candidate

NASA Astrophysics Data System (ADS)

Ravi, Vikram; Vedantham, Harish; Phinney, E. Sterl

2018-07-01

The dynamics of the high-velocity compact molecular cloud CO-0.40-0.22 have been interpreted as evidence for a ˜105 M⊙ black hole within 60 pc of Sgr A*. Recently, Oka et al. have identified a compact millimetre-continuum source, CO-0.40-0.22*, with this candidate black hole. Here we present a collation of radio and infrared data at this location. Australia Telescope Compact Array constraints on the radio spectrum, and the detection of a mid-infrared counterpart, are in tension with an Sgr A*-like model for CO-0.40-0.22* despite the comparable bolometric to the Eddington luminosity ratios under the intermediate-mass black hole interpretation. A protostellar-disc scenario is, however, tenable. CO-0.40-0.22(*) is positionally coincident with an arrowhead-shaped infrared-dark cloud (which we call the Freccia Rossa). If the VLSR ≈ 70 km s-1 systemic velocity of CO-0.40-0.22 is common to the entire Freccia Rossa system, we hypothesize that it is the remnant of a high-velocity cloud that has plunged into the Milky Way from the Galactic halo.

Update on the NASA Glenn PSL Ice Crystal Cloud Characterization (2016)

NASA Technical Reports Server (NTRS)

Van Zante, J.; Bencic, T.; Ratvasky, Thomas P.; Struk, Peter M.

2016-01-01

NASA Glenn's Propulsion Systems Laboratory (PSL) is an altitude engine research test facility capable of producing ice-crystal and supercooled liquid clouds. The cloud characterization parameter space is fairly large and complex, but the phase of the cloud seems primarily governed by wet bulb temperature. The presentation will discuss some of the issues uncovered through four cloud characterization efforts to date, as well as some of instrumentation that has been used to characterize cloud parameters including cloud uniformity, bulk total water content, median volumetric diameter and max-diameter, percent freeze-out, relative humidity, and an update on the NASA Glenn PSL Ice Crystal Cloud Characterization (2016).

iss031e116058

NASA Image and Video Library

2012-06-13

ISS031-E-116058 (13 June 2012) --- Polar mesospheric clouds in the Northern Hemisphere are featured in this image photographed by an Expedition 31 crew member on the International Space Station. In both the Northern and Southern Hemisphere, during their respective late spring and early summer seasons, polar mesospheric clouds are at the peak of their visibility. Visible from the ground during twilight, aircraft in flight, and the International Space Station, they typically appear as delicate shining threads against the darkness of space?hence their other name of noctilucent or ?night-shining? clouds. On the same day this image was taken from the space station while it was passing over the night-darkened Tibetan Plateau, polar mesospheric clouds were also visible to aircraft flying above Canada. In addition to this still image, the space station crew took a time-lapse image sequence of polar mesospheric clouds several days earlier (June 5, 2012) while passing over western Asia; this is first such sequence of images of the phenomena taken from orbit. Polar mesospheric clouds form between 76-85 kilometers above the Earth?s surface, when there is sufficient water vapor at these high altitudes to freeze into ice crystals. The clouds are illuminated by the setting sun while the ground surface below is in darkness, lending them their night-shining properties. In addition to the illuminated tracery of polar mesospheric clouds trending across the center of the image, lower layers of the atmosphere are also illuminated; the lowest layer of the atmosphere, the stratosphere, is indicated by dim orange and red tones. While the exact cause of formation of polar mesospheric clouds is still debated?dust from meteors, global warming, and rocket exhaust have all been suggested as contributing factors?recent research suggests that changes in atmospheric gas composition or temperature has caused the clouds to become brighter over time.

Primordial Black Holes as Generators of Cosmic Structures

NASA Astrophysics Data System (ADS)

Carr, Bernard; Silk, Joseph

2018-05-01

Primordial black holes (PBHs) could provide the dark matter in various mass windows below 102M⊙ and those of 30M⊙ might explain the LIGO events. PBHs much larger than this might have important consequences even if they provide only a small fraction of the dark matter. In particular, they could generate cosmological structure either individually through the `seed' effect or collectively through the `Poisson' effect, thereby alleviating some problems associated with the standard CDM scenario. If the PBHs all have a similar mass and make a small contribution to the dark matter, then the seed effect dominates on small scales, in which case PBHs could generate the supermassive black holes in galactic nuclei or even galaxies themselves. If they have a similar mass and provide the dark matter, the Poisson effect dominates on all scales and the first bound clouds would form earlier than in the usual scenario, with interesting observational consequences. If the PBHs have an extended mass spectrum, which is more likely, they could fulfill all three roles - providing the dark matter, binding the first bound clouds and generating galaxies. In this case, the galactic mass function naturally has the observed form, with the galaxy mass being simply related to the black hole mass. The stochastic gravitational wave background from the PBHs in this scenario would extend continuously from the LIGO frequency to the LISA frequency, offering a potential goal for future surveys.

Integrated approach using multi-platform sensors for enhanced high-resolution daily ice cover product

NASA Astrophysics Data System (ADS)

Bonev, George; Gladkova, Irina; Grossberg, Michael; Romanov, Peter; Helfrich, Sean

2016-09-01

The ultimate objective of this work is to improve characterization of the ice cover distribution in the polar areas, to improve sea ice mapping and to develop a new automated real-time high spatial resolution multi-sensor ice extent and ice edge product for use in operational applications. Despite a large number of currently available automated satellite-based sea ice extent datasets, analysts at the National Ice Center tend to rely on original satellite imagery (provided by satellite optical, passive microwave and active microwave sensors) mainly because the automated products derived from satellite optical data have gaps in the area coverage due to clouds and darkness, passive microwave products have poor spatial resolution, automated ice identifications based on radar data are not quite reliable due to a considerable difficulty in discriminating between the ice cover and rough ice-free ocean surface due to winds. We have developed a multisensor algorithm that first extracts maximum information on the sea ice cover from imaging instruments VIIRS and MODIS, including regions covered by thin, semitransparent clouds, then supplements the output by the microwave measurements and finally aggregates the results into a cloud gap free daily product. This ability to identify ice cover underneath thin clouds, which is usually masked out by traditional cloud detection algorithms, allows for expansion of the effective coverage of the sea ice maps and thus more accurate and detailed delineation of the ice edge. We have also developed a web-based monitoring system that allows comparison of our daily ice extent product with the several other independent operational daily products.

Searching for dark clouds in the outer galactic plane. I. A statistical approach for identifying extended red(dened) regions in 2MASS

NASA Astrophysics Data System (ADS)

Frieswijk, W. W. F.; Shipman, R. F.

2010-06-01

Context. Most of what is known about clustered star formation to date comes from well studied star forming regions located relatively nearby, such as Rho-Ophiuchus, Serpens and Perseus. However, the recent discovery of infrared dark clouds may give new insights in our understanding of this dominant mode of star formation in the Galaxy. Though the exact role of infrared dark clouds in the formation process is still somewhat unclear, they seem to provide useful laboratories to study the very early stages of clustered star formation. Infrared dark clouds have been identified predominantly toward the bright inner parts of the galactic plane. The low background emission makes it more difficult to identify similar objects in mid-infrared absorption in the outer parts. This is unfortunate, because the outer Galaxy represents the only nearby region where we can study effects of different (external) conditions on the star formation process. Aims: The aim of this paper is to identify extended red regions in the outer galactic plane based on reddening of stars in the near-infrared. We argue that these regions appear reddened mainly due to extinction caused by molecular clouds and young stellar objects. The work presented here is used as a basis for identifying star forming regions and in particular the very early stages. An accompanying paper describes the cross-identification of the identified regions with existing data, uncovering more on the nature of the reddening. Methods: We use the Mann-Whitney U-test, in combination with a friends-of-friends algorithm, to identify extended reddened regions in the 2MASS all-sky JHK survey. We process the data on a regular grid using two different resolutions, 60´´ and 90´´. The two resolutions have been chosen because the stellar surface density varies between the crowded spiral arm regions and the sparsely populated galactic anti-center region. Results: We identify 1320 extended red regions at the higher resolution and 1589 in the lower resolution run. The linear extent of the identified regions ranges from a few arc-minutes to about a degree. Conclusions: The majority of extended red regions are associated with major molecular cloud complexes, supporting our hypothesis that the reddening is mostly due to foreground clouds and embedded objects. The reliability of the identified regions is >99.9%. Because we choose to identify object with a high reliability we can not quantify the completeness of the list of regions. Full Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/515/A51

Jupiter in blue, ultraviolet and near infrared

NASA Technical Reports Server (NTRS)

2000-01-01

These three images of Jupiter, taken through the narrow angle camera of NASA's Cassini spacecraft from a distance of 77.6 million kilometers (48.2 million miles) on October 8, reveal more than is apparent to the naked eye through a telescope.

The image on the left was taken through the blue filter. The one in the middle was taken in the ultraviolet. The one on the right was taken in the near infrared.

The blue-light filter is within the part of the electromagnetic spectrum detectable by the human eye. The appearance of Jupiter in this image is, consequently, very familiar. The Great Red Spot (below and to the right of center) and the planet's well-known banded cloud lanes are obvious. The brighter bands of clouds are called zones and are probably composed of ammonia ice particles. The darker bands are called belts and are made dark by particles of unknown composition intermixed with the ammonia ice.

Jupiter's appearance changes dramatically in the ultraviolet and near infrared images. These images are near negatives of each other and illustrate the way in which observations in different wavelength regions can reveal different physical regimes on the planet.

All gases scatter sunlight efficiently at short wavelengths; this is why the sky appears blue on Earth. The effect is even more pronounced in the ultraviolet. The gases in Jupiter's atmosphere, above the clouds, are no different. They scatter strongly in the ultraviolet, making the deep banded cloud layers invisible in the middle image. Only the very high altitude haze appears dark against the bright background. The contrast is reversed in the near infrared, where methane gas, abundant on Jupiter but not on Earth, is strongly absorbing and therefore appears dark. Again the deep clouds are invisible, but now the high altitude haze appears relatively bright against the dark background. High altitude haze is seen over the poles and the equator.

The Great Red Spot, prominent in all images, is obviously a feature whose influence extends high in the atmosphere. As the Cassini cameras continue to return images of Jupiter, it will be possible to construct a three-dimensional picture of how clouds form and evolve by watching the changing appearance of Jupiter in different spectral regions.

JPL manages the Cassini mission for NASA's Office of Space Science, Washington, D.C. JPl is a division of the California Institute of Technology in Pasadena.

Earth Observations taken by the Expedition 16 Crew

NASA Image and Video Library

2008-02-05

ISS016-E-027426 (5 Feb. 2008) --- Cumulonimbus Cloud over Africa is featured in this image photographed by an Expedition 16 crewmember on the International Space Station. Deemed by many meteorologists as one of the most impressive of cloud formations, cumulonimbus (from the Latin for "puffy" and "dark") clouds form due to vigorous convection of warm and moist unstable air. Surface air warmed by the Sun-heated ground surface rises, and if sufficient atmospheric moisture is present, water droplets will condense as the air mass encounters cooler air at higher altitudes. The air mass itself also expands and cools as it rises due to decreasing atmospheric pressure, a process known as adiabatic cooling. This type of convection is common in tropical latitudes year-round and during the summer season at higher latitudes. As water in the rising air mass condenses and changes from a gaseous to a liquid state, it releases energy to its surroundings, further heating the surrounding air and leading to more convection and rising of the cloud mass to higher altitudes. This leads to the characteristic vertical "towers" associated with cumulonimbus clouds, an excellent example of which is visible in this image (right). If enough moisture is present to condense and continue heating the cloud mass through several convective cycles, a tower can rise to altitudes of approximately 10 kilometers at high latitudes to 20 kilometers in the tropics -- before encountering a region of the atmosphere known as the tropopause. The tropopause is characterized by a strong temperature inversion where the atmosphere is dryer and no longer cools with altitude. This halts further vertical motion of the cloud mass, and causes flattening and spreading of the cloud tops into an anvil-shaped cloud as illustrated by this oblique photograph. The view direction is at an angle from the vertical, rather than straight "down" towards the Earth's surface. The image, photographed while the International Space Station was passing over western Africa near the Senegal-Mali border, shows a fully-formed anvil cloud with numerous smaller cumulonimbus towers rising near it. The high energetics of these storm systems typically make them hazardous due to associated heavy precipitation, lightning, high wind speeds and possible tornadoes.

Instability analysis of cosmic viscoelastic gyro-gravitating clouds in the presence of dark matter

NASA Astrophysics Data System (ADS)

Karmakar, Pralay Kumar; Das, Papari

2017-08-01

A classical formalism for the weakly nonlinear instability analysis of a gravitating rotating viscoelastic gaseous cloud in the presence of gyratory dark matter is presented on the cosmic Jeans flat scales of space and time. The constituent neutral gaseous fluid (NGF) and dark matter fluid (DMF) are inter-coupled frictionally via mutual gravity alone. Application of standard nonlinear perturbation techniques over the complex gyro-gravitating clouds results in a unique conjugated pair of viscoelastic forced Burgers (VFB) equations. The VFB pair is conjointly twinned by correlational viscoelastic effects. There is no regular damping term here, unlike, in the conventional Burgers equation for the luminous (bright) matter solely. Instead, an interesting linear self-consistent derivative force-term naturalistically appears. A numerical illustrative platform is provided to reveal the micro-physical insights behind the weakly non-linear natural diffusive eigen-modes. It is fantastically seen that the perturbed NGF evolves as extended compressive solitons and compressive shock-like structures. In contrast, the perturbed DMF grows as rarefactive extended solitons and hybrid shocks. The latter is micro-physically composed of rarefactive solitons and compressive shocks. The consistency and reliability of the results are validated in the panoptic light of the existing reports based on the preeminent nonlinear advection-diffusion-based Burgers fabric. At the last, we highlight the main implications and non-trivial futuristic applications of the explored findings.

Dark Matter and Extragalactic Gas Clouds in the NGC 4532/DDO 137 System

NASA Technical Reports Server (NTRS)

Hoffman, G. L.; Lu, N. Y.; Salpeter, E. E.; Connell, B. M.

1998-01-01

H I synthesis mapping of NGC 4532 and DDO 137, a pair of Sm galaxies on the edge of the Virgo cluster, is used to determine rotation curves for each of the galaxies and to resolve the structure and kinematics of three extragalactic H I clouds embedded in an extended envelope of diffuse HI discovered in earlier Arecibo studies of the system.

Shedding light on baryonic dark matter.

PubMed

Silk, J

1991-02-01

Halo dark matter, if it is baryonic, may plausibly consist of compact stellar remnants. Jeans mass clouds containing 10(6) to 10(8) solar masses could have efficiently formed stars in the early universe and could plausibly have generated, for a suitably top-heavy stellar initial mass function, a high abundance of neutron stars as well as a small admixture of long-lived low mass stars. Within the resulting clusters of dark remnants, which eventually are tidally disrupted when halos eventually form, captures of neutron stars by non-degenerate stars resulted in formation of close binaries. These evolve to produce, by the present epoch, an observable x-ray signal associated with dark matter aggregations in galaxy halos and galaxy cluster cores.

APEX/SABOCA observations of small-scale structure of infrared-dark clouds . I. Early evolutionary stages of star-forming cores

NASA Astrophysics Data System (ADS)

Ragan, Sarah E.; Henning, Thomas; Beuther, Henrik

2013-11-01

Infrared-dark clouds (IRDCs) harbor the early phases of cluster and high-mass star formation and are comprised of cold (~20 K), dense (n > 104 cm-3) gas. The spectral energy distribution (SED) of IRDCs is dominated by the far-infrared and millimeter wavelength regime, and our initial Herschel study examined IRDCs at the peak of the SED with high angular resolution. Here we present a follow-up study using the SABOCA instrument on APEX which delivers 7.8″ angular resolution at 350 μm, matching the resolution we achieved with Herschel/PACS, and allowing us to characterize substructure on ~0.1 pc scales. Our sample of 11 nearby IRDCs are a mix of filamentary and clumpy morphologies, and the filamentary clouds show significant hierarchical structure, while the clumpy IRDCs exhibit little hierarchical structure. All IRDCs, regardless of morphology, have about 14% of their total mass in small scale core-like structures which roughly follow a trend of constant volume density over all size scales. Out of the 89 protostellar cores we identified in this sample with Herschel, we recover 40 of the brightest and re-fit their SEDs and find their properties agree fairly well with our previous estimates (⟨ T ⟩ ~ 19 K). We detect a new population of "cold cores" which have no 70 μm counterpart, but are 100 and 160 μm-bright, with colder temperatures (⟨ T ⟩ ~ 16 K). This latter population, along with SABOCA-only detections, are predominantly low-mass objects, but their evolutionary diagnostics are consistent with the earliest starless or prestellar phase of cores in IRDCs. Based on observations carried out with the Atacama Pathfinder Experiment (APEX). APEX is a collaboration between Max Planck Institut für Radioastronomie (MPIfR), Onsala Space Observatory (OSO), and the European Southern Observatory (ESO).Appendices are available in electronic form at http://www.aanda.org

Jupiter's Northern Hemisphere in False Color (Time Set 3)

NASA Technical Reports Server (NTRS)

1997-01-01

Mosaic of Jupiter's northern hemisphere between 10 and 50 degrees latitude. Jupiter's atmospheric circulation is dominated by alternating eastward and westward jets from equatorial to polar latitudes. The direction and speed of these jets in part determine the color and texture of the clouds seen in this mosaic. Also visible are several other common Jovian cloud features, including large white ovals, bright spots, dark spots, interacting vortices, and turbulent chaotic systems. The north-south dimension of each of the two interacting vortices in the upper half of the mosaic is about 3500 kilometers.

This mosaic uses the Galileo imaging camera's three near-infrared wavelengths (756 nanometers, 727 nanometers, and 889 nanometers displayed in red, green, and blue) to show variations in cloud height and thickness. Light blue clouds are high and thin, reddish clouds are deep, and white clouds are high and thick. The clouds and haze over the ovals are high, extending into Jupiter's stratosphere. Dark purple most likely represents a high haze overlying a clear deep atmosphere. Galileo is the first spacecraft to distinguish cloud layers on Jupiter.

North is at the top. The images are projected on a sphere, with features being foreshortened towards the north. The planetary limb runs along the right edge of the mosaic. Cloud patterns appear foreshortened as they approach the limb. The smallest resolved features are tens of kilometers in size. These images were taken on April 3, 1997, at a range of 1.4 million kilometers by the Solid State Imaging system (CCD) on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

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FAR-INFRARED EXTINCTION MAPPING OF INFRARED DARK CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Wanggi; Tan, Jonathan C.

Progress in understanding star formation requires detailed observational constraints on the initial conditions, i.e., dense clumps and cores in giant molecular clouds that are on the verge of gravitational instability. Such structures have been studied by their extinction of near-infrared and, more recently, mid-infrared (MIR) background light. It has been somewhat more of a surprise to find that there are regions that appear as dark shadows at far-infrared (FIR) wavelengths as long as ∼100 μm! Here we develop analysis methods of FIR images from Spitzer-MIPS and Herschel-PACS that allow quantitative measurements of cloud mass surface density, Σ. The method buildsmore » on that developed for MIR extinction mapping by Butler and Tan, in particular involving a search for independently saturated, i.e., very opaque, regions that allow measurement of the foreground intensity. We focus on three massive starless core/clumps in the Infrared Dark Cloud (IRDC) G028.37+00.07, deriving mass surface density maps from 3.5 to 70 μm. A by-product of this analysis is the measurement of the spectral energy distribution of the diffuse foreground emission. The lower opacity at 70 μm allows us to probe to higher Σ values, up to ∼1 g cm{sup –2} in the densest parts of the core/clumps. Comparison of the Σ maps at different wavelengths constrains the shape of the MIR-FIR dust opacity law in IRDCs. We find that it is most consistent with the thick ice mantle models of Ossenkopf and Henning. There is tentative evidence for grain ice mantle growth as one goes from lower to higher Σ regions.« less

Investigation of Jupiter's Equatorial Hotspots and Plumes Using Cassini ISS Observations

NASA Technical Reports Server (NTRS)

Choi, David S.; Showman, A. P.; Vasavada, A. R.; Simon-Miller, A. A.

2012-01-01

We present updated analysis of Jupiter's equatorial meteorology from Cassini observations. For two months preceding the spacecraft's closest approach, the ISS onboard regularly imaged the atmosphere. We created time-lapse movies from this period in order to analyze the dynamics of equatorial 5-micron hot spots and their interactions with adjacent latitudes. Hot spots are quasi-stable, rectangular dark areas on visible-wavelength images, with defined eastern edges that sharply contrast with surrounding clouds, but a diffuse western edge serving as a nebulous boundary with adjacent equatorial plumes. Hot spots exhibit significant variations in size and shape over timescales of days and weeks. Some of these changes correspond with passing vortex systems from adjacent latitudes interacting with hot spots. Strong anticyclonic gyres present to the south and southeast of the dark areas appear to circulate into hot spots. Impressive, bright white plumes occupy spaces in between hot spots. Compact cirrus-iike 'scooter' clouds flow rapidly through the plumes before disappearing within the dark areas. This raises the possibility that the plumes and fast-moving clouds are at higher altitudes, because their speed does not match previously published zonal wind profiles. Most profiles represent the drift speed of the hot spots at their latitude from pattern matching of the entire longitudinal image strip. If a downward branch of an equatorially-trapped Rossby waves controls the overall appearance of hot spots, however, the westward phase velocity of the wave leads to underestimates of the true jet stream speed. Instead, our expanded data set demonstrating the rapid flow of these scooter clouds may be more illustrative of the actual jet stream speed at these latitudes. This research was supported by a NASA JDAP grant and the NASA Postdoctoral Program.

The nature of the embedded population in the Rho Ophiuchi dark cloud - Mid-infrared observations

NASA Technical Reports Server (NTRS)

Lada, C. J.; Wilking, B. A.

1984-01-01

In combination with previous IR and optical data, the present 10-20 micron observations of previously identified members of the embedded population of the Rho Ophiuchi dark cloud allow determinations to be made of the broadband energy distributions for 32 of the 44 sources. The majority of the sources are found to emit the bulk of their luminosity in the 1-20 micron range, and to be surrounded by dust shells. Because they are, in light of these characteristics, probably premain-sequence in nature, relatively accurate bolometric luminosities for these objects can be obtained through integration of their energy distributions. It is found that 44 percent of the sources are less luminous than the sun, and are among the lowest luminosity premain-sequence/protostellar objects observed to date.

Eight new Milky Way companions discovered in first-year Dark Energy Survey data

DOE PAGES

Bechtol, K.

2015-06-30

We report the discovery of eight new Milky Way companions inmore » $$\\sim 1800\\;{\\mathrm{deg}}^{2}$$ of optical imaging data collected during the first year of the Dark Energy Survey (DES). Each system is identified as a statistically significant over-density of individual stars consistent with the expected isochrone and luminosity function of an old and metal-poor stellar population. The objects span a wide range of absolute magnitudes (MV from $-2.2$ to $$-7.4\\;\\mathrm{mag}$$), physical sizes ($$10-170\\;\\mathrm{pc}$$), and heliocentric distances ($$30-330\\;\\mathrm{kpc}$$). Based on the low surface brightnesses, large physical sizes, and/or large Galactocentric distances of these objects, several are likely to be new ultra-faint satellite galaxies of the Milky Way and/or Magellanic Clouds. We introduce a likelihood-based algorithm to search for and characterize stellar over-densities, as well as identify stars with high satellite membership probabilities. As a result, we also present completeness estimates for detecting ultra-faint galaxies of varying luminosities, sizes, and heliocentric distances in the first-year DES data.« less

Cores in Dwarf Galaxies from Fermi Repulsion

NASA Astrophysics Data System (ADS)

Randall, Lisa; Scholtz, Jakub; Unwin, James

2017-05-01

We show that Fermi repulsion can lead to cored density profiles in dwarf galaxies for sub-keV fermionic dark matter. We treat the dark matter as a quasi-degenerate self-gravitating Fermi gas and calculate its density profile assuming hydrostatic equilibrium. We find that suitable dwarf galaxy cores of size ≳130 pc can be achieved for fermion dark matter with mass in the range of 70-400 eV. While in conventional dark matter scenarios such sub-keV thermal dark matter would be excluded by free streaming bounds, the constraints are ameliorated in models with dark matter at a lower temperature than conventional thermal scenarios, such as the Flooded Dark Matter model that we have previously considered. Modifying the arguments of Tremaine and Gunn, we derive a conservative lower bound on the mass of fermionic dark matter of 70 eV and a stronger lower bound from Lymanα clouds of about 470 eV, leading to slightly smaller cores than have been observed. We comment on this result and how the tension is relaxed in dark matter scenarios with non-thermal momentum distributions.

Atmospheric Motion in Jupiter Northern Hemisphere

NASA Image and Video Library

2000-09-25

True-color (left) and false-color (right) mosaics of Jupiter's northern hemisphere between 10 and 50 degrees latitude. Jupiter's atmospheric motions are controlled by alternating eastward and westward bands of air between Jupiter's equator and polar regions. The direction and speed of these bands influences the color and texture of the clouds seen in this mosaic. The high and thin clouds are represented by light blue, deep clouds are reddish, and high and thick clouds are white. A high haze overlying a clear, deep atmosphere is represented by dark purple. This image was taken by NASA's Galileo spacecraft on April 3, 1997 at a distance of 1.4 million kilometers (.86 million miles). http://photojournal.jpl.nasa.gov/catalog/PIA03000

Reduction of tropical cloudiness by soot

PubMed

Ackerman; Toon; Stevens; Heymsfield; Ramanathan; Welton

2000-05-12

Measurements and models show that enhanced aerosol concentrations can augment cloud albedo not only by increasing total droplet cross-sectional area, but also by reducing precipitation and thereby increasing cloud water content and cloud coverage. Aerosol pollution is expected to exert a net cooling influence on the global climate through these conventional mechanisms. Here, we demonstrate an opposite mechanism through which aerosols can reduce cloud cover and thus significantly offset aerosol-induced radiative cooling at the top of the atmosphere on a regional scale. In model simulations, the daytime clearing of trade cumulus is hastened and intensified by solar heating in dark haze (as found over much of the northern Indian Ocean during the northeast monsoon).

ClipCard: Sharable, Searchable Visual Metadata Summaries on the Cloud to Render Big Data Actionable

NASA Astrophysics Data System (ADS)

Saripalli, P.; Davis, D.; Cunningham, R.

2013-12-01

Research firm IDC estimates that approximately 90 percent of the Enterprise Big Data go un-analyzed, as 'dark data' - an enormous corpus of undiscovered, untagged information residing on data warehouses, servers and Storage Area Networks (SAN). In the geosciences, these data range from unpublished model runs to vast survey data assets to raw sensor data. Many of these are now being collected instantaneously, at a greater volume and in new data formats. Not all of these data can be analyzed, nor processed in real time, and their features may not be well described at the time of collection. These dark data are a serious data management problem for science organizations of all types, especially ones with mandated or required data reporting and compliance requirements. Additionally, data curators and scientists are encouraged to quantify the impact of their data holdings as a way to measure research success. Deriving actionable insights is the foremost goal of Big Data Analytics (BDA), which is especially true with geoscience, given its direct impact on most of the pressing global issues. Clearly, there is a pressing need for innovative approaches to making dark data discoverable, measurable, and actionable. We report on ClipCard, a Cloud-based SaaS analytic platform for instant summarization, quick search, visualization and easy sharing of metadata summaries form the Dark Data at hierarchical levels of detail, thus rendering it 'white', i.e., actionable. We present a use case of the ClipCard platform, a cloud-based application which helps generate (abstracted) visual metadata summaries and meta-analytics for environmental data at hierarchical scales within and across big data containers. These summaries and analyses provide important new tools for managing big data and simplifying collaboration through easy to deploy sharing APIs. The ClipCard application solves a growing data management bottleneck by helping enterprises and large organizations to summarize, search, discover, and share the potential in their unused data and information assets. Using Cloud as the base platform enables wider reach, quick dissemination and easy sharing of the metadata summaries, without actually storing or sharing the original data assets per se.

What Goes Up Must Come Down: The Lifecycle of Convective Clouds (492nd Brookhaven Lecture)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jensen, Michael

Some clouds look like cotton balls and others like anvils. Some bring rain, some snow and sleet, and others, just shade. But, whether big and billowy or dark and stormy, clouds affect far more than the weather each day. Armed with measurements of clouds’ updrafts and downdrafts—which resemble airflow in a convection oven—and many other atmospheric interactions, scientists from Brookhaven Lab and other institutions around the world are developing models that are crucial for understanding Earth’s climate and forecasting future climate change. During his lecture, Dr. Jensen provides an overview of the importance of clouds in the Earth’s climate systemmore » before explaining how convective clouds form, grow, and dissipate. His discussion includes findings from the Midlatitude Continental Convective Clouds Experiment (MC3E), a major collaborative experiment between U.S. Department of Energy (DOE) and NASA scientists to document precipitation, clouds, winds, and moisture in 3-D for a holistic view of convective clouds and their environment.« less

Voyager 1 imaging and IRIS observations of Jovian methane absorption and thermal emission: Implications for cloud structure

NASA Technical Reports Server (NTRS)

West, R. A.; Kupferman, P. N.; Hart, H.

1984-01-01

Images from three filters of the Voyager 1 wide angle camera are used to measure the continuum reflectivity and spectral gradient near 6000 A and the 6190 A band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark barge features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition. Methane absorption is shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Methane absorption and five micrometer emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneous maps of five micrometer brightness temperature is quantitatively compared to realistic cloud structure models which include multiple scattering at five micrometer as well as in the visible. Variability in H2 quadrupole lines are also investigated.

Voyager 1 imaging and IRIS observations of Jovian methane absorption and thermal emission - Implications for cloud structure

NASA Technical Reports Server (NTRS)

West, R. A.; Kupferman, P. N.; Hart, H.

1985-01-01

Images from three filters of the Voyager 1 wide angle camera are used to measure the continuum reflectivity and spectral gradient near 6000 A and the 6190 A band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark barge features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition. Methane absorption is shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Methane absorption and five micrometer emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneous maps of five micrometer brightness temperature are quantitatively compared to realistic cloud structure models which include multiple scattering at five micrometer as well as in the visible. Variability in H2 quadrupole lines are also investigated.

Neptune

NASA Image and Video Library

1999-10-14

This photograph of Neptune shows three of the features that NASA Voyager 2 has been photographing during recent weeks. At the north is the Great Dark Spot, accompanied by bright, white clouds that undergo rapid changes in appearance.

Analysis of Individual Carbonaceous Particles Emitted from the Las Conchas Wildfire, Los Alamos, NM, in June-July 2011

NASA Astrophysics Data System (ADS)

Mazzoleni, C.; China, S.; Gorkowski, K.; Flowers, B. A.; Aiken, A. C.; Dubey, M. K.

2012-12-01

Carbonaceous aerosol emitted from biomass burning contributes significantly to atmospheric aerosol loadings regionally and globally. The net direct radiative forcing of biomass burning aerosol can be positive and/or negative and this depends on its composition, morphology and mixing state. Biomass burning aerosols can also change the cloud properties as they can act as cloud condensation nuclei. In this study we investigated biomass burning particles emitted from the Las Conchas wildfire in northern New Mexico that started on June 26, 2011 and burned an area of 245 square miles. Aerosol samples were collected on nucleopore filters at the Los Alamos National Laboratory during the third week of the wildfire event. Individual particles (~4000) were investigated using field-emission scanning electron microscopy and energy dispersive X-ray spectroscopy (EDS) to distinguish different carbonaceous particles and their shape, size, elemental composition and mixing state. A thermo-denuder was used to remove compounds that are volatile at temperatures up to 200 C, leaving behind the black carbon and any compounds that did not volatize completely. Smoke particles consisted of a) tar balls, which are amorphous spherical carbonaceous organic aerosols; b) organic particles with inorganic inclusions, c) soot particles and (d) soot with various inclusions. Two distinct kinds of tar balls, "electronically" dark and bright, were found using the field-emission scanning electron microscopy and were characterized for ambient and denuded conditions to understand coating effects and aging. It was found that dark tar balls are generally larger in size than the bright ones. Additionally, the difference between the size of ambient-bright and the size of denuded-bright tar balls was larger than the difference between the size of ambient-dark and the size of denuded-dark tar balls. EDS analysis showed that 70% of the dark tar balls had higher (~60%) relative oxygen content than in the bright tar balls. We conclude that there are two distinct kinds of biomass burning tar balls and that dark tar balls are less volatile than bright tar balls. The morphology of soot particles was also investigated by evaluating their fractal dimension for both ambient (coated with organic and inorganic material) and denuded samples at two different times of the day. The fractal dimension for ambient soot was found to be higher than for denuded soot due to the coating on the ambient soot particles. Finally, the monomer diameter decreased by up to 25% after denuding the particles. This study provides insights on the link between electron microscopy images of single particles and the mixing state, morphology, and evolution of different biomass burning aerosol at the beginning of their lifecycle.

Shedding light on baryonic dark matter

NASA Technical Reports Server (NTRS)

Silk, Joseph

1991-01-01

Halo dark matter, if it is baryonic, may plausibly consist of compact stellar remnants. Jeans mass clouds containing 10 to the 6th to 10 to the 8th solar masses could have efficiently formed stars in the early universe and could plausibly have generated, for a suitably top-heavy stellar initial mass function, a high abundance of neutron stars as well as a small admixture of long-lived low mass stars. Within the resulting clusters of dark remnants, which eventually are tidally disrupted when halos eventually form, captures of neutron stars by nondegenerate stars resulted in formation of close binaries. These evolve to produce, by the present epoch, an observable X-ray signal associated with dark matter aggregations in galaxy cluster cores.

Jupiter's Northern Hemisphere in False Color (Time Set 2)

NASA Technical Reports Server (NTRS)

1997-01-01

Mosaic of Jupiter's northern hemisphere between 10 and 50 degrees latitude. Jupiter's atmospheric circulation is dominated by alternating eastward and westward jets from equatorial to polar latitudes. The direction and speed of these jets in part determine the color and texture of the clouds seen in this mosaic. Also visible are several other common Jovian cloud features, including large white ovals, bright spots, dark spots, interacting vortices, and turbulent chaotic systems. The north-south dimension of each of the two interacting vortices in the upper half of the mosaic is about 3500 kilometers.

This mosaic uses the Galileo imaging camera's three near-infrared wavelengths (756 nanometers, 727 nanometers, and 889 nanometers displayed in red, green, and blue) to show variations in cloud height and thickness. Light blue clouds are high and thin, reddish clouds are deep, and white clouds are high and thick. The clouds and haze over the ovals are high, extending into Jupiter's stratosphere. Dark purple most likely represents a high haze overlying a clear deep atmosphere. Galileo is the first spacecraft to distinguish cloud layers on Jupiter.

North is at the top. The images are projected on a sphere, with features being foreshortened towards the north. The smallest resolved features are tens of kilometers in size. These images were taken on April 3, 1997, at a range of 1.4 million kilometers by the Solid State Imaging system (CCD) on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

Lambert-Amery

Atmospheric Science Data Center

2013-04-16

... exhibiting insufficient spatial contrast for stereoscopic retrieval are shown in dark gray. Clouds are apparent as a result of their ... their distributions, and retrieval of their heights provide information that will help to reduce this uncertainty. The Multi-angle ...

Shadow Strands

NASA Image and Video Library

2006-06-02

The soft, sweeping shadows of Saturn C ring cover bright patches of clouds in the planet atmosphere. The shadow-throwing rings stretch across the view at bottom. The dark inner edge of the B ring is visible at top

Dark Star-Making Factory

NASA Image and Video Library

2009-10-02

In this infrared view from the Herschel Observatory, a European Space Agency mission, blue shows the warmest dust, and red, the coolest. The choppy clouds of gas and dust are just starting to condense into new stars.

It Twins! Spitzer Finds Hidden Jet

NASA Image and Video Library

2011-04-04

NASA Spitzer Space Telescope took this image of a baby star sprouting two identical jets green lines emanating from fuzzy star. The left jet was hidden behind a dark cloud, which Spitzer can see through.

Absolute extinction and the influence of environment - Dark cloud sight lines toward VCT 10, 30, and Walker 67

NASA Technical Reports Server (NTRS)

Cardelli, Jason A.; Clayton, Geoffrey C.

1991-01-01

The range of validity of the average absolute extinction law (AAEL) proposed by Cardelli et al. (1988 and 1989) is investigated, combining published visible and NIR data with IUE UV observations for three lines of sight through dense dark cloud environments with high values of total-to-selective extinction. The characteristics of the data sets and the reduction and parameterization methods applied are described in detail, and the results are presented in extensive tables and graphs. Good agreement with the AAEL is demonstrated for wavelengths from 3.4 microns to 250 nm, but significant deviations are found at shorter wavelengths (where previous studies of lines of sight through bright nebulosity found good agreement with the AAEL). These differences are attributed to the effects of coatings on small-bump and FUV grains.

A new interstellar molecule - Tricarbon monoxide

NASA Technical Reports Server (NTRS)

Matthews, H. E.; Irvine, W. M.; Friberg, P.; Brown, R. D.; Godfrey, P. D.

1984-01-01

The C3O molecule, whose pure rotational spectrum has only recently been studied in the laboratory, has been detected in the cold, dark interstellar Taurus Molecular Cloud 1. Since C3O is the first interstelar carbon chain molecule to contain oxygen, its existence places an important new constraint on chemical schemes for cold interstellar clouds. The abundance of C3O can be understood in terms of purely gas-phase ion-molecule chemistry.

Sunrise, Earth Limb

NASA Technical Reports Server (NTRS)

1992-01-01

This sunrise scene (5.5S, 29.5E) was taken early in the morning, when the sun was still below the horizon and not yet illuminating the dark band of low level clouds on the Earth limb. Ranging from 13 to 18 km. above these low level clouds is a brown layer at the tropopause, an atmospheric temperature inversion which isolates the troposphere from the stratosphere and effectively concentrates particulates from both above and below this level.

Homogenizing Surface and Satellite Observations of Cloud. Aspects of Bias in Surface Data.

DTIC Science & Technology

1987-11-10

both ( pannus ), usually below fractus of bad weather, or both ( pannus ), usu- Altostratus or Nimbostratus ally below Altostratus or Nimbostratus 8 Cumulus...Stratocumulus, Stratus of an anvil; either accompanied or not by Cu- or pannus mulonimbus without anvil or fibrous upper part, by Cumulus, Stratocumulus...Stratus or pannus CL clouds invisible owing to darkness, fog, / Stratocumulus, Stratus, Cumulus and Cu- blowing dust or sand, or other similar mulonimbus

Proper motions of young stars in Chamaeleon. II. New kinematical candidate members of Chamaeleon I and II

NASA Astrophysics Data System (ADS)

López Martí, Belén; Jiménez-Esteban, Francisco; Bayo, Amelia; Barrado, David; Solano, Enrique; Bouy, Hervé; Rodrigo, Carlos

2013-08-01

Context. The Chamaeleon star-forming region has been extensively studied in the last decades. However, most studies have been confined to the densest parts of the clouds. In a previous paper, we analysed the kinematical properties of the spectroscopically confirmed population of the Chamaeleon I and II clouds. Aims: We want to search for new kinematical candidate members to the Chamaeleon I and II moving groups, extending the studied area beyond the clouds, and to characterize these new populations using available information from public databases and catalogues. We also want to check if the populations of the moving groups are confined to the present dark clouds. Methods: Kinematic candidate members were initially selected on the basis of proper motions and colours using the Fourth US Naval Observatory CCD Astrograph Catalog (UCAC4). The SEDs of the objects were constructed using photometry retrieved from the Virtual Observatory and other resources, and fitted to models of stellar photospheres to derive effective temperatures, gravity values, and luminosities. Masses and ages were estimated by comparison with theoretical evolutionary tracks in a Hertzprung-Russell diagram. Objects with ages ≲20 Myr were selected as probable members of the moving groups. Results: We have identified 51 and 14 candidate members to the Chamaeleon I and II moving groups, respectively, of which 17 and 1, respectively, are classified as probable young stars according to the SED analysis. Another object in Chamaeleon I located slightly above the 1 Myr isochrone is classified as a possible young star. All these objects are diskless stars with masses in the range 0.3 ≲ M/M⊙ ≲ 1.4 and ages consistent with those reported for the corresponding confirmed members. They tend to be located at the boundaries of or outside the dark clouds, preferably to the north-east and south-east in the case of Chamaeleon I, and to the north-east in the case of Chamaeleon II. Conclusions: The kinematical population of Chamaeleon I and II could be larger and spread over a larger area of the sky than suggested by previous studies. However, the results of this study should be confirmed with spectroscopic data and more precise kinematic information. Tables 2, 3, 4, 6 and 8 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/556/A144

Hubble Looks at Light and Dark in the Universe

NASA Image and Video Library

2014-08-29

This new NASA/ESA Hubble Space Telescope image shows a variety of intriguing cosmic phenomena. Surrounded by bright stars, towards the upper middle of the frame we see a small young stellar object (YSO) known as SSTC2D J033038.2+303212. Located in the constellation of Perseus, this star is in the early stages of its life and is still forming into a fully-grown star. In this view from Hubble’s Advanced Camera for Surveys(ACS) it appears to have a murky chimney of material emanating outwards and downwards, framed by bright bursts of gas flowing from the star itself. This fledgling star is actually surrounded by a bright disk of material swirling around it as it forms — a disc that we see edge-on from our perspective. However, this small bright speck is dwarfed by its cosmic neighbor towards the bottom of the frame, a clump of bright, wispy gas swirling around as it appears to spew dark material out into space. The bright cloud is a reflection nebula known as [B77] 63, a cloud of interstellar gas that is reflecting light from the stars embedded within it. There are actually a number of bright stars within [B77] 63, most notably the emission-line star LkHA 326, and it nearby neighbor LZK 18. These stars are lighting up the surrounding gas and sculpting it into the wispy shape seen in this image. However, the most dramatic part of the image seems to be a dark stream of smoke piling outwards from [B77] 63 and its stars — a dark nebula called Dobashi 4173. Dark nebulae are incredibly dense clouds of pitch-dark material that obscure the patches of sky behind them, seemingly creating great rips and eerily empty chunks of sky. The stars speckled on top of this extreme blackness actually lie between us and Dobashi 4173. Credit: ESA/NASA NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Aerosol-Forming Reactions of Glyoxal, Methylglyoxal and Amino Acids in Clouds

NASA Astrophysics Data System (ADS)

de Haan, D. O.; Smith, K. W.; Stroik, D. R.; Corrigan, A. L.; Lee, F. E.; Phan, J. T.; Conley, A. C.

2008-12-01

Glyoxal and methylglyoxal are two common aldehydes present in fog and cloud water. Amino acids are present in clouds at similar concentrations. Here we present bulk and aerosol mass spectroscopic data demonstrating that irreversible reactions between glyoxal and amino acids, triggered by droplet evaporation, produce N-derivatized imidazole compounds along with deeply colored Maillard reaction products. These reactions can occur in the dark and in the absence of oxidants. Reactions between methylglyoxal and amino acids produce analogous methylated products plus oligomers with masses up to m/z = 1000. These reactions, which go to completion on the 10-min-timescale of cloud processing, could be significant sources of secondary organic aerosol and humic-like substances (HULIS or brown carbon).

The abundance of CO in diffuse interstellar clouds - An ultraviolet survey

NASA Technical Reports Server (NTRS)

Federman, S. R.; Glassgold, A. E.; Jenkins, E. B.; Shaya, E. J.

1980-01-01

CO was detected in 17 directions and its upper limits were estimated in 21 directions by a UV survey carried out with the Copernicus satellite in the C-X 1088 A and E-X 1076 A lines toward 48 bright stars. The CO column densities range from 10 to the 12th to 10 to the 17th/sq cm and correlate with C I and H2. The tendency of the C I/CO ratio to be about 10 follows the ratio of particular atomic and molecular cross-sections and the physical parameters of interstellar clouds. Finally, the connection between UV observations in diffuse clouds and radio observations of (C-13)O in dark clouds is discussed.

Dark clouds in the vicinity of the emission nebula Sh2-205: interstellar extinction and distances

NASA Astrophysics Data System (ADS)

Straižys, V.; Čepas, V.; Boyle, R. P.; Zdanavičius, J.; Maskoliūnas, M.; Kazlauskas, A.; Zdanavičius, K.; Černis, K.

2016-05-01

Results of CCD photometry in the seven-colour Vilnius system for 922 stars down to V = 16-17 mag and for 302 stars down to 19.5 mag are used to investigate the interstellar extinction in an area of 1.5 square degrees in the direction of the P7 and P8 clumps of the dark cloud TGU H942, which lies in the vicinity of the emission nebula Sh2-205. In addition, we used 662 red clump giants that were identified by combining the 2MASS and WISE infrared surveys. The resulting plots of extinction versus distance were compared with previous results of the distribution and radial velocities of CO clouds and with dust maps in different passbands of the IRAS and WISE orbiting observatories. A possible distance of the front edge of the nearest cloud layer at 130 ± 10 pc was found. This dust layer probably covers all the investigated area, which results in extinction of up to 1.8 mag in some directions. A second rise of the extinction seems to be present at 500-600 pc. Within this layer, the clumps P7 and P8 of the dust cloud TGU H942, the Sh2-205 emission nebula, and the infrared cluster FSR 655 are probably located. In the direction of these clouds, we identified 88 young stellar objects and a new infrared cluster. Full Tables 1 and 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/590/A21

The chemistry of dense interstellar clouds

NASA Technical Reports Server (NTRS)

Irvine, W. M.

1991-01-01

The basic theme of this program is the study of molecular complexity and evolution in interstellar and circumstellar clouds incorporating the biogenic elements. Recent results include the identification of a new astronomical carbon-chain molecule, C4Si. This species was detected in the envelope expelled from the evolved star IRC+10216 in observations at the Nobeyama Radio Observatory in Japan. C4Si is the carrier of six unidentified lines which had previously been observed. This detection reveals the existence of a new series of carbon-chain molecules, C sub n Si (n equals 1, 2, 4). Such molecules may well be formed from the reaction of Si(+) with acetylene and acetylene derivatives. Other recent research has concentrated on the chemical composition of the cold, dark interstellar clouds, the nearest dense molecular clouds to the solar system. Such regions have very low kinetic temperatures, on the order of 10 K, and are known to be formation sites for solar-type stars. We have recently identified for the first time in such regions the species of H2S, NO, HCOOH (formic acid). The H2S abundance appears to exceed that predicted by gas-phase models of ion-molecule chemistry, perhaps suggesting the importance of synthesis on grain surfaces. Additional observations in dark clouds have studied the ratio of ortho- to para-thioformaldehyde. Since this ratio is expected to be unaffected by both radiative and ordinary collisional processes in the cloud, it may well reflect the formation conditions for this molecule. The ratio is observed to depart from that expected under conditions of chemical equilibrium at formation, perhaps reflecting efficient interchange between cold dust grains in the gas phase.

A search for pre-main-sequence stars in high-latitude molecular clouds. 3: A survey of the Einstein database

NASA Technical Reports Server (NTRS)

Caillault, Jean-Pierre; Magnani, Loris; Fryer, Chris

1995-01-01

In order to discern whether the high-latitude molecular clouds are regions of ongoing star formation, we have used X-ray emission as a tracer of youthful stars. The entire Einstein database yields 18 images which overlap 10 of the clouds mapped partially or completely in the CO (1-0) transition, providing a total of approximately 6 deg squared of overlap. Five previously unidentified X-ray sources were detected: one has an optical counterpart which is a pre-main-sequence (PMS) star, and two have normal main-sequence stellar counterparts, while the other two are probably extragalactic sources. The PMS star is located in a high Galactic latitude Lynds dark cloud, so this result is not too suprising. The translucent clouds, though, have yet to reveal any evidence of star formation.

Senkyo and Vortex

NASA Image and Video Library

2013-01-28

NASA Cassini spacecraft simultaneously peers through the haze in Titan equatorial region down to its surface and captures the vortex of clouds hovering over its south pole just to the right of the terminator on the moon dark side.

Serenity Above, Tempests Below

NASA Image and Video Library

2006-01-10

Whiffs of cloud dance in Saturn atmosphere, while the dim crescent of Rhea 1,528 kilometers, or 949 miles across hangs in the distance. The dark ringplane cuts a diagonal across the top left corner of this view

The Polar Winds of Saturn as Determined by Cassini/VIMS: Seasonally Variable or Not?

NASA Astrophysics Data System (ADS)

Momary, Thomas W.; Baines, K. H.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Nicholson, P. D.; Sotin, C.; Cassini/VIMS Science Team

2013-10-01

The high inclination of Cassini's current orbit allows VIMS to once again obtain spectacular views of Saturn’s poles, not seen since 2008. We present new imagery and investigate the effect of seasonal variability on Saturn’s polar winds. The north pole now basks in spring daylight and we again observe the long-enduring northern Polar Hexagon, discovered in Voyager imagery by Godfrey (Icarus 76, 335-356, 1988). This feature seemed to stay fixed in a rotational system defined by the Voyager-era radio rotation rate (Desch & Kaiser, Geophys. Res. Lett, 8, 253-256, 1981) in both original Voyager and 2008 VIMS observations. Yet new images indicate a shift, with the hexagon rotating ~10° of longitude from Nov. 2012 to May 2013. Discrete clouds still race around the edges of the 5-μm-bright hexagon at speeds of ~100 m/s, as we observed in 2008 (Baines, Momary, et al., Plan. Space. Sci 57, 1671-1681, 2009). We also recover a massive storm system residing just inside the hexagon edge at ~80° N. lat. Since 2008, this storm has shifted poleward by 1.5° and turned 5 μm dark (cloudy), where it was 5 μm bright when last observed (i.e. cloud free). It now moves zonally faster at ~25 m/s vs. ~14 m/s in 2008. This enduring "shepherd" storm may force and maintain the hexagon shape. We also recover twin 5-μm-dark storms (Snake Eyes) moving slowly at ~15 m/s near 67° N lat. However, while the two features appear to maintain a relatively constant zonal separation on average (14° ), with the trailing feature remaining near 67° N lat., the leading storm appears to oscillate ~1° in latitude and drift in longitude. At the south pole, discrete clouds whirl, now in darkness, around a hurricane-like vortex consisting of a cloudless "eye" extending at least 1 bar deeper than surrounding rings of clouds. These clouds still appear to be moving as a classical vortex with winds reaching a maximum of ~200 m/s near 87° S lat. and then falling off to zero at the pole. In contrast, clouds near 75° S. lat. are nearly stationary, consistent with 2008 observations. Our preliminary results suggest limited seasonal variability of Saturn’s polar winds.

Higher dimensional strange quark matter solutions in self creation cosmology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Şen, R., E-mail: ramazansen-1991@hotmail.com; Aygün, S., E-mail: saygun@comu.edu.tr

In this study, we have generalized the higher dimensional flat Friedmann-Robertson-Walker (FRW) universe solutions for a cloud of string with perfect fluid attached strange quark matter (SQM) in Self Creation Cosmology (SCC). We have obtained that the cloud of string with perfect fluid does not survive and the string tension density vanishes for this model. However, we get dark energy model for strange quark matter with positive density and negative pressure in self creation cosmology.

Alone on a wide wide sea. The origin of SECCO 1, an isolated star-forming gas cloud in the Virgo cluster*†‡

NASA Astrophysics Data System (ADS)

Bellazzini, M.; Armillotta, L.; Perina, S.; Magrini, L.; Cresci, G.; Beccari, G.; Battaglia, G.; Fraternali, F.; de Zeeuw, P. T.; Martin, N. F.; Calura, F.; Ibata, R.; Coccato, L.; Testa, V.; Correnti, M.

2018-06-01

SECCO 1 is an extremely dark, low-mass (M⋆ ≃ 105 M⊙), star-forming stellar system lying in the low-velocity cloud (LVC) substructure of the Virgo cluster of galaxies, and hosting several H II regions. Here, we review our knowledge of this remarkable system, and present the results of (a) additional analysis of our panoramic spectroscopic observations with MUSE, (b) the combined analysis of Hubble Space Telescope and MUSE data, and (c) new narrow-band observations obtained with OSIRIS@GTC to search for additional H II regions in the surroundings of the system. We provide new evidence supporting an age as young as ≲ 4 Myr for the stars that are currently ionizing the gas in SECCO 1. We identify only one new promising candidate H II region possibly associated with SECCO 1, thus confirming the extreme isolation of the system. We also identify three additional candidate pressure-supported dark clouds in Virgo among the targets of the SECCO survey. Various possible hypotheses for the nature and origin of SECCO 1 are considered and discussed, also with the help of dedicated hydrodynamical simulations showing that a hydrogen cloud with the characteristics of SECCO 1 can likely survive for ≳ 1 Gyr while travelling within the LVC Intra Cluster Medium.

The inception of star cluster formation revealed by [C II] emission around an Infrared Dark Cloud

NASA Astrophysics Data System (ADS)

Bisbas, Thomas G.; Tan, Jonathan C.; Csengeri, Timea; Wu, Benjamin; Lim, Wanggi; Caselli, Paola; Güsten, Rolf; Ricken, Oliver; Riquelme, Denise

2018-07-01

We present SOFIA-upGREAT observations of [C II] emission of Infrared Dark Cloud (IRDC) G035.39-00.33, designed to trace its atomic gas envelope and thus test models of the origins of such clouds. Several velocity components of [C II] emission are detected, tracing structures that are at a wide range of distances in the Galactic plane. We find a main component that is likely associated with the IRDC and its immediate surroundings. This strongest emission component has a velocity similar to that of the 13CO(2-1) emission of the IRDC, but offset by ˜3 km s-1 and with a larger velocity width of ˜9 km s-1. The spatial distribution of the [C II] emission of this component is also offset predominantly to one side of the dense filamentary structure of the IRDC. The C II column density is estimated to be of the order of ˜1017-1018 cm-2. We compare these results to the [C II] emission from numerical simulations of magnetized, dense gas filaments formed from giant molecular cloud (GMC) collisions, finding similar spatial and kinematic offsets. These observations and modellingof [C II] add further to the evidence that IRDC G035.39-00.33 has been formed by a process of GMC-GMC collision, which may thus be an important mechanism for initiating star cluster formation.

Brazil: Rondonia

Atmospheric Science Data Center

2016-12-30

... Places where clouds or other factors precluded an aerosol retrieval are shown in dark grey.   The main measurement site for the ... within World Reference System-2 path 231.   Further information about the CLAIRE campaign, and the Large-scale-Biosphere-Atmosphere ...

ASTER Images Merapi Continuing Eruption

NASA Image and Video Library

2010-11-18

This thermal infrared image from NASA Terra spacecraft of Merapi continuing eruption has been processed to reveal the dominant presence of volcanic ash in the eruption plume and clouds, displayed in dark red. The warm volcanic flow appears bright.

An Audience Favorite Nebula

NASA Image and Video Library

2012-03-08

This nebula, which is in the constellation of Scutum, has no common name since it is hidden behind dust clouds. It takes an infrared telescope like NASA Spitzer to see through this dark veil and reveal this spectacular hidden nebula.

Dark Reflections in the Southern Cross

NASA Image and Video Library

2010-10-27

NASA Wide-field Infrared Survey Explorer captured this colorful image of the reflection nebula IRAS 12116-6001. This cloud of interstellar dust cannot be seen directly in visible light, but WISE detectors observed the nebula at infrared wavelengths.

Microlensing towards the Magellanic Clouds and M31: is the quest for MACHOs still open?

NASA Astrophysics Data System (ADS)

Calchi Novati, Sebastiano

2012-03-01

Microlensing is the tool of choice for the search and the analysis of compact halo objects ("MACHOs"), a still viable class of dark matter candidates at the galactic scale. Different analyses point towards an agreement in excluding dark matter MACHOs of less than about 10-1 Modot; it remains however an ongoing debate for values in the mass range (0.1 - 1) Modot. The more robust constraints, though not all in agreement, come from the observational campaigns towards the Magellanic Clouds (the LMC and the SMC). The analyses towards the nearby galaxy of M31, in the so called "pixel lensing" regime, have expanded the perspectives in this field of research. In this contribution first we draw a critical view on recent results and then we focus on the pixel lensing analysis towards M31 of the PLAN collaboration.

IOCCG Report Number 16, 2015 Ocean Colour Remote Sensing in Polar Seas . Chapter 2; The Polar Environment: Sun, Clouds, and Ice

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Perovich, Don; Stamnes, Knut; Stuart, Venetia (Editor)

2015-01-01

The polar regions are places of extremes. There are months when the regions are enveloped in unending darkness, and months when they are in continuous daylight. During the daylight months the sun is low on the horizon and often obscured by clouds. In the dark winter months temperatures are brutally cold, and high winds and blowing snow are common. Even in summer, temperatures seldom rise above 0degC. The cold winter temperatures cause the ocean to freeze, forming sea ice. This sea ice cover acts as a barrier limiting the transfer of heat, moisture, and momentum between the atmosphere and the ocean. It also greatly complicates the optical signature of the surface. Taken together, these factors make the polar regions a highly challenging environment for optical remote sensing of the ocean.

Lidar and radar measurements of the melting layer: observations of dark and bright band phenomena

NASA Astrophysics Data System (ADS)

Di Girolamo, P.; Summa, D.; Cacciani, M.; Norton, E. G.; Peters, G.; Dufournet, Y.

2012-05-01

Multi-wavelength lidar measurements in the melting layer revealing the presence of dark and bright bands have been performed by the University of BASILicata Raman lidar system (BASIL) during a stratiform rain event. Simultaneously radar measurements have been also performed from the same site by the University of Hamburg cloud radar MIRA 36 (35.5 GHz), the University of Hamburg dual-polarization micro rain radar (24.15 GHz) and the University of Manchester UHF wind profiler (1.29 GHz). Measurements from BASIL and the radars are illustrated and discussed in this paper for a specific case study on 23 July 2007 during the Convective and Orographically-induced Precipitation Study (COPS). Simulations of the lidar dark and bright band based on the application of concentric/eccentric sphere Lorentz-Mie codes and a melting layer model are also provided. Lidar and radar measurements and model results are also compared with measurements from a disdrometer on ground and a two-dimensional cloud (2DC) probe on-board the ATR42 SAFIRE. Measurements and model results are found to confirm and support the conceptual microphysical/scattering model elaborated by Sassen et al. (2005).

The Nature of Carbon Dioxide Bearing Ices in Quiescent Molecular Clouds

NASA Astrophysics Data System (ADS)

Whittet, D. C. B.; Cook, A. M.; Chiar, J. E.; Pendleton, Y. J.; Shenoy, S. S.; Gerakines, P. A.

2009-04-01

The properties of the ices that form in dense molecular clouds represent an important set of initial conditions in the evolution of interstellar and preplanetary matter in regions of active star formation. Of the various spectral features available for study, the bending mode of solid CO2 near 15 μm has proven to be a particularly sensitive probe of physical conditions, especially temperature. We present new observations of this absorption feature in the spectrum of Q21-1, a background field star located behind a dark filament in the Cocoon Nebula (IC 5146). We show the profile of the feature to be consistent with a two-component (polar + nonpolar) model for the ices, based on spectra of laboratory analogs with temperatures in the range 10-20 K. The polar component accounts for ~85% of the CO2 in the line of sight. We compare for the first time 15 μm profiles in three widely separated dark clouds (Taurus, Serpens, and IC 5146), and show that they are indistinguishable to within observational scatter. Systematic differences in the observed CO2/H2O ratio in the three clouds have little or no effect on the 15 μm profile. The abundance of elemental oxygen in the ices appears to be a unifying factor, displaying consistent behavior in the three clouds. We conclude that the ice formation process is robust and uniformly efficient, notwithstanding compositional variations arising from differences in how the O is distributed between the primary species (H2O, CO2, and CO) in the ices.

A balloon-borne 102-cm telescope for far-infrared astronomy

NASA Technical Reports Server (NTRS)

Fazio, Giovanni G.

1990-01-01

In the early 1970's, the Smithsonian Astrophysical Observatory and the University of Arizona engaged in a cooperative program to develop a balloon-borne 102-cm telescope capable of carrying out far infrared (40 to 250 micron) observations of astronomical interest above the earth's atmosphere. Since 1972, the telescope has flown and successfully recovered a total of nineteen times. Thirteen of the flights produced high-quality astronomical data, resulting in more than 92.5 hours of photometric and spectroscopic observations of numerous objects, such as H 2 regions, dark clouds, molecular clouds, a planetary nebula, a galaxy, the galactic center, the planets, and an asteroid. From the launch site in Palestine, Texas, sources as far south as -50 degrees declination were observed. The balloon-borne telescope was one of the most sensitive instruments ever used for observation in the far infrared region of the spectrum. It was most productive in producing high resolution maps of large areas (typically square degrees) centered on known H 2 regions, molecular clouds, and dark cloud complexes. In many cases, these scans produced the first far infrared maps of these regions, and many new sources were discovered. The results have led to a better understanding of the distribution of gas and dust in these regions, the evolution of H 2 regions, and the processes of star formation in giant molecular clouds. The following topics are presented: (1) the focal plane instrumentation; (2) the history and flight record; (3) scientific results and publications; (4) eduational aspects; and (5) future planes.

Snow in Southwest United States

NASA Technical Reports Server (NTRS)

2002-01-01

In late December, the Southwest was blanketed with snow, and this scence was captured by MODIS on December 27, 2001. The white drape contrasts sharply with the red rock of the Colorado Plateau, a geologic region made up of a succession of plateaus and mesas composed mostly of sedimentary rock, whose reddish hues indicate the presence of oxidized iron. The Plateau covers the Four Corners area of the Southwest, including (clockwise from upper left) southern Utah, Colorado, New Mexico, and Arizona. The region gets its name from the Colorado River, seen most prominently as a dark ribbon running southwest through southern Utah. At the upper left of the image, a bank of low clouds partially obscures Utah's Great Salt Lake, but its faint outline is still visible. To the east and southeast of the lake, some high peaks of the Wasatch Mountain range break free of the clouds. The Park City area, one of the 2002 Winter Olympic venues, can be seen poking through the cloud deck about 75km southeast of the lake. Farther east, the dark Uinta Mountains follow the border between Colorado and Wyoming. The Uinta are one of the rare east-west running ranges of the Rocky Mountains.

Flight directions of passerine migrants in daylight and darkness: A radar and direct visual study

NASA Technical Reports Server (NTRS)

Gauthreaux, S. A., Jr.

1972-01-01

The application of radar and visual techniques to determine the migratory habits of passerine birds during daylight and darkness is discussed. The effects of wind on the direction of migration are examined. Scatter diagrams of daytime and nocturnal migration track directions correlated with wind direction are presented. It is concluded that migratory birds will fly at altitudes where wind direction and migratory direction are nearly the same. The effects of cloud cover and solar obscuration are considered negligible.

Venus Cloud Patterns (colorized and filtered)

NASA Technical Reports Server (NTRS)

1990-01-01

This picture of Venus was taken by the Galileo spacecrafts Solid State Imaging System on February 14, 1990, at a range of almost 1.7 million miles from the planet. A highpass spatial filter has been applied in order to emphasize the smaller scale cloud features, and the rendition has been colorized to a bluish hue in order to emphasize the subtle contrasts in the cloud markings and to indicate that it was taken through a violet filter. The sulfuric acid clouds indicate considerable convective activity, in the equatorial regions of the planet to the left and downwind of the subsolar point (afternoon on Venus). They are analogous to 'fair weather clouds' on Earth. The filamentary dark features visible in the colorized image are here revealed to be composed of several dark nodules, like beads on a string, each about 60 miles across. The Galileo Project is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory; its mission is to study Jupiter and its satellites and magnetosphere after multiple gravity assist flybys at Venus and Earth. These images of the Venus clouds were taken by Galileo's Solid State Imaging System February 13, 1990, at a range of about 1 million miles. The smallest detail visible is about 20 miles. The two right images show Venus in violet light, the top one at a time six hours later than the bottom one. They show the state of the clouds near the top of Venus's cloud deck. A right to left motion of the cloud features is evident and is consistent with westward winds of about 230 mph. The two left images show Venus in near infrared light, at the same times as the two right images. Sunlight penetrates through the clouds more deeply at the near infrared wavelengths, allowing a view near the bottom of the cloud deck. The westward motion of the clouds is slower (about 150 mph) at the lower altitude. The clouds are composed of sulfuric acid droplets and occupy a range of altitudes from 30 to 45 miles. The images have been spatially filtered to bring out small scale details and de-emphasize global shading. The filtering has introduced artifacts (wiggly lines running north/south) that are faintly visible in the infrared image. The Galileo Project is managed for NASA's Office of Space Science and Applications by the Jet Propulsion Laboratory; its mission is to study Jupiter and its satellites and magnetosphere after multiple gravity assist flybys at Venus and Earth.

Still from High-Clouds Jupiter Movie

NASA Technical Reports Server (NTRS)

2000-01-01

This image is one of seven from the narrow-angle camera on NASA's Cassini spacecraft assembled as a brief movie of high-altitude cloud movements on Jupiter. It was taken in early October 2000.

The images were taken at a wavelength that is absorbed by methane, one chemical in Jupiter's lower clouds. So, dark areas are relatively free of high clouds, and the camera sees through to the methane in a lower level. Bright areas are places with high, thick clouds that shield the methane below.

The area shown covers latitudes from 50 degrees north to 50 degrees south and a 100-degree sweep of longitude.

Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.

Extinction map of Chamaeleon I molecular cloud with DENIS star counts.

NASA Astrophysics Data System (ADS)

Cambresy, L.; Epchtein, N.; Copet, E.; de Batz, B.; Kimeswenger, S.; Le Bertre, T.; Rouan, D.; Tiphene, D.

1997-08-01

Massive, large scale star counts in the J (1.25μm) band provided by the Deep Near Infrared Survey of the Southern Sky (DENIS) are used for the first time to draw out an extinction map of the Chamaeleon I dark cloud. We derived a 2' resolution map of the cloud from J star counts within an area of 1.5°x3° around the centre of the cloud using an adaptive grid method and applying a wavelet decomposition. Possible contaminating young stellar objects within the cloud are removed, although they are shown to have a negligible effect on the counts. A comparison of our extinction map with the cold contribution of the IRAS 100μm emission shows an almost perfect matching. It is shown that J star counts supersede optical counts on Schmidt plate where A_V_>4.

Boundary Conditions for the Paleoenvironment: Chemical and Physical Processes in the Pre-Solar Nebula

NASA Technical Reports Server (NTRS)

Irvine, William M.; Schloerb, F. Peter

1997-01-01

The basic theme of this program is the study of molecular complexity and evolution in interstellar clouds and in primitive solar system objects. Research has included the detection and study of a number of new interstellar molecules and investigation of reaction pathways for astrochemistry from a comparison of theory and observed molecular abundances. The latter includes studies of cold, dark clouds in which ion-molecule chemistry should predominate, searches for the effects of interchange of material between the gas and solid phases in interstellar clouds, unbiased spectral surveys of particular sources, and systematic investigation of the interlinked chemistry and physics of dense interstellar clouds. In addition, the study of comets has allowed a comparison between the chemistry of such minimally thermally processed objects and that of interstellar clouds, shedding light on the evolution of the biogenic elements during the process of solar system formation.

NIMS Views of a Jovian 'Hot Spot'

NASA Technical Reports Server (NTRS)

1997-01-01

These four Galileo/NIMS near-infrared images of a small portion of the equatorial region of Jupiter show a dark clearing of clouds in the meteorologically-active troposphere of Jupiter. This region constitutes a 'hot spot', a nearly-clear area devoid of thick ammonia clouds which allows Jupiter's indigenous heat radiation to shine through at 5 microns (not shown). These features are thought to be areas of downwelling, dry (low ammonia and water humidity) air. The second image from the top, taken at a wavelength sensitive to methane absorption, has muted contrast, showing that a high-level optically-thin haze layer overlies the entire region. All other images, taken over a large range of methane-insensitive wavelengths from 0.76 to 2.74 microns, reveal such 5 micron bright hotspots as actually being dark in reflected sunlight, confirming clearings in the bright reflective surrounding cloud layer and perhaps indicating absorption by clouds and/or gases at relatively deep levels in the atmosphere.

These images were acquired December 17, 1996 from a distance of 1.43 million kilometers above the cloudtops. The large dark clearing near the middle of the image is approximately 7000 km wide in the east-west direction and 4000 km tall in the north-south direction, about twice the size of the continental U. S. Images shown are at 0.76, 1.61, 1.99, and 2.74 microns, proceeding from top to bottom.

The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov.

Deep Stromvil Photometry for Star Formation in the Head of the Pelican Nebula

NASA Astrophysics Data System (ADS)

Boyle, Richard P.; J., S.; Stott, J.; J., S.; Janusz, R.; J., S.; Straizys, V.

2010-01-01

The North America and Pelican Nebulae, and specifically the dark cloud L935 contain regions of active star formation (Herbig, G. H. 1958, ApJ, 128,259). Previously we reported on Vatican telescope observations by Stromvil intermediate-band filters in a 12-arcmin field in the "Gulf of Mexico" region of L935. There we classify A, F, and G-type stars. However, the many faint K and M-type dwarf stars remain somewhat ambiguous in calibration and classification. But attaining reasonable progress, we turn to another part of L935 located near the Pelican head. This area includes the "bright rim" which is formed by dust and gas condensed by the light pressure of an unseen O-type star hidden behind the dense dark cloud. Straizys and Laugalys (2008 Baltic Astronomy, 17, 143 ) have identified this star to be one of the 2MASS objects with Av=23 mag. A few concentrations of faint stars, V 13 to 14 mag. are immersed in this dark region. Among these stars are a few known emission-line objects (T-Tauri or post T-Tauri stars). A half degree nearby are some photometric Vilnius standards we use to calibrate our new field. We call on 2MASS data for correlative information. Also the Stromvil photometry offers candidate stars for spectral observations. The aim of this study in the Vilnius and Stromvil photometric systems is to classify stars down to V = 18 mag., to confirm the existence of the young star clusters, and to determine the distance of the cloud covering the suspected hidden ionizing star.

ARC-1979-AC79-7081

NASA Image and Video Library

1979-07-08

P-21747 C Range: 2,200,000 miles This image shows a region of the Jovian atmosphere from approximately 25° N to the equatorial region. The north temperate jet, at approximately 23° N, where the wind speed is about 150 meters per second, is seen as a dark brown line from the left-hand edge to the right-hand corner of the picture. The wispy clouds of the north equatorial belt appear as shades of brown. The lower right-hand corner of the image shows the brighter (white) clouds of the equatorial region. A small blue area is apparent near the lower edge, which corresponds to a region free of the upper clouds, where it is possible to penetrate to cloud layers approximately 60 kilometers below the visible surface.

ARC-1979-A79-7081

NASA Image and Video Library

1979-07-08

P-21747 BW Range: 2,200,000 miles This image shows a region of the Jovian atmosphere from approximately 25° N to the equatorial region. The north temperate jet, at approximately 23° N, where the wind speed is about 150 meters per second, is seen as a dark brown line from the left-hand edge to the right-hand corner of the picture. The wispy clouds of the north equatorial belt appear as shades of brown. The lower right-hand corner of the image shows the brighter (white) clouds of the equatorial region. A small blue area is apparent near the lower edge, which corresponds to a region free of the upper clouds, where it is possible to penetrate to cloud layers approximately 60 kilometers below the visible surface.

A Herschel [C ii] Galactic plane survey. I. The global distribution of ISM gas components

NASA Astrophysics Data System (ADS)

Pineda, J. L.; Langer, W. D.; Velusamy, T.; Goldsmith, P. F.

2013-06-01

Context. The [C ii] 158 μm line is an important tool for understanding the life cycle of interstellar matter. Ionized carbon is present in a variety of phases of the interstellar medium (ISM), including the diffuse ionized medium, warm and cold atomic clouds, clouds in transition from atomic to molecular, and dense and warm photon dominated regions. Aims: Velocity-resolved observations of [C ii] are the most powerful technique available to disentangle the emission produced by these components. These observations can also be used to trace CO-dark H2 gas and determine the total mass of the ISM. Methods: The Galactic Observations of Terahertz C+ (GOT C+) project surveys the [C ii] 158 μm line over the entire Galactic disk with velocity-resolved observations using the Herschel/HIFI instrument. We present the first longitude-velocity maps of the [C ii] emission for Galactic latitudes b = 0°, ±0.5°, and ±1.0°. We combine these maps with those of H i, 12CO, and 13CO to separate the different phases of the ISM and study their properties and distribution in the Galactic plane. Results: [C ii] emission is mostly associated with spiral arms, mainly emerging from Galactocentric distances between 4 and 10 kpc. It traces the envelopes of evolved clouds as well as clouds that are in the transition between atomic and molecular. We estimate that most of the observed [C ii] emission is produced by dense photon dominated regions (~47%), with smaller contributions from CO-dark H2 gas (~28%), cold atomic gas (~21%), and ionized gas (~4%). Atomic gas inside the Solar radius is mostly in the form of cold neutral medium (CNM), while the warm neutral medium gas dominates the outer galaxy. The average fraction of CNM relative to total atomic gas is ~43%. We find that the warm and diffuse CO-dark H2 is distributed over a larger range of Galactocentric distances (4-11 kpc) than the cold and dense H2 gas traced by 12CO and 13CO (4-8 kpc). The fraction of CO-dark H2 to total H2 increases with Galactocentric distance, ranging from ~20% at 4 kpc to ~80% at 10 kpc. On average, CO-dark H2 accounts for ~30% of the molecular mass of the Milky Way. When the CO-dark H2 component is included, the radial distribution of the CO-to-H2 conversion factor is steeper than that when only molecular gas traced by CO is considered. Most of the observed [C ii] emission emerging from dense photon dominated regions is associated with modest far-ultraviolet fields in the range χ0 ≃ 1 - 30. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at http://www.aanda.org

Hubble Sees the Force Awakening in a Newborn Star

NASA Image and Video Library

2015-12-17

In the center of this image from the Hubble Space Telescope, partially obscured by a dark cloud of dust, a newborn star shoots twin jets out into space as a sort of birth announcement to the universe.

Early phases in the stellar and substellar formation and evolution. Infrared and submillimeter data in the Barnard 30 dark cloud

NASA Astrophysics Data System (ADS)

Barrado, D.; de Gregorio Monsalvo, I.; Huélamo, N.; Morales-Calderón, M.; Bayo, A.; Palau, A.; Ruiz, M. T.; Rivière-Marichalar, P.; Bouy, H.; Morata, Ó.; Stauffer, J. R.; Eiroa, C.; Noriega-Crespo, A.

2018-04-01

Aims: The early evolutionary stage of brown dwarfs (BDs) is not very well characterized, especially during the embedded phase. Our goal is to gain insight into the dominant formation mechanism of very low-mass objects and BDs. Methods: We have conducted deep observations at 870 μm obtained with the LABOCA bolometer at the APEX telescope in order to identify young submillimeter (submm) sources in the Barnard 30 dark cloud. We have complemented these data with multi-wavelength observations from the optical to the far-IR and compiled complete spectral energy distributions in order to identify the counterparts, characterize the sources and to assess their membership to the association and stellar or substellar status based on the available photometric information. Results: We have identified 34 submm sources and a substantial number of possible and probable Barnard 30 members within each individual APEX/LABOCA beam. They can be classified into three distinct groups. First, 15 of these 34 have a clear optical or IR counterpart to the submm peak and nine of them are potential proto-BD candidates. Moreover, a substantial number of them could be multiple systems. A second group of 13 sources comprises candidate members with significant infrared excesses located away from the central submm emission. All of them include BD candidates, some displaying IR excess, but their association with submm emission is unclear. In addition, we have found six starless cores and, based on the total dust mass estimate, three might be pre-substellar (or pre-BDs) cores. Finally, the complete characterization of our APEX/LABOCA sources, focusing on those detected at 24 and/or 70 μm, indicates that in our sample of 34 submm sources there are, at least: two WTTs, four CTTs, five young stellar objects, eight proto-BD candidates (with another three dubious cases), and one very low luminosity objects. Conclusions: Our findings provide additional evidence concerning the BD formation mechanism, which seems to be a downsized version of the stellar formation. Tables 3-7 and reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/vol/page

Clouds on Hot Jupiters Illustration

NASA Image and Video Library

2016-10-18

Hot Jupiters are exoplanets that orbit their stars so tightly that their temperatures are extremely high, reaching over 2,400 degrees Fahrenheit (1600 Kelvin). They are also tidally locked, so one side of the planet always faces the sun and the other is in permanent darkness. Research suggests that the "dayside" is largely free of clouds, while the "nightside" is heavily clouded. This illustration represents how hot Jupiters of different temperatures and different cloud compositions might appear to a person flying over the dayside of these planets on a spaceship, based on computer modeling. Cooler planets are entirely cloudy, whereas hotter planets have morning clouds only. Clouds of different composition have different colors, whereas the clear sky is bluer than on Earth. For the hottest planets, the atmosphere is hot enough on the evening side to glow like a charcoal. Figure 1 shows an approximation of what various hot Jupiters might look like based on a combination of computer modeling and data from NASA's Kepler Space Telescope. From left to right it shows: sodium sulfide clouds (1000 to 1200 Kelvin), manganese sulfide clouds (1200 to 1600 Kelvin), magnesium silicate clouds (1600 to 1800 Kelvin), magnesium silicate and aluminum oxide clouds (1800 Kelvin) and clouds composed of magnesium silicate, aluminum oxide, iron and calcium titanate (1900 to 2200 Kelvin). http://photojournal.jpl.nasa.gov/catalog/PIA21074

A composite large-scale CO survey at high galactic latitudes in the second quadrant

NASA Technical Reports Server (NTRS)

Heithausen, A.; Stacy, J. G.; De Vries, H. W.; Mebold, U.; Thaddeus, P.

1993-01-01

Surveys undertaken in the 2nd quadrant of the Galaxy with the CfA 1.2 m telescope have been combined to produce a map covering about 620 sq deg in the 2.6 mm CO(J = 1 - 0) line at high galactic latitudes. There is CO emission from molecular 'cirrus' clouds in about 13 percent of the region surveyed. The CO clouds are grouped together into three major cloud complexes with 29 individual members. All clouds are associated with infrared emission at 100 micron, although there is no one-to-one correlation between the corresponding intensities. CO emission is detected in all bright and dark Lynds' nebulae cataloged in that region; however not all CO clouds are visible on optical photographs as reflection or absorption features. The clouds are probably local. At an adopted distance of 240 pc cloud sizes range from O.1 to 30 pc and cloud masses from 1 to 1600 solar masses. The molecular cirrus clouds contribute between 0.4 and 0.8 M solar mass/sq pc to the surface density of molecular gas in the galactic plane. Only 26 percent of the 'infrared-excess clouds' in the area surveyed actually show CO and about 2/3 of the clouds detected in CO do not show an infrared excess.

Nyx: Adaptive mesh, massively-parallel, cosmological simulation code

NASA Astrophysics Data System (ADS)

Almgren, Ann; Beckner, Vince; Friesen, Brian; Lukic, Zarija; Zhang, Weiqun

2017-12-01

Nyx code solves equations of compressible hydrodynamics on an adaptive grid hierarchy coupled with an N-body treatment of dark matter. The gas dynamics in Nyx use a finite volume methodology on an adaptive set of 3-D Eulerian grids; dark matter is represented as discrete particles moving under the influence of gravity. Particles are evolved via a particle-mesh method, using Cloud-in-Cell deposition/interpolation scheme. Both baryonic and dark matter contribute to the gravitational field. In addition, Nyx includes physics for accurately modeling the intergalactic medium; in optically thin limits and assuming ionization equilibrium, the code calculates heating and cooling processes of the primordial-composition gas in an ionizing ultraviolet background radiation field.

Gas-Grain Chemical Models: Inclusion of a Grain Size Distribution and a Study Of Young Stellar Objects in the Magellanic Clouds

NASA Astrophysics Data System (ADS)

Pauly, Tyler Andrew

2017-06-01

Computational models of interstellar gas-grain chemistry have aided in our understanding of star-forming regions. Chemical kinetics models rely on a network of chemical reactions and a set of physical conditions in which atomic and molecular species are allowed to form and react. We replace the canonical single grain-size in our chemical model MAGICKAL with a grain size distribution and analyze the effects on the chemical composition of the gas and grain surface in quiescent and collapsing dark cloud models. We find that a grain size distribution coupled with a temperature distribution across grain sizes can significantly affect the bulk ice composition when dust temperatures fall near critical values related to the surface binding energies of common interstellar chemical species. We then apply the updated model to a study of ice formation in the cold envelopes surrounding massive young stellar objects in the Magellanic Clouds. The Magellanic Clouds are local satellite galaxies of the Milky Way, and they provide nearby environments to study star formation at low metallicity. We expand the model calculation of dust temperature to include a treatment for increased interstellar radiation field intensity; we vary the radiation field to model the elevated dust temperatures observed in the Magellanic Clouds. We also adjust the initial elemental abundances used in the model, guided by observations of Magellanic Cloud HII regions. We are able to reproduce the relative ice fractions observed, indicating that metal depletion and elevated grain temperature are important drivers of the envelope ice composition. The observed shortfall in CO in Small Magellanic Cloud sources can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH 3OH abundance is found to be enhanced (relative to total carbon abundance) in low-metallicity models, providing seed material for complex organic molecule formation. We conclude with a preliminary study of the recently discovered hot core in the Large Magellanic Cloud; we create a grid of models to simulate hot core formation in Magellanic Cloud environments, comparing them to models and observations of well-characterized galactic counterparts.

C+/CO Transitions in the Diffuse ISM: Transitional Cloud Sample from the GOT C+ Survey of [CII] in the inner Galaxy at l = -30deg to 30deg

NASA Astrophysics Data System (ADS)

Velusamy, T.; Pineda, J. L.; Langer, W. D.; Willacy, K.; Goldsmith, P. F.

2011-05-01

Our knowledge of interstellar gas has been limited primarily to the diffuse atomic phase traced by HI and the well-shielded molecular phase traced by CO. Recently, using the first results of the Herschel Key Project GOT C+, a HIFI C+ survey of the Galactic plane, Velusamy, Langer, Pineda et al. (A&A 521, L18, 2010) have shown that in the diffuse interstellar transition clouds a significant fraction of the carbon exists primarily as C^+ with little C^0 and CO in a warm 'dark gas' layer in which hydrogen is mostly H_2 with little atomic H, surrounding a modest 12CO-emitting core. The [CII] fine structure transition, at 1.9 THz (158 μm) is the best tracer of this component of the interstellar medium, which is critical to our understanding of the atomic to molecular cloud transitions. The Herschel Key Project GOT C+ is designed to study such clouds by observing with HIFI the [CII] line emission along 500 lines of sight (LOSs) throughout the Galactic disk. Here we present the identification and chemical status of a few hundred diffuse and transition clouds traced by [CII], along with auxiliary HI and CO data covering ~100 LOSs in the inner Galaxy between l= -30° and 30°. We identify transition clouds as [CII] components that are characterized by the presence of both HI and 12CO, but no 13CO emission. The intensities, I(CII) and I(HI), are used as measures of the visual extinction, AV, in the cloud up to the C^+/C^0/CO transition layer and a comparison with I(12CO) yields a more complete H_2 molecular inventory. Our results show that [CII] emission is an excellent tool to study transition clouds and their carbon chemistry in the ISM, in particular as a unique tracer of molecular H_2, which is not easily observed by other means. The large sample presented here will serve as a resource to study the chemical and physical status of diffuse transition clouds in a wide range of Galactic environments and constrain the physical parameters such as the FUV intensity and cosmic ray ionization rate that drive the CO chemistry in the diffuse ISM.

Simultaneous colour visualizations of multiple ALS point cloud attributes for land cover and vegetation analysis

NASA Astrophysics Data System (ADS)

Zlinszky, András; Schroiff, Anke; Otepka, Johannes; Mandlburger, Gottfried; Pfeifer, Norbert

2014-05-01

LIDAR point clouds hold valuable information for land cover and vegetation analysis, not only in the spatial distribution of the points but also in their various attributes. However, LIDAR point clouds are rarely used for visual interpretation, since for most users, the point cloud is difficult to interpret compared to passive optical imagery. Meanwhile, point cloud viewing software is available allowing interactive 3D interpretation, but typically only one attribute at a time. This results in a large number of points with the same colour, crowding the scene and often obscuring detail. We developed a scheme for mapping information from multiple LIDAR point attributes to the Red, Green, and Blue channels of a widely used LIDAR data format, which are otherwise mostly used to add information from imagery to create "photorealistic" point clouds. The possible combinations of parameters are therefore represented in a wide range of colours, but relative differences in individual parameter values of points can be well understood. The visualization was implemented in OPALS software, using a simple and robust batch script, and is viewer independent since the information is stored in the point cloud data file itself. In our case, the following colour channel assignment delivered best results: Echo amplitude in the Red, echo width in the Green and normalized height above a Digital Terrain Model in the Blue channel. With correct parameter scaling (but completely without point classification), points belonging to asphalt and bare soil are dark red, low grassland and crop vegetation are bright red to yellow, shrubs and low trees are green and high trees are blue. Depending on roof material and DTM quality, buildings are shown from red through purple to dark blue. Erroneously high or low points, or points with incorrect amplitude or echo width usually have colours contrasting from terrain or vegetation. This allows efficient visual interpretation of the point cloud in planar, profile and 3D views since it reduces crowding of the scene and delivers intuitive contextual information. The resulting visualization has proved useful for vegetation analysis for habitat mapping, and can also be applied as a first step for point cloud level classification. An interactive demonstration of the visualization script is shown during poster attendance, including the opportunity to view your own point cloud sample files.

Carbon Chemistry in Transitional Clouds from the GOT C+ Survey of CII 158 micron Emission in the Galactic Plane

NASA Astrophysics Data System (ADS)

Langer, W. D.; Velusamy, T.; Pineda, J.; Willacy, K.; Goldsmith, P. F.

2011-05-01

In understanding the lifecycle and chemistry of the interstellar gas, the transition from diffuse atomic to molecular gas clouds is a very important stage. The evolution of carbon from C+ to C0 and CO is a fundamental part of this transition, and C+ along with its carbon chemistry is a key diagnostic. Until now our knowledge of interstellar gas has been limited primarily to the diffuse atomic phase traced by HI and the dense molecular H2 phase traced by CO. However, we have generally been missing an important layer in diffuse and transition clouds, which is denoted by the warm "dark gas'', that is mostly H2 and little HI and CO, and is best traced with C+. Here, we discuss the chemistry in the transition from C+ to C0 and CO in these clouds as understood by a survey of the CII 1.9 THz (158 micron) line from a sparse survey of the inner galaxy over about 40 degrees in longitude as part of the Galactic Observations of Terahertz C+ (GOT C+) program, a Herschel Space Observatory Open Time Key Program to study interstellar clouds by sampling ionized carbon. Using the first results from GOT C+ along 11 LOSs, in a sample of 53 transition clouds, Velusamy, Langer et al. (A&A 521, L18, 2010) detected an excess of CII intensities indicative of a thick H2 layer (a significant warm H2, "dark gas'' component) around the 12CO core. Here we present a much larger, statistically significant sample of a few hundred diffuse and transition clouds traced by CII, along with auxiliary HI and CO data in the inner Galaxy between l=-30° and +30°. Our new and more extensive sample of transition clouds is used to elucidate the time dependent physical and carbon chemical evolution of diffuse to transition clouds, and transition layers. We consider the C+ to CO conversion pathways such as H++ O and C+ + H2 chemistry for CO production to constrain the physical parameters such as the FUV intensity and cosmic ray ionization rate that drive the CO chemistry in the diffuse transition clouds.

A new method to unveil embedded stellar clusters

NASA Astrophysics Data System (ADS)

Lombardi, Marco; Lada, Charles J.; Alves, João

2017-11-01

In this paper we present a novel method to identify and characterize stellar clusters deeply embedded in a dark molecular cloud. The method is based on measuring stellar surface density in wide-field infrared images using star counting techniques. It takes advantage of the differing H-band luminosity functions (HLFs) of field stars and young stellar populations and is able to statistically associate each star in an image as a member of either the background stellar population or a young stellar population projected on or near the cloud. Moreover, the technique corrects for the effects of differential extinction toward each individual star. We have tested this method against simulations as well as observations. In particular, we have applied the method to 2MASS point sources observed in the Orion A and B complexes, and the results obtained compare very well with those obtained from deep Spitzer and Chandra observations where presence of infrared excess or X-ray emission directly determines membership status for every star. Additionally, our method also identifies unobscured clusters and a low resolution version of the Orion stellar surface density map shows clearly the relatively unobscured and diffuse OB 1a and 1b sub-groups and provides useful insights on their spatial distribution.

Molecules in interstellar clouds. [physical and chemical conditions of star formation and biological evolution

NASA Technical Reports Server (NTRS)

Irvine, W. M.; Hjalmarson, A.; Rydbeck, O. E. H.

1981-01-01

The physical conditions and chemical compositions of the gas in interstellar clouds are reviewed in light of the importance of interstellar clouds for star formation and the origin of life. The Orion A region is discussed as an example of a giant molecular cloud where massive stars are being formed, and it is pointed out that conditions in the core of the cloud, with a kinetic temperature of about 75 K and a density of 100,000-1,000,000 molecules/cu cm, may support gas phase ion-molecule chemistry. The Taurus Molecular Clouds are then considered as examples of cold, dark, relatively dense interstellar clouds which may be the birthplaces of solar-type stars and which have been found to contain the heaviest interstellar molecules yet discovered. The molecular species identified in each of these regions are tabulated, including such building blocks of biological monomers as H2O, NH3, H2CO, CO, H2S, CH3CN and H2, and more complex species such as HCOOCH3 and CH3CH2CN.

Airborne observations and simulations of three-dimensional radiative interactions between Arctic boundary layer clouds and ice floes

NASA Astrophysics Data System (ADS)

Schäfer, M.; Bierwirth, E.; Ehrlich, A.; Jäkel, E.; Wendisch, M.

2015-07-01

Based on airborne spectral imaging observations, three-dimensional (3-D) radiative effects between Arctic boundary layer clouds and highly variable Arctic surfaces were identified and quantified. A method is presented to discriminate between sea ice and open water under cloudy conditions based on airborne nadir reflectivity γλ measurements in the visible spectral range. In cloudy cases the transition of γλ from open water to sea ice is not instantaneous but horizontally smoothed. In general, clouds reduce γλ above bright surfaces in the vicinity of open water, while γλ above open sea is enhanced. With the help of observations and 3-D radiative transfer simulations, this effect was quantified to range between 0 and 2200 m distance to the sea ice edge (for a dark-ocean albedo of αwater = 0.042 and a sea-ice albedo of αice = 0.91 at 645 nm wavelength). The affected distance Δ L was found to depend on both cloud and sea ice properties. For a low-level cloud at 0-200 m altitude, as observed during the Arctic field campaign VERtical Distribution of Ice in Arctic clouds (VERDI) in 2012, an increase in the cloud optical thickness τ from 1 to 10 leads to a decrease in Δ L from 600 to 250 m. An increase in the cloud base altitude or cloud geometrical thickness results in an increase in Δ L; for τ = 1/10 Δ L = 2200 m/1250 m in case of a cloud at 500-1000 m altitude. To quantify the effect for different shapes and sizes of ice floes, radiative transfer simulations were performed with various albedo fields (infinitely long straight ice edge, circular ice floes, squares, realistic ice floe field). The simulations show that Δ L increases with increasing radius of the ice floe and reaches maximum values for ice floes with radii larger than 6 km (500-1000 m cloud altitude), which matches the results found for an infinitely long, straight ice edge. Furthermore, the influence of these 3-D radiative effects on the retrieved cloud optical properties was investigated. The enhanced brightness of a dark pixel next to an ice edge results in uncertainties of up to 90 and 30 % in retrievals of τ and effective radius reff, respectively. With the help of Δ L, an estimate of the distance to the ice edge is given, where the retrieval uncertainties due to 3-D radiative effects are negligible.

Two Pairs of Storms

NASA Image and Video Library

2004-06-04

Two pairs of dark spots, or storms, in Saturn atmosphere squeeze past each other as they dance around the planet. In this group of four storms, the top left and lower right storms are fringed with white clouds as seen by NASA Cassini spacecraft.

Interstellar and Cometary Dust

NASA Technical Reports Server (NTRS)

Mathis, John S.

1997-01-01

'Interstellar dust' forms a continuum of materials with differing properties which I divide into three classes on the basis of observations: (a) diffuse dust, in the low-density interstellar medium; (b) outer-cloud dust, observed in stars close enough to the outer edges of molecular clouds to be observed in the optical and ultraviolet regions of the spectrum, and (c) inner-cloud dust, deep within the cores of molecular clouds, and observed only in the infrared by means of absorption bands of C-H, C=O, 0-H, C(triple bond)N, etc. There is a surprising regularity of the extinction laws between diffuse- and outer-cloud dust. The entire mean extinction law from infrared through the observable ultraviolet spectrum can be characterized by a single parameter. There are real deviations from this mean law, larger than observational uncertainties, but they are much smaller than differences of the mean laws in diffuse- and outer-cloud dust. This fact shows that there are processes which operate over the entire distribution of grain sizes, and which change size distributions extremely efficiently. There is no evidence for mantles on grains in local diffuse and outer-cloud dust. The only published spectra of the star VI Cyg 12, the best candidate for showing mantles, does not show the 3.4 micro-m band which appreciable mantles would produce. Grains are larger in outer-cloud dust than diffuse dust because of coagulation, not accretion of extensive mantles. Core-mantle grains favored by J. M. Greenberg and collaborators, and composite grains of Mathis and Whiffen (1989), are discussed more extensively (naturally, I prefer the latter). The composite grains are fluffy and consist of silicates, amorphous carbon, and some graphite in the same grain. Grains deep within molecular clouds but before any processing within the solar system are presumably formed from the accretion of icy mantles on and within the coagulated outer-cloud grains. They should contain a mineral/carbonaceous matrix, without organic refractory mantles, in between the ices. Unfortunately, they may be significantly processed by chemical processes accompanying the warming (over the 10 K of the dark cloud cores) which occurs in the outer solar system. Evidence of this processing is the chemical anomalies present in interplanetary dust particles collected in the stratosphere, which may be the most primitive materials we have obtained to date. The comet return mission would greatly clarify the situation, and probably provide samples of genuine interstellar grains.

Earth observations taken during the STS-71 mission

NASA Image and Video Library

1995-06-29

STS071-701-098 (27 June-7 July 1995) --- This wide-angle, west-looking view shows all of California, from the Los Angeles basin (left, at the coast), to the Oregon border (far right). A large cloud mass occupies the Pacific Ocean all the way to the horizon. The effect of interaction between the land and sea can be seen by the cloud patterns at the coast. San Francisco lies in the bay where clouds penetrate inland farthest (right of center). The central valley of California stands out very well as a cigar-shaped feature across the center of view - green in the middle, surrounded by a brown line, with dark green (forests) surrounding that.

Deflection of jets induced by jet-cloud and jet-galaxy interactions

NASA Astrophysics Data System (ADS)

Mendoza, S.; Longair, M. S.

2001-06-01

The model first introduced by Raga & Cantó in which astrophysical jets are deflected on passing through an isothermal high-density region is generalized by taking into account gravitational effects on the motion of the jet as it crosses the high-density cloud. The problem is also generalized for relativistic jets in which gravitational effects induced by the cloud are neglected. Two further cases, classical and relativistic, are discussed for the cases in which the jet is deflected on passing through the interstellar gas of a galaxy in which a dark matter halo dominates the gravitational potential. The criteria for the stability of jets due to the formation of internal shocks are also discussed.

Earth Observing-1 Advanced Land Imager: Dark Current and Noise Characterization and Anomalous Detectors

NASA Technical Reports Server (NTRS)

Mendenhall, J. A.

2001-01-01

The dark current and noise characteristics of the Earth Observing-1 Advanced Land Imager measured during ground calibration at MIT Lincoln Laboratory are presented. Data were collected for the nominal focal plane operating temperature of 220 K as well as supplemental operating temperatures (215 and 225 K). Dark current baseline values are provided, and noise characterization includes the evaluation of white, coherent, low frequency, and high frequency components. Finally, anomalous detectors, characterized by unusual dark current, noise, gain, or cross-talk properties are investigated.

Spectrum from Embedded Star in Herbig-Haro 46/47

NASA Technical Reports Server (NTRS)

2003-01-01

NASA's Spitzer Space Telescope has lifted the cosmic veil to see an otherwise hidden newborn star, while detecting the presence of water and carbon dioxide ices, as well as organic molecules. Using near-infrared light, Spitzer pierces through an optically dark cloud to detect the embedded outflow in an object called HH 46/47. Herbig-Haro (HH) objects are bright, nebulous regions of gas and dust that are usually buried within dark dust clouds. They are formed when supersonic gas ejected from a forming protostar, or embryonic star, interacts with the surrounding interstellar medium. These young stars are often detected only in the infrared.

HH 46/47 is a striking example of a low mass protostar ejecting a jet and creating a bipolar, or two-sided, outflow. The central protostar lies inside a dark cloud (known as a 'Bok globule') which is illuminated by the nearby Gum Nebula. Located at a distance of 1140 light-years and found in the constellation Vela, the protostar is hidden from view in the visible-light image (inset). With Spitzer, the star and its dazzling jets of molecular gas appear with clarity.

The Spitzer image (inset) was obtained with the infrared array camera and is a three-color mosaic. Emission at 3.6 microns is shown as blue, emission from 4.5 and 5.8 microns has been combined as green, and 8.0 micron emission is depicted as red. The 8-micron channel of the camera is sensitive to emission from polycyclic aromatic hydrocarbons. These organic molecules, comprised of carbon and hydrogen, are excited by the surrounding radiation field and become luminescent, accounting for the reddish cloud. Note that the boundary layer of the 8-micron mission corresponds to the lower right edge of the dark cloud in the visible-light picture.

The primary image shows a spectrum obtained with Spitzer's infrared spectrograph instrument, stretching from wavelengths of 5.5 microns (left) to 20 microns (right). Spectra are graphical representations of a celestial object's unique blend of light. Characteristic patterns, or fingerprints, within the spectra allow astronomers to identify the object's chemical composition.

The broad depression in the center of the spectrum signifies the presence of silicates, which are chemically similar to beach sand. The depth of the silicate absorption feature indicates that the dusty cocoon surrounding the embedded protostar star is extremely thick Other absorption dips are produced by water ice (blue) and carbon dioxide ice (green). The fact that water and carbon dioxide appear in solid form suggests that the material immediately surrounding the protostar is cold. In addition, the Spitzer spectrum includes the chemical signatures of methane (purple) and methyl alcohol (tan).

Equilibrium Slab Models of Lyman-Alpha Clouds

NASA Technical Reports Server (NTRS)

Charlton, Jane C.; Salpeter, Edwin E.; Hogan, Craig J.

1993-01-01

We model the L(sub y(alpha)) clouds as slabs of hydrogen with an ionizing extragalactic radiation field incident from both sides. In general, the equilibrium configuration of a slab at redshift z approx. less than 5 is determined by a balance of the gas pressure, gravity (including the effects of a dark matter halo), and the pressure exerted by the inter-galactic medium, P(sub ext). These models have been used to make predictions of the number of slabs as a function of the neutral hydrogen column density, N(sub H). A break in the curve is predicted at the transition between regimes where gravity and pressure are the dominant confining forces, with a less rapid decrease at larger N(sub H). The transition from optically thin to optically thick slabs leads to a gap in the distribution, whose location is governed largely by the spectrum of ionizing radiation. There are certain parallels between lines of sight through the outer HI disk of spiral galaxy with increasing radius, and the progression from damped, to Lyman limit, to forest clouds. We discuss briefly the possibility that at least some of the observed low z forest clouds may be a separate population, associated with galaxies, as suggested by the observations of Bahcall et al. This population could dominate the forest at present if the dark matter attached to galaxies should lead to gravity confinement for this disk population, while the isolated clouds remain pressure confined. The formalism developed in this paper will allow a more detailed study. We also discuss a more general parameter study of the equilibrium configuration of slabs, including mock gravity and L(sub y(alpha)) photon trapping.

Close-Up Views of Jupiter North Pole

NASA Image and Video Library

2016-09-02

Storm systems and weather activity unlike anything encountered in the solar system are on view in these color images of Jupiter's north polar region from NASA's Juno spacecraft. Two versions of the image have been contrast-enhanced differently to bring out detail near the dark terminator and near the bright limb. The JunoCam instrument took the images to create this color view on August 27, when the spacecraft was about 48,000 miles (78,000 kilometers) above the polar cloud tops. A wavy boundary is visible halfway between the grayish region at left (closer to the pole and the nightside shadow) and the lighter-colored area on the right. The wavy appearance of the boundary represents a Rossby wave -- a north-south meandering of a predominantly east-west flow in an atmospheric jet. This may be caused by a difference in temperature between air to the north and south of this boundary, as is often the case with such waves in Earth's atmosphere. The polar region is filled with a variety of discrete atmospheric features. Some of these are ovals, but the larger and brighter features have a "pinwheel" shape reminiscent of the shape of terrestrial hurricanes. Tracking the motion and evolution of these features across multiple orbits will provide clues about the dynamics of the Jovian atmosphere. This image also provides the first example of cloud shadowing on Jupiter: near the top of the image, a high cloud feature is seen past the normal boundary between day and night, illuminated above the cloud deck below. While subtle color differences are visible in the image, some of these are likely the result of scattered light within the JunoCam optics. Work is ongoing to characterize these effects. http://photojournal.jpl.nasa.gov/catalog/PIA21031

Widespread deuteration across the IRDC G035.39-00.33

NASA Astrophysics Data System (ADS)

Barnes, A. T.; Kong, S.; Tan, J. C.; Henshaw, J. D.; Caselli, P.; Jiménez-Serra, I.; Fontani, F.

2016-05-01

Infrared Dark Clouds (IRDCs) are cold, dense regions that are usually found within Giant Molecular Clouds. Ongoing star formation within IRDCs is typically still deeply embedded within the surrounding molecular gas. Characterizing the properties of relatively quiescent IRDCs may therefore help us to understand the earliest phases of the star formation process. Studies of local molecular clouds have revealed that deuterated species are enhanced in the earliest phases of star formation. In this paper, we test this towards IRDC G035.39-00.33. We present an 80 arcsec by 140 arcsec map of the J = 2 → 1 transition of N2D+, obtained with the Institut de Radioastronomie Millimétrique 30 m telescope telescope. We find that N2D+ is widespread throughout G035.39-00.33. Complementary observations of N2H+ (1 - 0) are used to estimate the deuterium fraction, D_frac^N_2H^+ ≡ N(N2D+)/N(N2H+). We report a mean D_frac^N_2H^+ = 0.04 ± 0.01, with a maximum of D_frac^N_2H^+ = 0.09 ± 0.02. The mean deuterium fraction is ˜3 orders of magnitude greater than the interstellar [D]/[H] ratio. High angular resolution observations are required to exclude beam dilution effects of compact deuterated cores. Using chemical modelling, we find that the average observed values of D_frac^N_2H^+are in agreement with an equilibrium deuterium fraction, given the general properties of the cloud. This implies that the IRDC is at least ˜3 Myr old, which is ˜8 times longer than the mean free-fall time of the observed deuterated region.

THE MAGNETIC FIELD OF L1544. I. NEAR-INFRARED POLARIMETRY AND THE NON-UNIFORM ENVELOPE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clemens, Dan P.; Tassis, K.; Goldsmith, Paul F., E-mail: clemens@bu.edu, E-mail: tassis@physics.uoc.gr, E-mail: paul.f.goldsmith@jpl.nasa.gov

2016-12-20

The magnetic field ( B -field) of the starless dark cloud L1544 has been studied using near-infrared (NIR) background starlight polarimetry (BSP) and archival data in order to characterize the properties of the plane-of-sky B -field. NIR linear polarization measurements of over 1700 stars were obtained in the H band and 201 of these were also measured in the K band. The NIR BSP properties are correlated with reddening, as traced using the Rayleigh–Jeans color excess ( H – M ) method, and with thermal dust emission from the L1544 cloud and envelope seen in Herschel maps. The NIR polarizationmore » position angles change at the location of the cloud and exhibit their lowest dispersion there, offering strong evidence that NIR polarization traces the plane-of-sky B -field of L1544. In this paper, the uniformity of the plane-of-sky B -field in the envelope region of L1544 is quantitatively assessed. This allows evaluation of the approach of assuming uniform field geometry when measuring relative mass-to-flux ratios in the cloud envelope and core based on averaging of the radio Zeeman observations in the envelope, as done by Crutcher et al. In L1544, the NIR BSP shows the envelope B -field to be significantly non-uniform and likely not suitable for averaging Zeeman properties without treating intrinsic variations. Deeper analyses of the NIR BSP and related data sets, including estimates of the B -field strength and testing how it varies with position and gas density, are the subjects of later papers in this series.« less

Baryonic Dark Matter: The Results from Microlensing Surveys

NASA Astrophysics Data System (ADS)

Alcock, Charles; Allsman, Robyn A.; Alves, David; Axelrod, Tim S.; Becker, Andrew C.; Bennett, David; Cook, Kem H.; Drake, Andrew J.; Freeman, Ken C.; Griest, Kim; Lehner, Matt; Marshall, Stuart; Minniti, Dante; Peterson, Bruce; Pratt, Mark; Quinn, Peter; Rodgers, Alex; Stubbs, Chris; Sutherland, Will; Tomaney, Austin; Vandehei, Thor; Welch, Doug L.

Baryonic material can exist in several dark forms: ``planets," brown dwarfs, very old degenerate dwarf stars, and neutron stars. (Black holes are frequently added to this list, even though a black hole has no baryon number.) These objects, most of which emit some light but at levels below present day detection thresholds, are collectively known as Machos. Several groups have exploited the gravitational microlens signature to search for Machos in the dark halo of the Milky Way. Over 200 microlensing events have been reported (most by the MACHO Project, which uses the Great Melbourne Telescope near this conference site), of which about 20 are toward the Magellanic Clouds. The most straightforward interpretation of the results is that Machos make up between 20% and 100% of the dark matter in the halo, and that these objects weigh about 0.5 msun. Objects of substellar mass do not comprise much of the dark matter. Many alternative interpretations of these results have been proposed. We will discuss strategies for resolving the differences among these competing explanations.

Radar Evaluation of Optical Cloud Constraints to Space Launch Operations

NASA Technical Reports Server (NTRS)

Merceret, Francis J.; Short, David A.; Ward, Jennifer G.

2005-01-01

Weather constraints to launching space vehicles are designed to prevent loss of the vehicle or mission due to weather hazards (See, e.g., Ref 1). Constraints include Lightning Launch Commit Criteria (LLCC) designed to avoid natural and triggered lightning. The LLCC currently in use at most American launch sites including the Eastern Range and Kennedy Space Center require the Launch Weather Officer to determine the height of cloud bases and tops, the location of cloud edges, and cloud transparency. The preferred method of making these determinations is visual observation, but when that isn't possible due to darkness or obscured vision, it is permissible to use radar. This note examines the relationship between visual and radar observations in three ways: A theoretical consideration of the relationship between radar reflectivity and optical transparency. An observational study relating radar reflectivity to cloud edge determined from in-situ measurements of cloud particle concentrations that determine the visible cloud edge. An observational study relating standard radar products to anvil cloud transparency. It is shown that these three approaches yield results consistent with each other and with the radar threshold specified in Reference 2 for LLCC evaluation.

Abundances and Excitation of H2, H3+ & CO in Star-Forming Regions

NASA Astrophysics Data System (ADS)

Kulesa, Craig A.

Although most of the 123 reported interstellar molecules to date have been detected through millimeter-wave emission-line spectroscopy, this technique is inapplicable to non-polar molecules like H2 and H3+, which are central to our understanding of interstellar chemistry. Thus high resolution infrared absorption-line spectroscopy bears an important role in interstellar studies: chemically important non-polar molecules can be observed, and their abundances and excitation conditions can be referred to the same ``pencil beam'' absorbing column. In particular, through a weak quadrupole absorption line spectrum at near-infrared wavelengths, the abundance of cold H2 in dark molecular clouds and star forming regions can now be accurately measured and compared along the same ``pencil beam'' line of sight with the abundance of its most commonly cited surrogate, CO, and its rare isotopomers. Also detected via infrared line absorption is the pivotal molecular ion H3+, whose abundance provides the most direct measurement of the cosmic ray ionization rate in dark molecular clouds, a process that initiates the formation of many other observed molecules there. Our growing sample of H2 and CO detections now includes detailed multi-beam studies of the ρ Ophiuchi molecular cloud and NGC 2024 in Orion. We explore the excitation and degree of ortho- and para-H2 thermalization in dark clouds, variation of the CO abundance over a cloud, and the relation of H2 column density to infrared extinction mapping, far-infrared/submillimeter dust continuum emission, and large scale submillimeter CO, [C I] and HCO+ line emission -- all commonly invoked to indirectly trace H2 during the past 30+ years. For each of the distinct velocity components seen toward some embedded young stellar objects, we are also able to determine the temperature, density, and a CO/H2 abundance ratio, thus unraveling some of the internal structure of a star-forming cloud. H2 and H3+ continue to surprise and delight us with more mysteries. We present imaging and spectroscopy of excited H2 line emission from two Crab Nebula filaments, leading to intriguing questions -- such as the rapid formation, excitation, and continued survival of hydrogen molecules in such a hostile environment. Similarly, we depict the recent detection of CO and H3+ emission from the circumstellar disks of nearby Herbig AeBe stars, providing an outstanding diagnostic of energetic pre-planetary environments and a valuable study of the non-thermal excitation of H3+ in its own right. These studies spotlight the role of molecules as regulators and probes of physical processes in molecular clouds and star- & planet-forming regions. See: http://loke.as.arizona.edu/˜ckulesa/research/ for preprints & more information

NASA Satellite Images Annual Spring Thaw, Red River, North Dakota

NASA Image and Video Library

2011-04-21

NASA Terra spacecraft shows the annual spring thaw in the upper Midwest is underway. Snow-covered ground contrasts with the dark tones of water under broken cloud cover. Along the Red River in North Dakota, floodwaters are moving northward into Canada.

Retrieving Neptune's aerosol properties from Keck OSIRIS observations. I. Dark regions

NASA Astrophysics Data System (ADS)

Luszcz-Cook, S. H.; de Kleer, K.; de Pater, I.; Adamkovics, M.; Hammel, H. B.

2016-09-01

We present and analyze three-dimensional data cubes of Neptune from the OSIRIS integral-field spectrograph on the 10-m W.M. Keck II telescope, from 26 July 2009. These data have a spatial resolution of 0.035/pixel and spectral resolution of R ∼3800 in the H (1.47-1.80 μm) and K (1.97-2.38 μm) broad bands. We focus our analysis on regions of Neptune's atmosphere that are near-infrared dark - that is, free of discrete bright cloud features. We use a forward model coupled to a Markov chain Monte Carlo algorithm to retrieve properties of Neptune's aerosol structure and methane profile above ∼4 bar in these near-infrared dark regions. We construct a set of high signal-to-noise spectra spanning a range of viewing geometries to constrain the vertical structure of Neptune's aerosols in a cloud-free latitude band from 2-12°N. We find that Neptune's cloud opacity at these wavelengths is dominated by a compact, optically thick cloud layer with a base near 3 bar. Using the pyDISORT algorithm for the radiative transfer and assuming a Henyey-Greenstein phase function, we observe this cloud to be composed of low albedo (single scattering albedo = 0.45-0.01+0.01), forward scattering (asymmetry parameter g = 0.50-0.02+0.02) particles, with an assumed characteristic size of ∼1μm. Above this cloud, we require an aerosol layer of smaller (∼0.1μm) particles forming a vertically extended haze, which reaches from the upper troposphere (0.59-0.03+0.04 bar) into the stratosphere. The particles in this haze are brighter (single scattering albedo = 0.91-0.05+0.06) and more isotropically scattering (asymmetry parameter g = 0.24-0.03+0.02) than those in the deep cloud. When we extend our analysis to 18 cloud-free locations from 20°N to 87°S, we observe that the optical depth in aerosols above 0.5 bar decreases by a factor of 2-3 or more at mid- and high-southern latitudes relative to low latitudes. We also consider Neptune's methane (CH4) profile, and find that our retrievals indicate a strong preference for a low methane relative humidity at pressures where methane is expected to condense. When we include in our fits a parameter for methane depletion below the CH4 condensation pressure, our preferred solution at most locations is for a methane relative humidity below 10% near the tropopause in addition to methane depletion down to 2.0-2.5 bar. We tentatively identify a trend of lower CH4 columns above 2.5 bar at mid- and high-southern latitudes over low latitudes, qualitatively consistent with what is found by Karkoschka and Tomasko (2011), and similar to, but weaker than, the trend observed for Uranus.

sunset

NASA Image and Video Library

2013-08-04

ISS036-E-028913 (4 Aug. 2013) --- A sunset over the Aleutian Islands, with noctilucent clouds, is featured in this image photographed by an Expedition 36 crew member on the International Space Station. The crew member took this panoramic view looking north from the Aleutian Islands when the space station was flying east at ?the top of the orbit,? the northernmost latitude reached by the orbital complex (51.6 degrees north). If the sun had been higher, the string of Aleutian Islands would have been visible in the foreground. Here the islands are on the dark side of the day-night line. From their vantage point at 222 kilometers altitude on this day, crew members were able to see as far north as the Arctic Ocean and the midnight sun. This image was taken just 20 minutes after local midnight in early August 2013. The midnight sun makes the red, diamond-shaped teardrop reflection (lower center)?perhaps a reflection within the camera lens, or from the window frame, or some item inside the ISS. Long blue-white stringers can be seen in the atmosphere above the midnight sun. These are known as noctilucent clouds (night-shining clouds). Some crew members say these wispy, rippling, iridescent clouds are the most beautiful phenomena they see from orbit. Noctilucents are thin so that they are best seen after sunset when the viewer is on the night side of the day-night line, but while these high clouds are still lit by the sun. Crews are trained in this somewhat complicated geometry?of clouds being lit from beneath, with the spacecraft in sunlight though the ground directly beneath is in darkness. Noctilucent clouds are also known as polar mesospheric clouds (PMCs) as they appear in the summer hemisphere over polar latitudes. Some data suggest that they are becoming brighter, and appearing at lower latitudes, perhaps as an effect of global warming. A comparison of noctilucent cloud formation from 2012 and 2013 has been compiled using data from NASA?s Aeronomy of Ice in the Mesosphere (AIM) shows an earlier start and an increase in the area covered by these clouds in 2013. Polar mesospheric clouds are interesting to scientists because they form much higher in the atmosphere (75-90 kilometers) compared with altitudes of normal rainclouds that form in the lowest, densest ?weather-layer? below approximately 15 kilometers. The weather layer, or troposphere, is most distinct in this image as a thin orange line along the left horizon.

New Views of a Familiar Beauty

NASA Image and Video Library

2005-01-12

This image composite compares the well-known visible-light picture of the glowing Trifid Nebula (left panel) with infrared views from NASA's Spitzer Space Telescope (remaining three panels). The Trifid Nebula is a giant star-forming cloud of gas and dust located 5,400 light-years away in the constellation Sagittarius. The false-color Spitzer images reveal a different side of the Trifid Nebula. Where dark lanes of dust are visible trisecting the nebula in the visible-light picture, bright regions of star-forming activity are seen in the Spitzer pictures. All together, Spitzer uncovered 30 massive embryonic stars and 120 smaller newborn stars throughout the Trifid Nebula, in both its dark lanes and luminous clouds. These stars are visible in all the Spitzer images, mainly as yellow or red spots. Embryonic stars are developing stars about to burst into existence. Ten of the 30 massive embryos discovered by Spitzer were found in four dark cores, or stellar "incubators," where stars are born. Astronomers using data from the Institute of Radioastronomy millimeter telescope in Spain had previously identified these cores but thought they were not quite ripe for stars. Spitzer's highly sensitive infrared eyes were able to penetrate all four cores to reveal rapidly growing embryos. http://photojournal.jpl.nasa.gov/catalog/PIA07225

X-ray emitting class I protostars in the Serpens dark cloud

NASA Astrophysics Data System (ADS)

Preibisch, T.

2004-12-01

We analyze a set of three individual XMM-Newton X-ray observation of the Serpens dark cloud. In addition to the 45 sources already reported in the analysis of the first of these XMM-Newton observations by Preibisch (\\cite{Preibisch2003), the complete combined data set leads to the detection of X-ray emission from four of the 19 known class I protostars in the region. The set of three observations allows us to study the variability of the sources on timescales from minutes to several months. The lightcurves of two of the four X-ray detected class I protostars show evidence for significant variability; the data suggest at least four flare-like events on these objects. This relatively high level of variability in the X-ray emission from the class I protostars is in qualitative agreement with the result by Imanishi et al. (\\cite{Imanishi2001}), who found that the class I protostars in the ρ Ophiuchi dark cloud show a higher level of variability than that of more evolved class II and class III young stellar objects. This may support non-coronal X-ray emission mechanisms for class I protostars and is in agreement with the predictions of models that assume magnetic interactions between the protostar and its surrounding disk as a source of high-energy emission. We also find a strong variation (by a factor of ˜10) in the X-ray luminosity of the class II object EC 74 between the three observations, which may be explained by a long duration flare or by rotational modulation. Finally, we find no evidence for X-ray emission from the five class 0 protostars in the region.

Testing the variability of the proton-to-electron mass ratio from observations of methanol in the dark cloud core L1498

NASA Astrophysics Data System (ADS)

Daprà, M.; Henkel, C.; Levshakov, S. A.; Menten, K. M.; Muller, S.; Bethlem, H. L.; Leurini, S.; Lapinov, A. V.; Ubachs, W.

2017-12-01

The dependence of the proton-to-electron mass ratio, μ, on the local matter density was investigated using methanol emission in the dense dark cloud core L1498. Towards two different positions in L1498, five methanol transitions were detected and an extra line was tentatively detected at a lower confidence level in one of the positions. The observed centroid frequencies were then compared with their rest-frame frequencies derived from least-squares fitting to a large data set. Systematic effects, as the underlying methanol hyperfine structure and the Doppler tracking of the telescope, were investigated and their effects were included in the total error budget. The comparison between the observations and the rest-frame frequencies constrains potential μ variation at the level of Δμ/μ < 6 × 10-8, at a 3σ confidence level. For the dark cloud, we determine a total CH3OH (A+E) beam averaged column density of ∼3-4 × 1012 cm-2 (within roughly a factor of two), an E- to A-type methanol column density ratio of N(A-CH3OH)/N(E-CH3OH) ∼1.00 ± 0.15, a density of n(H2) = 3 × 105 cm-3 (again within a factor of two) and a kinetic temperature of Tkin = 6 ± 1 K. In a kinetic model including the line intensities observed for the methanol lines, the n(H2) density is higher and the temperature is lower than that derived in previous studies based on different molecular species; the intensity of the 10 → 1-1 E line strength is not well reproduced.

Lightning-produced Carbon Species in the Atmosphere of Saturn

NASA Astrophysics Data System (ADS)

Delitsky, Mona; Baines, K. H.

2010-10-01

Recent studies by Baines et al (2009) indicate that thunderstorm-associated clouds on Saturn are spectrally dark from 0.7 to 4 um, darker than regular clouds. This darkening is found to be consistent with the presence of particles of elemental carbon, such as in the form of soot particles mixed in with spectrally bright condensates. This carbon is thought to be generated by lightning-induced dissociation of methane. Lightning on Saturn will input large amounts of energy to a narrow column of atmosphere and generate products at high energies such as radicals and ions. After the column cools down, the new chemical species recombine and are frozen into a new chemical equilibrium. Experimental studies in the literature of reactions of methane and other gases in plasma discharges (which simulate lightning) indicate that, even with high ratios of hydrogen/methane, the elemental carbon obtained will form solid dark particles that persist and have a very high C/H ratio. Basically, they are mostly pure carbon, in the form of soot, amorphous carbon, graphite, graphene, polycyclic aromatic hydrocarbons, carbon black, carbon onions, etc. Hydrogen will act as a sealant onto the particles and attach to dangling bonds on their growing surfaces. Even in experiments to form the most crystalline allotrope of carbon, that is, diamond, the presence of hydrogen does not inhibit diamond formation, even at the low pressures in the atmospheres of the Jovian planets or in the interstellar medium (Allamandola et al 1991). Therefore, some form of elemental carbon is likely produced in Saturnian storm clouds and may occur as dark particles of either amorphous carbon, PAHs or crystalline carbon in a form such as graphite. ..Refs: Baines et al., PSS 57, 1650-1658 (2009) ; Allamandola et al., Meteoritics 26, 313 (1991).

Assessing the Time Variability of Jupiter's Tropospheric Properties from 1996 to 2011

NASA Technical Reports Server (NTRS)

Orton, G. S.; Fletcher, L. N.; Yanamandra-Fisher, P. A.; Simon-Miller, A. A.; Greco, J.; Wakefield, L.

2012-01-01

We acquired and analyzed mid-infrared images of Jupiter's disk at selected wavelengths from NASA's Infrared Telescope Facility (IRTF) from 1996 to 2011, including a period of large-scale changes of cloud color and albedo. We derived the 100-300 mbar temperature structure, together with tracers of vertical motion: the thickness of a 600- mbar cloud layer, the 300-mbar abundance of the condensable gas NH3, and the 400- mbar para- vs. ortho-H2 ratio. The biggest visual change was detected in the normally dark South Equatorial Belt (SEB) that 'faded' to a light color in 2010, during which both cloud thickness and NH3 abundance rose; both returned to their pre-fade levels in 2011, as the SEB regained its normal dark color. The cloud thickness in Jupiter's North Temperate Belt (NTB) increased in 2002, coincident with its visible brightening, and its NH3 abundance spiked in 2002-2003. Jupiter's Equatorial Zone (EZ), a region marked by more subtle but widespread color and albedo change, showed high cloud thickness variability between 2007 and 2009. In Jupiter's North Equatorial Belt (NEB), the cloud thickened in 2005, then slowly decreased to a minimum value in 2010-2011. No temperature variations were associated with any of these changes, but we discovered temperature oscillations of approx.2-4 K in all regions, with 4- or 8-year periods and phasing that was dissimilar in the different regions. There was also no detectable change in the para- vs. ortho-H2 ratio over time, leading to the possibility that it is driven from much deeper atmospheric levels and may be time-invariant. Our future work will continue to survey the variability of these properties through the Juno mission, which arrives at Jupiter in 2016, and to connect these observations with those made using raster-scanned images from 1980 to 1993 (Orton et al. 1996 Science 265, 625).

Clumpy filaments of the Chamaeleon I cloud: C18O mapping with the SEST

NASA Astrophysics Data System (ADS)

Haikala, L. K.; Harju, J.; Mattila, K.; Toriseva, M.

2005-02-01

The Chamaeleon I dark cloud (Cha I) has been mapped in C18O with an angular resolution of 1 arcmin using the SEST telescope. The large scale structures previously observed with lower spatial resolution in the cloud turn into a network of clumpy filaments. The automatic Clumpfind routine developed by \\cite{williams1994} is used to identify individual clumps in a consistent way. Altogether 71 clumps were found and the total mass of these clumps is 230 M⊙. The dense ``cores'' detected with the NANTEN telescope (\\cite{mizuno1999}) and the very cold cores detected in the ISOPHOT serendipity survey (\\cite{toth2000}) form parts of these filaments but decompose into numerous ``clumps''. The filaments are preferentially oriented at right angles to the large-scale magnetic field in the region. We discuss the cloud structure, the physical characteristics of the clumps and the distribution of young stars. The observed clump mass spectrum is compared with the predictions of the turbulent fragmentation model of \\cite{padoan2002}. Agreement is found if fragmentation has been driven by very large-scale hypersonic turbulence, and if by now it has had time to dissipate into modestly supersonic turbulence in the interclump gas. According to numerical simulations, large-scale turbulence should have resulted in filamentary structures as seen in Cha I. The well-oriented magnetic field does not, however, support this picture, but suggests magnetically steered large-scale collapse. The origin of filaments and clumps in Cha I is thus controversial. A possible solution is that the characterization of the driving turbulence fails and that in fact different processes have been effective on small and large scales in this cloud. Based on observations collected at the European Southern Observatory, La Silla, Chile. FITS files are only available in electronic form at http://www.edpsciences.org

THE DARKEST SHADOWS: DEEP MID-INFRARED EXTINCTION MAPPING OF A MASSIVE PROTOCLUSTER

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butler, Michael J.; Tan, Jonathan C.; Kainulainen, Jouni

We use deep 8 μm Spitzer-IRAC imaging of massive Infrared Dark Cloud (IRDC) G028.37+00.07 to construct a mid-infrared (MIR) extinction map that probes mass surface densities up to Σ ∼ 1 g cm{sup –2} (A{sub V} ∼ 200 mag), amongst the highest values yet probed by extinction mapping. Merging with an NIR extinction map of the region creates a high dynamic range map that reveals structures down to A{sub V} ∼ 1 mag. We utilize the map to: (1) measure a cloud mass ∼7 × 10{sup 4} M {sub ☉} within a radius of ∼8 pc. {sup 13}CO kinematics indicate thatmore » the cloud is gravitationally bound. It thus has the potential to form one of the most massive young star clusters known in the Galaxy. (2) Characterize the structures of 16 massive cores within the IRDC, finding they can be fit by singular polytropic spheres with ρ∝r{sup −k{sub ρ}} and k {sub ρ} = 1.3 ± 0.3. They have Σ-bar ≃0.1--0.4 g cm{sup −2}—relatively low values that, along with their measured cold temperatures, suggest that magnetic fields, rather than accretion-powered radiative heating, are important for controlling fragmentation of these cores. (3) Determine the Σ (equivalently column density or A{sub V} ) probability distribution function (PDF) for a region that is nearly complete for A{sub V} > 3 mag. The PDF is well fit by a single log-normal with mean A-bar {sub V}≃9 mag, high compared to other known clouds. It does not exhibit a separate high-end power law tail, which has been claimed to indicate the importance of self-gravity. However, we suggest that the PDF does result from a self-similar, self-gravitating hierarchy of structures present over a wide range of scales in the cloud.« less

Movie of High Clouds on Jupiter

NASA Technical Reports Server (NTRS)

2000-01-01

Jupiter's high-altitude clouds are seen in this brief movie made from seven frames taken by the narrow-angle camera of NASA's Cassini spacecraft. This is the first time a movie sequence of Jupiter has been made that illustrates the motions of the high-altitude clouds on a global scale.

The images were taken at a wavelength that is absorbed by methane, one chemical in Jupiter's lower clouds. So, dark areas are relatively free of high clouds, and the camera sees through to the methane in a lower level. Bright areas are places with high, thick clouds that shield the methane below.

Jupiter's equator and Great Red Spot are covered with high-altitude, hazy clouds.

The movie covers the time period between Oct. 1 and Oct. 5, 2000, latitudes from 50 degrees north to 50 degrees south, and a 100-degree sweep of longitude. Those factors were the same for a Cassini movie of cloud motions previously released (PIA02829), but that movie used frames taken through a blue filter, which showed deeper cloud levels and sharper detail. Features in this methane-filter movie appear more diffuse.

Among the nearly stationary features are the Red Spot and some bright ovals at mid-latitudes in both hemispheres. These are anticyclonic (counter-clockwise rotating) storms. They are bright in the methane band because of their high clouds associated with rising gas. They behave differently from terrestrial cyclones, which swirl in the opposite direction. The mechanism making the Red Spot and similar spots stable apparently has no similarity to the mechanism which feeds terrestrial cyclones.

Some small-scale features are fascinating because of their brightness fluctuations. Such fluctuations observed in the methane band are probably caused by strong vertical motions, which form clouds rapidly, as in Earth's thunderstorms. Near the upper left corner in this movie, a number of smaller clouds appear to circulate counterclockwise around a dark spot, and these clouds fluctuate in brightness, so they may be candidates for lightning storms.

A pattern of lighter areas between darker patches can be seen in the darkest band a little north of the bright equatorial region. This may be tied to a wave-like temperature variation across the planet. If confirmed, this would be the first time such large-scale stratospheric temperature waves have been visibly linked to variations in haze thickness.

Cassini is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini mission for NASA's Office of Space Science, Washington, D.C.

Probing Storm Activity on Jupiter

NASA Technical Reports Server (NTRS)

2007-01-01

Scientists assume Jupiter's clouds are composed primarily of ammonia, but only about 1% of the cloud area displays the characteristic spectral fingerprint of ammonia. This composite of infrared images taken by the New Horizons Linear Etalon Infrared Spectral Imager (LEISA) captures several eruptions of this relatively rare breed of ammonia cloud and follows the evolution of the clouds over two Jovian days. (One day on Jupiter is approximately 10 hours, which is how long it takes Jupiter to make one complete rotation about its axis.)

The New Horizons spacecraft was still closing in on the giant planet when it made these observations: Jupiter was 3.4 million kilometers (2.1 million miles) from the New Horizons spacecraft for the LEISA image taken at 19:35 Universal Time on February 26, 2007, and the distance decreased to 2.5 million kilometers (1.6 million miles) for the last image shown. LEISA's spatial resolution scale varied from approximately 210 kilometers (130 miles) for the first image to 160 kilometers (100 miles) for the last one.

New Horizons scientists originally targeted the region slightly northwest (up and to the left) of the Great Red Spot to search for these special ammonia clouds because that's where they were most easily seen during infrared spectral observations made by the Galileo spacecraft. But unlike the churning, turbulent cloud structures seen near the Great Red Spot during the Galileo era, this region has been quieting down during the past several months and was unusually tranquil when New Horizons passed by. Nevertheless, LEISA managed to find other regions of fresh, upwelling ammonia clouds, and the temporal evolution of one such region is displayed in this figure. In the first image, a fresh ammonia cloud (the blue region) sprouts from between white clouds and a dark elongated region. This blue cloud subsequently stretches along the white-dark border in the next two images.

These fresh ammonia clouds trace the strong upwelling of gases from the largely hidden depths of Jupiter to higher altitudes. Presumably, water is also being dragged up from below, and the subsequent condensation of that water, which is far more abundant than ammonia in Jupiter's atmosphere, into cloud droplets energizes the lower troposphere.

LEISA produces images at infrared wavelengths, which is heat radiation that cannot be sensed by the human eye. These 'false color' images were produced by putting images of Jupiter at wavelengths of 1.99 micrometers, 1.94 micrometers and 2.04 micrometers into the red, green and blue channels, respectively, of the image display. Ammonia has an absorption feature at 1.99 microns, and when the colors are combined in this way the fresh ammonia clouds take on a bluish hue.

Fire impacts on the cryosphere

NASA Astrophysics Data System (ADS)

Kehrwald, N. M.; Zennaro, P.; Skiles, M.; Barbante, C.

2015-12-01

Continental-scale smog clouds and massive boreal smoke plumes deposit dark particles on glaciers, darkening their surfaces and altering surface albedo. These atmospheric brown clouds are primarily comprised of both fossil fuel and biomass burning combustion products. Here, we examine the biomass burning contribution to aerosols trapped in the cryosphere through investigating the specific molecular marker levoglucosan (1,6-anhydro-β-D-glucopyranose) in ice cores. Levoglucosan is only produced by cellulose combustion, and therefore is an ideal comparison for multi-proxy investigations incorporating other markers with multiple sources. Wildfire combustion products are a major component of dark aerosols deposited on the Greenland ice sheet during the 2012 melt event. Levoglucosan concentrations that demonstrate the biomass burning contribution are similar to black carbon concentrations that record both fossil fuel and biomass burning during this same event. This similarity is especially important as levoglucosan and black carbon trends differ during the industrial era in the NEEM, Greenland ice core, demonstrating different contributions of fossil fuel and biomass burning to the Greenland ice sheet. These differences are also present in the EPICA Dome C Antarctic ice core. Low-latitude ice cores such as Kilimanjaro, Tanzania and Muztag, Tibet demonstrate that climate is still the primary control over fire activity in these regions, even with increased modern biomass burning and the possible impacts of atmospheric brown clouds.

Cloud Spirals and Outflow in Tropical Storm Katrina

NASA Technical Reports Server (NTRS)

2005-01-01

On Tuesday, August 30, 2005, NASA's Multi-angle Imaging SpectroRadiometer retrieved cloud-top heights and cloud-tracked wind velocities for Tropical Storm Katrina, as the center of the storm was situated over the Tennessee valley. At this time Katrina was weakening and no longer classified as a hurricane, and would soon become an extratropical depression. Measurements such as these can help atmospheric scientists compare results of computer-generated hurricane simulations with observed conditions, ultimately allowing them to better represent and understand physical processes occurring in hurricanes.

Because air currents are influenced by the Coriolis force (caused by the rotation of the Earth), Northern Hemisphere hurricanes are characterized by an inward counterclockwise (cyclonic) rotation towards the center. It is less widely known that, at high altitudes, outward-spreading bands of cloud rotate in a clockwise (anticyclonic) direction. The image on the left shows the retrieved cloud-tracked winds as red arrows superimposed across the natural color view from MISR's nadir (vertical-viewing) camera. Both the counter-clockwise motion for the lower-level storm clouds and the clockwise motion for the upper clouds are apparent in these images. The speeds for the clockwise upper level winds have typical values between 40 and 45 m/s (144-162 km/hr). The low level counterclockwise winds have typical values between 7 and 24 m/s (25-86 km/hr), weakening with distance from the storm center. The image on the right displays the cloud-top height retrievals. Areas where cloud heights could not be retrieved are shown in dark gray. Both the wind velocity vectors and the cloud-top height field were produced by automated computer recognition of displacements in spatial features within successive MISR images acquired at different view angles and at slightly different times.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously, viewing the entire globe between 82o north and 82o south latitude every nine days. This image covers an area of about 380 kilometers by 1970 kilometers. These data products were generated from a portion of the imagery acquired during Terra orbit 30324 and utilize data from blocks 55-68 within World Reference System-2 path 22.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Science Mission Directorate, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is managed for NASA by the California Institute of Technology.

ARC-1981-AC81-7065

NASA Image and Video Library

1981-08-23

Range : 2.3 million km. ( 1.4 million miles ) P-24067C This Voyager 2 photograph of Titan, a satellite of Saturn, shows some detail in the cloud systems. The southern hemisphere appears lighter in contrast, a well defined band is seen near the equator, and a dark collar is evident at the north pole. All these bands are associated with the cloud circulation in titan's atmosphere. The extended haze, composed of of sub-micron size particles, is seen clearly around the satellite's limb. This image was composed from blue, green, and violet frames.

View of the early morning launch of STS 41-G Challenger

NASA Image and Video Library

1984-10-05

View of the early morning launch of STS 41-G Challenger. The dark launch complex is illuminated by spotlights as the orbiter begins its ascent from the pad. The light is reflected off the clouds of smoke from the orbiter's engines.

Jupiter with Satellites Io and Europa

NASA Image and Video Library

1996-01-29

NASA's Voyager 1 took this photo of Jupiter and two of its satellites Io, left, and Europa on Feb. 13, 1979. Io is above Jupiter Great Red Spot; Europa is above Jupiter clouds. The poles are dark and reddish. http://photojournal.jpl.nasa.gov/catalog/PIA00144

History of Hubble Space Telescope (HST)

NASA Image and Video Library

1995-01-01

These eerie, dark, pillar-like structures are actually columns of cool interstellar hydrogen gas and dust that are also incubators for new stars. The pillars protrude from the interior wall of a dark molecular cloud like stalagmites from the floor of a cavern. They are part of the Eagle Nebula (also called M16), a nearby star-forming region 7,000 light-years away, in the constellation Serpens. The ultraviolet light from hot, massive, newborn stars is responsible for illuminating the convoluted surfaces of the columns and the ghostly streamers of gas boiling away from their surfaces, producing the dramatic visual effects that highlight the three-dimensional nature of the clouds. This image was taken on April 1, 1995 with the Hubble Space Telescope Wide Field Planetary Camera 2. The color image is constructed from three separate images taken in the light of emission from different types of atoms. Red shows emissions from singly-ionized sulfur atoms, green shows emissions from hydrogen, and blue shows light emitted by doubly-ionized oxygen atoms.

Jupiter's Colorful Cloud Belts

NASA Image and Video Library

2018-01-12

Colorful swirling cloud belts dominate Jupiter's southern hemisphere in this image captured by NASA's Juno spacecraft. Jupiter appears in this color-enhanced image as a tapestry of vibrant cloud bands and storms. The dark region in the far left is called the South Temperate Belt. Intersecting the belt is a ghost-like feature of slithering white clouds. This is the largest feature in Jupiter's low latitudes that's a cyclone (rotating with clockwise motion). This image was taken on Dec. 16, 2017 at 10:12 PST (1:12 p.m. EST), as Juno performed its tenth close flyby of Jupiter. At the time the image was taken, the spacecraft was about 8,453 miles (13,604 kilometers) from the tops of the clouds of the planet at a latitude of 27.9 degrees south. The spatial scale in this image is 5.6 miles/pixel (9.1 kilometers/pixel). Citizen scientist Kevin M. Gill processed this image using data from the JunoCam imager. https://photojournal.jpl.nasa.gov/catalog/PIA21974

Cold Water Vapor in the Barnard 5 Molecular Cloud

NASA Technical Reports Server (NTRS)

Wirstrom, E. S.; Charnley, S. B.; Persson, C. M.; Buckle, J. V.; Cordiner, M. A.; Takakuwa, S.

2014-01-01

After more than 30 yr of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds; however, there is only one region where cold ((is) approximately 10 K) water vapor has been detected-L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work-likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 110-101) at 556.9360 GHz toward two positions in the cold molecular cloud, Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

A new characterization of supercooled clouds below 10,000 feet AGL

NASA Technical Reports Server (NTRS)

Masters, C. O.

1985-01-01

Icing caused by supercooled clouds below 10,000 feet were characterized with a view toward a change in FAA standards for civil aircraft ice protection standards. Current techniques in cloud physics were employed.

High speed spectral measurements of IED detonation fireballs

NASA Astrophysics Data System (ADS)

Gordon, J. Motos; Spidell, Matthew T.; Pitz, Jeremey; Gross, Kevin C.; Perram, Glen P.

2010-04-01

Several homemade explosives (HMEs) were manufactured and detonated at a desert test facility. Visible and infrared signatures were collected using two Fourier transformspectrometers, two thermal imaging cameras, a radiometer, and a commercial digital video camera. Spectral emissions from the post-detonation combustion fireball were dominated by continuum radiation. The events were short-lived, decaying in total intensity by an order of magnitude within approximately 300ms after detonation. The HME detonation produced a dust cloud in the immediate area that surrounded and attenuated the emitted radiation from the fireball. Visible imagery revealed a dark particulate (soot) cloud within the larger surrounding dust cloud. The ejected dust clouds attenuated much of the radiation from the post-detonation combustion fireballs, thereby reducing the signal-to-noise ratio. The poor SNR at later times made it difficult to detect selective radiation from by-product gases on the time scale (~500ms) in which they have been observed in other HME detonations.

MTR BUILDING AND BALCONY FLOORS. CAMERA FACING EASTERLY. PHOTOGRAPHER DID ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

MTR BUILDING AND BALCONY FLOORS. CAMERA FACING EASTERLY. PHOTOGRAPHER DID NOT EXPLAIN DARK CLOUD. MTR WING WILL ATTACH TO GROUND FLOOR. INL NEGATIVE NO. 1567. Unknown Photographer, 2/28/1951 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

A survey of interstellar HI from L alpha absorption measurements 2

NASA Technical Reports Server (NTRS)

Bohlin, R. C.; Savage, B. D.; Drake, J. F.

1977-01-01

The Copernicus satellite surveyed the spectral region near L alpha to obtain column densities of interstellar HI toward 100 stars. The distance to 10 stars exceeds 2 kpc and 34 stars lie beyond 1 kpc. Stars with color excess E(B-V) up to 0.5 mag are observed. The value of the mean ratio of total neutral hydrogen to color excess was found to equal 5.8 x 10 to the 21st power atoms per (sq cm x mag). For stars with accurate E(B-V), the deviations from this mean are generally less than a factor of 1.5. A notable exception is the dark cloud star, rho Oph. A reduction in visual reddening efficiency for the grains that are larger than normal in the rho Oph dark cloud probably explains this result. The conversion of atomic hydrogen into molecular form in dense clouds was observed in the gas to E(B-V) correlation plots. The best estimate for the mean total gas density for clouds and the intercloud medium, as a whole, in the solar neighborhood and in the plane of the galaxy is 1.15 atoms per cu. cm; those for the atomic gas and molecular gas alone are 0.86 atoms per cu cm and 0.143 molecules per cu cm respectively. For the intercloud medium, where molecular hydrogen is a negligible fraction of the total gas, atomic gas density was found to equal 0.16 atoms per cu cm with a Gaussian scale height perpendicular to the plane of about 350 pc, as derived from high latitude stars.

Shallow cumulus rooted in photosynthesis

NASA Astrophysics Data System (ADS)

Vila-Guerau Arellano, J.; Ouwersloot, H.; Horn, G.; Sikma, M.; Jacobs, C. M.; Baldocchi, D.

2014-12-01

We investigate the interaction between plant evapotranspiration, controlled by photosynthesis (for a low vegetation cover by C3 and C4 grasses), and the moist thermals that are responsible for the formation and development of shallow cumulus clouds (SCu). We perform systematic numerical experiments at fine spatial scales using large-eddy simulations explicitly coupled to a plant-physiology model. To break down the complexity of the vegetation-atmospheric system at the diurnal scales, we design the following experiments with increasing complexity: (a) clouds that are transparent to radiation, (b) clouds that shade the surface from the incoming shortwave radiation and (c) plant stomata whose apertures react with an adjustment in time to cloud perturbations. The shading by SCu leads to a strong spatial variability in photosynthesis and the surface energy balance. As a result, experiment (b) simulates SCu that are characterized by less extreme and less skewed values of the liquid water path and cloud-base height. These findings are corroborated by the calculation of characteristics lengths scales of the thermals and clouds using autocorrelation and spectral analysis methods. We find that experiments (a) and (b) are characterized by similar cloud cover evolution, but different cloud population characteristics. Experiment (b), including cloud shading, is characterized by smaller clouds, but closer to each other. By performing a sensitivity analysis on the exchange of water vapor and carbon dioxide at the canopy level, we show that the larger water-use efficiency of C4 grass leads to two opposing effects that directly influence boundary-layer clouds: the thermals below the clouds are more vigorous and deeper driven by a larger buoyancy surface flux (positive effect), but are characterized by less moisture content (negative effect). We conclude that under the investigated mid-latitude atmospheric and well-watered soil conditions, SCu over C4 grass fields is characterized by larger cloud cover and an enhanced liquid water path compared to C3 grass fields.

Infrared Image of Low Clouds on Venus

NASA Technical Reports Server (NTRS)

1993-01-01

This false-color image is a near-infrared map of lower-level clouds on the night side of Venus, obtained by the Near Infrared Mapping Spectrometer aboard the Galileo spacecraft as it approached the planet's night side on February 10, 1990. Bright slivers of sunlit high clouds are visible above and below the dark, glowing hemisphere. The spacecraft is about 100,000 kilometers (60,000 miles) above the planet. An infrared wavelength of 2.3 microns (about three times the longest wavelength visible to the human eye) was used. The map shows the turbulent, cloudy middle atmosphere some 50-55 kilometers (30- 33 miles) above the surface, 10-16 kilometers or 6-10 miles below the visible cloudtops. The red color represents the radiant heat from the lower atmosphere (about 400 degrees Fahrenheit) shining through the sulfuric acid clouds, which appear as much as 10 times darker than the bright gaps between clouds. This cloud layer is at about -30 degrees Fahrenheit, at a pressure about 1/2 Earth's surface atmospheric pressure. Near the equator, the clouds appear fluffy and blocky; farther north, they are stretched out into East-West filaments by winds estimated at more than 150 mph, while the poles are capped by thick clouds at this altitude.

Spatial and Temporal Distribution of Clouds as Observed by MODIS Onboard the Terra and Aqua Satellites

NASA Technical Reports Server (NTRS)

King, Michael D.; Platnick, Steven; Menzel, Paul; Ackerman, Steven A.

2006-01-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) was developed by NASA and launched onboard the Terra spacecraft on December 18,1999 and Aqua spacecraft on May 4, 2002. It achieved its final orbit and began Earth observations on February 24,2000 for Terra and June 24,2002 for Aqua. A comprehensive set of remote sensing algorithms for cloud masking and the retrieval of cloud physical and optical properties has been developed by members of the MODIS atmosphere science team. The archived products from these algorithms have applications in climate change studies, climate modeling, numerical weather prediction, and fundamental atmospheric research. In addition to an extensive cloud mask, products include cloud-top properties (temperature, pressure, effective emissivity), cloud thermodynamic phase, cloud optical and microphysical parameters (optical thickness, effective particle radius, water path), as well as derived statistics. Over the last year, extensive improvements and enhancements in the global cloud products have been implemented, and reprocessing of all MODIS data on Terra has commenced since first light in February 2000. In the cloud mask algorithm, the most extensive improvements were in distinguishing clouds at nighttime, including the challenging polar darkness regions of the world. Additional improvements have been made to properly distinguish sunglint from clouds in the tropical ocean regions, and to improve the identification of clouds from snow during daytime in Polar Regions. We will show global monthly mean cloud fraction for both Terra and Aqua, and show how similar the global daytime cloud fraction is from these morning and afternoon orbits, respectively. We will also show the zonal distribution of cloud fraction over land and ocean regions for both Terra and Aqua, and show the time series of global cloud fraction from July 2002 through June 2006.

Static structure of chameleon dark matter as an explanation of dwarf spheroidal galaxy cores

NASA Astrophysics Data System (ADS)

Chanda, Prolay Krishna; Das, Subinoy

2017-04-01

We propose a novel mechanism that explains the cored dark matter density profile in recently observed dark matter rich dwarf spheroidal galaxies. In our scenario, dark matter particle mass decreases gradually as a function of distance towards the center of a dwarf galaxy due to its interaction with a chameleon scalar. At closer distance towards the Galactic center the strength of attractive scalar fifth force becomes much stronger than gravity and is balanced by the Fermi pressure of the dark matter cloud; thus, an equilibrium static configuration of the dark matter halo is obtained. Like the case of soliton star or fermion Q-star, the stability of the dark matter halo is obtained as the scalar achieves a static profile and reaches an asymptotic value away from the Galactic center. For simple scalar-dark matter interaction and quadratic scalar self-interaction potential, we show that dark matter behaves exactly like cold dark matter (CDM) beyond a few kpc away from the Galactic center but at closer distance it becomes lighter and Fermi pressure cannot be ignored anymore. Using Thomas-Fermi approximation, we numerically solve the radial static profile of the scalar field, fermion mass and dark matter energy density as a function of distance. We find that for fifth force mediated by an ultralight scalar, it is possible to obtain a flattened dark matter density profile towards the Galactic center. In our scenario, the fifth force can be neglected at distance r ≥1 kpc from the Galactic center and dark matter can be simply treated as heavy nonrelativistic particles beyond this distance, thus reproducing the success of CDM at large scales.

Designing Payloads

ERIC Educational Resources Information Center

Kehr, Linda

2009-01-01

Imagine soaring in the Earth's atmosphere to near the edge of space. Is there air to breathe? Is it dark? Are there clouds? What about air pressure? Fifth-grade students from Ferguson Elementary in Klamath Falls, Oregon, were wondering these questions as they participated in "To the Edge of Space," an exciting, yearlong collaborative…

KSC-02pd0996

NASA Image and Video Library

2002-06-18

KENNEDY SPACE CENTER, FLA. - Dark, rain-filled clouds blanket the sky over the Vehicle Assembly Building and Launch Control Center, bringing thunder and heavy rain to the area. This type of weather convinced flight control managers to wave off the two scheduled landing attempts at KSC for Endeavour, returning from mission STS-111

X ray absorption by dark nebulae (HEAO-2 guest investigator program)

NASA Technical Reports Server (NTRS)

Sanders, W. T.

1991-01-01

A study is described of data obtained from the Imaging Proportional Counter (IPC) x ray detector aboard the HEAO-2 satellite (Einstein Observatory). The research project involved a search for absorption of diffuse low energy x ray background emission by galactic dark nebulae. The commonly accepted picture that the bulk of the C band emission originates locally, closer that a few hundred parsec, and the bulk of the M band emission originates farther away than a few hundred parsec, was tested. The idea was to look for evidence of absorption of the diffuse background radiation by nearby interstellar clouds.

Extensive Coronal Hole

NASA Image and Video Library

2017-09-02

A large coronal hole has been spewing solar wind particles in the general direction of Earth over the past few days (Aug. 31- Sept. 1, 2017). It is the extensive dark area that stretches from the top of the sun and angles down to the right. Coronal holes are areas of open magnetic field, which allow charge particles to escape into space. They appear dark in certain wavelengths of extreme ultraviolet light such as shown here. These clouds of particles can cause aurora to appear, particularly in higher latitude regions. Movies are available at https://photojournal.jpl.nasa.gov/catalog/PIA21942

MEST-Tyche will take its dark comets to impact our solar system in 20 years

NASA Astrophysics Data System (ADS)

Cao, Dayong

2012-03-01

Tyche has many dark comets like Oort cloud. It went near our solar system every 25-27 million years. It could take its dark comets to impact our earth. Tyche and its dark comet absorb light like a dark light which is a negative black-body radiation. (1) Eddν=-c1dνd^3dνe^c2dνd/Td-1. Among it, Ed: the dark energy, νd: the dark frequence, Td: the dark temperature, c1d,c2d: the constant. So when they go near us, their wave has a against Doppler redshift as 0.000165. And they will inbreak solar system at the rate of 99AU/y, from the distance of 1,500AU and in 20 years. It can cause the broken ozonosphere, the lithosphere to crack, many big activity volcanic and the continental drift. And it can darked the light and colded the climate to the Great Ice Age. Not only it will break our environment by a special ``nuclear explosion'' under low temperature, but also the dark life will change the Genetic code of our life. So it will kill many lives and will produce new life. So it could trigger the Mass Extinction. We can bulid up a new pair of nuclear reactor (include dark nuclear energy) to drive a universal craft and can change the orbit of our earth for evading the impaction. We need a new life-information technology to develop our life and consciousness.

Cloudy Earth

NASA Image and Video Library

2015-05-08

Decades of satellite observations and astronaut photographs show that clouds dominate space-based views of Earth. One study based on nearly a decade of satellite data estimated that about 67 percent of Earth’s surface is typically covered by clouds. This is especially the case over the oceans, where other research shows less than 10 percent of the sky is completely clear of clouds at any one time. Over land, 30 percent of skies are completely cloud free. Earth’s cloudy nature is unmistakable in this global cloud fraction map, based on data collected by the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite. While MODIS collects enough data to make a new global map of cloudiness every day, this version of the map shows an average of all of the satellite’s cloud observations between July 2002 and April 2015. Colors range from dark blue (no clouds) to light blue (some clouds) to white (frequent clouds). Read more here: 1.usa.gov/1P6lbMU Credit: NASA Earth Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Enhanced ClO from 10 to 12 km Near the Winter Polar Tropopause During SOLVE/THESEO-2000

NASA Technical Reports Server (NTRS)

Toohey, Darin W.; Thornton, Brett F.; Avery, Melody A.; Avallone, Linnea M.; Harder, Hartwig; Martinez, Monica; Simpas, James B.; Brune, William H.

2002-01-01

Abundances of chlorine oxide have been measured in situ near the tropopause from the NASA DC-8 aircraft during the SOLVE/THESEO-2000 campaign. Significant abundances, averaging 15-20 parts per trillion, were observed throughout the lowermost stratosphere at high latitudes during winter. Mixing ratios of ClO generally increased with increasing ozone (the latter an indicator of stratospheric air) as has been observed at other latitudes and seasons. However, the ratio of ClO to inorganic chlorine ([ClO]/[Cl(sub y)]) was found to be largest in air characterized by low abundances of ozone (approximately l00-250). It was within this range of ozone values that cirrus clouds were also observed occasionally throughout the measurement period, although distinct enhancements of ClO were not commonly observed directly within cirrus clouds. Elevated abundances of ClO were also apparently observed in polar darkness. However, we attribute these measurements to OClO, a species that can also be detected by the DC-8 instrument under the conditions encountered during SOLVE/THESEO-2000. Using a photochemical box model constrained by daytime abundances of ClO, we infer that BrO mixing ratios in this region were approximately 2-4 ppt, consistent with previous measurements from balloon-borne remote sensors.

A Ten-Year Global Record of Absorbing Aerosols Above Clouds from OMI's Near-UV Observations

NASA Technical Reports Server (NTRS)

Jethva, Hiren; Torres, Omar; Ahn, Changwoo

2016-01-01

Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes associated with the aerosol-cloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regional of the world. Contrary to the cloud-free scenario over dark surface, for which aerosols are known to produce a net cooling effect (negative radiative forcing) on climate, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud depends directly on the aerosol loading, microphysical-optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of optical depth of absorbing aerosols above clouds retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. The presence of absorbing aerosols above cloud reduces the upwelling radiation reflected by cloud and produces a strong 'color ratio' effect in the near-UV region, which can be unambiguously detected in the OMI measurements. Physically based on this effect, the OMACA algorithm retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. The algorithm architecture and results from a ten-year global record including global climatology of frequency of occurrence and above-cloud aerosol optical depth, and a discussion on related future field campaigns are presented.

Above-Cloud Precipitable Water Retrievals using the MODIS 0.94 micron Band with Applications for Multi-Layer Cloud Detection

NASA Technical Reports Server (NTRS)

Platnick, S.; Wind, G.

2004-01-01

In order to perform satellite retrievals of cloud properties, it is important to account for the effect of the above-cloud atmosphere on the observations. The solar bands used in the operational MODIS Terra and Aqua cloud optical and microphysical algorithms (visible, NIR, and SWIR spectral windows) are primarily affected by water vapor, and to a lesser extent by well-mixed gases. For water vapor, the above-cloud column amount, or precipitable water, provides adequate information for an atmospheric correction; details of the vertical vapor distribution are not typically necessary for the level of correction required. Cloud-top pressure has a secondary effect due to pressure broadening influences. For well- mixed gases, cloud-top pressure is also required for estimates of above-cloud abundances. We present a method for obtaining above-cloud precipitable water over dark Ocean surfaces using the MODIS 0.94 pm vapor absorption band. The retrieval includes an iterative procedure for establishing cloud-top temperature and pressure, and is useful for both single layer water and ice clouds. Knowledge of cloud thermodynamic phase is fundamental in retrieving cloud optical and microphysical properties. However, in cases of optically thin cirrus overlapping lower water clouds, the concept of a single unique phase is ill- defined and depends, at least, on the spectral region of interest. We will present a method for multi-layer and multi-phase cloud detection which uses above-cloud precipitable water retrievals along with several existing MODIS operational cloud products (cloud-top pressure derived from a C02 slicing algorithm, IR and SWIR phase retrievals). Results are catagorized by whether the radiative signature in the MODIS solar bands is primarily that of a water cloud with ice cloud contamination, or visa-versa. Examples in polar and mid-latitude regions will be shown.

Update on the NASA Glenn Propulsion Systems Lab Ice Crystal Cloud Characterization (2015, 2016)

NASA Technical Reports Server (NTRS)

Van Zante, Judith; Bencic, Timothy; Ratvasky, Thomas

2016-01-01

NASA Glenn's Propulsion Systems Lab, an altitude engine test facility, was outfitted with a spray system to generate ice crystals in 2011. Turbine engines and driven rigs can experience ice crystal icing at flight altitudes, temperatures and Mach numbers. To support these tests, four ice crystal characterizations have been conducted in two different facility configurations. In addition, super-cooled liquid and mixed phase clouds have also been generated. This paper represents a work in progress. It will describe some of the 11-parameter calibration space, and how those parameters interact with each other, the instrumentation used to characterize the cloud and present a sample of the cloud characterization results.

On The Missing Dwarf Problem In Clusters And Around The Nearby Galaxy M33

NASA Astrophysics Data System (ADS)

Keenan, Olivia Charlotte

2017-08-01

This thesis explores possible solutions to the dwarf galaxy problem. This is a discrepancy between the number of dwarf galaxies we observe, and the number predicted from cosmological computer simulations. Simulations predict around ten times more dwarf galaxy satellites than are currently observed. I have investigated two possible solutions: dark galaxies and the low surface brightness universe. Dark galaxies are dark matter halos which contain gas, but few or no stars, hence are optically dark. As part of the Arecibo Galaxy Environment Survey I surveyed the neutral hydrogen gas around the nearby galaxy M33. I found 32 gas clouds, 11 of which are new detections. Amongst these there was one particularly interesting cloud. AGESM33-32 is ring shaped and larger than M33 itself, if at the same distance. It has a velocity width which is similar to the velocity dispersion of gas in a disk galaxy, as well as having a clear velocity gradient across it which may be due to rotation. The fact that it also currently has no observed associated stars means it is a dark galaxy candidate. Optically, dwarf galaxies may be out there, but too faint for us to detect. This means that with newer, deeper, images we may be able to unveil a large, low surface brightness, population of dwarf galaxies. However, the question remains as to how these can be distinguished from background galaxies. I have used Next Generation Virgo Survey (NGVS) data to carry out photometry on 852 Virgo galaxies in four bands. I also measured the photometric properties of galaxies on a background (non-cluster) NGVS frame. I discovered that a combination of colour, magnitude and surface brightness information could be used to identify cluster dwarf galaxies from background field galaxies. The most effective method is to use the surface brightness-magnitude relation.

ARC-1989-A89-7007

NASA Image and Video Library

1989-08-21

The bright cirrus-like clouds of Neptune change rapidly, often forming and dissipation over periods of several to tens of hours. In this sequence spanning two rotations of Neptune (about 36 hours) Voyager 2 observed cloud evolution in the region around the Great Dark Spot (GDS) at an effective resolution of about 100 km (62 miles) per pixel. The surprisingly rapid changes which occur over the 18 hours separating each panel shows that in this region Neptune's weather is perhaps as dynamic and variable as that of the Earth. However, the scale is immense by our standards--the Earth and the GDS are of similar size -- and in Neptune's frigid atmosphere, where temperatures are as low as 55 degree Kelvin (-360F), the cirrus clouds are composed of frozen methane rather than Earth's crystalse of water ice.

Radiative Transfer in a Translucent Cloud Illuminated by an Extended Background Source

NASA Astrophysics Data System (ADS)

Biganzoli, Davide; Potenza, Marco A. C.; Robberto, Massimo

2017-05-01

We discuss the radiative transfer theory for translucent clouds illuminated by an extended background source. First, we derive a rigorous solution based on the assumption that multiple scatterings produce an isotropic flux. Then we derive a more manageable analytic approximation showing that it nicely matches the results of the rigorous approach. To validate our model, we compare our predictions with accurate laboratory measurements for various types of well-characterized grains, including purely dielectric and strongly absorbing materials representative of astronomical icy and metallic grains, respectively, finding excellent agreement without the need to add free parameters. We use our model to explore the behavior of an astrophysical cloud illuminated by a diffuse source with dust grains having parameters typical of the classic ISM grains of Draine & Lee and protoplanetary disks, with an application to the dark silhouette disk 114-426 in Orion Nebula. We find that the scattering term modifies the transmitted radiation, both in terms of intensity (extinction) and shape (reddening) of the spectral distribution. In particular, for small optical thickness, our results show that scattering makes reddening almost negligible at visible wavelengths. Once the optical thickness increases enough and the probability of scattering events becomes close to or larger than 1, reddening becomes present but is appreciably modified with respect to the standard expression for line-of-sight absorption. Moreover, variations of the grain refractive index, in particular the amount of absorption, also play an important role in changing the shape of the spectral transmission curve, with dielectric grains showing the minimum amount of reddening.

Update on the NASA Glenn Propulsion Systems Lab Ice Crystal Cloud Characterization (2015)

NASA Technical Reports Server (NTRS)

Van Zante, Judith F.; Bencic, Timothy J.; Ratvasky, Thomas P.

2016-01-01

NASA Glenn's Propulsion Systems Lab (PSL), an altitude engine test facility, was outfitted with a spray system to generate ice crystals. The first ice crystal characterization test occurred in 2012. At PSL, turbine engines and driven rigs can experience ice crystal icing at flight altitudes, temperatures and Mach numbers. To support these tests, four ice crystal characterizations have been conducted in two different facility configurations. In addition, super-cooled liquid and mixed phase clouds have also been generated. This paper will discuss the recent learning from the previous two calibrations. It will describe some of the 12-parameter calibration space, and how those parameters interact with each other, the instrumentation used to characterize the cloud and present a sample of the cloud characterization results.

On the Surface Formation of NH3 and HNCO in Dark Molecular Clouds - Searching for Wöhler Synthesis in the Interstellar Medium

NASA Astrophysics Data System (ADS)

Fedoseev, Gleb; Lamberts, Thanja; Linnartz, Harold; Ioppolo, Sergio; Zhao, Dongfeng

Despite its potential to reveal the link between the formation of simple species and more complex molecules (e.g., amino acids), the nitrogen chemistry of the interstellar medium (ISM) is still poorly understood. Ammonia (NH _{3}) is one of the few nitrogen-bearing species that have been observed in interstellar ices toward young stellar objects (YSOs) and quiescent molecular clouds. The aim of the present work is to experimentally investigate surface formation routes of NH _{3} and HNCO through non-energetic surface reactions in interstellar ice analogues under fully controlled laboratory conditions and at astrochemically relevant cryogenic temperatures. This study focuses on the formation of NH _{3} and HNCO in CO-rich (non-polar) interstellar ices that simulate the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing start to become predominant. Our work confirms the surface formation of ammonia through the sequential addition of three hydrogen/deuterium atoms to a single nitrogen atom at low temperature. The H/D fractionation of the formed ammonia is also shown. Furthermore, we show the surface formation of solid HNCO through the interaction of CO molecules with NH radicals - one of the intermediates in the formation of solid NH _{3}. Finally, we discuss the implications of HNCO in astrobiology, as a possible starting point for the formation of more complex prebiotic species.

ARC-1989-A89-7058

NASA Image and Video Library

1989-08-24

Voyager II Imagery; Neptune. This bulls-eye view of Neptune's small dark spot (D2) was obtained by Voyager 2's narrow-angle camera , when Neptune was within 1.1 million km (680,000 miles) of the planet. The smallest structures that can be seen are 20 km (12 miles) across. This unplanned photograph was obtained when the infrared spectrograph was mapping the the highest-resolution view of the feature taken during the flyby. Banding surrounding the feature indicates unseen strong winds, while structues within the bright spot suggest both active upwelling of clouds and rotation about the center. A rotation rate has not yet been measured, but the v-shaped structure near the right edge of the bright area indicates that the spot rotates clockwise. Unlike the Great Red Spot on Jupiter, which rotates counterclockwise, if the D2 spot on Neptune rotates clockwise, the material will be descending in the dark oval region. The fact that infrared data will yield temperature information about the region above the clouds makes this observation especially valuable. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applicaitons. (JPL ref: P-34749 Voyager N-71) taken during the flyby. Banding surrounding the feature indicates unseen strong winds, while structures within the bright spot suggest both active upwelling of clouds and rotation about the center. A rotation rate has not yest been measured, but the Vv-sphped

Satellite and Surface Data Synergy for Developing a 3D Cloud Structure and Properties Characterization Over the ARM SGP. Stage 1: Cloud Amounts, Optical Depths, and Cloud Heights Reconciliation

NASA Technical Reports Server (NTRS)

Genkova, I.; Long, C. N.; Heck, P. W.; Minnis, P.

2003-01-01

One of the primary Atmospheric Radiation Measurement (ARM) Program objectives is to obtain measurements applicable to the development of models for better understanding of radiative processes in the atmosphere. We address this goal by building a three-dimensional (3D) characterization of the cloud structure and properties over the ARM Southern Great Plains (SGP). We take the approach of juxtaposing the cloud properties as retrieved from independent satellite and ground-based retrievals, and looking at the statistics of the cloud field properties. Once these retrievals are well understood, they will be used to populate the 3D characterization database. As a first step we determine the relationship between surface fractional sky cover and satellite viewing angle dependent cloud fraction (CF). We elaborate on the agreement intercomparing optical depth (OD) datasets from satellite and ground using available retrieval algorithms with relation to the CF, cloud height, multi-layer cloud presence, and solar zenith angle (SZA). For the SGP Central Facility, where output from the active remote sensing cloud layer (ARSCL) valueadded product (VAP) is available, we study the uncertainty of satellite estimated cloud heights and evaluate the impact of this uncertainty for radiative studies.

Ammonia Ice Clouds on Jupiter

NASA Technical Reports Server (NTRS)

2007-01-01

The top cloud layer on Jupiter is thought to consist of ammonia ice, but most of that ammonia 'hides' from spectrometers. It does not absorb light in the same way ammonia does. To many scientists, this implies that ammonia churned up from lower layers of the atmosphere 'ages' in some way after it condenses, possibly by being covered with a photochemically generated hydrocarbon mixture. The New Horizons Linear Etalon Imaging Spectral Array (LEISA), the half of the Ralph instrument that is able to 'see' in infrared wavelengths that are absorbed by ammonia ice, spotted these clouds and watched them evolve over five Jupiter days (about 40 Earth hours). In these images, spectroscopically identified fresh ammonia clouds are shown in bright blue. The largest cloud appeared as a localized source on day 1, intensified and broadened on day 2, became more diffuse on days 3 and 4, and disappeared on day 5. The diffusion seemed to follow the movement of a dark spot along the boundary of the oval region. Because the source of this ammonia lies deeper than the cloud, images like these can tell scientists much about the dynamics and heat conduction in Jupiter's lower atmosphere.

Boundary conditions for the paleoenvironment: Chemical and physical processes in the pre-solar nebula

NASA Technical Reports Server (NTRS)

Irvine, William M.; Schloerb, F. Peter

1987-01-01

Detailed study of the first interstellar hydrocarbon ring, cyclopropenylidene (C3H2), is continuing. The singly deuterated isotope of this molecule, C3HD, was observed in several cold interstellar clouds. The results of a large survey for C3H2 in galactic sources of various types will soon be completed. It appears that cyclopropenylidene is present in virtually all interstellar clouds of at least moderate density. In order to make the first determinations of the CO2/CO abundance ratio in interstellar sources, observations of protonated CO2 were pursued. The spectrum from 18.5 to 22 GHz for several interstellar clouds is being systematically measured. Particular attention is being given to the cold, dark clouds TMC-1 and L124N, which may be formation sites for solar mass stars. The phenomena of maser emission from molecules of methanol is being studied in certain interstellar clouds. A comparison of 1 millimeter continuum emission from dust with the column density of carbon monoxide as determined from the rare C(18)O isotope for 4 molecular clouds in the Galaxy is nearing completion. Papers published during the period of this report are listed.

The simulation of molecular clouds formation in the Milky Way

NASA Astrophysics Data System (ADS)

Khoperskov, S. A.; Vasiliev, E. O.; Sobolev, A. M.; Khoperskov, A. V.

2013-01-01

Using 3D hydrodynamic calculations we simulate formation of molecular clouds in the Galaxy. The simulations take into account molecular hydrogen chemical kinetics, cooling and heating processes. Comprehensive gravitational potential accounts for contributions from the stellar bulge, two- and four-armed spiral structure, stellar disc, dark halo and takes into account self-gravitation of the gaseous component. Gas clouds in our model form in the spiral arms due to shear and wiggle instabilities and turn into molecular clouds after t ≳ 100 Myr. At the times t ˜ 100-300 Myr the clouds form hierarchical structures and agglomerations with the sizes of 100 pc and greater. We analyse physical properties of the simulated clouds and find that synthetic statistical distributions like mass spectrum, `mass-size' relation and velocity dispersion are close to those observed in the Galaxy. The synthetic l-v (galactic longitude-radial velocity) diagram of the simulated molecular gas distribution resembles observed one and displays a structure with appearance similar to molecular ring of the Galaxy. Existence of this structure in our modelling can be explained by superposition of emission from the galactic bar and the spiral arms at ˜3-4 kpc.

San Jose, Costa Rica

NASA Technical Reports Server (NTRS)

2007-01-01

San Jose, capital city of Costa Rica, fills the valley between two steep mountain ranges. In this image made from data collected by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) instrument on NASA's Terra satellite, visible, shortwave, and near-infrared wavelengths of light that the sensor observed have been combined to produce a false-color version of the scene in which vegetation is red, urban areas are silvery gray, water is dark blue, and clouds are white. The image was captured on February 8, 2007. San Jose is in the center of the image. The Rio Torres winds through downtown San Jose. Cartago, the much smaller colonial capital, sits in the lower right corner, while the city of Alajuela appears across the river, northwest of San Jose. The cities' manmade surfaces contrast sharply with the lushly vegetated landscape surrounding the city. Greenhouses are common in the region, and their glass roofs may be the brilliant white spots around the outer edges the cities. The long, straight runway of the Tobias Bolanos International Airport is visible as a dark line southeast of Alajuela. The landscape around the two cities shown here is rugged. Steep mountain peaks cast dark shadows across their leeward slopes. Patches of dark red vegetation on the mountains north of San Jose may be rainforest. Coffee plantations also cover the slopes of the mountains around the city. February is the dry season in Costa Rica. During the rainy season, from about April to November, clouds usually block the satellite's view of this tropical location. NASA image created by Jesse Allen, using data provided courtesy of Asaf Ullah and Tim Gubbels, SERVIR project.

Earth Observation

NASA Image and Video Library

2011-08-02

ISS028-E-020276 (2 Aug. 2011) --- This photograph of polar mesospheric clouds was acquired at an altitude of just over 202 nautical miles (about 322 kilometers) in the evening hours (03:19:54 Greenwich Mean Time) on Aug. 2, 2011, as the International Space Station was passing over the English Channel. The nadir coordinates of the station were 49.1 degrees north latitude and 5.5 degrees west longitude. Polar mesospheric clouds (also known as noctilucent, or ?night-shining? clouds) are transient, upper atmospheric phenomena that are usually observed in the summer months at high latitudes (greater than 50 degrees) of both the Northern and Southern Hemispheres. They appear bright and cloudlike while in deep twilight. They are illuminated by sunlight when the lower layers of the atmosphere are in the darkness of Earth?s shadow. The horizon of Earth appears at the bottom of the image, with some layers of the lower atmosphere already illuminated by the rising sun. The higher, bluish-colored clouds look much like wispy cirrus clouds, which can be found as high as 60,000 feet (18 kilometers) in the atmosphere. However noctilucent clouds, as seen here, are observed in the mesosphere at altitudes of 250,000 to 280,000 feet (about 76 to 85 kilometers). Astronaut observations of polar mesospheric clouds over northern Europe in the summer are not uncommon.

Where were you when the sun went out?

NASA Astrophysics Data System (ADS)

1999-11-01

The total solar eclipse of 1999 will no doubt have left an impression on millions of people. Members of the Editorial Board for Physics Education share some of their feelings and memories of the event. Simon Carson writes: My children and I were at home in Driffield, East Yorkshire, on said day. Out we went in the back garden with our big refracting telescope and eight-year-old James's Early Learning Centre telescope (plastic, cheap and jolly good for the price!) and our special glasses. Come the witching hour, we trained our telescopes, with white card behind them, on the Sun. Gradually we saw the Moon's shadow edge across the Sun. As James said, `It went cold and dark and the picture on the card looked like a thin glowing line'. It was surprisingly impressive given the distance from totality. The most remarkable effect was the drop in temperature and the fact that our bright sunny mid-morning in August became more like a chilly autumn dusk. Katharine, age 6, remembers performing cartwheels in the dark! Bob Kibble writes: My partner Jean, and I, holidayed in Trier, Germany, just outside the path of totality. On the big day we awoke to rain and clouds, as did most of central Europe. The trusty motorbike, laden with a picnic and photographic gear, took us south into France. We stopped just outside Metz at a service station along with dozens of like-minded but damp and dismal onlookers. Cloud cover was layered with darker rain-bearing cloud drifting at the lowest level. Mobile phone links confirmed that it was raining in Paris, Dijon and Munich. We decided to settle for the event - at least there was a shop and `facilities'. We were joined by a group of bikers, two of whom had travelled 480 km from Denmark that very morning. The shifting cloud cover offered tantalising glimpses of the partial phase as the light level fell. There was nothing we could do but put our faith in the weather. Now you see it, now you don't. As darkness fell and the temperature likewise the strangest thing happened. Just as totality approached the cloud above seemed to thin out, enabling us to see the whole event. We watched in amazement as the last thin bright patch disappeared. There were cheers, horns sounding and applause as the full spectacle was revealed before us - two full minutes of totality. I took photographs through a 600 mm mirror lens, cursing the instability of my flimsy tripod but able to see prominences in some detail. Despite my forward planning the 36 exposure film ran out just as last contact appeared. The excitement of the event prevented any serious, logical and measured photography. I just fired away. As soon as last contact had passed, the clouds reformed and neither Sun nor Moon were seen again until later that afternoon. We had witnessed what is apparently known as the `Red Sea effect' and is caused by the localized cooling due to the umbral shadow `punching' a hole in the cloud cover. The event left us speechless, moved and tearful. Words seemed so inadequate. I had given a number of presentations leading up to this event but nothing could have prepared me for the experience of totality. Darkness came upon us so quickly that we were taken by surprise. Looking up above our heads meant that few of us had noticed the horizon. Friends who were not so lucky with the weather remarked on the beauty of the illuminated horizon. For us it was the nearest thing to a miracle we had ever seen. Roll on 2001! Helen Reynolds writes: My memory of the eclipse will be of lying in a field on a cliff in France staring out to sea. No-one prepares you for the moment of totality; the hairs on the back of your neck literally stand on end. This is not normal. The speed with which darkness falls is frightening. It is inconceivable that minutes ago there was 95%+ coverage of the Sun - the Moon seemed to have no effect and then, suddenly in all senses of the word, darkness literally falls from the sky. The sounds are unreal and the colours are nothing you have seen before. The calls and cries of the children are muted, cameras click but the sound is dulled. There seem to be bands of colours falling from the sky onto the horizon, pinks and a hint of that colour we call indigo. For once you do not try to work out why this is happening; there is so little time to soak up the moment before it is gone. The fastest two minutes of my life to date. Jill Membrey writes: I have to admit to a somewhat disappointing Eclipse experience! I had made the decision early on to travel down to Plymouth from Bristol, so as to be in the path of totality and share the event `at home' with my mother. The morning of 11 August dawned bright and we were eager with anticipation, but sadly the cloud thickened and deepened as the morning progressed. By 11 am the cloud cover was so thick that there was no indication of the Sun's position at all, let alone any of the phases. We had to resort to the television screen to find out what was actually going on. It was also difficult to tell whether the darkness was due to the normal Plymouth weather or to some other factor. However, by 11.12 it was sufficiently dark outside for us to trigger the security light when we went into the garden! I was quite amazed at how quickly the sky lightened afterwards, although we still never got a glimpse of the Sun. In fact I never saw any sunshine until I returned to Bristol that evening, and then heard my husband gloat over his experience of the (almost) total eclipse witnessed between the broken clouds over his office. Just typical! I knew I should have stayed in Bristol... Jonathan Allday writes: I went with my wife Carolyn on a package tour to Paris to see the eclipse. On the day itself we were taken by coach to a park just outside Rheims to see the totality. Apparently our tour company shifted 6000 people that day. As we were making our way to the park the clouds would open occasionally to give us a view of the partial phase. The traffic was heavy and we were far from sure that we would make it in time. I was fretting and weighing up trying to convince the driver to stop at any point to let us out at the moment of totality. However, we made it and the park was a wonderful vantage point. I will never forget the quiet that came over this huge park with thousands of people in it as totality came. I remember looking across the lake and seeing camera flashes going off as the darkness descended. Periodic announcements over the PA system kept track of what was happening and sensibly gave warnings about how to view the eclipse. I had sworn that I would not take any pictures, figuring that by the time I had sorted out exposures the eclipse would be over. As it turned out the clouds were light so that the totality could be viewed through them and picture taking was easy. Consequently I was lying on my back staring through the camera lens and firing off photographs when the orange tinted shadow edge arrived over the hills. I missed it. Totality itself was glimpsed along with the corona through hazy clouds but that was a wonderful sight. Conclusions - next time I want to see it with no clouds. Liz Whitelegg writes: I'd been preparing for eclipse day for a whole 12 months by reading articles and going to talks about the eclipse, buying the special glasses at the ASE annual meeting, talking to eclipse experts etc. I even secured accommodation in some `friends' holiday home in Cornwall by lending a hand in the restoration process the year before! Having spent the very same week in Cornwall in '98 when it was hot and sunny all week, I was convinced that the heavens would shine on us and we'd get a spectacular totality. However, it was not to be. The weather forecast was for cloud cover and showers - but the day before the event was lovely and sunny, so who believes in weather forecasts anyway? But as we scanned the sky on awakening on 11 August, it seems the Met Office had got it right for once. We stuck to our plan anyway and caught the local train from St Ives to Lelant in order to climb to the highest point for miles around - Trencrom hill where (on a clear day) there was a good view of the north and south Cornish coasts. We were not alone, however. Hundreds of others had the same idea and it was pretty crowded up there. As we waited on the crowed hill top the weather got wetter and wetter, and I wasn't very impressed with the New Age contingent who chanted and drummed to encourage the clouds to retreat - their `music' sounded more like a rain dance to me! The only comfort was the sight of the Radio 1 roadshow revellers, who were down the road at Marazion, getting a soaking too - the wonders of modern technology enabled us to watch them on top of the hill on a miniature TV! Well, it did get very dark and it was strange to see the flashes of hundreds of cameras going off all over the surrounding countryside. But I must admit that as I got soaked to the skin (I discovered that my rainproof jacket isn't!) and as the rain turned to hail as the temperature fell, I wondered what all the fuss was about. I was very glad to return to our friends' cottage and dry off. The real the highlight of the day was watching the latest Austin Powers film at the local cinema - so you can tell that the eclipse was a pretty disappointing experience! Norman Fancey writes: I was on a camp site in Austria just inside the boundary of totality. As a physicist, I was familiar with the theory and knew what to expect. Nevertheless, even in the period leading up to the total eclipse, I found the slowly increasing section being eaten out of the Sun's disc to be most interesting and the few seconds of totality and almost complete darkness to be an experience I will never forget. My previous reading about eclipses did not prepare me for the beautiful colours reflected from the clouds near to the line of sight to the Sun for the few minutes on either side of the few seconds of complete darkness. Philip Britton writes: What do I remember most about the eclipse? We were near Salzburg, on the School Venture Scout Expedition. The boys experienced the eclipse at altitude, passing between mountain huts, so it got very cold. Thin cloud made for good observation. With no artificial light it was certainly dark. But above all I remember teenage boys being impressed by something!

Neptune's Stormy Disposition

NASA Technical Reports Server (NTRS)

1998-01-01

Using powerful ground-and space-based telescopes, scientists have obtained a moving look at some of the wildest, weirdest weather in the solar system.

Combining simultaneous observations of Neptune made with the Hubble Space Telescope and NASA's Infrared Telescope Facility on Mauna Kea, Hawaii, a team of scientists led by Lawrence A. Sromovsky of the University of Wisconsin-Madison has captured the most insightful images to date of a planet whose blustery weather -- monster storms and equatorial winds of 900 miles per hour -- bewilders scientists.

Blending a series of Hubble images, Sromovsky's team constructed a time-lapse rotation movie of Neptune, permitting scientists to watch the ebb and flow of the distant planet's weather. And while the observations, presented here at a meeting of the American Astronomical Society's Division of Planetary Science, are helping scientists tease out clues to the planet's stormy weather, they also are deepening some of Neptune's mysteries, said Sromovsky.

The weather on Neptune, the eighth planet from the sun, is an enigma to begin with. The mechanism that drives its near-supersonic winds and giant storms has yet to be discerned.

On Earth, weather is driven by energy from the sun as it heats the atmosphere and oceans. On Neptune, the sun is 900 times dimmer and scientists have yet to understand how Neptune's weather-generating machinery can be so efficient.

'It's an efficient weather machine compared to Earth,' said Sromovsky. 'It seems to run on almost no energy.'

In an effort to dissect the distant planet's atmosphere and monitor its bizarre weather, Sromovsky and his colleagues obtained a series of measurements and images over the span of three of Neptune's rotations.

From those observations, Sromovsky said it is possible to measure Neptune's circulation and view a 'strange menagerie of variable, discrete cloud features and zonal bands' of weather. Moreover, the new observations enabled Sromovsky's team to probe some of the deeper features of the atmosphere and to map Neptune's cloud tops.

'We can show some clouds are higher than others, that altitudes vary,' he said. Knowing something about the topography of Neptune's clouds, provides a direct way to measure Neptune's powerful winds.

A looming mystery, he said, is the fate of huge dark spots, possibly giant storms. When the planetary probe Voyager visited Neptune in 1989, it detected the Great Dark Spot, a pulsating feature nearly the size of the Earth itself. Two years ago, Hubble observations showed the spot had disappeared, and that another, smaller spot had emerged. But instead of growing to a large-scale storm like the Great Dark Spot, the new spot appears to be trapped at a fixed latitude and may be declining in intensity, said Sromovsky, a senior scientist at UW-Madison's Space Science and Engineering Center.

'They behave like storms, and the Great Dark Spot was an exaggerated features we haven't seen on any other planet. They seem to come and go, and rather than an exciting development of these dark spots, they dissipate.'

Another strange aspect of the distant planet's weather are distinct bands of weather that run parallel to the Neptunian equator. The weather bands encircle the planet and, in some respects, may be similar to the equatorial region of the Earth where tropical heat provides abundant energy to make clouds.

'We can see regions of latitude where Neptune consistently generates bright clouds,' said Sromovsky. The regions are both above and below the planet's equator, but he added that it was uncertain what their explanation is in terms of atmospheric circulation.

Sromovsky said that compared to the look provided by the Voyager spacecraft, Neptune is a different place: 'The character of Neptune is different from what it was at the time of Voyager. The planet seems stable, yet different.'

Sromovsky's Hubble observations were made with Wide Field Planetary Camera 2 and the Near Infrared Camera and Multi-Object Spectrometer. The different instruments allowed observations to be made in a variety of wavelengths, each providing a different set of information about Neptune's clouds, their structures and how they circulate.

Center for Adaptive Optics | News

Science.gov Websites

* Methane Clouds Observed Near Titan's Equator May Explain Presence of Riverbeds on the Surface * 'Dark Center for Adaptive Optics A University of California Science and Technology Center home AO of Cosmic Time * Celebration of Science and Technology Centers Class of 2000 AO Headlines 2009

Shrinking Endowments Are Smaller Targets

ERIC Educational Resources Information Center

Field, Kelly

2008-01-01

This article reports that if there's a silver lining in the dark cloud hanging over campus budgets, it may be that colleges' investment losses could ease Congress's demands for mandatory endowment payouts, at least in the short term. In part that's because colleges tend to spend greater portions of their assets when endowments dip, even if overall…

The Origin and Significance of the CCAM Line: Evidence from Chondrules and Dark Inclusions in Allende (CV3)

NASA Technical Reports Server (NTRS)

Greenwood, R. C.; Franchi, I. A.; Zolensky, M. E.; Buchanan, P. C.

2016-01-01

The process responsible for the mass independent oxygen isotope variation observed in Solar System materials remains poorly understood. While self-shielding of CO, either in the early solar nebula, or precursor molecular cloud, appears to be a viable mechanism, alternative models have also been proposed.

"Leveraged Footprints", "Dark Clouds" and "Bleeding Millions": Perspectives on Australian Universities' Offshore Campuses

ERIC Educational Resources Information Center

McBurnie, Grant

2006-01-01

Australia is a leading proponent of trade liberalisation, including education services. It is a major provider of fee-charging education to international students, both in Australia and offshore. This paper focuses on the three key motivations for Australian universities to establish offshore campuses--academic, financial, reputational--and…

Apollo XIII Spacecraft - Splashdown - South Pacific Ocean

NASA Image and Video Library

1970-04-17

S70-35652 (17 April 1970) --- The Apollo 13 spacecraft heads toward a splashdown in the South Pacific Ocean. The Apollo 13 Command Module splashed down in the South Pacific at 12:07:44 p.m., April 17, 1970. Note the capsule and its parachutes just visible against a gap in the dark clouds.

ARC-1989-AC89-7001

NASA Image and Video Library

1989-08-21

Photo by Voyager 2 (JPL) During August 16 and 17, 1989, the Voyager 2 narrow-angle camera was used to photograph Neptune almost continuously, recording approximately two and one-half rotations of the planet. These images represent the most complete set of full disk Neptune images that the spacecraft will acquire. This picture from the sequence shows two of the four cloud features which have been tracked by the Voyager cameras during the past two months. The large dark oval near the western limb (the left edge) is at a latitude of 22 degrees south and circuits Neptune every 18.3 hours. The bright clouds immediately to the south and east of this oval are seen to substantially change their appearances in periods as short as four hours. The second dark spot, at 54 degrees south latitude near the terminator (lower right edge), circuits Neptune every 16.1 hours. This image has been processed to enchance the visibility of small features, at some sacrifice of color fidelity. The Voyager Mission is conducted by JPL for NASA's Office of Space Science and Applications. (JPL Ref: A-34611 Voyager 2-N29)

Instability behaviour of cosmic gravito-coupled correlative complex bi-fluidic admixture

NASA Astrophysics Data System (ADS)

Das, Papari; Karmakar, Pralay Kumar

2017-10-01

The gravitational instability of an unbounded infinitely extended composite gravitating cloud system composed of gravito-coupled neutral gaseous fluid (NGF) and dark matter fluid (DMF) is theoretically investigated in a classical framework. It is based on a spatially-flat geometry approximation (1D, sheet-like, boundless) at the backdrop that the radius of curvature of the gravito-confined bi-fluidic-boundary is much larger than all the hydro-characteristic scale lengths of interest. The relevant collective correlative dynamics, via the lowest-order mnemonic viscoelasticity, is mooted. We apply a standard formalism of normal mode analysis to yield a unique brand of generalized quadratic dispersion relation having variable multi-parametric coefficients dependent on the diversified equilibrium properties. It is parametrically seen that the DMF flow speed and the DMF viscoelasticity introduce stabilizing effects against the composite cloud collapse. The instability physiognomies, as specialized extreme corollaries, are in good accord with the previously reported predictions. The analysis may be widely useful to see the gravito-thermally coupled wave dynamics leading to the formation of large-scale hierarchical non-homologous structures in dark-matter-dominated dwarf galaxies.

A Global, Decadal, Quantitative Record of Absorbing Aerosols above Cloud Using OMI's Near-UV Observations

NASA Astrophysics Data System (ADS)

Torres, O.; Jethva, H. T.; Ahn, C.

2016-12-01

Aerosol-cloud interaction continues to be one of the leading uncertain components of climate models, primarily due to the lack of an adequate knowledge of the complex microphysical and radiative processes of the aerosol-cloud system. The situations when aerosols and clouds are found in the same atmospheric column, for instance, when light-absorbing aerosols such as biomass burning generated carbonaceous particles or wind-blown dust overlay low-level cloud decks, are commonly found over several regions of the world. Contrary to the known cooling effects of these aerosols in cloud-free scenario over dark surface, the overlapping situation of absorbing aerosols over cloud can potentially exert a significant level of atmospheric absorption and produces a positive radiative forcing (warming) at top-of-atmosphere. The magnitude of direct radiative effects of aerosols above cloud directly depends on the aerosol loading, microphysical and optical properties of the aerosol layer and the underlying cloud deck, and geometric cloud fraction. We help in addressing this problem by introducing a novel product of above-cloud aerosol optical depth (ACAOD) of absorbing aerosols retrieved from near-UV observations made by the Ozone Monitoring Instrument (OMI) on board NASA's Aura platform. Physically based on the strong `color ratio' effect in the near-UV caused by the spectral absorption of aerosols above cloud, the algorithm, formally named as OMACA, retrieves the optical depths of aerosols and clouds simultaneously under a prescribed state of atmosphere. Here, we present the algorithm architecture and results from an 11-year global record (2005-2015) including global climatology of frequency of occurrence and ACAOD. The theoretical uncertainty analysis and planned validation activities using measurements from upcoming field campaigns are also discussed.

Cloud Optical Depth Measured with Ground-Based, Uncooled Infrared Imagers

NASA Technical Reports Server (NTRS)

Shaw, Joseph A.; Nugent, Paul W.; Pust, Nathan J.; Redman, Brian J.; Piazzolla, Sabino

2012-01-01

Recent advances in uncooled, low-cost, long-wave infrared imagers provide excellent opportunities for remotely deployed ground-based remote sensing systems. However, the use of these imagers in demanding atmospheric sensing applications requires that careful attention be paid to characterizing and calibrating the system. We have developed and are using several versions of the ground-based "Infrared Cloud Imager (ICI)" instrument to measure spatial and temporal statistics of clouds and cloud optical depth or attenuation for both climate research and Earth-space optical communications path characterization. In this paper we summarize the ICI instruments and calibration methodology, then show ICI-derived cloud optical depths that are validated using a dual-polarization cloud lidar system for thin clouds (optical depth of approximately 4 or less).

Massive superclusters as a probe of the nature and amplitude of primordial density fluctuations

NASA Technical Reports Server (NTRS)

Kaiser, N.; Davis, M.

1985-01-01

It is pointed out that correlation studies of galaxy positions have been widely used in the search for information about the large-scale matter distribution. The study of rare condensations on large scales provides an approach to extend the existing knowledge of large-scale structure into the weakly clustered regime. Shane (1975) provides a description of several apparent massive condensations within the Shane-Wirtanen catalog, taking into account the Serpens-Virgo cloud and the Corona cloud. In the present study, a description is given of a model for estimating the frequency of condensations which evolve from initially Gaussian fluctuations. This model is applied to the Corona cloud to estimate its 'rareness' and thereby estimate the rms density contrast on this mass scale. An attempt is made to find a conflict between the density fluctuations derived from the Corona cloud and independent constraints. A comparison is conducted of the estimate and the density fluctuations predicted to arise in a universe dominated by cold dark matter.

STS-55 Earth observation of the Timor Sea

NASA Technical Reports Server (NTRS)

1993-01-01

STS-55 Earth observation taken from Columbia, Orbiter Vehicle (OV) 102, shows the Timor Sea along the south coast of Timor. The sunglint pattern shows a sharp boundary in sea surface temperature, with cooler water along the coast and warmer water offshore. The sunglint brightness reveals water surface roughness with bright indicating smooth water and dark representing rough water. Cooler water is smoother because it acts to stabilize the atmospheric boundary layer, while the warm water acts to destabilize the atmosphere. Another indication of water temperature is the cloud pattern. Advection within the atmosphere as a result of warming at the sea surface forms low-level clouds with the small, popcorn-like appearance seen in upper right corner of the photograph. The cool water, on the other hand, is relatively free of the popcorn-like clouds. The distribution of the clouds indicates that the wind is blowing toward the upper right corner of the photograph. Also note the line of low-level

A global cloud map of the nearest known brown dwarf.

PubMed

Crossfield, I J M; Biller, B; Schlieder, J E; Deacon, N R; Bonnefoy, M; Homeier, D; Allard, F; Buenzli, E; Henning, Th; Brandner, W; Goldman, B; Kopytova, T

2014-01-30

Brown dwarfs--substellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars--are born hot and slowly cool as they age. As they cool below about 2,300 kelvin, liquid or crystalline particles composed of calcium aluminates, silicates and iron condense into atmospheric 'dust', which disappears at still cooler temperatures (around 1,300 kelvin). Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unobservable atmosphere and breakup of the cloud into scattered patches (as seen on Jupiter and Saturn). However, hitherto observations of brown dwarfs have been limited to globally integrated measurements, which can reveal surface inhomogeneities but cannot unambiguously resolve surface features. Here we report a two-dimensional map of a brown dwarf's surface that allows identification of large-scale bright and dark features, indicative of patchy clouds. Monitoring suggests that the characteristic timescale for the evolution of global weather patterns is approximately one day.

Hazard mitigation with cloud model based rainfall and convective data

NASA Astrophysics Data System (ADS)

Gernowo, R.; Adi, K.; Yulianto, T.; Seniyatis, S.; Yatunnisa, A. A.

2018-05-01

Heavy rain in Semarang 15 January 2013 causes flood. It is related to dynamic of weather’s parameter, especially with convection process, clouds and rainfall data. In this case, weather condition analysis uses Weather Research and Forecasting (WRF) model used to analyze. Some weather’s parameters show significant result. Their fluctuations prove there is a strong convection that produces convective cloud (Cumulonimbus). Nesting and 2 domains on WRF model show good output to represent weather’s condition commonly. The results of this study different between output cloud cover rate of observation result and output of model around 6-12 hours is because spinning-up of processing. Satellite Images of MTSAT (Multifunctional Transport Satellite) are used as a verification data to prove the result of WRF. White color of satellite image is Coldest Dark Grey (CDG) that indicates there is cloud’s top. This image consolidates that the output of WRF is good enough to analyze Semarang’s condition when the case happened.

Molecular Anions in Protostars, Prestellar Cores and Dark Clouds

NASA Technical Reports Server (NTRS)

Cordiner, Martin; Charnley, Steven; Buckle, Jane; Wash, Catherine; Millar, Tom

2011-01-01

From our recent survey work using the Green Bank Telescope, microwave emission lines from the hydrocarbon anion C6H(-) and its parent neutral C6H have been detected in six new sources. Using HC3N = 10(exp -9) emission maps, we targeted the most carbon-chain-rich sources for our anion survey, which included the low-mass Class 0 protostar L1251A-IRS3, the prestellar cores L1389-SMM1 and L1512, and the interstellar clouds Ll172A, TMC-1C and L1495B. Derived [C6H(-)]/[C6H] anion-to-neutral ratios are approximately 1-10. The greatest C6H(-) column densities are found in the quiescent clouds TMC-1C and L1495B, but the anion-to-neutral ratios are greatest in the prestellar cores and protostars. These results are interpreted in terms of the physical and chemical properties of the sources, and the implications for molecular cloud chemistry are discussed.

The Sword of Orion

NASA Technical Reports Server (NTRS)

2006-01-01

[figure removed for brevity, see original site] [figure removed for brevity, see original site] AnimationFigure 1

This infrared image from NASA's Spitzer Space Telescope shows the Orion nebula, our closest massive star-making factory, 1,450 light-years from Earth. The nebula is close enough to appear to the naked eye as a fuzzy star in the sword of the popular hunter constellation.

The nebula itself is located on the lower half of the image, surrounded by a ring of dust. It formed in a cold cloud of gas and dust and contains about 1,000 young stars. These stars illuminate the cloud, creating the beautiful nebulosity, or swirls of material, seen here in infrared.

In the center of the nebula (bottom inset of figure 1) are four monstrously massive stars, up to 100,000 times as luminous as our sun, called the Trapezium (tiny yellow smudge to the lower left of green splotches. Radiation and winds from these stars are blasting gas and dust away, excavating a cavity walled in by the large ring of dust.

Behind the Trapezium, still buried deeply in the cloud, a second generation of massive stars is forming (in the area with green splotches). The speckled green fuzz in this bright region is created when bullets of gas shoot out from the juvenile stars and ram into the surrounding cloud.

Above this region of intense activity are networks of cold material that appear as dark veins against the pinkish nebulosity (upper inset pf figure 1). These dark veins contain embryonic stars. Some of the natal stars illuminate the cloud, creating small, aqua-colored wisps. In addition, jets of gas from the stars ram into the cloud, resulting in the green horseshoe-shaped globs.

Spitzer surveyed a significant swath of the Orion constellation, beyond what is highlighted in this image. Within that region, called the Orion cloud complex, the telescope found 2,300 stars circled by disks of planet-forming dust and 200 stellar embryos too young to have developed disks.

This image shows infrared light captured by Spitzer's infrared array camera. Light with wavelengths of 8 and 5.8 microns (red and orange) comes mainly from dust that has been heated by starlight. Light of 4.5 microns (green) shows hot gas and dust; and light of 3.6 microns (blue) is from starlight.

SOFIA Observations of S106: Dynamics of the Warm Gas

NASA Technical Reports Server (NTRS)

Simon, R.; Schneider, N.; Stutzki, J.; Gusten, R.; Graf, U. U.; Hartogh, P.; Guan, X.; Staguhn, J. G.; Benford, D. J.

2012-01-01

Context The H II region/PDR/molecular cloud complex S106 is excited by a single O-star. The full extent of the warm and dense gas close to the star has not been mapped in spectrally resolved high-J CO or [C II] lines, so the kinematics of the warm. partially ionized gas, are unknown. Whether the prominent dark lane bisecting the hourglass-shaped nebula is due solely to the shadow cast by a small disk around the exciting star or also to extinction in high column foreground gas was an open question until now. Aims. To disentangle the morphology and kinematics of warm neutral and ionized gas close to the star, study their relation to the bulk of the molecular gas. and to investigate the nature of the dark lane. Methods. We use the heterodyne receiver GREAT on board SOFIA to observe velocity resolved spectral lines of [C II] and CO 11 yields 10 in comparison with so far unpublished submm continuum data at 350 micron (8HARC-Il) and complementary molecular line data. Results. The high angular and spectral resolution observations show a very complex morphology and kinematics of the inner S106 region, with many different components at different excitation conditions contributing to the observed emission. The [C II] lines are found to be bright and very broad. tracing high velocity gas close to the interface of molecular cloud and H II region. CO 11 yields 10 emission is more confined.. both spatially and in velocity, to the immediate surroundings of S 106 IR showing the presence of warm, high density (clumpy) gas. Our high angular resolution submm continuum observations rule out the scenario where the dark lane separating the two lobes is due solely to the shadow cast by a small disk close to the star. The lane is clearly seen also as warm, high column density gas at the boundary of the molecular cloud and H II region.

Ultra-compact High Velocity Clouds as Minihalos and Dwarf Galaxies

NASA Astrophysics Data System (ADS)

Faerman, Yakov; Sternberg, Amiel; McKee, Christopher F.

2013-11-01

We present dark matter minihalo models for the Ultra-Compact, High-Velocity H I Clouds (UCHVCs) recently discovered in the 21 cm ALFALFA survey. We assume gravitational confinement of 104 K H I gas by flat-cored dark-matter subhalos within the Local Group. We show that for flat cores, typical (median) tidally stripped cosmological subhalos at redshift z = 0 have dark-matter masses of ~107 M ⊙ within the central 300 pc (independent of total halo mass), consistent with the "Strigari mass scale" observed in low-luminosity dwarf galaxies. Flat-cored subhalos also resolve the mass discrepancy between simulated and observed satellites around the Milky Way. For the UCHVCs, we calculate the photoionization-limited hydrostatic gas profiles for any distance-dependent total observed H I mass and predict the associated (projected) H I half-mass radii, assuming the clouds are embedded in distant (d >~ 300 kpc) and unstripped subhalos. For a typical UCHVC (0.9 Jy km s-1), we predict physical H I half-mass radii of 0.18 to 0.35 kpc (or angular sizes of 0.'6 to 2.'1) for distances ranging from 300 kpc to 2 Mpc. As a consistency check, we model the gas-rich dwarf galaxy Leo T, for which there is a well-resolved H I column density profile and a known distance (420 kpc). For Leo T, we find that a subhalo with M 300 = 8 (± 0.2) × 106 M ⊙ best fits the observed H I profile. We derive an upper limit of P HIM <~ 150 cm-3 K for the pressure of any enveloping hot intergalactic medium gas at the distance of Leo T. Our analysis suggests that some of the UCHVCs may in fact constitute a population of 21 cm-selected but optically faint dwarf galaxies in the Local Group.

Adaptive Weibull Multiplicative Model and Multilayer Perceptron Neural Networks for Dark-Spot Detection from SAR Imagery

PubMed Central

Taravat, Alireza; Oppelt, Natascha

2014-01-01

Oil spills represent a major threat to ocean ecosystems and their environmental status. Previous studies have shown that Synthetic Aperture Radar (SAR), as its recording is independent of clouds and weather, can be effectively used for the detection and classification of oil spills. Dark formation detection is the first and critical stage in oil-spill detection procedures. In this paper, a novel approach for automated dark-spot detection in SAR imagery is presented. A new approach from the combination of adaptive Weibull Multiplicative Model (WMM) and MultiLayer Perceptron (MLP) neural networks is proposed to differentiate between dark spots and the background. The results have been compared with the results of a model combining non-adaptive WMM and pulse coupled neural networks. The presented approach overcomes the non-adaptive WMM filter setting parameters by developing an adaptive WMM model which is a step ahead towards a full automatic dark spot detection. The proposed approach was tested on 60 ENVISAT and ERS2 images which contained dark spots. For the overall dataset, an average accuracy of 94.65% was obtained. Our experimental results demonstrate that the proposed approach is very robust and effective where the non-adaptive WMM & pulse coupled neural network (PCNN) model generates poor accuracies. PMID:25474376

In-Situ Characterization of Potential-Induced Degradation in Crystalline Silicon Photovoltaic Modules Through Dark I–V Measurements

DOE PAGES

Luo, Wei; Hacke, Peter; Singh, Jai Prakash; ...

2016-11-14

Here, a temperature correction methodology for in-situ dark I-V(DIV) characterization of conventional p-type crystalline silicon photovoltaic (PV) modules undergoing potential-induced degradation (PID) is proposed.

Neptune Long-Lived Atmospheric Features in 2013 - 2015 from Small (28-cm) to Large (10-m) Telescopes

NASA Technical Reports Server (NTRS)

Hueso, R.; de Pater, I.; Simon, A.; Sanchez-Lavega, A.; Delcroix, M.; Wong, M. H.; Tollefson, J. W.; Baranec, C.; de Kleer, K.; Luszcz-Cook, S. H.;

H2CS abundances and ortho-to-para ratios in interstellar clouds

NASA Technical Reports Server (NTRS)

Minh, Y. C.; Irvine, W. M.; Brewer, M. K.

1991-01-01

Several H2CS ortho and para transitions have been observed toward interstellar molecular clouds, including cold, dark clouds and star-forming regions. H2CS fractional abundances f(H2CS) about 1-2 10 to the -9th relative to molecular hydrogen toward TMC-1, Orion A, and NGC 7538, and about 5 10 to the -10th for L134N are derived. The H2CS ortho-to-para ratios in TMC-1 are about 1.8 toward the cyanopolyyne peak and the ammonia peak, which may indicate the thermalization of H2CS on 10 K grains. A ratio of about 3, the statistical value, for Orion (3N, 1E) and NGC 7538 is derived, while a value of about 2 for Orion (KL) is found.

Aerosol and Cloud Microphysical Properties in the Asir region of Saudi Arabia

NASA Astrophysics Data System (ADS)

Axisa, Duncan; Kucera, Paul; Burger, Roelof; Li, Runjun; Collins, Don; Freney, Evelyn; Posada, Rafael; Buseck, Peter

2010-05-01

In recent advertent and inadvertent weather modification studies, a considerable effort has been made to understand the impact of varying aerosol properties and concentration on cloud properties. Significant uncertainties exist with aerosol-cloud interactions for which complex microphysical processes link the aerosol and cloud properties. Under almost all environmental conditions, increased aerosol concentrations within polluted air masses will enhance cloud droplet concentration relative to that in unperturbed regions. The interaction between dust particles and clouds are significant, yet the conditions in which dust particles become cloud condensation nuclei (CCN) are uncertain. In order to quantify this aerosol effect on clouds and precipitation, a field campaign was launched in the Asir region of Saudi Arabia as part of a Precipitation Enhancement Feasibility Study. Ground measurements of aerosol size distributions, hygroscopic growth factor, CCN concentrations as well as aircraft measurements of cloud hydrometeor size distributions were done in the Asir region of Saudi Arabia in August 2009. Research aircraft operations focused primarily on conducting measurements in clouds that are targeted for cloud top-seeding, on their microphysical characterization, especially the preconditions necessary for precipitation; understanding the evolution of droplet coalescence, supercooled liquid water, cloud ice and precipitation hydrometeors is necessary if advances are to be made in the study of cloud modification by cloud seeding. Non-precipitating mixed-phase clouds less than 3km in diameter that developed on top of the stable inversion were characterized by flying at the convective cloud top just above the inversion. Aerosol measurements were also done during the climb to cloud base height. The presentation will include a summary of the analysis and results with a focus on the unique features of the Asir region in producing convective clouds, characterization of the aerosol prior to convective development and the microphysical properties of convective clouds in the Asir region of Saudi Arabia.

Distance to Dark Bodies

NASA Technical Reports Server (NTRS)

2007-01-01

Using the unique orbit of NASA's Spitzer Space Telescope and a depth-perceiving trick called parallax, astronomers have determined the distance to an invisible Milky Way object called OGLE-2005-SMC-001. This artist's concept illustrates how this trick works: different views from both Spitzer and telescopes on Earth are combined to give depth perception.

Our Milky Way galaxy is heavier than it looks, and scientists use the term 'dark matter' to describe all the 'heavy stuff' in the universe that seems to be present but invisible to our telescopes. While much of this dark matter is likely made up of exotic materials, different from the ordinary particles that make up the world around us, some may consist of dark celestial bodies -- like planets, black holes, or failed stars -- that do not produce light or are too faint to detect from Earth. OGLE-2005-SMC-001 is one of these dark celestial bodies.

Although astronomers cannot see a dark body, they can sense its presence from the way light acts around it. When a dark body like OGLE-2005-SMC-001 passes in front of a bright star, its gravity causes the background starlight to bend and brighten, a process called gravitational microlensing. When the observing telescope, dark body, and star system are closely aligned, the microlensing event reaches maximum, or peak, brightness.

A team of astronomers first sensed OGLE-2005-SMC-001's presence when it passed in front of a star in a neighboring satellite galaxy called the Small Magellanic Cloud. In this artist's rendering, the satellite galaxy is depicted as the fuzzy structure sitting to the left of Earth. Once they detected this microlensing event, the scientists used Spitzer and the principle of parallax to figure out its distance. Humans naturally use parallax to determine distance. Each eye sees the distance of an object differently. The brain takes each eye's perspective and instantaneously calculates how far away the object is.

To determine OGLE-2005-SMC-001's distance, astronomers measured the microlensing event over several months with both Spitzer in space and the Earth-based telescopes. Careful analysis of the data revealed the time of the peak brightness differed slightly between the two locations.

Because astronomers knew the exact distance between Earth and Spitzer and the time lag between the peak-observed brightness, they could determine OGLE-2005-SMC-001's speed. Using trigonometric equations and graphs to do the 'brain's' job, scientists then inferred the dark body's location to be in the outer portion, or halo, of our galaxy.

The picture of the Small Magellanic Cloud in this concept is a two-color image from two Digitized Sky Survey 2 observations The Digitized Sky Survey is based at the Space Telescope Science Institute in Baltimore, Md.

Distribution of Aerosols in the Arctic as Observed by CALIOP

NASA Astrophysics Data System (ADS)

Winker, D.; Kittaka, C.

2007-12-01

The Arctic climate is now recognized to be uniquely sensitive to atmospheric perturbations. Pollution aerosols and smoke from boreal fires have potentially important impacts on Arctic climate but there are many uncertainties. Aerosol in the Arctic, generally referred to as "Arctic haze", has been studied with great interest for over thirty years. Much has been learned about the composition and sources of the haze yet our knowledge is largely based on long term measurements at a very few widely dispersed sites, augmented by modeling activities and occasional field campaigns. Transport pathways from source regions into the Arctic are not well understood. Emission patterns have changed over the last several decades, but the impact of this on concentrations and distribution of Arctic haze are understood only in the crudest sense. Due to poor lighting conditions, extended periods of darkness, and surfaces covered by snow and ice, satellite sensors have been unable to provide much information on Arctic haze to date. The CALIPSO satellite carries CALIOP, a two-wavelength polarization lidar, optimized for profiling clouds and aerosols. CALIOP has been acquiring global observations since June 2006 and provides our first opportunity to observe the distribution and seasonal variation of aerosol in the Arctic. The Arctic is characterized by the prevalence of optically thin ice clouds and clouds composed of supercooled water, often occurring in the same atmospheric column along with aerosol. CALIOP depolarization signals are used to discriminate Arctic haze from optically thin cirrus and diamond dust. Two-wavelength returns aid in the discrimination of aerosol and optically thin water cloud. Results of initial analyses of CALIOP aerosol observations in the Arctic will be presented. This work is a preliminary analysis in support of the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) field campaign planned for April 2008.

The Envelope Kinematics and a Possible Disk around the Class 0 Protostar within BHR7

NASA Astrophysics Data System (ADS)

Tobin, John J.; Bos, Steven P.; Dunham, Michael M.; Bourke, Tyler L.; van der Marel, Nienke

2018-04-01

We present a characterization of the protostar embedded within the BHR7 dark cloud, based on both photometric measurements from the near-infrared to millimeter and interferometric continuum and molecular line observations at millimeter wavelengths. We find that this protostar is a Class 0 system, the youngest class of protostars, measuring its bolometric temperature to be 50.5 K, with a bolometric luminosity of 9.3 L ⊙. The near-infrared and Spitzer imaging show a prominent dark lane from dust extinction separating clear bipolar outflow cavities. Observations of 13CO (J=2\\to 1), C18O (J=2\\to 1), and other molecular lines with the Submillimeter Array (SMA) exhibit a clear rotation signature on scales <1300 au. The rotation can be traced to an inner radius of ∼170 au and the rotation curve is consistent with an R ‑1 profile, implying that angular momentum is being conserved. Observations of the 1.3 mm dust continuum with the SMA reveal a resolved continuum source, extended in the direction of the dark lane, orthogonal to the outflow. The deconvolved size of the continuum indicates a radius of ∼100 au for the continuum source at the assumed distance of 400 pc. The visibility amplitude profile of the continuum emission cannot be reproduced by an envelope alone and needs a compact component. Thus, we posit that the resolved continuum source could be tracing a Keplerian disk in this very young system. If we assume that the continuum radius traces a Keplerian disk (R ∼ 120 au) the observed rotation profile is consistent with a protostar mass of 1.0 M ⊙.

Typhoon Sinlaku

NASA Technical Reports Server (NTRS)

2002-01-01

One of the more destructive cyclones to emerge from the northern hemisphere 2002 summer storm season was Typhoon Sinlaku. Several attributes of this storm event are portrayed in these data products from the Multi-angle Imaging SpectroRadiometer. The images were acquired on September 5, when the western portion of the storm was situated over the Okinawan island chain. Over the next few days it moved west-northwest, sweeping over Taiwan before making landfall along China's Zhejian province on the 7th. The typhoon forced hundreds of thousands of people from their homes, caused major power outages, and at least 26 people were reported dead or missing before the storm weakened as it moved inland.

While the nature and formation of individual storm events is relatively well understood, the influence of clouds on climate is difficult to assess due to the variable nature of cloud cover at various altitudes. MISR's data products are designed to help understand these influences. Typhoon Sinlaku is shown at left as a natural-color view observed by MISR's vertical-viewing (nadir)camera. The center panel shows the cloud-top height field derived using automated stereoscopic processing of data from multiple MISR cameras. Relative height variations, such as the clearing within the storm's eye, are well represented. Areas where heights could not be retrieved are shown in dark gray.

Clouds have a significant influence on the global radiation balance of the Earth's atmosphere, and the improvement of climate models requires more accurate information on how different types of clouds influence Earth's energy budget. One measure of this influence is albedo, which is the amount of sunlight reflected back to space divided by amount of incident sunlight. Bright objects have high albedo. Retrieved local albedo values for Typhoon Sinlaku are shown at right. Generation of this product is dependent on observed cloud radiances as a function of viewing angle and the cloud height field. Over the short distances (2.2 kilometers) that MISR's local albedo product is generated, values can be greater than 1.0 due to the contributions from the sides of the clouds. Areas where albedo could not be retrieved are shown in dark gray.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and views almost the entire globe every 9 days. This image is a portion of the data acquired during Terra orbit 14442, and covers an area of about 380 kilometers x 1408 kilometers. It utilizes data from blocks 65 to 74 within World Reference System-2 path 113.

Mapping all the mass in the universe (with weak gravitational lensing) - Oral Presentation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Everett, Spencer

Recent discoveries have shown that most of the universe is made of an exotic dark matter that behaves much differently than the normal matter that we experience in everyday life. As we cannot detect dark matter directly, we must infer its location in the universe by indirect effects, such as the distortion of light from distant galaxies as it travels through large clouds of dark matter. While the degree of distortion should be proportional to the amount of dark matter present, we don't know the original shape of the galaxy so the distortion is difficult to quantify. If we hadmore » a model of how dark matter is linked to galaxies, and thus be able predict the amount of distortion that should occur, we could apply the model to galaxy surveys to map out the dark matter in our universe. In this research, I attach a spherical 'halo' of dark matter to each galaxy in a simulated universe to approximate its known complex dark matter structure. I then predict how the halos distort the light from distant galaxies generated behind the halos. As the data is simulated, the true distortion of the light is known which is compared to the halo-predicted distortion. I find that, on average, the model under-predicts the degree of distortion on all scales and fails to capture distortions from large-scale dark matter structure. These issues are likely due to missing features in the model, as the halo model is a greatly simplified version of the actual distribution of dark matter. Potential improvements to the model for future work are discussed.« less

Iapetus Bright and Dark Terrains

NASA Technical Reports Server (NTRS)

1990-01-01

Saturn's outermost large moon, Iapetus, has a bright, heavily cratered icy terrain and a dark terrain, as shown in this Voyager 2 image taken on August 22, 1981. Amazingly, the dark material covers precisely the side of Iapetus that leads in the direction of orbital motion around Saturn (except for the poles), whereas the bright material occurs on the trailing hemisphere and at the poles. The bright terrain is made of dirty ice, and the dark terrain is surfaced by carbonaceous molecules, according to measurements made with Earth-based telescopes. Iapetus' dark hemisphere has been likened to tar or asphalt and is so dark that no details within this terrain were visible to Voyager 2. The bright icy hemisphere, likened to dirty snow, shows many large impact craters. The closest approach by Voyager 2 to Iapetus was a relatively distant 600,000 miles, so that our best images, such as this, have a resolution of about 12 miles. The dark material is made of organic substances, probably including poisonous cyano compounds such as frozen hydrogen cyanide polymers. Though we know a little about the dark terrain's chemical nature, we do not understand its origin. Two theories have been developed, but neither is fully satisfactory--(1) the dark material may be organic dust knocked off the small neighboring satellite Phoebe and 'painted' onto the leading side of Iapetus as the dust spirals toward Saturn and Iapetus hurtles through the tenuous dust cloud, or (2) the dark material may be made of icy-cold carbonaceous 'cryovolcanic' lavas that were erupted from Iapetus' interior and then blackened by solar radiation, charged particles, and cosmic rays. A determination of the actual cause, as well as discovery of any other geologic features smaller than 12 miles across, awaits the Cassini Saturn orbiter to arrive in 2004.

Dark Galaxies and Lost Baryons (IAU S244)

NASA Astrophysics Data System (ADS)

Davies, Jonathan I.; Disney, Michael J.

2008-05-01

Preface; Conference prelims; The HI that barked in the night M. J. Disney; The detection of dark galaxies in blind HI surveys J. I. Davies; Red haloes of galaxies - reservoirs of baryonic dark matter? E. Zackrisson, N. Bergvall, C. Flynn, G. Ostlin, G. Micheva and B. Baldwell; Constraints on dark and visible mass in galaxies from strong gravitational lensing S. Dye and S. Warren; Lost baryons at low redshift S. Mathur, F. Nicastro and R. Williams; Observed properties of dark matter on small spatial scales R. Wyse and G. Gilmore; The mass distribution in spiral galaxies P. Salucci; Connecting lost baryons and dark galaxies via QSO absorption lines T. Tripp; ALFALFA: HI cosmology in the local universe R. Giovanelli; The ALFALFA search for (almost) dark galaxies across the HI mass function M. Haynes; HI clouds detected towards Virgo with the Arecibo Legacy Fast ALFA Survey B. Kent; Cosmic variance in the HI mass function S. Schneider; The Arecibo Galaxy Environments Survey - potential for finding dark galaxies and results so far R. Minchin et al.; Free-floating HI clouds in the M81 group E. Brinks, F. Walter and E. Skillman; Where are the stars in dark galaxies J. Rosenberg, J. Salzer and J. Cannon; The halo by halo missing baryon problem S. McGaugh; The local void is really empty R. Tully; Voids in the local volume: a limit on appearance of a galaxy in a dark matter halo A. Tikhonov and A. Klypin; Dim baryons in the cosmic web C. Impey; A census of baryons in galaxy clusters and groups A. Gonzalez, D. Zaritsky and A. Zabludo; Statistical properties of the intercluster light from SDSS image stacking S. Zibetti; QSO strong gravitational lensing and the detection of dark halos A. Maccio; Strong gravitational lensing: bright galaxies and lost dark-matter L. Koopmans; Mapping the distribution of luminous and dark matter in strong lensing galaxies I. Ferreras, P. Saha, L. Williams and S. Burles; Tidal debris posing as dark galaxies P. Duc, F. Bournaud and E. Brinks; Numerical simulation of the dwarf companions of giant galaxies A. Nelson and P. Williams; Delayed galaxies C. Struck, M. Hancock, B. Smith, P. Appleton, V. Charmandaris and M. Giroux; Probe of dark galaxies via disturbed/lopsided isolated galaxies I. Karachentsev, V. Karachentseva, W. Huchtmeier, D. Makarov and S. Kaisin; Star formation thresholds J. Schaye; Scaling relations of dwarf galaxies without supernova-driven winds K. Tassis, A. Kravtsov and N. Gnedin; Star formation in massive low surface brightness galaxies K. O'Neil; Linking clustering properties and the evolution of low surface brightness galaxies D. Bomans and S. Rosenbaum; Too small to form a galaxy: how the UV background determines the baryon fraction M. Hoeft, G. Yepes and S. Gottlober; Star formation in damped Lyman selected galaxies L. Christensen; Dark-matter content of early-type galaxies with planetary nebulae N. Napolitano et al.; Hunting for ghosts: low surface brightnesses from pixels R. Scaramella and S. Sabatini; Baryonic properties of the darkest galaxies E. Grebel; The dwarf low surface brightness population in different environments of the local universe S. Sabatini, J. Davies, S. Roberts and R. Scaramella; Mass modelling of dwarf spheroidal galaxies J. Klimentowski et al.; Evolution of dwarf galaxies in the Centaurus A Group L. Makarova and D. Makarov; A flat faint end of the Fornax cluster galaxy luminosity function S. Mieske, M. Hilker, L. Infante and C. Mendes de Oliveira; Can massive dark halos destroy the discs of dwarf galaxies? B. Fuchs and O. Esquivel; 'Dark galaxies' and local very metal-poor gas-rich galaxies: possible interrelations S. Pustilnik; Morphology and environment of dwarf galaxies in the local universe H. Ann; Arecibo survey of HI emission from disk galaxies at redshift z 0.2 B. Catinella, M. Haynes, J. Gardner, A. Connolly and R. Giovanelli; AGES observations of

Imaging diffuse clouds: bright and dark gas mapped in CO

NASA Astrophysics Data System (ADS)

Liszt, H. S.; Pety, J.

2012-05-01

Aims: We wish to relate the degree scale structure of galactic diffuse clouds to sub-arcsecond atomic and molecular absorption spectra obtained against extragalactic continuum background sources. Methods: We used the ARO 12 m telescope to map J = 1-0 CO emission at 1' resolution over 30' fields around the positions of 11 background sources occulted by 20 molecular absorption line components, of which 11 had CO emission counterparts. We compared maps of CO emission to sub-arcsec atomic and molecular absorption spectra and to the large-scale distribution of interstellar reddening. Results: 1) The same clouds, identified by their velocity, were seen in absorption and emission and atomic and molecular phases, not necessarily in the same direction. Sub-arcsecond absorption spectra are a preview of what is seen in CO emission away from the continuum. 2) The CO emission structure was amorphous in 9 cases, quasi-periodic or wave-like around B0528+134 and tangled and filamentary around BL Lac. 3) Strong emission, typically 4-5 K at EB - V ≤ 0.15 mag and up to 10-12 K at EB - V ≲ 0.3 mag was found, much brighter than toward the background targets. Typical covering factors of individual features at the 1 K km s-1 level were 20%. 4) CO-H2 conversion factors as much as 4-5 times below the mean value N(H2)/WCO = 2 × 1020 H2 cm-2 (K km s-1)-1 are required to explain the luminosity of CO emission at/above the level of 1 K km s-1. Small conversion factors and sharp variability of the conversion factor on arcminute scales are due primarily to CO chemistry and need not represent unresolved variations in reddening or total column density. Conclusions: Like Fermi and Planck we see some gas that is dark in CO and other gas in which CO is overluminous per H2. A standard CO-H2 conversion factor applies overall owing to balance between the luminosities per H2 and surface covering factors of bright and dark CO, but with wide variations between sightlines and across the faces of individual clouds. Based on observations obtained with the ARO Kitt Peak 12 m telescope.Appendices are available in electronic form at http://www.aanda.org

Dark Clouds and Deadly Skies: Assessing the Strategic Effectiveness of Using Remotely Piloted Aircraft Outside of Designated Combat Zones

DTIC Science & Technology

2015-06-01

embassy bombings in Kenya and Tanzania that killed 225 people. An Islamist spokesman claimed that many nomadic tribesmen, including children, were...remained in the single digits . In September of 2011, Press TV, which is an Iranian news organization, claimed that there had been over 80 drone strikes

Lidar and Radar Measurements of the melting layer in the frame of the Convective and Orographically-induced Precipitation Study

NASA Astrophysics Data System (ADS)

Di Girolamo, Paolo; Summa, Donato; Bhawar, Rohini; Di Iorio, Tatiana; Vaughan, Geraint; Norton, Emily; Peters, Gerhard

2009-03-01

During the Convective and Orographically-induced Precipitation Study (COPS), lidar dark bands were observed by the Univ. of BASILicata Raman lidar system (BASIL) on several IOPs and SOPs (among others, 23 July, 15 August, 17 August). Dark band signatures appear in the lidar measurements of particle backscattering at 355, 532 and 1064 nm and particle extinction at 355 and 532 nm, as well as in particle depolarization measurements. Lidar data are supported by measurements from the University of Hamburg cloud radar MIRA 36 (36 GHz), the University of Hamburg dual-polarization micro rain radars (24.1 GHz) and the University of Manchester Radio UHF clear air wind profiler (1.29 GHz). Results from BASIL and the radars are illustrated and discussed to support in the comprehension of the microphysical and scattering processes responsible for the appearance of the lidar dark band and radar bright band.

Cloud Retrieval Information Content Studies with the Pre-Aerosol, Cloud and ocean Ecosystem (PACE) Ocean Color Imager (OCI)

NASA Astrophysics Data System (ADS)

Coddington, Odele; Platnick, Steven; Pilewskie, Peter; Schmidt, Sebastian

2016-04-01

The NASA Pre-Aerosol, Cloud and ocean Ecosystem (PACE) Science Definition Team (SDT) report released in 2012 defined imager stability requirements for the Ocean Color Instrument (OCI) at the sub-percent level. While the instrument suite and measurement requirements are currently being determined, the PACE SDT report provided details on imager options and spectral specifications. The options for a threshold instrument included a hyperspectral imager from 350-800 nm, two near-infrared (NIR) channels, and three short wave infrared (SWIR) channels at 1240, 1640, and 2130 nm. Other instrument options include a variation of the threshold instrument with 3 additional spectral channels at 940, 1378, and 2250 nm and the inclusion of a spectral polarimeter. In this work, we present cloud retrieval information content studies of optical thickness, droplet effective radius, and thermodynamic phase to quantify the potential for continuing the low cloud climate data record established by the MOderate Resolution and Imaging Spectroradiometer (MODIS) and Visible Infrared Imaging Radiometer Suite (VIIRS) missions with the PACE OCI instrument (i.e., non-polarized cloud reflectances and in the absence of midwave and longwave infrared channels). The information content analysis is performed using the GEneralized Nonlinear Retrieval Analysis (GENRA) methodology and the Collection 6 simulated cloud reflectance data for the common MODIS/VIIRS algorithm (MODAWG) for Cloud Mask, Cloud-Top, and Optical Properties. We show that using both channels near 2 microns improves the probability of cloud phase discrimination with shortwave-only cloud reflectance retrievals. Ongoing work will extend the information content analysis, currently performed for dark ocean surfaces, to different land surface types.

Detailed CO(J = 1-0, 2-1, and 3-2) observations toward an H II region RCW 32 in the Vela Molecular Ridge

NASA Astrophysics Data System (ADS)

Enokiya, Rei; Sano, Hidetoshi; Hayashi, Katsuhiro; Tachihara, Kengo; Torii, Kazufumi; Yamamoto, Hiroaki; Hattori, Yusuke; Hasegawa, Yutaka; Ohama, Akio; Kimura, Kimihiro; Ogawa, Hideo; Fukui, Yasuo

2018-05-01

We performed CO(J = 1-0, 2-1, and 3-2) observations toward an H II region RCW 32 in the Vela Molecular Ridge. The CO gas distribution associated with the H II region was revealed for the first time at a high resolution of 22″. The results revealed three distinct velocity components which show correspondence with the optical dark lanes and/or Hα distribution. Two of the components show complementary spatial distribution which suggests collisional interaction between them at a relative velocity of ˜ 4 km s-1. Based on these results, we present a hypothesis that a cloud-cloud collision determined the cloud distribution and triggered formation of the exciting star ionizing RCW 32. The collision time scale is estimated from the cloud size and the velocity separation to be ˜2 Myr and the collision terminated ˜1 Myr ago, which is consistent with the age of the exciting star and the associated cluster. By combing the previous works on the H II regions in the Vela Molecular Ridge, we argue that the majority (at least four) of the H II regions in the Ridge were formed by triggering of cloud-cloud collision.

Potential Impact of Microbial Activity on the Oxidant Capacity and the Organic Carbon Budget in Clouds (Invited)

NASA Astrophysics Data System (ADS)

Delort, A.

2013-12-01

Within cloud water, microorganisms are metabolically active; so they are suspected to contribute to atmospheric chemistry. This paper is focused on the interactions between microorganisms and Reactive Oxygenated Species present in cloud water since these chemical compounds are driving the oxidant capacity of the cloud system. For this, real cloud waters with contrasting features (marine, continental, urban) were sampled at the puy de Dôme mountain (France). They exhibit high microbial biodiversity and complex chemical composition. These media were incubated in the dark and subjected to UV-light radiation in specifically designed photo-bio-reactors. The concentrations of hydrogen peroxide (H2O2), organic compounds and the ATP/ADP ratio were monitored during the incubation period. Microorganisms remained metabolically active in the presence of hydroxyl radicals photo-produced from H2O2. This oxidant and major carbon compounds (formaldehyde and carboxylic acids) were biodegraded by the endogenous microflora. This work suggests that microorganisms could play a double role in atmospheric chemistry: first, they could directly metabolize organic carbon species; second they could reduce the available source of radicals due to their oxidative metabolism. Consequently, molecules such as H2O2 would be no longer available for photochemical or other chemical reactions, decreasing the cloud oxidant capacity.

Variations between Dust and Gas in the Diffuse Interstellar Medium. III. Changes in Dust Properties

NASA Astrophysics Data System (ADS)

Reach, William T.; Bernard, Jean-Philippe; Jarrett, Thomas H.; Heiles, Carl

2017-12-01

We study infrared emission of 17 isolated, diffuse clouds with masses of order {10}2 {M}ȯ to test the hypothesis that grain property variations cause the apparently low gas-to-dust ratios that have been measured in those clouds. Maps of the clouds were constructed from Wide-field Infrared Survey Explorer (WISE) data and directly compared with the maps of dust optical depth from Planck. The mid-infrared emission per unit dust optical depth has a significant trend toward lower values at higher optical depths. The trend can be quantitatively explained by the extinction of starlight within the clouds. The relative amounts of polycyclic aromatic hydrocarbon and very small grains traced by WISE, compared with large grains tracked by Planck, are consistent with being constant. The temperature of the large grains significantly decreases for clouds with larger dust optical depth; this trend is partially due to dust property variations, but is primarily due to extinction of starlight. We updated the prediction for molecular hydrogen column density, taking into account variations in dust properties, and find it can explain the observed dust optical depth per unit gas column density. Thus, the low gas-to-dust ratios in the clouds are most likely due to “dark gas” that is molecular hydrogen.

Potential impact of microbial activity on the oxidant capacity and organic carbon budget in clouds

NASA Astrophysics Data System (ADS)

Vaïtilingom, Mickael; Deguillaume, Laurent; Vinatier, Virginie; Sancelme, Martine; Amato, Pierre; Chaumerliac, Nadine; Delort, Anne-Marie

2013-01-01

Within cloud water, microorganisms are metabolically active and, thus, are expected to contribute to the atmospheric chemistry. This article investigates the interactions between microorganisms and the reactive oxygenated species that are present in cloud water because these chemical compounds drive the oxidant capacity of the cloud system. Real cloud water samples with contrasting features (marine, continental, and urban) were taken from the puy de Dôme mountain (France). The samples exhibited a high microbial biodiversity and complex chemical composition. The media were incubated in the dark and subjected to UV radiation in specifically designed photo-bioreactors. The concentrations of H2O2, organic compounds, and the ATP/ADP ratio were monitored during the incubation period. The microorganisms remained metabolically active in the presence of ●OH radicals that were photo-produced from H2O2. This oxidant and major carbon compounds (formaldehyde and carboxylic acids) were biodegraded by the endogenous microflora. This work suggests that microorganisms could play a double role in atmospheric chemistry; first, they could directly metabolize organic carbon species, and second, they could reduce the available source of radicals through their oxidative metabolism. Consequently, molecules such as H2O2 would no longer be available for photochemical or other chemical reactions, which would decrease the cloud oxidant capacity.

The variability of tropical ice cloud properties as a function of the large-scale context from ground-based radar-lidar observations over Darwin, Australia

NASA Astrophysics Data System (ADS)

Protat, A.; Delanoë, J.; May, P. T.; Haynes, J.; Jakob, C.; O'Connor, E.; Pope, M.; Wheeler, M. C.

2011-08-01

The high complexity of cloud parameterizations now held in models puts more pressure on observational studies to provide useful means to evaluate them. One approach to the problem put forth in the modelling community is to evaluate under what atmospheric conditions the parameterizations fail to simulate the cloud properties and under what conditions they do a good job. It is the ambition of this paper to characterize the variability of the statistical properties of tropical ice clouds in different tropical "regimes" recently identified in the literature to aid the development of better process-oriented parameterizations in models. For this purpose, the statistical properties of non-precipitating tropical ice clouds over Darwin, Australia are characterized using ground-based radar-lidar observations from the Atmospheric Radiation Measurement (ARM) Program. The ice cloud properties analysed are the frequency of ice cloud occurrence, the morphological properties (cloud top height and thickness), and the microphysical and radiative properties (ice water content, visible extinction, effective radius, and total concentration). The variability of these tropical ice cloud properties is then studied as a function of the large-scale cloud regimes derived from the International Satellite Cloud Climatology Project (ISCCP), the amplitude and phase of the Madden-Julian Oscillation (MJO), and the large-scale atmospheric regime as derived from a long-term record of radiosonde observations over Darwin. The vertical variability of ice cloud occurrence and microphysical properties is largest in all regimes (1.5 order of magnitude for ice water content and extinction, a factor 3 in effective radius, and three orders of magnitude in concentration, typically). 98 % of ice clouds in our dataset are characterized by either a small cloud fraction (smaller than 0.3) or a very large cloud fraction (larger than 0.9). In the ice part of the troposphere three distinct layers characterized by different statistically-dominant microphysical processes are identified. The variability of the ice cloud properties as a function of the large-scale atmospheric regime, cloud regime, and MJO phase is large, producing mean differences of up to a factor 8 in the frequency of ice cloud occurrence between large-scale atmospheric regimes and mean differences of a factor 2 typically in all microphysical properties. Finally, the diurnal cycle of the frequency of occurrence of ice clouds is also very different between regimes and MJO phases, with diurnal amplitudes of the vertically-integrated frequency of ice cloud occurrence ranging from as low as 0.2 (weak diurnal amplitude) to values in excess of 2.0 (very large diurnal amplitude). Modellers should now use these results to check if their model cloud parameterizations are capable of translating a given atmospheric forcing into the correct statistical ice cloud properties.

Cloud effects on ultraviolet photoclimatology

NASA Technical Reports Server (NTRS)

Green, A. E. S.; Spinhirne, J. D.

1978-01-01

The purpose of this study is to quantify for the needs of photobiology the influence of clouds upon the ultraviolet spectral irradiance reaching the ground. Towards this end, analytic formulas are developed which approximately characterize the influence of clouds upon total solar radiation. These may be used in conjunction with a solar pyranometer to assign an effective visual optical depth for the cloud cover. A formula is also developed which characterizes the influence of the optical depth of clouds upon the UV spectral irradiance in the 280-340 nm region. Thus total solar energy observations to assign cloud optical properties can be used to calculate the UV spectral irradiance at the ground in the presence of these clouds. As incidental by-products of this effort, convenient formulas are found for the direct and diffuse components of total solar energy.

Differentiating Dark Triad Traits Within and Across Interpersonal Circumplex Surfaces.

PubMed

Dowgwillo, Emily A; Pincus, Aaron L

2017-01-01

Recent discussions surrounding the Dark Triad (narcissism, psychopathy, and Machiavellianism) have centered on areas of distinctiveness and overlap. Given that interpersonal dysfunction is a core feature of Dark Triad traits, the current study uses self-report data from 562 undergraduate students to examine the interpersonal characteristics associated with narcissism, psychopathy, and Machiavellianism on four interpersonal circumplex (IPC) surfaces. The distinctiveness of these characteristics was examined using a novel bootstrapping methodology for computing confidence intervals around circumplex structural summary method parameters. Results suggest that Dark Triad traits exhibit distinct structural summary method parameters with narcissism characterized by high dominance, psychopathy characterized by a blend of high dominance and low affiliation, and Machiavellianism characterized by low affiliation on the problems, values, and efficacies IPC surfaces. Additionally, there was some heterogeneity in findings for different measures of psychopathy. Gender differences in structural summary parameters were examined, finding similar parameter values despite mean-level differences in Dark Triad traits. Finally, interpersonal information was integrated across different IPC surfaces to create profiles associated with each Dark Triad trait and to provide a more in-depth portrait of associated interpersonal dynamics. © The Author(s) 2016.

Interactions of stars and interstellar matter in Scorpio Centaurus

NASA Technical Reports Server (NTRS)

De Geus, E. J.

1992-01-01

The interaction of the stars in the Scorpio-Centaurus OB association with the ambient interstellar medium is investigated. Large H I loops in the fourth galactic quadrant are parts of expanding shells surrounding the subgroups of the association. The energy output of the original stellar population of the subgroups is calculated. Comparison with the kinetic energy of the shells shows that the energy output of the stars in the subgroups is sufficient to form the shells. The masses of the shells are consistent with those of giant molecular clouds GMCs, suggesting that the shells consist of swept-up, original GMC material. The influence of the expanding shell around the young Upper-Scorpius subgroup on the morphology of the Ophiuchus molecular clouds is investigated. The interaction of the shell with the Ophiuchus clouds accounts for the presence of a slow shock and for the shape of the elongated dark clouds connected to the Rho Oph dense cloud. The close passage of the trajectory of the runaway star Zeta Oph by the center of the Upper-Scorpius shell, combined with the time scale of formation of the shell, strongly suggests that the star has originated in the Upper-Scorpius subgroup.

Soft X-ray observations of pre-main sequence stars in the chamaeleon dark cloud

NASA Technical Reports Server (NTRS)

Feigelson, Eric D.; Kriss, Gerard A.

1987-01-01

Einstein IPC observations of the nearby Chamaeleon I star forming cloud show 22 well-resolved soft X-ray sources in a 1x2 deg region. Twelve are associated with H-alpha emission line pre-main sequence (PMS) stars, and four with optically selected PMS stars. Several X-ray sources have two or more PMS stars in their error circles. Optical spectra were obtained at CTIO of possible stellar counterparts of the remaining X-ray sources. They reveal 5 probable new cloud members, K7-MO stars with weak or absent emission lines. These naked X-ray selected PMS stars are similar to those found in the Taurus-Auriga cloud. The spatial distributions and H-R diagrams of the X-ray and optically selected PMS stars in the cloud are very similar. Luminosity functions indicate the Chamaeleon stars are on average approximately 5 times more X-ray luminous than Pleiad dwarfs. A significant correlation between L sub x and optical magnitude suggests this trend may continue within the PMS phase of stellar evolution. The relation of increasing X-ray luminosity with decreasing stellar ages is thus extended to stellar ages as young as 1 million years.

ARC-1990-A91-2001

NASA Image and Video Library

1990-02-19

Range : 60,000 miles These images are two versions of a near-infrafed map of lower-level clouds on the night side of Venus, obtained by the Near Infrared Mapping Spectrometer aboard the Galileo spacecraft.The map shows the turbulent, cloudy middle atmosphere some 30-33 miles above the surface, 6-10 miles below the visible cloudtops. The image to the left shows the radiant heat from the lower atmosphere (about 400 degrees F) ahining through the sulfuric acid clouds, which appear as much as 10 times darker than the bright gaps between clouds. This cloud layer is at about 170 degrees F, at a pressure about 1/2 Earth's atmospheric pressure. About 2/3 of the dark hemisphere is visible, centered on longitude 350 West, with bright slsivers of daylit high clouds visible at top and bottom left. The right image, a modified negative, represents what scientists believe would be the visual appearance of this mid-level cloud deck in daylight, with the clouds reflecting sunlight instead of clocking out infrared from the hot planet and lower atmosphere. Near the equator, the clouds appear fluffy and clocky; farther north, they are stretched out into East-West filaments by winds estimated at more than 150 mph, while the poles are capped by thick clouds at this altitude. The Near Infrared Mapping Spectrometer (NIMS) on the Galileo is a combined mapping (imaging) and spectral instrument. It can sense 408 contiguous wavelengths from 0.7 microns (deep red) to 5.2 microns, and can construct a map or image by mechanical scanning. It can spectroscopic-ally analyze atmospheres and surfaces and construct thermal and chemical maps.

ARC-1990-A91-2002

NASA Image and Video Library

1990-02-10

Range : 60,000 miles These images are two versions of a near-infrafed map of lower-level clouds on the night side of Venus, obtained by the Near Infrared Mapping Spectrometer aboard the Galileo spacecraft.The map shows the turbulent, cloudy middle atmosphere some 30-33 miles above the surface, 6-10 miles below the visible cloudtops. The image to the left shows the radiant heat from the lower atmosphere (about 400 degrees F) ahining through the sulfuric acid clouds, which appear as much as 10 times darker than the bright gaps between clouds. This cloud layer is at about 170 degrees F, at a pressure about 1/2 Earth's atmospheric pressure. About 2/3 of the dark hemisphere is visible, centered on longitude 350 West, with bright slsivers of daylit high clouds visible at top and bottom left. The right image, a modified negative, represents what scientists believe would be the visual appearance of this mid-level cloud deck in daylight, with the clouds reflecting sunlight instead of clocking out infrared from the hot planet and lower atmosphere. Near the equator, the clouds appear fluffy and clocky; farther north, they are stretched out into East-West filaments by winds estimated at more than 150 mph, while the poles are capped by thick clouds at this altitude. The Near Infrared Mapping Spectrometer (NIMS) on the Galileo is a combined mapping (imaging) and spectral instrument. It can sense 408 contiguous wavelengths from 0.7 microns (deep red) to 5.2 microns, and can construct a map or image by mechanical scanning. It can spectroscopic-ally analyze atmospheres and surfaces and construct thermal and chemical maps.

A Solar Reflectance Method for Retrieving Cloud Optical Thickness and Droplet Size Over Snow and Ice Surfaces

NASA Technical Reports Server (NTRS)

Platnick, S.; Li, J. Y.; King, M. D.; Gerber, H.; Hobbs, P. V.

1999-01-01

Cloud optical thickness and effective radius retrievals from solar reflectance measurements are traditionally implemented using a combination of spectral channels that are absorbing and non-absorbing for water particles. Reflectances in non-absorbing channels (e.g., 0.67, 0.86, 1.2 micron spectral window bands) are largely dependent on cloud optical thickness, while longer wavelength absorbing channels (1.6, 2. 1, and 3.7 micron window bands) provide cloud particle size information. Cloud retrievals over ice and snow surfaces present serious difficulties. At the shorter wavelengths, ice is bright and highly variable, both characteristics acting to significantly increase cloud retrieval uncertainty. In contrast, reflectances at the longer wavelengths are relatively small and may be comparable to that of dark open water. A modification to the traditional cloud retrieval technique is devised. The new algorithm uses only a combination of absorbing spectral channels for which the snow/ice albedo is relatively small. Using this approach, retrievals have been made with the MODIS Airborne Simulator (MAS) imager flown aboard the NASA ER-2 from May - June 1998 during the Arctic FIRE-ACE field deployment. Data from several coordinated ER-2 and University of Washington CV-580 in situ aircraft observations of liquid water stratus clouds are examined. MAS retrievals of optical thickness, droplet effective radius, and liquid water path are shown to be in good agreement with the in situ measurements. The initial success of the technique has implications for future operational satellite cloud retrieval algorithms in polar and wintertime regions.

Wide-field Infrared Survey Explorer

NASA Technical Reports Server (NTRS)

Padgett, Deborah

2012-01-01

We present WISE (Wide-field Infrared Survey Explorer) mid-infrared photometry of young stellar object candidates in the Canis Majoris clouds at a distance of 1 kpc. WISE has identified 682 objects with apparent 12 and 22 micron excess emission in a 7 deg x 10 deg field around the CMa Rl cloud . While a substantial fraction of these candidates are likely galaxies, AGB stars, and artifacts from confusion along the galactic plane, others are part of a spectacular cluster of YSOs imaged by WISE along a dark filament in the R1 cloud. Palomar Double Spectrograph observations of several sources in this cluster confirm their identity as young A and B stars with strong emission lines. In this contribution, we plot the optical -mid-infrared spectral energy distribution for the WISE YSO candidates and discuss potential contaminants to the sample . The data demonstrate the utility of WISE in performing wide-area surveys for young stellar objects.

The sensitivity of gas-phase models of dense interstellar clouds to changes in dissociative recombination branching ratios

NASA Technical Reports Server (NTRS)

Millar, T. J.; Defrees, D. J.; Mclean, A. D.; Herbst, E.

1988-01-01

The approach of Bates to the determination of neutral product branching ratios in ion-electron dissociative recombination reactions has been utilized in conjunction with quantum chemical techniques to redetermine branching ratios for a wide variety of important reactions of this class in dense interstellar clouds. The branching ratios have then been used in a pseudo time-dependent model calculation of the gas phase chemistry of a dark cloud resembling TMC-1 and the results compared with an analogous model containing previously used branching ratios. In general, the changes in branching ratios lead to stronger effects on calculated molecular abundances at steady state than at earlier times and often lead to reductions in the calculated abundances of complex molecules. However, at the so-called 'early time' when complex molecule synthesis is most efficient, the abundances of complex molecules are hardly affected by the newly used branching ratios.

Detecting the building blocks of aromatics

NASA Astrophysics Data System (ADS)

Joblin, Christine; Cernicharo, José

2018-01-01

Interstellar clouds are sites of active organic chemistry (1). Many small, gasphase molecules are found in the dark parts of the clouds that are protected from ultraviolet (UV) photons, but these molecules photodissociate in the external layers of the cloud that are exposed to stellar radiation (see the photo). These irradiated regions are populated by large polycyclic aromatic hydrocarbons (PAHs) with characteristic infrared (IR) emission features. These large aromatics are expected to form from benzene (C6H6), which is, however, difficult to detect because it does not have a permanent dipole moment and can only be detected via its IR absorption transitions against a strong background source (2). On page 202 of this issue, McGuire et al. (3) report the detection of benzonitrile (c-C6H5CN) with radio telescopes. Benzonitrile likely forms in the reaction of CN with benzene; from its observation, it is therefore possible to estimate the abundance of benzene itself.

Competition between pressure and gravity confinement in Lyman Alpha forest observations

NASA Technical Reports Server (NTRS)

Charlton, Jane C.; Salpeter, Edwin E.; Linder, Suzanne M.

1994-01-01

A break in the distribution function of Lyman Alpha clouds (at a typical redshift of 2.5) has been reported by Petit-jean et al. (1993). This feature is what would be expected from a transition between pressure confinement and gravity confinement (as predicted in Charlton, Salpeter & Hogan 1993). The column density at which the feature occurs has been used to determine the external confining pressure approximately 10 per cu cm K, which could be due to a hot, intergalactic medium. For models that provide a good fit to the data, the contribution of the gas in clouds to omega is small. The specific shape of the distribution function at the transition (predicted by models to have a nonmonotonic slope) can serve as a diagnostic of the distribution of dark matter around Lyman Alpha forest clouds, and the present data already eliminate certain models.

ARC-1990-AC91-2004

NASA Image and Video Library

1990-02-14

Range : 1.7 million miles This colorized picture of Venus was taken about 6 days after Galileo's closest approach to the planet. It has been colorized to a bluish hue to emphasize subtle contrasts in the cloud markings and to indicate that it was taken through a violet filter. Features in the sulfuric acid clouds near the top of the planet's atmosphere are most prominent in violet and ultraviolet light. This image shows the east-to-west-trending cloud banding and the brighter polar hoods familiar from past studies of Venus. The features are embedded in winds that flow from east to west at about 230 mph. The smallest features visible are about 45 miles across. An intriguing filamentary dark pattern is seen immediately left of the bright region at the subsolar point (equatorial 'noon'). North is at the top and the evening terminator is to the left.

The Transition from Diffuse to Dense Gas in Herschel Dust Emission Maps

NASA Astrophysics Data System (ADS)

Goldsmith, Paul

Dense cores in dark clouds are the sites where young stars form. These regions manifest as relatively small (<0.1pc) pockets of cold and dense gas. If we wish to understand the star formation process, we have to understand the physical conditions in dense cores. This has been a main aim of star formation research in the past decade. Today, we do indeed possess a good knowledge of the density and velocity structure of cores, as well as their chemical evolution and physical lifetime. However, we do not understand well how dense cores form out of the diffuse gas clouds surrounding them. It is crucial that we constrain the relationship between dense cores and their environment: if we only understand dense cores, we may be able to understand how individual stars form --- but we would not know how the star forming dense cores themselves come into existence. We therefore propose to obtain data sets that reveal both dense cores and the clouds containing them in the same map. Based on these maps, we will study how dense cores form out of their natal clouds. Since cores form stars, this knowledge is crucial for the development of a complete theoretical and observational understanding of the formation of stars and their planets, as envisioned in NASA's Strategic Science Plan. Fortunately, existing archival data allow to derive exactly the sort of maps we need for our analysis. Here, we describe a program that exclusively builds on PACS and SPIRE dust emission imaging data from the NASA-supported Herschel mission. The degree-sized wide-field Herschel maps of the nearby (<260pc) Polaris Flare and Aquila Rift clouds are ideal for our work. They permit to resolve dense cores (<0.1pc), while the maps also reveal large-scale cloud structure (5pc and larger). We will generate column density maps from these dust emission maps and then run a tree-based hierarchical multi-scale structure analysis on them. Only this procedure permits to exploit the full potential of the maps: we will characterize cloud structure over a vast range of spatial scales. This work has many advantages over previous studies, where information about dense cores and their environment was pieced together using a variety of methods an instruments. Now, the Herschel maps permit for the first time to characterize both molecular clouds and their cores in one shot in a single data set. We use these data to answer a variety of simple yet very important questions. First, we study whether dense cores have sharp boundaries. If such boundaries exist, they would indicate that dense cores have an individual identity well-separate from the near-fractal cloud structure on larger spatial scales. Second, we will --- in very approximate sense --- derive global density gradients for molecular clouds from radii <0.1pc to 5pc and larger. These "synoptic" density gradients provide a useful quantitative description of the relation between cloud material at very different spatial scales. Also, these measurements can be compared to synoptic density gradients derived in the same fashion for theoretical cloud models. Third, we study how dense cores are nested into the "clumps" forming molecular clouds, i.e., we study whether the most massive dense cores in a cloud (<0.1pc) reside in the most massive regions identified on lager spatial scale (1pc and larger). This will show how the properties of dense cores are influenced by their environment. Our study will derive unique constraints to cloud structure. But our small sample forbids to make strong statements. This pilot study does thus prepare future larger efforts. Our entire project builds on data reduction and analysis methods which our team has used in the past. This guarantees a swift completion of the project with predictable efficiency. We present pilot studies that demonstrate that the data and analysis methods are suited to tackle the science goals. This project is thus guaranteed to return significant results.

A method for characterizing after-pulsing and dark noise of PMTs and SiPMs

NASA Astrophysics Data System (ADS)

Butcher, A.; Doria, L.; Monroe, J.; Retière, F.; Smith, B.; Walding, J.

2017-12-01

Photo-multiplier tubes (PMTs) and silicon photo-multipliers (SiPMs) are detectors sensitive to single photons that are widely used for the detection of scintillation and Cerenkov light in subatomic physics and medical imaging. This paper presents a method for characterizing two of the main noise sources that PMTs and SiPMs share: dark noise and correlated noise (after-pulsing). The proposed method allows for a model-independent measurement of the after-pulsing timing distribution and dark noise rate.

Voyager 2 at Neptune - Imaging science results

NASA Technical Reports Server (NTRS)

Smith, B. A.; Soderblom, L. A.; Banfield, D.; Barnet, C.; Beebe, R. F.; Bazilevskii, A. T.; Bollinger, K.; Boyce, J. M.; Briggs, G. A.; Brahic, A.

1989-01-01

Neptune's atmosphere is revealed by Voyager 2 images to contain clouds of methane ice above a lower deck of hydrogen sulfide or ammonia ices, and to be dominated by an anticyclonic storm system designated the 'Great Dark Spot'; this bears both similarities and differences to the Great Red Spot of Jupiter. Like the rings of Uranus, those of Neptune are composed of very dark, but in addition very dusty, material. Six new regular satellites have been discovered whose radii range from 25 to 200 km. Triton is noted to be a differentiated body showing evidence of early surface-melting episodes. At least two active plumes are found on Triton, which may be driven by solar heating.

Characterization of the cloud conditions at Ny-Ålesund using sensor synergy and representativeness of the observed clouds across Arctic sites

NASA Astrophysics Data System (ADS)

Nomokonova, Tatiana; Ebell, Kerstin; Löhnert, Ulrich; Maturilli, Marion

2017-04-01

Clouds are one of the crucial components of the hydrological and energy cycles and thus affecting the global climate. Their special importance in Arctic regions is defined by cloud's influence on the radiation budget. Arctic clouds usually occur at low altitudes and often contain highly concentrated tiny liquid drops. During winter, spring, and autumn periods such clouds tend to conserve the long-wave radiation in the atmosphere and, thus, produce warming of the Arctic climate. In summer though clouds efficiently scatter the solar radiation back to space and, therefore, induce a cooling effect. An accurate characterization of the net effect of clouds on the Arctic climate requires long-term and precise observations. However, only a few measurement sites exist which perform continuous, vertically resolved observations of clouds in the Arctic, e.g. in Alaska, Canada, and Greenland. These sites typically make use of a combination of different ground-based remote sensing instruments, e.g. cloud radar, ceilometer and microwave radiometer in order to characterize clouds. Within the Transregional Collaborative Research Center (TR 172) "Arctic Amplification: Climate Relevant Atmospheric and Surface Processes, and Feedback Mechanisms (AC)3" comprehensive observations of the atmospheric column are performed at the German-French Research Station AWIPEV at Ny-Ålesund, Svalbard. Ny-Ålesund is located in the warmest part of the Arctic where climate is significantly influenced by adiabatic heating from the warm ocean. Thus, measurements at Ny-Ålesund will complement our understanding of cloud formation and development in the Arctic. This particular study is devoted to the characterization of the cloud macro- and microphysical properties at Ny-Ålesund and of the atmospheric conditions, under which these clouds form and develop. To this end, the information of the various instrumentation at the AWIPEV observatory is synergistically analysed: information about the thermodynamic structure of the atmosphere is obtained from long-term radiosonde launches. In addition, continuous vertical profiles of temperature and humidity are provided by the microwave radiometer HATPRO. A set of active remote sensing instruments performs cloud observations at Ny-Ålesund: a ceilometer and a Doppler lidar operating since 2011 and 2013, respectively, are now complemented with a novel 94 GHz FMCW cloud radar. As a first step, the CLOUDNET algorithms, including a target categorization and classification, are applied to the observations. In this study, we will present a first analysis of cloud properties at Ny-Ålesund including for example cloud occurrence, cloud geometry (cloud base, cloud top, and thickness) and cloud type (liquid, ice, mixed-phase). The different types of clouds are set into context to the environmental conditions such as temperature, amount of water vapour, and liquid water. We also expect that the cloud properties strongly depend on the wind direction. The first results of this analysis will be also shown.

Theory of droplet. Part 1: Renormalized laws of droplet vaporization in non-dilute sprays

NASA Technical Reports Server (NTRS)

Chiu, H. H.

1989-01-01

The vaporization of a droplet, interacting with its neighbors in a non-dilute spray environment is examined as well as a vaporization scaling law established on the basis of a recently developed theory of renormalized droplet. The interacting droplet consists of a centrally located droplet and its vapor bubble which is surrounded by a cloud of droplets. The distribution of the droplets and the size of the cloud are characterized by a pair-distribution function. The vaporization of a droplet is retarded by the collective thermal quenching, the vapor concentration accumulated in the outer sphere, and by the limited percolative passages for mass, momentum and energy fluxes. The retardation is scaled by the local collective interaction parameters (group combustion number of renormalized droplet, droplet spacing, renormalization number and local ambient conditions). The numerical results of a selected case study reveal that the vaporization correction factor falls from unity monotonically as the group combustion number increases, and saturation is likely to occur when the group combustion number reaches 35 to 40 with interdroplet spacing of 7.5 diameters and an environment temperature of 500 K. The scaling law suggests that dense sprays can be classified into: (1) a diffusively dense cloud characterized by uniform thermal quenching in the cloud; (2) a stratified dense cloud characterized by a radial stratification in temperature by the differential thermal quenching of the cloud; or (3) a sharply dense cloud marked by fine structure in the quasi-droplet cloud and the corresponding variation in the correction factor due to the variation in the topological structure of the cloud characterized by a pair-distribution function of quasi-droplets.

Star Formation in the Filamentary Dark Cloud GF-9: a Multi-Wavelength Intra-Cloud Comparative Study

NASA Astrophysics Data System (ADS)

Ciardi, David Robert

Filamentary dark clouds (FDCs) are a subclass of small molecular clouds containing small numbers of somewhat regularly spaced dense cores connected by lower density gas and dust. Most of the previous work performed on FDCs has concerned the star formation properties of individual dense cores within the FDCs and has not concerned the FDCs as entities of their own. As a result little is known about the general star formation properties of FDCs. The primary question addressed in this work is 'Within filamentary dark clouds, how does the star formation process within a core region compare to that within a filamentary region?' In order to address the above question, a multi-wavelength observational comparative study has been performed upon a representative dense core (hereafter, GF9-Core) and filamentary region (hereafter, GF9-Fila) within the FDC GF-9 (LDN 1082). At the Five College Radio Astronomy Observatory, the core and filamentary region were observed in the rotational transitions of 12CO/ (J=1/to0),/ 13CO/ (J=1/to0)/ and/ CS/ (J=2/to1) covering a region of 10' x 8'. The temperature, density and kinematic structures of the two regions were deduced from the radio imaging spectroscopy data and were used to estimate the energy balance of the regions. We also obtained 70, 100, 135 and 200 μm images from the Infrared Space Observatory (ISO) covering approximately 12' x 9' which were used to investigate the temperature and density distributions of the dust within the two regions. Finally, at the Wyoming Infrared Observatory using the Aerospace Corporation NICMOS3 camera, the core and filament were imaged in the near-infrared broadband filters J, H, and K-short covering a slightly smaller region of 7' x 7'. The near-infrared survey data were used to search for embedded Class I and Class II protostars and to investigate the density distribution of the dust. We have found that the evolutionary processes of the core region and the filament region proceed along similar evolutionary paths but are governed by the amount of mass within each region. GF9-Core has a greater mass and density than GF9-Fila, and therefore, gravity has a stronger influence on the fate of the dust and gas. Because of the larger mass, GF9-Core has proceeded along the star formation path and is currently engaged at the Class 0 protostar stage. In contrast, GF9-Fila is still in the earlier stages of contraction through ambipolar diffusion and may form a star sometime in the future.

ARC-1990-AC91-2005

NASA Image and Video Library

1990-02-10

Range : 60,000 miles This image is a false-color version of a near- infrared map of lower-level clouds on the night side of Venus, obtained by the Near Infrared Mapping Spectrometer aboard Galileo. Taken at an infrared wavelength of 2.3 microns (about three times the longest wavelength visible to the human eye) the map shows the turbulent, cloudy middle atmosphere some 30-33 miles above the surface, 6-10 miles below the visible cloudtops. The image shows the radiant heat from the lower atmosphere (about 400 degrees F) shining through the sulfuric acid clouds, which appear as much as 10 times darker than the bright gaps between clouds. The colors indicate relative cloud transparency; white and red show thin cloud regions, while black and blue represent relatively this clouds. This cloud layer is at about 170 degrees F., at a pressure about 1/2 Earth's atmospheric pressure. About 2/3 of the dark hemisphere is visible, centered on longitude 350 West, with bright slivers of daylit high clouds visible at top and bottom left. Near the equator, the clouds appear fluffy and blocky; farther north, they are stretched out into East-West filaments by winds estimated at more than 150 mph, while the poles are capped by thick clouds at this altitude. The Near Infrared Mapping Spectrometer (NIMS) on the Galileo is a combined mapping (imaging) and spectral instrument. It can sense 408 contiguous wavelengths from 0.7 microns (deep red) to 5.2 microns, and can construct a map or image by mechanical scanning. It can spectroscopic-ally analyze atmospheres and surfaces and construct thermal and chemical maps. Designed and operated by scientists and engineers at the JPL, NIMS involves 15 scientists in the US, England and France.

Earth Science

NASA Image and Video Library

2002-12-04

International Space Station (ISS) crew members were able to document a rare occurrence. The dark area near the center of the frame is actually a shadow cast by the moon during the total solar eclipse of December 4, 2002. The shadow obscures an area of cloud cover. The Station, with three Expedition Six crew members aboard, was over the Indian Ocean at the time of the eclipse.

Mars: Atmosphere

NASA Astrophysics Data System (ADS)

Moroz, V.; Murdin, P.

2001-07-01

The atmosphere of MARS is much thinner than the terrestrial one. However, even the simplest visual telescopic observations show a set of atmospheric events such as seasonal exchange of material between polar caps, temporal appearance of clouds and changes of visibility of dark regions on the disk of the planet. In 1947 the prominent CO2 bands in the near-infrared part of the Martian spectrum were...

Research Says/The X Factor in College Success

ERIC Educational Resources Information Center

Goodwin, Bryan; Hein, Heather

2016-01-01

U.S. high school graduation rates have risen steadily for the past decade, hitting an all-time high of 82 percent in 2013-14 (Rich, 2015). Yet there's a dark cloud behind this silver lining. According to the most recent data from the U.S. Department of Education (2015), only 59 percent of students who enter four-year colleges complete their…

Far-infrared observations of a star-forming region in the Corona Australis dark cloud

NASA Technical Reports Server (NTRS)

Cruz-Gonzalez, I.; Mcbreen, B.; Fazio, G. G.

1984-01-01

A high-resolution far-IR (40-250-micron) survey of a 0.9-sq-deg section of the core region of the Corona Australis dark cloud (containing very young stellar objects such as T Tauri stars, Herbig Ae and Be stars, Herbig-Haro objects, and compact H II regions) is presented. Two extended far-IR sources were found, one associated with the Herbig emission-line star R CrA and the other with the irregular emission-line variable star TY CrA. The two sources have substantially more far-IR radiation than could be expected from a blackbody extrapolation of their near-IR fluxes. The total luminosities of these sources are 145 and 58 solar luminosity, respectively, implying that the embedded objects are of intermediate or low mass. The infrared observations of the sources associated with R CrA and TY CrA are consistent with models of the evolution of protostellar envelopes of intermediate mass. However, the TY CrA source appears to have passed the evolutionary stage of expelling most of the hot dust near the central source, yielding an age of about 1 Myr.

Understanding the Star Formation Process in the Filamentary Dark Cloud GF 9: Near-Infrared Observations

NASA Technical Reports Server (NTRS)

Ciardi, David R.; Woodward, Charles E.; Clemens, Dan P.; Harker, David E.; Rudy, Richard J.

1998-01-01

We have performed a near-infrared JHK survey of a dense core and a diffuse filament region within the filamentary dark cloud GF 9 (LDN 1082). The core region is associated with the IRAS point source PSC 20503+6006 and is suspected of being a site of star formation. The diffuse filament region has no associated IRAS point sources and is likely quiescent. We find that neither the core nor the filament region appears to contain a Class I or Class II young stellar object. As traced by the dust extinction, the core and filament regions contain 26 and 22 solar mass, respectively, with an average H2 volume density for both regions of approximately 2500/cu cm. The core region contains a centrally condensed extinction maximum with a peak extinction of A(sub v) greater than or approximately equal to 10 mag that appears to be associated with the IRAS point source. The average H2 volume density of the extinction core is approximately 8000/cu cm. The dust within the filament, however, shows no sign of a central condensation and is consistent with a uniform-density cylindrical distribution.

The new Be-type star HD 147196 in the Rho Ophiuchi dark cloud region

NASA Technical Reports Server (NTRS)

The, P. S.; Perez, M. R.; De Winter, D.; Van Den Ancker, M. E.

1993-01-01

The newly discovered hot-emission line star, HD 147196 in the Rho Oph dark cloud region was observed spectroscopically and photometrically and high and low resolution IUE spectra were obtained. The finding of Irvine (1990) that this relatively bright star show its H-alpha-line in emission is confirmed. Previous H-alpha-surveys of the Rho Oph star-forming region did not detect HD 147196 as an H-alpha-emission star, meaning that it must recently be very active and has perhaps transformed itself from a B-type star at shell phase to a Be-phase. The Mg II h + k resonance lines are in absorption and they appear to be interstellar in nature, which means that either the abundance of Mg in the extended atmosphere of the star is low or that the shell is not extended enough to produce emission lines of Mg II. Photometric observations of this B8 V type star do not show any variations during at least the years covered by our monitoring or any excess of NIR radiation in its spectral energy distribution up to the M-passband at 4.8 microns.

Characterizing Sorghum Panicles using 3D Point Clouds

NASA Astrophysics Data System (ADS)

Lonesome, M.; Popescu, S. C.; Horne, D. W.; Pugh, N. A.; Rooney, W.

2017-12-01

To address demands of population growth and impacts of global climate change, plant breeders must increase crop yield through genetic improvement. However, plant phenotyping, the characterization of a plant's physical attributes, remains a primary bottleneck in modern crop improvement programs. 3D point clouds generated from terrestrial laser scanning (TLS) and unmanned aerial systems (UAS) based structure from motion (SfM) are a promising data source to increase the efficiency of screening plant material in breeding programs. This study develops and evaluates methods for characterizing sorghum (Sorghum bicolor) panicles (heads) in field plots from both TLS and UAS-based SfM point clouds. The TLS point cloud over experimental sorghum field at Texas A&M farm in Burleston County TX were collected using a FARO Focus X330 3D laser scanner. SfM point cloud was generated from UAS imagery captured using a Phantom 3 Professional UAS at 10m altitude and 85% image overlap. The panicle detection method applies point cloud reflectance, height and point density attributes characteristic of sorghum panicles to detect them and estimate their dimensions (panicle length and width) through image classification and clustering procedures. We compare the derived panicle counts and panicle sizes with field-based and manually digitized measurements in selected plots and study the strengths and limitations of each data source for sorghum panicle characterization.

First Monthly CERES Global Longwave and Shortwave Radiation

NASA Technical Reports Server (NTRS)

2002-01-01

Clouds and the Earth's Radiant Energy System, CERES, monitors solar energy reflected from the Earth and heat energy emitted from the Earth. In this image, heat energy radiated from the earth is shown in varying shades of yellow, red, blue and white. The brightest yellow areas, such as the Sahara Desert and Arabian Peninsula, are emitting the most energy out to space, while the dark blue polar regions and bright white clouds are the coldest areas on Earth, and are emitting the least energy. The animation (1.5MB) (high-res (4MB)) shows roughly a week of CERES data. For more information: CERES images through Visible Earth. CERES web site Image courtesy of the CERES instrument team

CERES Detects Earth's Heat and Energy

NASA Technical Reports Server (NTRS)

2002-01-01

Clouds and the Earth's Radiant Energy System, CERES, monitors solar energy reflected from the Earth and heat energy emitted from the Earth. In this image, heat energy radiated from the earth is shown in varying shades of yellow, red, blue and white. The brightest yellow areas, such as the Sahara Desert and Arabian Peninsula, are emitting the most energy out to space, while the dark blue polar regions and bright white clouds are the coldest areas on Earth, and are emitting the least energy. The animation (1.5MB) (high-res (4MB)) shows roughly a week of CERES data. For more information: CERES images through Visible Earth. CERES web site Image courtesy of the CERES instrument team

Saturn's tropospheric composition and clouds from Cassini/VIMS 4.6-5.1 μm nightside spectroscopy

NASA Astrophysics Data System (ADS)

Fletcher, Leigh N.; Baines, Kevin H.; Momary, Thomas W.; Showman, Adam P.; Irwin, Patrick G. J.; Orton, Glenn S.; Roos-Serote, Maarten; Merlet, C.

2011-08-01

The latitudinal variation of Saturn's tropospheric composition (NH 3, PH 3 and AsH 3) and aerosol properties (cloud altitudes and opacities) are derived from Cassini/VIMS 4.6-5.1 μm thermal emission spectroscopy on the planet's nightside (April 22, 2006). The gaseous and aerosol distributions are used to trace atmospheric circulation and chemistry within and below Saturn's cloud decks (in the 1- to 4-bar region). Extensive testing of VIMS spectral models is used to assess and minimise the effects of degeneracies between retrieved variables and sensitivity to the choice of aerosol properties. Best fits indicate cloud opacity in two regimes: (a) a compact cloud deck centred in the 2.5-2.8 bar region, symmetric between the northern and southern hemispheres, with small-scale opacity variations responsible for numerous narrow light/dark axisymmetric lanes; and (b) a hemispherically asymmetric population of aerosols at pressures less than 1.4 bar (whose exact altitude and vertical structure is not constrained by nightside spectra) which is 1.5-2.0× more opaque in the summer hemisphere than in the north and shows an equatorial maximum between ±10° (planetocentric). Saturn's NH 3 spatial variability shows significant enhancement by vertical advection within ±5° of the equator and in axisymmetric bands at 23-25°S and 42-47°N. The latter is consistent with extratropical upwelling in a dark band on the poleward side of the prograde jet at 41°N (planetocentric). PH 3 dominates the morphology of the VIMS spectrum, and high-altitude PH 3 at p < 1.3 bar has an equatorial maximum and a mid-latitude asymmetry (elevated in the summer hemisphere), whereas deep PH 3 is latitudinally-uniform with off-equatorial maxima near ±10°. The spatial distribution of AsH 3 shows similar off-equatorial maxima at ±7° with a global abundance of 2-3 ppb. VIMS appears to be sensitive to both (i) an upper tropospheric circulation (sensed by NH 3 and upper-tropospheric PH 3 and hazes) and (ii) a lower tropospheric circulation (sensed by deep PH 3, AsH 3 and the lower cloud deck).

Magnetic fields in the Perseus Spiral Arm and in Infrared Dark Clouds

NASA Astrophysics Data System (ADS)

Hoq, Sadia

2017-04-01

The magnetic (B) field is ubiquitous throughout the Milky Way. Several fundamental questions about the B-field in the cool, star-forming interstellar medium (ISM) remain unanswered. In this dissertation, near-infrared (NIR) polarimetric observations are used to study the large-scale Galactic B-field in the cool ISM in a spiral arm and to determine the role of B-fields in the formation of Infrared Dark Clouds (IRDCs). NIR polarimetry of 31 star clusters, located in and around the Perseus spiral arm, were obtained to determine the orientation of the plane-of-sky B-field in the outer Galaxy, and whether the presence of a spiral arm influenced B-field properties. Cluster distances, which provide upper limits to the B-field probed by observations, were estimated by developing a maximum likelihood method to fit theoretical stellar isochrones to stars in cluster color-magnitude diagrams (CMDs). Using the distance estimates, the cluster locations relative to the Perseus arm were found. The cluster polarization percentages and orientations were compared between clusters foreground to the arm and clusters inside or behind the arm. The cluster polarization orientations are predominantly parallel to the Galactic plane. Clusters inside and behind the arm have larger polarization percentages, likely a result of more polarizing material along the line of sight. The cluster polarization data were also compared to optical, inner Galaxy NIR, and Planck submm polarimetry data, and showed agreement with all three data sets. The polarimetric properties of one IRDC, G28.23, were determined using deep NIR observations. The polarization orientations relative to the cloud major axis were found to change directions with distance from the cloud axis. The B-field strength was estimated to be 10 to 100microG. Despite these large inferred B-field strengths, the B-field was found not to be the dominant force in the formation of the IRDC, though the B-field morphology was influenced by the cloud. Using NIR observations, the B-field of 27 IRDCs were studied. The relative polarization orientations with respect to the cloud major axes were found. No preferential relative orientation was found, implying that the B-field did not greatly influence the formation of this sample of IRDCs.

Fundamental Particle Structure in the Cosmological Dark Matter

NASA Astrophysics Data System (ADS)

Khlopov, Maxim

2013-11-01

The nonbaryonic dark matter of the universe is assumed to consist of new stable forms of matter. Their stability reflects symmetry of micro-world and mechanisms of its symmetry breaking. Particle candidates for cosmological dark matter are lightest particles that bear new conserved quantum numbers. Dark matter particles may represent ideal gas of noninteracting particles. Self-interacting dark matter weakly or superweakly coupled to ordinary matter is also possible, reflecting nontrivial pattern of particle symmetry in the hidden sector of particle theory. In the early universe the structure of particle symmetry breaking gives rise to cosmological phase transitions, from which macroscopic cosmological defects or primordial nonlinear structures can be originated. Primordial black holes (PBHs) can be not only a candidate for dark matter, but also represent a universal probe for superhigh energy physics in the early universe. Evaporating PBHs turn to be a source of even superweakly interacting particles, while clouds of massive PBHs can serve as nonlinear seeds for galaxy formation. The observed broken symmetry of the three known families may provide a simultaneous solution for the problems of the mass of neutrino and strong CP-violation in the unique framework of models of horizontal unification. Dark matter candidates can also appear in the new families of quarks and leptons and the existence of new stable charged leptons and quarks is possible, hidden in elusive "dark atoms." Such possibility, strongly restricted by the constraints on anomalous isotopes of light elements, is not excluded in scenarios that predict stable double charged particles. The excessive -2 charged particles are bound in these scenarios with primordial helium in O-helium "atoms," maintaining specific nuclear-interacting form of the dark matter, which may provide an interesting solution for the puzzles of the direct dark matter searches. In the context of cosmoparticle physics, studying fundamental relationship of micro- and macro-worlds, the problem of cosmological dark matter implies cross disciplinary theoretical, experimental and observational studies for its solution.

Meteorological interpretation of clouds or cloud systems appearing on pictures of the Alpine region received from the Earth Resources Technology Satellite (ERTS-1)

NASA Technical Reports Server (NTRS)

Piaget, A.

1973-01-01

The author has identified the following significant results. Three examples of cloud-interpretation from ERTS-1 pictures are presented. When the wind speed is large enough, the cumuli are found arranged in lines that are in average two kilometers apart from each other. These lines are grouped in lines made of small cumuli and in lines made up of well developed ones. These last lines are fused on the APT picture and appear as single lines. Fog-mapping for a given region is possible if the topography of the region is known. The stratified clouds lying over mountains or in valleys begin to dissolve above the middle of the valleys and not against the slopes. As water shows a weak albedo in the near infrared, wet surfaces will appear darker than their neighborhoods. This feature seems to be confirmed by the dark spot in the north of Bozen (Southern Tyrol) that can be seen on the ERTS-1 picture taken on 31 August 1972.

Properties of Local Group galaxies in hydrodynamical simulations of sterile neutrino dark matter cosmologies

NASA Astrophysics Data System (ADS)

Lovell, Mark R.; Bose, Sownak; Boyarsky, Alexey; Crain, Robert A.; Frenk, Carlos S.; Hellwing, Wojciech A.; Ludlow, Aaron D.; Navarro, Julio F.; Ruchayskiy, Oleg; Sawala, Till; Schaller, Matthieu; Schaye, Joop; Theuns, Tom

2017-07-01

We study galaxy formation in sterile neutrino dark matter models that differ significantly from both cold and from 'warm thermal relic' models. We use the eagle code to carry out hydrodynamic simulations of the evolution of pairs of galaxies chosen to resemble the Local Group, as part of the APOSTLE simulations project. We compare cold dark matter (CDM) with two sterile neutrino models with 7 keV mass: one, the warmest among all models of this mass (LA120) and the other, a relatively cold case (LA10). We show that the lower concentration of sterile neutrino subhaloes compared to their CDM counterparts makes the inferred inner dark matter content of galaxies like Fornax (or Magellanic Clouds) less of an outlier in the sterile neutrino cosmologies. In terms of the galaxy number counts, the LA10 simulations are indistinguishable from CDM when one takes into account halo-to-halo (or 'simulation-to-simulation') scatter. In order for the LA120 model to match the number of Local Group dwarf galaxies, a higher fraction of low-mass haloes is required to form galaxies than is predicted by the eagle simulations. As the census of the Local Group galaxies nears completion, this population may provide a strong discriminant between cold and warm dark matter models.

Simulations of Early Structure Formation: Primordial Gas Clouds

NASA Astrophysics Data System (ADS)

Yoshida, Naoki; Abel, Tom; Hernquist, Lars; Sugiyama, Naoshi

2003-08-01

We use cosmological simulations to study the origin of primordial star-forming clouds in a ΛCDM universe, by following the formation of dark matter halos and the cooling of gas within them. To model the physics of chemically pristine gas, we employ a nonequilibrium treatment of the chemistry of nine species (e-, H, H+, He, He+, He++, H2, H+2, H-) and include cooling by molecular hydrogen. By considering cosmological volumes, we are able to study the statistical properties of primordial halos, and the high resolution of our simulations enables us to examine these objects in detail. In particular, we explore the hierarchical growth of bound structures forming at redshifts z~25-30 with total masses in the range ~105-106Msolar. We find that when the amount of molecular hydrogen in these objects reaches a critical level, cooling by rotational line emission is efficient, and dense clumps of cold gas form. We identify these ``gas clouds'' as sites for primordial star formation. In our simulations, the threshold for gas cloud formation by molecular cooling corresponds to a critical halo mass of ~5×105h-1Msolar, in agreement with earlier estimates, but with a weak dependence on redshift in the range z>16. The complex interplay between the gravitational formation of dark halos and the thermodynamic and chemical evolution of the gas clouds compromises analytic estimates of the critical H2 fraction. Dynamical heating from mass accretion and mergers opposes relatively inefficient cooling by molecular hydrogen, delaying the production of star-forming clouds in rapidly growing halos. We also investigate the effect of photodissociating ultraviolet radiation on the formation of primordial gas clouds. We consider two extreme cases, first by including a uniform radiation field in the optically thin limit and second by accounting for the maximum effect of gas self-shielding in virialized regions. For radiation with Lyman-Werner band flux J>10-23 ergs s-1 cm-2 Hz-1 sr-1, hydrogen molecules are rapidly dissociated, rendering gas cooling inefficient. In both the cases we consider, the overall effect can be described by computing an equilibrium H2 abundance for the radiation flux and defining an effective shielding factor. Based on our numerical results, we develop a semianalytic model of the formation of the first stars and demonstrate how it can be coupled with large N-body simulations to predict the star formation rate in the early universe.

Infrared Cloud Imager Development for Atmospheric Optical Communication Characterization, and Measurements at the JPL Table Mountain Facility

NASA Astrophysics Data System (ADS)

Nugent, P. W.; Shaw, J. A.; Piazzolla, S.

2013-02-01

The continuous demand for high data return in deep space and near-Earth satellite missions has led NASA and international institutions to consider alternative technologies for high-data-rate communications. One solution is the establishment of wide-bandwidth Earth-space optical communication links, which require (among other things) a nearly obstruction-free atmospheric path. Considering the atmospheric channel, the most common and most apparent impairments on Earth-space optical communication paths arise from clouds. Therefore, the characterization of the statistical behavior of cloud coverage for optical communication ground station candidate sites is of vital importance. In this article, we describe the development and deployment of a ground-based, long-wavelength infrared cloud imaging system able to monitor and characterize the cloud coverage. This system is based on a commercially available camera with a 62-deg diagonal field of view. A novel internal-shutter-based calibration technique allows radiometric calibration of the camera, which operates without a thermoelectric cooler. This cloud imaging system provides continuous day-night cloud detection with constant sensitivity. The cloud imaging system also includes data-processing algorithms that calculate and remove atmospheric emission to isolate cloud signatures, and enable classification of clouds according to their optical attenuation. Measurements of long-wavelength infrared cloud radiance are used to retrieve the optical attenuation (cloud optical depth due to absorption and scattering) in the wavelength range of interest from visible to near-infrared, where the cloud attenuation is quite constant. This article addresses the specifics of the operation, calibration, and data processing of the imaging system that was deployed at the NASA/JPL Table Mountain Facility (TMF) in California. Data are reported from July 2008 to July 2010. These data describe seasonal variability in cloud cover at the TMF site, with cloud amount (percentage of cloudy pixels) peaking at just over 51 percent during February, of which more than 60 percent had optical attenuation exceeding 12 dB at wavelengths in the range from the visible to the near-infrared. The lowest cloud amount was found during August, averaging 19.6 percent, and these clouds were mostly optically thin, with low attenuation.

Clouds and Ice of the Lambert-Amery System, East Antarctica

NASA Technical Reports Server (NTRS)

2002-01-01

These views from the Multi-angle Imaging SpectroRadiometer (MISR) illustrate ice surface textures and cloud-top heights over the Amery Ice Shelf/Lambert Glacier system in East Antarctica on October 25, 2002.

The left-hand panel is a natural-color view from MISR's downward-looking (nadir) camera. The center panel is a multi-angular composite from three MISR cameras, in which color acts as a proxy for angular reflectance variations related to texture. Here, data from the red-band of MISR's 60o forward-viewing, nadir and 60o backward-viewing cameras are displayed as red, green and blue, respectively. With this display technique, surfaces which predominantly exhibit backward-scattering (generally rough surfaces) appear red/orange, while surfaces which predominantly exhibit forward-scattering (generally smooth surfaces) appear blue. Textural variation for both the grounded and sea ice are apparent. The red/orange pixels in the lower portion of the image correspond with a rough and crevassed region near the grounding zone, that is, the area where the Lambert and four other smaller glaciers merge and the ice starts to float as it forms the Amery Ice Shelf. In the natural-color view, this rough ice is spectrally blue in color.

Clouds exhibit both forward and backward-scattering properties in the middle panel and thus appear purple, in distinct contrast with the underlying ice and snow. An additional multi-angular technique for differentiating clouds from ice is shown in the right-hand panel, which is a stereoscopically derived height field retrieved using automated pattern recognition involving data from multiple MISR cameras. Areas exhibiting insufficient spatial contrast for stereoscopic retrieval are shown in dark gray. Clouds are apparent as a result of their heights above the surface terrain. Polar clouds are an important factor in weather and climate. Inadequate characterization of cloud properties is currently responsible for large uncertainties in climate prediction models. Identification of polar clouds, mapping of their distributions, and retrieval of their heights provide information that will help to reduce this uncertainty.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously and every 9 days views the entire Earth between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 15171. The panels cover an area of 380 kilometers x 984 kilometers, and utilize data from blocks 145 to 151 within World Reference System-2 path 127.

MISR was built and is managed by NASA's Jet Propulsion Laboratory,Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center,Greenbelt, MD. JPL is a division of the California Institute of Technology.

Cloud cover analysis associated to cut-off low-pressure systems over Europe using Meteosat Imagery

NASA Astrophysics Data System (ADS)

Delgado, G.; Redaño, A.; Lorente, J.; Nieto, R.; Gimeno, L.; Ribera, P.; Barriopedro, D.; García-Herrera, R.; Serrano, A.

2007-04-01

This paper reports a cloud cover analysis of cut-off low pressure systems (COL) using a pattern recognition method applied to IR and VIS bispectral histograms. 35 COL occurrences were studied over five years (1994-1998). Five cloud types were identified in COLs, of which high clouds (HCC) and deep convective clouds (DCC) were found to be the most relevant to characterize COL systems, though not the most numerous. Cloud cover in a COL is highly dependent on its stage of development, but a higher percentage of cloud cover is always present in the frontal zone, attributable due to higher amounts of high and deep convective clouds. These general characteristics are most marked during the first stage (when the amplitude of the geopotencial wave increases) and second stage (characterized by the development of a cold upper level low), closed cyclonic circulation minimizing differences between rearward and frontal zones during the third stage. The probability of heavy rains during this stage decreases considerably. The centres of mass of high and deep convective clouds move towards the COL-axis centre during COL evolution.

The New Worlds Observer: The Astrophysics Strategic Mission Concept Study

DTIC Science & Technology

2009-08-01

of galaxies and galaxy clusters • Tracing the cosmic evolution of dark energy • Mapping the distribution of dark matter • Characterization of the...imaging of these fields will be used to map the distribution of dark matter us- ing the distortions of galaxy images produced by weak gravitational...dedicated to specific science goals such as mapping dark matter , tracing dark energy, or prob- ing star formation in the local Universe. In the dif

E4 True and False Color Hot Spot Mosaic

NASA Image and Video Library

1998-03-06

True and false color views of Jupiter from NASA's Galileo spacecraft show an equatorial "hotspot" on Jupiter. These images cover an area 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles). The top mosaic combines the violet and near infrared continuum filter images to create an image similar to how Jupiter would appear to human eyes. Differences in coloration are due to the composition and abundances of trace chemicals in Jupiter's atmosphere. The bottom mosaic uses Galileo's three near-infrared wavelengths displayed in red, green, and blue) to show variations in cloud height and thickness. Bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the deep cloud with an overlying thin haze. The light blue region to the left is covered by a very high haze layer. The multicolored region to the right has overlapping cloud layers of different heights. Galileo is the first spacecraft to distinguish cloud layers on Jupiter. North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging camera system aboard Galileo. http://photojournal.jpl.nasa.gov/catalog/PIA00602

Earth Observations taken by Expedition 34 crewmember

NASA Image and Video Library

2013-01-05

ISS034-E-024622 (5 Jan. 2013) --- Polar mesospheric clouds over the South Pacific Ocean are featured in this image photographed by an Expedition 34 crew member on the International Space Station. Polar mesospheric clouds—also known as noctilucent, or “night shining” clouds—are formed 76 to 85 kilometers above Earth’s surface near the mesosphere-thermosphere boundary of the atmosphere, a region known as the mesopause. At these altitudes, water vapor can freeze into clouds of ice crystals. When the sun is below the horizon such that the ground is in darkness, these high clouds may still be illuminated—lending them their ethereal, “night shining” qualities. Noctilucent clouds have been observed from all human vantage points in both the Northern and Southern Hemispheres – from the surface, in aircraft, and in orbit from the space station—and tend to be most visible during the late spring and early summer seasons. Polar mesospheric clouds also are of interest to scientists studying the atmosphere. While some scientists seek to understand their mechanisms of formation, others have identified them as potential indicators of atmospheric changes resulting from increases in greenhouse gas concentrations. This photograph was taken when the station was over the Pacific Ocean south of French Polynesia. While most polar mesospheric cloud images are taken from the orbital complex with relatively short focal length lens to maximize the field of view, this image was taken with a long lens (400 mm) allowing for additional detail of the cloud forms to be seen. Below the brightly-lit noctilucent clouds in the center of the image, the pale orange band indicates the stratosphere.

Importance of molecular Rayleigh scattering in the enhancement of clear sky reflectance in the vicinity of boundary layer cumulus clouds

NASA Astrophysics Data System (ADS)

Wen, Guoyong; Marshak, Alexander; Cahalan, Robert F.

2008-12-01

Clouds increase the complexity of atmospheric radiative transfer processes, particularly for aerosol retrievals in clear regions in the vicinity of clouds. This study focuses on identifying mechanisms responsible for the enhancement of nadir reflectance in clear regions in the vicinity of cumulus clouds and quantifies the relative importance of each mechanism. Using cloud optical properties and surface albedo derived from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and Moderate Resolution Imaging Spectroradiometer (MODIS), we performed extensive Monte Carlo simulations of radiative transfer in two cumulus scenes in a biomass burning region in Brazil. The results show that the scattering of radiation by clouds, followed by upward Rayleigh scattering by molecules above cloud top over clear gaps, is the dominant mechanism for the enhancement of visible reflectance in clear regions in boundary layer cumulus field over dark surfaces with aerosols trapped in the boundary layer. The Rayleigh scattering contributes ˜80% and ˜50% to the total enhancement for wavelengths 0.47 μm (with aerosol optical thickness 0.2) and 0.66 μm (with aerosol optical thickness 0.1), respectively. Out of the total contribution of molecular scattering, ˜90% arises from the clear atmosphere above cloud top height. The mechanism is valid for a large range of aerosol optical thicknesses (up to 1 in this study) for 0.47 μm, and for aerosol optical thickness up to 0.2 for 0.66 μm. Our results provide a basis to develop simplifications for future aerosol remote sensing from satellite.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pauly, Tyler; Garrod, Robin T., E-mail: tap74@cornell.edu

Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays amore » significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface–gas interactions.« less

Boundary Conditions for the Paleoenvironment: Chemical and Physical Processes in Dense Interstellar Clouds: Summary of Research

NASA Technical Reports Server (NTRS)

Irvine, William M.

1999-01-01

The basic theme of this program was the study of molecular complexity and evolution for the biogenic elements and compounds in interstellar clouds and in primitive solar system objects. Research included the detection and study of new interstellar and cometary molecules and investigation of reaction pathways for astrochemistry from a comparison of theory and observed molecular abundances. The latter includes studies of cold, dark clouds in which ion-molecule chemistry should predominate, searches for the effects of interchange of material between the gas and solid phases in interstellar clouds, unbiased spectral surveys of particular sources, and systematic investigation of the interlinked chemistry and physics of dense interstellar clouds. In addition, the study of comets has allowed a comparison between the chemistry of such minimally thermally processed objects and that of interstellar clouds, shedding light on the evolution of the biogenic elements during the process of solar system formation. One PhD dissertation on this research was completed by a graduate student at the University of Massachusetts. An additional 4 graduate students at the University of Massachusetts and 5 graduate students from other institutions participated in research supported by this grant, with 6 of these thus far receiving PhD degrees from the University of Massachusetts or their home institutions. Four postdoctoral research associates at the University of Massachusetts also participated in research supported by this grant, receiving valuable training.

Aerosol and Cloud Microphysical Characteristics of Rifts and Gradients in Maritime Stratocumulus Clouds

NASA Technical Reports Server (NTRS)

Sharon, Tarah M.; Albrecht, Bruce A.; Jonsson, Haflidi H.; Minnis, Patrick; Khaiyer, Mandana M.; Van Reken, Timothy; Seinfeld, John; Flagan, Rick

2008-01-01

A cloud rift is characterized as a large-scale, persistent area of broken, low reflectivity stratocumulus clouds usually surrounded by a solid deck of stratocumulus. A rift observed off the coast of Monterey Bay, California on 16 July 1999 was studied to compare the aerosol and cloud microphysical properties in the rift with those of the surrounding solid stratus deck. Variables measured from an instrumented aircraft included temperature, water vapor, and cloud liquid water. These measurements characterized the thermodynamic properties of the solid deck and rift areas. Microphysical measurements made included aerosol, cloud drop and drizzle drop concentrations and cloud condensation nuclei (CCN) concentrations. The microphysical characteristics in a solid stratus deck differ substantially from those of a broken, cellular rift where cloud droplet concentrations are a factor of 2 lower than those in the solid cloud. Further, CCN concentrations were found to be about 3 times greater in the solid cloud area compared with those in the rift and aerosol concentrations showed a similar difference as well. Although drizzle was observed near cloud top in parts of the solid stratus cloud, the largest drizzle rates were associated with the broken clouds within the rift area. In addition to marked differences in particle concentrations, evidence of a mesoscale circulation near the solid cloud rift boundary is presented. This mesoscale circulation provides a mechanism for maintaining a rift, but further study is required to understand the initiation of a rift and the conditions that may cause it to fill.

Is the gas-phase OH+H2CO reaction a source of HCO in interstellar cold dark clouds? A kinetic, dynamic and modelling study

PubMed Central

Ocaña, A. J.; Jiménez, E.; Ballesteros, B.; Canosa, A.; Antiñolo, M.; Albaladejo, J.; Agúndez, M.; Cernicharo, J.; Zanchet, A.; del Mazo, P.; Roncero, O.; Aguado, A.

2018-01-01

Chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T∼10-100K). Scarce kinetic information is currently available for this kind of reactions at T<200 K. In this work we use the CRESU (Cinétique de Réaction en Ecoulement Supersonique Uniforme, which means Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients (k) of the gas-phase OH+H2CO reaction between 22 and 107 K. k values greatly increase from 2.1×10-11 cm3 s-1 at 107 K to 1.2×10-10 cm3 s-1 at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and ab initio potential energy surface, recently developed which generates highly accurate potential and includes long range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+H2CO reaction. In order to revisit the chemistry of HCO in cold dense clouds, k is reasonably extrapolated from the experimental results at 10K (2.6×10-10 cm3 s-1). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 105-106 yrs. The different sources of production of HCO are presented and the uncertainties in the chemical networks discussed. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. The present reaction is shown to account for a few percent of the total HCO production rate. Extensions to photodissociation regions and diffuse clouds environments are also commented. PMID:29880977

Dark and Stormy Jupiter

NASA Image and Video Library

2018-06-14

This image captures the intensity of the jets and vortices in Jupiter's North North Temperate Belt. NASA's Juno spacecraft took this color-enhanced image at 10:31 p.m. PDT on May 23, 2018 (1:31 a.m. EDT on May 24), as Juno performed its 13th close flyby of Jupiter. At the time, the spacecraft was about 4,900 miles (7,900 kilometers) from the tops of the clouds of the gas giant planet at a northern latitude of about 41 degrees. The view is oriented with south on Jupiter toward upper left and north toward lower right. The North North Temperate Belt is the prominent reddish-orange band left of center. It rotates in the same direction as the planet and is predominantly cyclonic, which in the northern hemisphere means its features spin in a counter-clockwise direction. Within the belt are two gray-colored anticyclones. To the left of the belt is a brighter band (the North North Temperate Zone) with high clouds whose vertical relief is accentuated by the low angle of sunlight near the terminator. These clouds are likely made of ammonia-ice crystals, or possibly a combination of ammonia ice and water. Although the region as a whole appears chaotic, there is an alternating pattern of rotating, lighter-colored features on the zone's north and south sides. Scientists think the large-scale dark regions are places where the clouds are deeper, based on infrared observations made at the same time by Juno's JIRAM experiment and Earth-based supporting observations. Those observations show warmer, and thus deeper, thermal emission from these regions. To the right of the bright zone, and farther north on the planet, Jupiter's striking banded structure becomes less evident and a region of individual cyclones can be seen, interspersed with smaller, darker anticyclones. https://photojournal.jpl.nasa.gov/catalog/PIA22423

Is the Gas-phase OH+H2CO Reaction a Source of HCO in Interstellar Cold Dark Clouds? A Kinetic, Dynamic, and Modeling Study

NASA Astrophysics Data System (ADS)

Ocaña, A. J.; Jiménez, E.; Ballesteros, B.; Canosa, A.; Antiñolo, M.; Albaladejo, J.; Agúndez, M.; Cernicharo, J.; Zanchet, A.; del Mazo, P.; Roncero, O.; Aguado, A.

2017-11-01

The chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T ˜ 10-100 K). Scarce kinetic information is currently available for these kinds of reactions at T < 200 K. In this work, we use the Cinétique de Réaction en Ecoulement Supersonique Uniforme (CRESU; Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients (k) of the gas-phase OH+H2CO reaction between 22 and 107 K. The k values greatly increase from 2.1 × 10-11 cm3 s-1 at 107 K to 1.2 × 10-10 cm3 s-1 at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and ab initio potential energy surface that generates highly accurate potential and includes long-range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+H2CO reaction. In order to revisit the chemistry of HCO in cold dense clouds, k is reasonably extrapolated from the experimental results at 10 K (2.6 × 10-10 cm3 s-1). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 105-106 yr. The different sources of production of HCO are presented and the uncertainties in the chemical networks are discussed. The present reaction is shown to account for a few percent of the total HCO production rate. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. Extensions to photodissociation regions and diffuse cloud environments are also addressed.

Is the gas-phase OH+H2CO reaction a source of HCO in interstellar cold dark clouds? A kinetic, dynamic and modelling study.

PubMed

Ocaña, A J; Jiménez, E; Ballesteros, B; Canosa, A; Antiñolo, M; Albaladejo, J; Agúndez, M; Cernicharo, J; Zanchet, A; Del Mazo, P; Roncero, O; Aguado, A

2017-11-20

Chemical kinetics of neutral-neutral gas-phase reactions at ultralow temperatures is a fascinating research subject with important implications on the chemistry of complex organic molecules in the interstellar medium (T∼10-100K). Scarce kinetic information is currently available for this kind of reactions at T<200 K. In this work we use the CRESU ( Cinétique de Réaction en Ecoulement Supersonique Uniforme , which means Reaction Kinetics in a Uniform Supersonic Flow) technique to measure for the first time the rate coefficients ( k ) of the gas-phase OH+H 2 CO reaction between 22 and 107 K. k values greatly increase from 2.1×10 -11 cm 3 s -1 at 107 K to 1.2×10 -10 cm 3 s -1 at 22 K. This is also confirmed by quasi-classical trajectories (QCT) at collision energies down to 0.1 meV performed using a new full dimension and ab initio potential energy surface, recently developed which generates highly accurate potential and includes long range dipole-dipole interactions. QCT calculations indicate that at low temperatures HCO is the exclusive product for the OH+H 2 CO reaction. In order to revisit the chemistry of HCO in cold dense clouds, k is reasonably extrapolated from the experimental results at 10K (2.6×10 -10 cm 3 s -1 ). The modeled abundances of HCO are in agreement with the observations in cold dark clouds for an evolving time of 10 5 -10 6 yrs. The different sources of production of HCO are presented and the uncertainties in the chemical networks discussed. This reaction can be expected to be a competitive process in the chemistry of prestellar cores. The present reaction is shown to account for a few percent of the total HCO production rate. Extensions to photodissociation regions and diffuse clouds environments are also commented.

Kinetic Monte Carlo simulations of water ice porosity: extrapolations of deposition parameters from the laboratory to interstellar space

NASA Astrophysics Data System (ADS)

Clements, Aspen R.; Berk, Brandon; Cooke, Ilsa R.; Garrod, Robin T.

2018-02-01

Using an off-lattice kinetic Monte Carlo model we reproduce experimental laboratory trends in the density of amorphous solid water (ASW) for varied deposition angle, rate and surface temperature. Extrapolation of the model to conditions appropriate to protoplanetary disks and interstellar dark clouds indicate that these ices may be less porous than laboratory ices.

Hubble Provides Infrared View of Jupiter's Moon, Ring, and Clouds

NASA Technical Reports Server (NTRS)

1997-01-01

Probing Jupiter's atmosphere for the first time, the Hubble Space Telescope's new Near Infrared Camera and Multi-Object Spectrometer (NICMOS) provides a sharp glimpse of the planet's ring, moon, and high-altitude clouds.

The presence of methane in Jupiter's hydrogen- and helium-rich atmosphere has allowed NICMOS to plumb Jupiter's atmosphere, revealing bands of high-altitude clouds. Visible light observations cannot provide a clear view of these high clouds because the underlying clouds reflect so much visible light that the higher level clouds are indistinguishable from the lower layer. The methane gas between the main cloud deck and the high clouds absorbs the reflected infrared light, allowing those clouds that are above most of the atmosphere to appear bright. Scientists will use NICMOS to study the high altitude portion of Jupiter's atmosphere to study clouds at lower levels. They will then analyze those images along with visible light information to compile a clearer picture of the planet's weather. Clouds at different levels tell unique stories. On Earth, for example, ice crystal (cirrus) clouds are found at high altitudes while water (cumulus) clouds are at lower levels.

Besides showing details of the planet's high-altitude clouds, NICMOS also provides a clear view of the ring and the moon, Metis. Jupiter's ring plane, seen nearly edge-on, is visible as a faint line on the upper right portion of the NICMOS image. Metis can be seen in the ring plane (the bright circle on the ring's outer edge). The moon is 25 miles wide and about 80,000 miles from Jupiter.

Because of the near-infrared camera's narrow field of view, this image is a mosaic constructed from three individual images taken Sept. 17, 1997. The color intensity was adjusted to accentuate the high-altitude clouds. The dark circle on the disk of Jupiter (center of image) is an artifact of the imaging system.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

Dark Signal Characterization of 1.7 micron cutoff devices for SNAP

NASA Astrophysics Data System (ADS)

Smith, R. M.; SNAP Collaboration

2004-12-01

We report initial progress characterizing non-photometric sources of error -- dark current, noise, and zero point drift -- for 1.7 micron cutoff HgCdTe and InGaAs detectors under development by Raytheon, Rockwell, and Sensors Unlimited for SNAP. Dark current specifications can already be met with several detector types. Changes to the manufacturing process are being explored to improve the noise reduction available through multiple sampling. In some cases, a significant number of pixels suffer from popcorn noise, with a few percent of all pixels exhibiting a ten fold noise increase. A careful study of zero point drifts is also under way, since these errors can dominate dark current, and may contribute to the noise degradation seen in long exposures.

The Clouds of Isidore

NASA Technical Reports Server (NTRS)

2002-01-01

These views of Hurricane Isidore were acquired by the Multi-angle Imaging SpectroRadiometer (MISR) on September 20, 2002. After bringing large-scale flooding to western Cuba, Isidore was upgraded (on September 21) from a tropical storm to a category 3hurricane. Sweeping westward to Mexico's Yucatan Peninsula, the hurricane caused major destruction and left hundreds of thousands of people homeless. Although weakened after passing over the Yucatan landmass, Isidore regained strength as it moved northward over the Gulf of Mexico.

At left is a colorful visualization of cloud extent that superimposes MISR's radiometric camera-by-camera cloud mask (RCCM) over natural-color radiance imagery, both derived from data acquired with the instrument's vertical-viewing (nadir) camera. Using brightness and statistical metrics, the RCCM is one of several techniques MISR uses to determine whether an area is clear or cloudy. In this rendition, the RCCM has been color-coded, and purple = cloudy with high confidence, blue = cloudy with low confidence, green = clear with low confidence, and red = clear with high confidence.

In addition to providing information on meteorological events, MISR's data products are designed to help improve our understanding of the influences of clouds on climate. Cloud heights and albedos are among the variables that govern these influences. (Albedo is the amount of sunlight reflected back to space divided by the amount of incident sunlight.) The center panel is the cloud-top height field retrieved using automated stereoscopic processing of data from multiple MISR cameras. Areas where heights could not be retrieved are shown in dark gray. In some areas, such as the southern portion of the image, the stereo retrieval was able to detect thin, high clouds that were not picked up by the RCCM's nadir view. Retrieved local albedo values for Isidore are shown at right. Generation of the albedo product is dependent upon observed cloud radiances as a function of viewing angle as well as the height field. Note that over the short distances (2.2 kilometers) that the local albedo product is generated, values can be greater than 1.0 due to contributions from cloud sides. Areas where albedo could not be retrieved are shown in dark gray.

The Multi-angle Imaging SpectroRadiometer observes the daylit Earth continuously from pole to pole, and every 9 days views the entire globe between 82 degrees north and 82 degrees south latitude. These data products were generated from a portion of the imagery acquired during Terra orbit 14669. The panels cover an area of about 380 kilometers x 704 kilometers, and utilize data from blocks 70 to 79within World Reference System-2 path 17.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Jupiter Equatorial Region in a Methane Band Time Set 1

NASA Image and Video Library

1998-03-06

Mosaic of an equatorial "hotspot" on Jupiter at 889 nanometers (nm). The mosaic covers an area of 34,000 kilometers by 11,000 kilometers. Light at 889 nm is strongly absorbed by atmospheric methane. This image shows the features of a hazy cloud layer tens of kilometers above Jupiter's main visible cloud deck. This haze varies in height but appears to be present over the entire region. Small patches of very bright clouds may be similar to terrestrial thunderstorms. The dark region near the center of the mosaic is an equatorial "hotspot" similar to the Galileo Probe entry site. These features are holes in the bright, reflective, equatorial cloud layer where warmer thermal emission from Jupiter's deep atmosphere can pass through. The circulation patterns observed here along with the composition measurements from the Galileo Probe suggest that dry air may be converging and sinking over these regions, maintaining their cloud-free appearance. North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees West. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers by the Solid State Imaging system aboard NASA's Galileo spacecraft. http://photojournal.jpl.nasa.gov/catalog/PIA01200

Scanning Backscatter Lidar Observations for Characterizing 4-D Cloud and Aerosol Fields to Improve Radiative Transfer Parameterizations

NASA Technical Reports Server (NTRS)

Schwemmer, Geary K.; Miller, David O.

2005-01-01

Clouds have a powerful influence on atmospheric radiative transfer and hence are crucial to understanding and interpreting the exchange of radiation between the Earth's surface, the atmosphere, and space. Because clouds are highly variable in space, time and physical makeup, it is important to be able to observe them in three dimensions (3-D) with sufficient resolution that the data can be used to generate and validate parameterizations of cloud fields at the resolution scale of global climate models (GCMs). Simulation of photon transport in three dimensionally inhomogeneous cloud fields show that spatial inhomogeneities tend to decrease cloud reflection and absorption and increase direct and diffuse transmission, Therefore it is an important task to characterize cloud spatial structures in three dimensions on the scale of GCM grid elements. In order to validate cloud parameterizations that represent the ensemble, or mean and variance of cloud properties within a GCM grid element, measurements of the parameters must be obtained on a much finer scale so that the statistics on those measurements are truly representative. High spatial sampling resolution is required, on the order of 1 km or less. Since the radiation fields respond almost instantaneously to changes in the cloud field, and clouds changes occur on scales of seconds and less when viewed on scales of approximately 100m, the temporal resolution of cloud properties should be measured and characterized on second time scales. GCM time steps are typically on the order of an hour, but in order to obtain sufficient statistical representations of cloud properties in the parameterizations that are used as model inputs, averaged values of cloud properties should be calculated on time scales on the order of 10-100 s. The Holographic Airborne Rotating Lidar Instrument Experiment (HARLIE) provides exceptional temporal (100 ms) and spatial (30 m) resolution measurements of aerosol and cloud backscatter in three dimensions. HARLIE was used in a ground-based configuration in several recent field campaigns. Principal data products include aerosol backscatter profiles, boundary layer heights, entrainment zone thickness, cloud fraction as a function of altitude and horizontal wind vector profiles based on correlating the motions of clouds and aerosol structures across portions of the scan. Comparisons will be made between various cloud detecting instruments to develop a baseline performance metric.

Cryogenic Characterization of FBK RGB-HD SiPMs

NASA Astrophysics Data System (ADS)

Aalseth, C. E.; Acerbi, F.; Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; Alici, A.; Alton, A. K.; Ampudia, P.; Antonioli, P.; Arcelli, S.; Ardito, R.; Arnquist, I. J.; Asner, D. M.; Back, H. O.; Batignani, G.; Bertoldo, E.; Bettarini, S.; Bisogni, M. G.; Bocci, V.; Bondar, A.; Bonfini, G.; Bonivento, W.; Bossa, M.; Bottino, B.; Bunker, R.; Bussino, S.; Buzulutskov, A.; Cadeddu, M.; Cadoni, M.; Caminata, A.; Canci, N.; Candela, A.; Cantini, C.; Caravati, M.; Cariello, M.; Carlini, M.; Carpinelli, M.; Castellani, A.; Catalanotti, S.; Cataudella, V.; Cavalcante, P.; Cereseto, R.; Chen, Y.; Chepurnov, A.; Chiavassa, A.; Cicalò, C.; Cifarelli, L.; Citterio, M.; Cocco, A. G.; Colocci, M.; Corgiolu, S.; Covone, G.; Crivelli, P.; D'Antone, I.; D'Incecco, M.; Da Rocha Rolo, M. D.; Daniel, M.; Davini, S.; De Candia, A.; De Cecco, S.; De Deo, M.; De Filippis, G.; De Guido, G.; De Rosa, G.; Dellacasa, G.; Demontis, P.; Derbin, A. V.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Dolgov, A.; Dormia, I.; Dussoni, S.; Empl, A.; Ferri, A.; Filip, C.; Fiorillo, G.; Fomenko, K.; Franco, D.; Froudakis, G. E.; Gabriele, F.; Gabrieli, A.; Galbiati, C.; Garcia Abia, P.; Gendotti, A.; Ghisi, A.; Giagu, S.; Gibertoni, G.; Giganti, C.; Giorgi, M.; Giovanetti, G. K.; Gligan, M. L.; Gola, A.; Gorchakov, O.; Goretti, A. M.; Granato, F.; Grassi, M.; Grate, J. W.; Grigoriev, G. Y.; Gromov, M.; Guan, M.; Guerra, M. B. B.; Guerzoni, M.; Gulino, M.; Haaland, R. K.; Harrop, B.; Hoppe, E. W.; Horikawa, S.; Hosseini, B.; Hughes, D.; Humble, P.; Hungerford, E. V.; Ianni, An.; Jimenez Cabre, S.; Johnson, T. N.; Keeter, K.; Kendziora, C. L.; Kim, S.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Kugathasan, R.; Kuss, M.; Li, X.; Lissia, M.; Lodi, G. U.; Loer, B.; Longo, G.; Lussana, R.; Luzzi, L.; Ma, Y.; Machado, A. A.; Machulin, I. N.; Mais, L.; Mandarano, A.; Mapelli, L.; Marcante, M.; Margotti, A.; Mari, S. M.; Mariani, M.; Maricic, J.; Marinelli, M.; Marras, D.; Martoff, C. J.; Mascia, M.; Messina, A.; Meyers, P. D.; Milincic, R.; Moggi, A.; Moioli, S.; Monasterio, S.; Monroe, J.; Monte, A.; Morrocchi, M.; Mu, W.; Muratova, V. N.; Murphy, S.; Musico, P.; Nania, R.; Napolitano, J.; Navrer Agasson, A.; Nikulin, I.; Nosov, V.; Nozdrina, A. O.; Nurakhov, N. N.; Oleinik, A.; Oleynikov, V.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Palmas, S.; Pandola, L.; Pantic, E.; Paoloni, E.; Paternoster, G.; Pavletcov, V.; Pazzona, F.; Pelczar, K.; Pellegrini, L. A.; Pelliccia, N.; Perotti, F.; Perruzza, R.; Piemonte, C.; Pilo, F.; Pocar, A.; Portaluppi, D.; Poudel, S. S.; Pugachev, D. A.; Qian, H.; Radics, B.; Raffaelli, F.; Ragusa, F.; Randle, K.; Razeti, M.; Razeto, A.; Regazzoni, V.; Regenfus, C.; Reinhold, B.; Renshaw, A. L.; Rescigno, M.; Riffard, Q.; Rivetti, A.; Romani, A.; Romero, L.; Rossi, B.; Rossi, N.; Rubbia, A.; Sablone, D.; Salatino, P.; Samoylov, O.; Sands, W.; Sant, M.; Santorelli, R.; Savarese, C.; Scapparone, E.; Schlitzer, B.; Scioli, G.; Sechi, E.; Segreto, E.; Seifert, A.; Semenov, D. A.; Serci, S.; Shchagin, A.; Shekhtman, L.; Shemyakina, E.; Sheshukov, A.; Simeone, M.; Singh, P. N.; Skorokhvatov, M. D.; Smirnov, O.; Sobrero, G.; Sokolov, A.; Sotnikov, A.; Stanford, C.; Suffritti, G. B.; Suvorov, Y.; Tartaglia, R.; Testera, G.; Tonazzo, A.; Tosi, A.; Trinchese, P.; Unzhakov, E. V.; Vacca, A.; Verducci, M.; Viant, T.; Villa, F.; Vishneva, A.; Vogelaar, B.; Wada, M.; Wahl, J.; Walker, S.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, J.; Williams, R.; Wojcik, M. M.; Wu, S.; Xiang, X.; Xiao, X.; Yang, C.; Ye, Z.; Zappa, F.; Zappalà, G.; Zhu, C.; Zichichi, A.; Zuzel, G.

2017-09-01

We report on the cryogenic characterization of Red Green Blue - High Density (RGB-HD) SiPMs developed at Fondazione Bruno Kessler (FBK) as part of the DarkSide program of dark matter searches with liquid argon time projection chambers. A cryogenic setup was used to operate the SiPMs at varying temperatures and a custom data acquisition system and analysis software were used to precisely characterize the primary dark noise, the correlated noise, and the gain of the devices. We demonstrate that FBK RGB-HD SiPMs with low quenching resistance (RGB-HD-LRq) can be operated from 40 K to 300 K with gains in the range 105 to 106 and noise rates at a level of around 1 Hz/mm2.

Dark matter as a trigger for periodic comet impacts.

PubMed

Randall, Lisa; Reece, Matthew

2014-04-25

Although statistical evidence is not overwhelming, possible support for an approximately 35×106  yr periodicity in the crater record on Earth could indicate a nonrandom underlying enhancement of meteorite impacts at regular intervals. A proposed explanation in terms of tidal effects on Oort cloud comet perturbations as the Solar System passes through the galactic midplane is hampered by lack of an underlying cause for sufficiently enhanced gravitational effects over a sufficiently short time interval and by the time frame between such possible enhancements. We show that a smooth dark disk in the galactic midplane would address both these issues and create a periodic enhancement of the sort that has potentially been observed. Such a disk is motivated by a novel dark matter component with dissipative cooling that we considered in earlier work. We show how to evaluate the statistical evidence for periodicity by input of appropriate measured priors from the galactic model, justifying or ruling out periodic cratering with more confidence than by evaluating the data without an underlying model. We find that, marginalizing over astrophysical uncertainties, the likelihood ratio for such a model relative to one with a constant cratering rate is 3.0, which moderately favors the dark disk model. Our analysis furthermore yields a posterior distribution that, based on current crater data, singles out a dark matter disk surface density of approximately 10M⊙/pc2. The geological record thereby motivates a particular model of dark matter that will be probed in the near future.

A Massive Prestellar Clump Hosting No High-mass Cores

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanhueza, Patricio; Lu, Xing; Tatematsu, Ken’ichi

The infrared dark cloud (IRDC) G028.23-00.19 hosts a massive (1500 M {sub ⊙}), cold (12 K), and 3.6–70 μ m IR dark clump (MM1) that has the potential to form high-mass stars. We observed this prestellar clump candidate with the Submillimeter Array (∼3.″5 resolution) and Jansky Very Large Array (∼2.″1 resolution) in order to characterize the early stages of high-mass star formation and to constrain theoretical models. Dust emission at 1.3 mm wavelength reveals five cores with masses ≤15 M {sub ⊙}. None of the cores currently have the mass reservoir to form a high-mass star in the prestellar phase.more » If the MM1 clump will ultimately form high-mass stars, its embedded cores must gather a significant amount of additional mass over time. No molecular outflows are detected in the CO (2-1) and SiO (5-4) transitions, suggesting that the SMA cores are starless. By using the NH{sub 3} (1, 1) line, the velocity dispersion of the gas is determined to be transonic or mildly supersonic (Δ V {sub nt}/Δ V {sub th} ∼ 1.1–1.8). The cores are not highly supersonic as some theories of high-mass star formation predict. The embedded cores are four to seven times more massive than the clump thermal Jeans mass and the most massive core (SMA1) is nine times less massive than the clump turbulent Jeans mass. These values indicate that neither thermal pressure nor turbulent pressure dominates the fragmentation of MM1. The low virial parameters of the cores (0.1–0.5) suggest that they are not in virial equilibrium, unless strong magnetic fields of ∼1–2 mG are present. We discuss high-mass star formation scenarios in a context based on IRDC G028.23-00.19, a study case believed to represent the initial fragmentation of molecular clouds that will form high-mass stars.« less

Screaming Clouds

NASA Astrophysics Data System (ADS)

Fikke, Svein; Egill Kristjánsson, Jón; Nordli, Øyvind

2017-04-01

"Mother-of-pearl clouds" appear irregularly in the winter stratosphere at high northern latitudes, about 20-30 km above the surface of the Earth. The size range of the cloud particles is near that of visible light, which explains their extraordinary beautiful colours. We argue that the Norwegian painter Edvard Munch could well have been terrified when the sky all of a sudden turned "bloodish red" after sunset, when darkness was expected. Hence, there is a high probability that it was an event of mother-of-pearl clouds which was the background for Munch's experience in nature, and for his iconic Scream. Currently, the leading hypothesis for explaining the dramatic colours of the sky in Munch's famous painting is that the artist was captivated by colourful sunsets following the enormous Krakatoa eruption in 1883. After carefully considering the historical accounts of some of Munch's contemporaries, especially the physicist Carl Störmer, we suggest an alternative hypothesis, namely that Munch was inspired by spectacular occurrences of mother-of-pearl clouds. Such clouds, which have a wave-like structure akin to that seen in the Scream were first observed and described only a few years before the first version of this motive was released in 1892. Unlike clouds related to conventional weather systems in the troposphere, mother-of-pearl clouds appear in the stratosphere, where significantly different physical conditions prevail. This result in droplet sizes within the range of visible light, creating the spectacular colour patterns these clouds are famous for. Carl Störmer observed such clouds, and described them in minute details at the age of 16, but already with a profound interest in science. He later noted that "..these mother-of-pearl clouds was a vision of indescribable beauty!" The authors find it logical that the same vision could appear scaring in the sensible mind of a young artist unknown to such phenomena.

New features to the night sky radiance model illumina: Hyperspectral support, improved obstacles and cloud reflection

NASA Astrophysics Data System (ADS)

Aubé, M.; Simoneau, A.

2018-05-01

Illumina is one of the most physically detailed artificial night sky brightness model to date. It has been in continuous development since 2005 [1]. In 2016-17, many improvements were made to the Illumina code including an overhead cloud scheme, an improved blocking scheme for subgrid obstacles (trees and buildings), and most importantly, a full hyperspectral modeling approach. Code optimization resulted in significant reduction in execution time enabling users to run the model on standard personal computers for some applications. After describing the new schemes introduced in the model, we give some examples of applications for a peri-urban and a rural site both located inside the International Dark Sky reserve of Mont-Mégantic (QC, Canada).

Upper limits for the ethyl-cyanide abundances in TMC-1 and L134N - Chemical implications

NASA Technical Reports Server (NTRS)

Minh, Y. C.; Irvine, W. M.

1991-01-01

Interstellar ethyl-cyanide has been sought via its 2(02)-1(01) transition towards two cold, dark clouds, and upper limits of the total column densities of 3 x 10 to the 12th/sq cm and 2 x 10 to the 12th/sq cm for TMC-1 and L134N, respectively. The 2(02)-1(01) transition of vynil cyanide, previously identified in TMC-1 by Matthews and Sears (1983b), was also observed. The detection of vinyl cyanide and the nondetection of ethyl cyanide in TMC-1 are consistent with gas phase ion-molecule chemical models, and there is thus no necessity of invoking grain surface synthesis for vinyl cyanide in cold clouds.

Dark Skies and Clouds Move in at Phoenix site

NASA Technical Reports Server (NTRS)

2008-01-01

Clouds of dust and ice swirl past the Surface Stereo Imager (SSI) camera on NASA's Phoenix Mars Lander in a series of images taken on the 132nd Martian day of the mission (Oct. 7, 2008). The images show the increase in storm activity and potential for snowfall.

The solar powered spacecraft was disabled by decreased light from heavy dust storms in the area a few weeks later. The last communication heard from the lander occurred on Nov. 2, 2008.

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

Diagnosing AIRS Sampling with CloudSat Cloud Classes

NASA Technical Reports Server (NTRS)

Fetzer, Eric; Yue, Qing; Guillaume, Alexandre; Kahn, Brian

2011-01-01

AIRS yield and sampling vary with cloud state. Careful utilization of collocated multiple satellite sensors is necessary. Profile differences between AIRS and ECMWF model analyses indicate that AIRS has high sampling and excellent accuracy for certain meteorological conditions. Cloud-dependent sampling biases may have large impact on AIRS L2 and L3 data in climate research. MBL clouds / lower tropospheric stability relationship is one example. AIRS and CloudSat reveal a reasonable climatology in the MBL cloud regime despite limited sampling in stratocumulus. Thermodynamic parameters such as EIS derived from AIRS data map these cloud conditions successfully. We are working on characterizing AIRS scenes with mixed cloud types.

Characterizing the Protostars in the Herschel Survey of Cygnus-X

NASA Astrophysics Data System (ADS)

Kirk, James; Hora, J. L.; Smith, H. A.; Herschel Cygnus-X Group

2014-01-01

The Cygnus-X complex is an extremely active region of massive star formation at a distance of ~1.4 kpc which can be studied with higher sensitivity and less confusion than more distant regions. The study of this region is important in improving our understanding of the formation processes and protostellar phases of massive stars. A previous Spitzer Legacy survey of Cygnus-X mapped the distributions of Class I and Class II YSOs within the region and studied the interaction between massive young stars and clusters of YSOs. Using data from the recent Herschel survey of the region, taken with the PACS and SPIRE instrument (70-500 microns), we are expanding this study of star formation to the youngest and most deeply embedded objects. Using these data we will expand the sample of massive protostars and YSOs in Cygnus-X, analyze the population of infrared dark clouds and their embedded objects, construct Spectral Energy Distributions (SEDs) using pre-existing Spitzer and near-IR data sets (1-500 microns), and fit these sources with models of protostars to derive luminosities and envelope masses. The derived luminosities and masses will enable us to create evolutionary diagrams and test models of high-mass star formation. We will also investigate what role OB associations, such as Cyg OB2, play in causing subsequent star formation in neighboring clouds, providing us with a comprehensive picture of star formation within this extremely active complex.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biganzoli, Davide; Potenza, Marco A. C.; Robberto, Massimo, E-mail: robberto@stsci.edu

We discuss the radiative transfer theory for translucent clouds illuminated by an extended background source. First, we derive a rigorous solution based on the assumption that multiple scatterings produce an isotropic flux. Then we derive a more manageable analytic approximation showing that it nicely matches the results of the rigorous approach. To validate our model, we compare our predictions with accurate laboratory measurements for various types of well-characterized grains, including purely dielectric and strongly absorbing materials representative of astronomical icy and metallic grains, respectively, finding excellent agreement without the need to add free parameters. We use our model to exploremore » the behavior of an astrophysical cloud illuminated by a diffuse source with dust grains having parameters typical of the classic ISM grains of Draine and Lee and protoplanetary disks, with an application to the dark silhouette disk 114–426 in Orion Nebula. We find that the scattering term modifies the transmitted radiation, both in terms of intensity (extinction) and shape (reddening) of the spectral distribution. In particular, for small optical thickness, our results show that scattering makes reddening almost negligible at visible wavelengths. Once the optical thickness increases enough and the probability of scattering events becomes close to or larger than 1, reddening becomes present but is appreciably modified with respect to the standard expression for line-of-sight absorption. Moreover, variations of the grain refractive index, in particular the amount of absorption, also play an important role in changing the shape of the spectral transmission curve, with dielectric grains showing the minimum amount of reddening.« less

Characterization of molecular structural changes in pectin during juice cloud destabilization in frozen concentrated orange juice

USDA-ARS?s Scientific Manuscript database

Pectin comprises one of the major components of cloud material in citrus juices. Juice cloud is a complex mixture of polysaccharides, proteins and lower molecular weight compounds that are responsible for the turbid appearance of citrus juices. The stability of juice cloud depends on a number of fac...

Experimental evidence for glycolaldehyde and ethylene glycol formation by surface hydrogenation of CO molecules under dense molecular cloud conditions

NASA Astrophysics Data System (ADS)

Fedoseev, G.; Cuppen, H. M.; Ioppolo, S.; Lamberts, T.; Linnartz, H.

2015-04-01

This study focuses on the formation of two molecules of astrobiological importance - glycolaldehyde (HC(O)CH2OH) and ethylene glycol (H2C(OH)CH2OH) - by surface hydrogenation of CO molecules. Our experiments aim at simulating the CO freeze-out stage in interstellar dark cloud regions, well before thermal and energetic processing become dominant. It is shown that along with the formation of H2CO and CH3OH - two well-established products of CO hydrogenation - also molecules with more than one carbon atom form. The key step in this process is believed to be the recombination of two HCO radicals followed by the formation of a C-C bond. The experimentally established reaction pathways are implemented into a continuous-time random-walk Monte Carlo model, previously used to model the formation of CH3OH on astrochemical time-scales, to study their impact on the solid-state abundances in dense interstellar clouds of glycolaldehyde and ethylene glycol.

On the Chemistry of Hydrides of N Atoms and O+ Ions

NASA Astrophysics Data System (ADS)

Awad, Zainab; Viti, Serena; Williams, David A.

2016-08-01

Previous work by various authors has suggested that the detection by Herschel/HIFI of nitrogen hydrides along the low-density lines of sight toward G10.6-0.4 (W31C) cannot be accounted for by gas-phase chemical models. In this paper we investigate the role of surface reactions on dust grains in diffuse regions, and we find that formation of the hydrides by surface reactions on dust grains with efficiency comparable to that for H2 formation reconciles models with observations of nitrogen hydrides. However, similar surface reactions do not contribute significantly to the hydrides of O+ ions detected by Herschel/HIFI that are present along many sight lines in the Galaxy. The O+ hydrides can be accounted for by conventional gas-phase chemistry either in diffuse clouds of very low density with normal cosmic-ray fluxes or in somewhat denser diffuse clouds with high cosmic-ray fluxes. Hydride chemistry in dense dark clouds appears to be dominated by gas-phase ion-molecule reactions.

The Pelican Nebula and its Vicinity: a New Look at Stellar Population in the Cloud and around It

NASA Astrophysics Data System (ADS)

Boyle, Richard P.; Janusz, R.; Vrba, F. J.; Straizys, V.; Laugalys, V.; Kazlauskas, A.; Stott, J.; Philip, A. G. D.

2011-01-01

A region of active star formation is located in the complex of dust and molecular clouds known as the Pelican Nebula and the dark cloud L935. In this paper we describe the results of our investigation in the area bounded by the coordinates (2000) RA 20h50m - 20h54m and DEC +44d20m - 44m55d. Our CCD photometry in the Vilnius seven-color system, obtained on the 1.8 m Vatican Advanced Technology Telescope, Mt. Graham, and the 1 m telescope of the USNO Flagstaff Station, is used to classify stars down to V = 17 mag in spectral and luminosity classes. The interstellar extinction values and distances to these stars are determined. Additionally, the data from the 2MASS, MegaCam, IPHAS and Spitzer surveys are analyzed. We present star population maps in the foreground and background of the complex and within it. The known and newly identified YSOs in the area are tabulated.

Volcanic Eruptions on Io

NASA Technical Reports Server (NTRS)

1979-01-01

This dramatic view of Jupiter's satellite Io shows two simultaneously occurring volcanic eruptions. One can be seen on the limb, (at lower right) in which ash clouds are rising more than 150 miles (260 kilometers) above the satellite's surface. The second can be seen on the terminator (shadow between day and night) where the volcanic cloud is catching the rays of the rising sun. The dark hemisphere of Io is made visible by light reflected from Jupiter. Seen in Io's night sky, Jupiter looms almost 40 times larger and 200 times brighter than our own full Moon. This photo was taken by Voyager 1 on March 8, 1979, looking back 2.6 million miles (4.5 million kilometers) at Io, three days after its historic encounter. This is the same image in which Linda A. Morabito, a JPL engineer, discovered the first extraterrestrial volcanic eruption (the bright curved volcanic cloud on the limb). Jet Propulsion Laboratory manages and controls the Voyager project for NASA's Office of Space Science.

Intergalactic Helium Absorption toward High-Redshift Quasars

NASA Technical Reports Server (NTRS)

Giroux, Mark L.; Fardal, Mark A.; Shull, J. Michael

1995-01-01

The recent Hubble Space Telescope (HST) observations of the z(q) = 3.286 quasar Q0302-003 (Jakobsen et at. 1994) and the z(q) = 3.185 quasar Q1935-67 by Tytler (1995) show absorption edges at the redshifted wavelength of He II 304 A. A key goal is to distinguish between contributions from discrete Ly-alpha forest clouds and a smoothly distributed intergalactic medium (IGM). We model the contributions from each of these sources of He II absorption, including the distribution of line Doppler widths and column densities, the 'He II proximity effect' from the quasar, and a self-consistent derivation of the He II opacity of the universe as a function of the spectrum of ionizing sources, with the assumption that both the clouds and the IGM are photoionized. The He II edge can be fully accounted for by He II line blanketing for reasonable distributions of line widths and column densities in the Ly-alpha forest, provided that the ionizing sources have spectral index alpha(s) greater than 1.5, and any He II proximity effect is neglected. Even with some contribution from a diffuse IGM, it is difficult to account for the edge observed by Jakobsen et al. (1994) with a 'hard' source spectrum (alpha(s) less than 1.3). The proximity effect modifies the relative contributions of the clouds and IGM to tau(He II) near the quasar (z approx. less than z(q)) and markedly increases the amount of He II absorption required. This implies, for example, that to account for the He II edge with line blanketing alone, the minimum spectral index alpha(s) must be increased from 1.5 to 1.9. We demonstrate the need for higher resolution observations that characterize the change in transmission as z approaches z(q) and resolve line-free gaps in the continuum. We set limits on the density of the diffuse IGM and suggest that the IGM and Ly-alpha clouds are likely to be a significant repository for dark baryons.

Discovery and Characterization of a Caustic Crossing Microlensing Event in the Small Magellanic Cloud

NASA Astrophysics Data System (ADS)

Alcock, C.; Allsman, R. A.; Alves, D.; Axelrod, T. S.; Becker, A. C.; Bennett, D. P.; Cook, K. H.; Drake, A. J.; Freeman, K. C.; Griest, K.; King, L. J.; Lehner, M. J.; Marshall, S. L.; Minniti, D.; Peterson, B. A.; Pratt, M. R.; Quinn, P. J.; Rhie, S. H.; Rodgers, A. W.; Stetson, P. B.; Stubbs, C. W.; Sutherland, W.; Tomaney, A.; Vandehei, T.

1999-06-01

We present photometric observations and analysis of the second microlensing event detected toward the Small Magellanic Cloud (SMC), MACHO Alert 98-SMC-1. This event was detected early enough to allow intensive observation of the light curve. These observations revealed 98-SMC-1 to be the first caustic crossing binary microlensing event toward the Magellanic Clouds to be discovered in progress. Frequent coverage of the evolving light curve allowed an accurate prediction for the date of the source crossing out of the lens caustic structure. The caustic crossing temporal width, along with the angular size of the source star, measures the proper motion of the lens with respect to the source and thus allows an estimate of the location of the lens. Lenses located in the Galactic halo would have a velocity projected to the SMC of v̂~1500 kms-1, while an SMC lens would typically have v̂~60 kms-1. The event light curve allows us to obtain a unique fit to the parameters of the binary lens and to estimate the proper motion of the lensing system. We have performed a joint fit to the MACHO/GMAN data presented here, including recent EROS data of this event from Afonso and collaborators. These joint data are sufficient to constrain the time t* for the lens to move an angle equal to the source angular radius: t*=0.116+/-0.010 days. We estimate a radius for the lensed source of R*=1.1+/-0.1 Rsolar from its unblended color and magnitude. This yields a projected velocity of v̂=76+/-10 kms-1. Only 0.12% of halo lenses would be expected to have a v̂ value at least as small as this, while 38% of SMC lenses would be expected to have v̂ as large as this. This implies that the lensing system is more likely to reside in the SMC than in the Galactic halo. Similar observations of future Magellanic Cloud microlensing events will help to determine the contribution of MACHOS to the Galaxy's dark halo.

“Lidar Investigations of Aerosol, Cloud, and Boundary Layer Properties Over the ARM ACRF Sites”

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ferrare, Richard; Turner, David

2015-01-13

Project goals; Characterize the aerosol and ice vertical distributions over the ARM NSA site, and in particular to discriminate between elevated aerosol layers and ice clouds in optically thin scattering layers; Characterize the water vapor and aerosol vertical distributions over the ARM Darwin site, how these distributions vary seasonally, and quantify the amount of water vapor and aerosol that is above the boundary layer; Use the high temporal resolution Raman lidar data to examine how aerosol properties vary near clouds; Use the high temporal resolution Raman lidar and Atmospheric Emitted Radiance Interferometer (AERI) data to quantify entrainment in optically thinmore » continental cumulus clouds; and Use the high temporal Raman lidar data to continue to characterize the turbulence within the convective boundary layer and how the turbulence statistics (e.g., variance, skewness) is correlated with larger scale variables predicted by models.« less

Cloud Effects on Ocean Mixed Layer in the Northeast Pacific Ocean

DTIC Science & Technology

1991-06-01

examining this phenomenon is the disproportionate darkness of the long January nights (-16 hours). The greenhouse effect was particularly active...increase in entrainment velocity thereby deepening the mixed layer and cooling the ocean surface. The greenhouse effect had little significant impact...This result is similar to the results found in the short-term experiment of Event #1, where the greenhouse effect is the dominant factor on the MLD

Reflection spectra of solids of planetary interest

NASA Technical Reports Server (NTRS)

Sill, G. T.

1973-01-01

The spectra of solids are reproduced which might be found on the surfaces of planetary bodies or as solid condensates in the upper planetary atmosphere. Among these are spectra of various iron compounds of interest in the study of the clouds of Venus. Other spectra are included of various sulfides, some at low temperature, relevant to the planet Jupiter. Meteorite and coal abstracts are also included, to illustrate dark carbon compounds.

Reflection spectra of solids of planetary interest

NASA Technical Reports Server (NTRS)

Sill, G. T.; Carm, O.

1973-01-01

This paper reproduces the spectra of solids which might be found on the surfaces of planetary bodies or as solid condensates in the upper planetary atmosphere. Among these are spectra of various iron compounds of interest in the study of the clouds of Venus. Other spectra (some at low temperature) are included for various sulfides relevant to the planet Jupiter. Meteorite and coal spectra are also included to illustrate dark carbon compounds.

Jets and Water Clouds on Jupiter

NASA Astrophysics Data System (ADS)

Lian, Yuan; Showman, A. P.

2012-10-01

Ground-based and spacecraft observations show that Jupiter exhibits multiple banded zonal jet structures. These banded jets correlate with dark and bright clouds, often called "belts" and "zones". The mechanisms that produce these banded zonal jets and clouds are poorly understood. Our previous studies showed that the latent heat released by condensation of water vapor could produce equatorial superrotation along with multiple zonal jets in the mid-to-high latitudes. However, that previous work assumed complete and instant removal of condensate and therefore could not predict the cloud formation. Here we present an improved 3D Jupiter model to investigate some effects of cloud microphysics on large-scale dynamics using a closed water cycle that includes condensation, three-dimensional advection of cloud material by the large-scale circulation, evaporation and sedimentation. We use a dry convective adjustment scheme to adjust the temperature towards a dry adiabat when atmospheric columns become convectively unstable, and the tracers are mixed within the unstable layers accordingly. Other physics parameterizations included in our model are the bottom drag and internal heat flux as well as the choices of either Newtonian heating scheme or gray radiative transfer. Given the poorly understood cloud microphysics, we perform case studies by treating the particle size and condensation/evaporation time scale as free parameters. We find that, in some cases, the active water cycle can produce multiple banded jets and clouds. However, the equatorial jet is generally very weak in all the cases because of insufficient supply of eastward eddy momentum fluxes. These differences may result from differences in the overall vertical stratification, baroclinicity, and moisture distribution in our new models relative to the older ones; we expect to elucidate the dynamical mechanisms in continuing work.

Effect of target color and scanning geometry on terrestrial LiDAR point-cloud noise and plane fitting

NASA Astrophysics Data System (ADS)

Bolkas, Dimitrios; Martinez, Aaron

2018-01-01

Point-cloud coordinate information derived from terrestrial Light Detection And Ranging (LiDAR) is important for several applications in surveying and civil engineering. Plane fitting and segmentation of target-surfaces is an important step in several applications such as in the monitoring of structures. Reliable parametric modeling and segmentation relies on the underlying quality of the point-cloud. Therefore, understanding how point-cloud errors affect fitting of planes and segmentation is important. Point-cloud intensity, which accompanies the point-cloud data, often goes hand-in-hand with point-cloud noise. This study uses industrial particle boards painted with eight different colors (black, white, grey, red, green, blue, brown, and yellow) and two different sheens (flat and semi-gloss) to explore how noise and plane residuals vary with scanning geometry (i.e., distance and incidence angle) and target-color. Results show that darker colors, such as black and brown, can produce point clouds that are several times noisier than bright targets, such as white. In addition, semi-gloss targets manage to reduce noise in dark targets by about 2-3 times. The study of plane residuals with scanning geometry reveals that, in many of the cases tested, residuals decrease with increasing incidence angles, which can assist in understanding the distribution of plane residuals in a dataset. Finally, a scheme is developed to derive survey guidelines based on the data collected in this experiment. Three examples demonstrate that users should consider instrument specification, required precision of plane residuals, required point-spacing, target-color, and target-sheen, when selecting scanning locations. Outcomes of this study can aid users to select appropriate instrumentation and improve planning of terrestrial LiDAR data-acquisition.

Optical Thickness and Effective Radius Retrievals of Liquid Water Clouds over Ice and Snow Surface

NASA Technical Reports Server (NTRS)

Platnick, S.; King, M. D.; Tsay, S.-C.; Arnold, G. T.; Gerber, H.; Hobbs, P. V.; Rangno, A.

1999-01-01

Cloud optical thickness and effective radius retrievals from solar reflectance measurements traditionally depend on a combination of spectral channels that are absorbing and non-absorbing for liquid water droplets. Reflectances in non-absorbing channels (e.g., 0.67, 0.86 micrometer bands) are largely dependent on cloud optical thickness, while longer wavelength absorbing channels (1.6, 2.1, and 3.7 micrometer window bands) provide cloud particle size information. Retrievals are complicated by the presence of an underlying ice/snow surface. At the shorter wavelengths, sea ice is both bright and highly variable, significantly increasing cloud retrieval uncertainty. However, reflectances at the longer wavelengths are relatively small and may be comparable to that of dark open water. Sea ice spectral albedos derived from Cloud Absorption Radiometer (CAR) measurements during April 1992 and June 1995 Arctic field deployments are used to illustrate these statements. A modification to the traditional retrieval technique is devised. The new algorithm uses a combination of absorbing spectral channels for which the snow/ice albedo is relatively small. Using this approach, preliminary retrievals have been made with the MODIS Airborne Simulator (MAS) imager flown aboard the NASA ER-2 during FIRE-ACE. Data from coordinated ER-2 and University of Washington CV-580 aircraft observations of liquid water stratus clouds on June 3 and June 6, 1998 have been examined. Size retrievals are compared with in situ cloud profile measurements of effective radius made with the CV-580 PMS FSSP probe, and optical thickness retrievals are compared with extinction profiles derived from the Gerber Scientific "g-meter" probe. MAS retrievals are shown to be in good agreement with the in situ measurements.

Environmental risk perception from visual cues: the psychophysics of tornado risk perception

NASA Astrophysics Data System (ADS)

Dewitt, Barry; Fischhoff, Baruch; Davis, Alexander; Broomell, Stephen B.

2015-12-01

Lay judgments of environmental risks are central to both immediate decisions (e.g., taking shelter from a storm) and long-term ones (e.g., building in locations subject to storm surges). Using methods from quantitative psychology, we provide a general approach to studying lay perceptions of environmental risks. As a first application of these methods, we investigate a setting where lay decisions have not taken full advantage of advances in natural science understanding: tornado forecasts in the US and Canada. Because official forecasts are imperfect, members of the public must often evaluate the risks on their own, by checking environmental cues (such as cloud formations) before deciding whether to take protective action. We study lay perceptions of cloud formations, demonstrating an approach that could be applied to other environmental judgments. We use signal detection theory to analyse how well people can distinguish tornadic from non-tornadic clouds, and multidimensional scaling to determine how people make these judgments. We find that participants (N = 400 recruited from Amazon Mechanical Turk) have heuristics that generally serve them well, helping participants to separate tornadic from non-tornadic clouds, but which also lead them to misjudge the tornado risk of certain cloud types. The signal detection task revealed confusion regarding shelf clouds, mammatus clouds, and clouds with upper- and mid-level tornadic features, which the multidimensional scaling task suggested was the result of participants focusing on the darkness of the weather scene and the ease of discerning its features. We recommend procedures for training (e.g., for storm spotters) and communications (e.g., tornado warnings) that will reduce systematic misclassifications of tornadicity arising from observers’ reliance on otherwise useful heuristics.

The Smith Cloud: surviving a high-speed transit of the Galactic disc

NASA Astrophysics Data System (ADS)

Tepper-García, Thor; Bland-Hawthorn, Joss

2018-02-01

The origin and survival of the Smith high-velocity H I cloud has so far defied explanation. This object has several remarkable properties: (i) its prograde orbit is ≈100 km s-1 faster than the underlying Galactic rotation; (ii) its total gas mass (≳ 4 × 106 M⊙) exceeds the mass of all other high-velocity clouds (HVCs) outside of the Magellanic Stream; (iii) its head-tail morphology extends to the Galactic H I disc, indicating some sort of interaction. The Smith Cloud's kinetic energy rules out models based on ejection from the disc. We construct a dynamically self-consistent, multi-phase model of the Galaxy with a view to exploring whether the Smith Cloud can be understood in terms of an infalling, compact HVC that has transited the Galactic disc. We show that while a dark-matter (DM) free HVC of sufficient mass and density can reach the disc, it does not survive the transit. The most important ingredient to survival during a transit is a confining DM subhalo around the cloud; radiative gas cooling and high spatial resolution (≲ 10pc) are also essential. In our model, the cloud develops a head-tail morphology within ∼10 Myr before and after its first disc crossing; after the event, the tail is left behind and accretes on to the disc within ∼400 Myr. In our interpretation, the Smith Cloud corresponds to a gas 'streamer' that detaches, falls back and fades after the DM subhalo, distorted by the disc passage, has moved on. We conclude that subhaloes with MDM ≲ 109 M⊙ have accreted ∼109 M⊙ of gas into the Galaxy over cosmic time - a small fraction of the total baryon budget.

DUST AND GAS IN THE MAGELLANIC CLOUDS FROM THE HERITAGE HERSCHEL KEY PROJECT. II. GAS-TO-DUST RATIO VARIATIONS ACROSS INTERSTELLAR MEDIUM PHASES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roman-Duval, Julia; Gordon, Karl D.; Meixner, Margaret

2014-12-20

The spatial variations of the gas-to-dust ratio (GDR) provide constraints on the chemical evolution and lifecycle of dust in galaxies. We examine the relation between dust and gas at 10-50 pc resolution in the Large and Small Magellanic Clouds (LMC and SMC) based on Herschel far-infrared (FIR), H I 21 cm, CO, and Hα observations. In the diffuse atomic interstellar medium (ISM), we derive the GDR as the slope of the dust-gas relation and find GDRs of 380{sub −130}{sup +250} ± 3 in the LMC, and 1200{sub −420}{sup +1600} ± 120 in the SMC, not including helium. The atomic-to-molecular transition is locatedmore » at dust surface densities of 0.05 M {sub ☉} pc{sup –2} in the LMC and 0.03 M {sub ☉} pc{sup –2} in the SMC, corresponding to A {sub V} ∼ 0.4 and 0.2, respectively. We investigate the range of CO-to-H{sub 2} conversion factor to best account for all the molecular gas in the beam of the observations, and find upper limits on X {sub CO} to be 6 × 10{sup 20} cm{sup –2} K{sup –1} km{sup –1} s in the LMC (Z = 0.5 Z {sub ☉}) at 15 pc resolution, and 4 × 10{sup 21} cm{sup –2} K{sup –1} km{sup –1} s in the SMC (Z = 0.2 Z {sub ☉}) at 45 pc resolution. In the LMC, the slope of the dust-gas relation in the dense ISM is lower than in the diffuse ISM by a factor ∼2, even after accounting for the effects of CO-dark H{sub 2} in the translucent envelopes of molecular clouds. Coagulation of dust grains and the subsequent dust emissivity increase in molecular clouds, and/or accretion of gas-phase metals onto dust grains, and the subsequent dust abundance (dust-to-gas ratio) increase in molecular clouds could explain the observations. In the SMC, variations in the dust-gas slope caused by coagulation or accretion are degenerate with the effects of CO-dark H{sub 2}. Within the expected 5-20 times Galactic X {sub CO} range, the dust-gas slope can be either constant or decrease by a factor of several across ISM phases. Further modeling and observations are required to break the degeneracy between dust grain coagulation, accretion, and CO-dark H{sub 2}. Our analysis demonstrates that obtaining robust ISM masses remains a non-trivial endeavor even in the local Universe using state-of-the-art maps of thermal dust emission.« less

Evidence for Natural Variability in Marine Stratocumulus Cloud Properties Due to Cloud-Aerosol

NASA Technical Reports Server (NTRS)

Albrecht, Bruce; Sharon, Tarah; Jonsson, Haf; Minnis, Patrick; Minnis, Patrick; Ayers, J. Kirk; Khaiyer, Mandana M.

2004-01-01

In this study, aircraft observations from the Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Twin Otter are used to characterize the variability in drizzle, cloud, and aerosol properties associated with cloud rifts and the surrounding solid clouds observed off the coast of California. A flight made on 16 July 1999 provided measurements directly across an interface between solid and rift cloud conditions. Aircraft instrumentation allowed for measurements of aerosol, cloud droplet, and drizzle spectra. CCN concentrations were measured in addition to standard thermodynamic variables and the winds. A Forward Scatter Spectrometer Probe (FSSP) measured size distribution of cloud-sized droplets. A Cloud Imaging Probe (CIP) was used to measure distributions of drizzle-sized droplets. Aerosol distributions were obtained from a Cloud Aerosol Scatterprobe (CAS). The CAS probe measured aerosols, cloud droplets and drizzle-sized drops; for this study. The CAS probe was used to measure aerosols in the size range of 0.5 micron - 1 micron. Smaller aerosols were characterized using an Ultrafine Condensation Particle Counter (CPC) sensor. The CPC was used to measure particles with diameters greater than 0.003 micron. By subtracting different count concentrations measured with the CPC, this probe was capable of identifying ultrafine particles those falling in the size range of 3 nanometers - 7 nanometers that are believed to be associated with new particle production.

Study of the Outflow and Disk surrounding a Post-Outburst FU-Orionis Star

NASA Astrophysics Data System (ADS)

Mellon, Samuel N.; Perez, L. M.

2014-01-01

PP 13 is a fan-shaped cometary nebula located in the constellation of Perseus and embedded in the L1473 dark cloud. At optical wavelengths this region is obscured by the surrounding dark cloud, while at infrared and longer wavelengths two northern objects (PP13Na & PP13Nb) and one southern object (PP13S) are revealed. In the past, the young stellar object inside PP13S, called PP13S*, experienced an FU-Orionis type outburst due to a massive accretion episode and is currently returning to its quiescent state. Studying the FU-Orionis phase is crucial to our understanding of how low mass stars form; it is theorized that all low-mass stars go through this outburst phase while they are forming. I used CARMA 3mm interferometric observations of the PP13 region to study the continuum and molecular line emissions from PP13. With these observations, I determined the source of the previously detected outflow and learned new information about the double star system PP13Na and PP13Nb. Although I was not able to detect the accretion disk in the gas emissions, I plan to use computer modeling to help provide constraints on the properties of PP13S* and its outflow.

The Mass Surface Density Distribution of a High-Mass Protocluster forming from an IRDC and GMC

NASA Astrophysics Data System (ADS)

Lim, Wanggi; Tan, Jonathan C.; Kainulainen, Jouni; Ma, Bo; Butler, Michael

2016-01-01

We study the probability distribution function (PDF) of mass surface densities of infrared dark cloud (IRDC) G028.36+00.07 and its surrounding giant molecular cloud (GMC). Such PDF analysis has the potential to probe the physical processes that are controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 parsecs, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a high-mass, "super star cluster". We study mass surface densities in two ways. First, we use a combination of NIR, MIR and FIR extinction maps that are able to probe the bulk of the cloud structure that is not yet forming stars. This analysis also shows evidence for flattening of the IR extinction law as mass surface density increases, consistent with increasing grain size and/or growth of ice mantles. Second, we study the FIR and sub-mm dust continuum emission from the cloud, especially utlizing Herschel PACS and SPIRE images. We first subtract off the contribution of the foreground diffuse emission that contaminates these images. Next we examine the effects of background subtraction and choice of dust opacities on the derived mass surface density PDF. The final derived PDFs from both methods are compared, including also with other published studies of this cloud. The implications for theoretical models and simulations of cloud structure, including the role of turbulence and magnetic fields, are discussed.

First stars of the ρ Ophiuchi dark cloud. XMM-Newton view of ρ Oph and its neighbors

NASA Astrophysics Data System (ADS)

Pillitteri, I.; Wolk, S. J.; Chen, H. H.; Goodman, A.

2016-08-01

Star formation in molecular clouds can be triggered by the dynamical action of winds from massive stars. Furthermore, X-ray and UV fluxes from massive stars can influence the life time of surrounding circumstellar disks. We present the results of a 53 ks XMM-Newton observation centered on the ρ Ophiuchi A+B binary system. ρ Ophiuchi lies in the center of a ring of dust, likely formed by the action of its winds. This region is different from the dense core of the cloud (L1688 Core F) where star formation is at work. X-rays are detected from ρ Ophiuchi as well as a group of surrounding X-ray sources. We detected 89 X-ray sources, 47 of them have at least one counterpart in 2MASS+All-WISE catalogs. Based on IR and X-ray properties, we can distinguish between young stellar objects (YSOs) belonging to the cloud and background objects. Among the cloud members, we detect three debris-disk objects and 22 disk-less - Class III young stars.We show that these stars have ages in 5-10 Myr, and are significantly older than the YSOs in L1688. We speculate that they are the result of an early burst of star formation in the cloud. An X-ray energy of ≥5 × 1044 erg has been injected into the surrounding mediumover the past 5 Myr, we discuss the effects of such energy budget in relation to the cloud properties and dynamics.

Radiative characteristics of Clouds embedded in and occurring beneath Smoke analyzed using airborne multiangular measurements

NASA Astrophysics Data System (ADS)

Gautam, R.; Gatebe, C. K.; Varnai, T.; Singh, M.; Poudyal, R.

2016-12-01

Clouds in the presence of absorbing aerosols results in their apparent darkening, observed at the Top of Atmosphere (TOA), which is associated with the radiative effects of aerosol absorption. Owing to the warming/darkening effect and potential impacts on regional climate via semidirect and thermodynamic pathways, above-cloud aerosols have been characterized in recent satellite-based studies. While satellite data are particularly useful in showing the radiative impact of above-cloud aerosols at the TOA, retrievals of aerosol and cloud properties are affected by large uncertainties when they co-occur. In this study, we present radiative characteristics of clouds in the presence of wildfire smoke using airborne data primarily from NASA's Cloud Absorption Radiometer (CAR), collected during the ARCTAS and SAFARI campaigns in Canada and southern Africa, respectively. Scattered cumulus clouds embedded in dense smoke over land (Canada) as well as smoke aerosols above marine stratocumulus clouds (southeast Atlantic) show characteristic spectral gradient across the UV-visible-NIR spectrum using CAR data. In general, clouds in the presence of smoke are impacted by absorbing aerosol-induced darkening at the shorter wavelengths (e.g. UV and blue bands), as opposed to an (expected) negative gradient for cloud-free smoke and a flat spectrum for smoke-free cloud cover. The circular and spiral flights not only allowed the complete characterization of the angular distribution of smoke-cloud radiative interactions, but also provided the vertical distribution of smoke and clouds. Overall, the observational-based smoke-cloud radiative interactions were found to be physically consistent with theoretical 1D and 3D radiation calculations. These airborne observations are also complemented by satellite data from MODIS reflectances and CERES shortwave fluxes, providing a synergistic radiative impact assessment of clouds in the presence of smoke. http://car.gsfc.nasa.gov/

Toward the Characterization of Mixed-Phase Clouds Using Remote Sensing

NASA Astrophysics Data System (ADS)

Andronache, C.

2015-12-01

Mixed-phase clouds consist of a mixture of ice particles and liquid droplets at temperatures below 0 deg C. They are present in all seasons in many regions of the world, account for about 30% of the global cloud coverage, and are linked to cloud electrification and aircraft icing. The mix of ice particles, liquid droplets, and water vapor is unstable, and such clouds are thought to have a short lifetime. A characteristic parameter is the phase composition of mixed-phase clouds. It affects the cloud life cycle and the rate of precipitation. This parameter is important for cloud parameters retrievals by radar, lidar, and satellite and is relevant for climate modeling. The phase transformation includes the remarkable Wegener-Bergeron-Findeisen (WBF) process. The direction and the rate of the phase transformations depend on the local thermodynamic and microphysical properties. Cloud condensation nuclei (CCN) and ice nuclei (IN) particles determine to a large extent cloud microstructure and the dynamic response of clouds to aerosols. The complexity of dynamics and microphysics involved in mixed-phase clouds requires a set of observational and modeling tools that continue to be refined. Among these techniques, the remote sensing methods provide an increasing number of parameters, covering large regions of the world. Thus, a series of studies were dedicated to stratiform mixed-phase clouds revealing longer lifetime than previously thought. Satellite data and aircraft in situ measurements in deep convective clouds suggest that highly supercooled water often occurs in vigorous continental convective storms. In this study, we use cases of convective clouds to discuss the feasibility of mixed-phase clouds characterization and potential advantages of remote sensing.

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blanchard, Yann; Royer, Alain; O'Neill, Norman T.

Multiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances for 150 semitransparent ice clouds cases were acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80° N, 86° W). We analyzed and quantified the sensitivity of downwelling thermal radiance to several cloud parameters including optical depth, effective particle diameter and shape, water vapor content, cloud geometric thickness and cloud base altitude. A lookupmore » table retrieval method was used to successfully extract, through an optimal estimation method, cloud optical depth up to a maximum value of 2.6 and to separate thin ice clouds into two classes: (1) TIC1 clouds characterized by small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter > 30 µm). The retrieval technique was validated using data from the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud Radar (MMCR). Inversions were performed over three polar winters and results showed a significant correlation ( R 2 = 0.95) for cloud optical depth retrievals and an overall accuracy of 83 % for the classification of TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on high spectral resolution downwelling IR radiance measurements between 8 and 21µm was also performed. It confirms the robustness of the optical depth retrieval and the fact that the broadband thermal radiometer retrieval was sensitive to small particle (TIC1) sizes.« less

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

NASA Astrophysics Data System (ADS)

Blanchard, Yann; Royer, Alain; O'Neill, Norman T.; Turner, David D.; Eloranta, Edwin W.

2017-06-01

Multiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances for 150 semitransparent ice clouds cases were acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80° N, 86° W). We analyzed and quantified the sensitivity of downwelling thermal radiance to several cloud parameters including optical depth, effective particle diameter and shape, water vapor content, cloud geometric thickness and cloud base altitude. A lookup table retrieval method was used to successfully extract, through an optimal estimation method, cloud optical depth up to a maximum value of 2.6 and to separate thin ice clouds into two classes: (1) TIC1 clouds characterized by small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter > 30 µm). The retrieval technique was validated using data from the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud Radar (MMCR). Inversions were performed over three polar winters and results showed a significant correlation (R2 = 0.95) for cloud optical depth retrievals and an overall accuracy of 83 % for the classification of TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on high spectral resolution downwelling IR radiance measurements between 8 and 21 µm was also performed. It confirms the robustness of the optical depth retrieval and the fact that the broadband thermal radiometer retrieval was sensitive to small particle (TIC1) sizes.

Thin ice clouds in the Arctic: cloud optical depth and particle size retrieved from ground-based thermal infrared radiometry

DOE PAGES

Blanchard, Yann; Royer, Alain; O'Neill, Norman T.; ...

2017-06-09

Multiband downwelling thermal measurements of zenith sky radiance, along with cloud boundary heights, were used in a retrieval algorithm to estimate cloud optical depth and effective particle diameter of thin ice clouds in the Canadian High Arctic. Ground-based thermal infrared (IR) radiances for 150 semitransparent ice clouds cases were acquired at the Polar Environment Atmospheric Research Laboratory (PEARL) in Eureka, Nunavut, Canada (80° N, 86° W). We analyzed and quantified the sensitivity of downwelling thermal radiance to several cloud parameters including optical depth, effective particle diameter and shape, water vapor content, cloud geometric thickness and cloud base altitude. A lookupmore » table retrieval method was used to successfully extract, through an optimal estimation method, cloud optical depth up to a maximum value of 2.6 and to separate thin ice clouds into two classes: (1) TIC1 clouds characterized by small crystals (effective particle diameter ≤ 30 µm), and (2) TIC2 clouds characterized by large ice crystals (effective particle diameter > 30 µm). The retrieval technique was validated using data from the Arctic High Spectral Resolution Lidar (AHSRL) and Millimeter Wave Cloud Radar (MMCR). Inversions were performed over three polar winters and results showed a significant correlation ( R 2 = 0.95) for cloud optical depth retrievals and an overall accuracy of 83 % for the classification of TIC1 and TIC2 clouds. A partial validation relative to an algorithm based on high spectral resolution downwelling IR radiance measurements between 8 and 21µm was also performed. It confirms the robustness of the optical depth retrieval and the fact that the broadband thermal radiometer retrieval was sensitive to small particle (TIC1) sizes.« less

AIRS Subpixel Cloud Characterization Using MODIS Cloud Products.

NASA Astrophysics Data System (ADS)

Li, Jun; Menzel, W. Paul; Sun, Fengying; Schmit, Timothy J.; Gurka, James

2004-08-01

The Moderate Resolution Imaging Spectroradiometer (MODIS) and the Atmospheric Infrared Sounder (AIRS) measurements from the Earth Observing System's (EOS's) Aqua satellite enable improved global monitoring of the distribution of clouds. MODIS is able to provide, at high spatial resolution (1 5 km), a cloud mask, surface and cloud types, cloud phase, cloud-top pressure (CTP), effective cloud amount (ECA), cloud particle size (CPS), and cloud optical thickness (COT). AIRS is able to provide CTP, ECA, CPS, and COT at coarser spatial resolution (13.5 km at nadir) but with much better accuracy using its high-spectral-resolution measurements. The combined MODIS AIRS system offers the opportunity for improved cloud products over those possible from either system alone. The key steps for synergistic use of imager and sounder radiance measurements are 1) collocation in space and time and 2) imager cloud amount, type, and phase determination within the sounder pixel. The MODIS and AIRS measurements from the EOS Aqua satellite provide the opportunity to study the synergistic use of advanced imager and sounder measurements. As the first step, the MODIS classification procedure is applied to identify various surface and cloud types within an AIRS footprint. Cloud-layer information (lower, midlevel, or high clouds) and phase information (water, ice, or mixed-phase clouds) within the AIRS footprint are sorted and characterized using MODIS 1-km-spatial-resolution data. The combined MODIS and AIRS data for various scenes are analyzed to study the utility of the synergistic use of high-spatial-resolution imager products and high-spectral-resolution sounder radiance measurements. There is relevance to the optimal use of data from the Advanced Baseline Imager (ABI) and Hyperspectral Environmental Suite (HES) systems, which are to fly on the Geostationary Operational Environmental Satellite (GOES)-R.

Vegetation-zonation patterns across a temperate mountain cloud forest ecotone are not explained by variation in hydraulic functioning or water relations.

PubMed

Berry, Z Carter; Johnson, Daniel M; Reinhardt, Keith

2015-09-01

Many studies have demonstrated linkages between the occurrence of fog and ecophysiological functioning in cloud forests, but few have investigated hydraulic functioning as a determining factor that explains sharp changes in vegetation. The objective of this study was to compare the plant water status during cloud-immersed and non-immersed conditions and hydraulic vulnerability in branches and roots of species across a temperate, mountain fog ecotone. Because cloud forests are often dark, cool and very moist, we expected cloud forest species to have less drought-tolerant characteristics (i.e., lower Pe and P50-the pressures required to induce a 12 and 50% loss in hydraulic conductivity, respectively) relative to non-cloud forest species in adjacent (lower elevation) forests. Additionally, due to the ability of cloud forest species to absorb cloud-fog water, we predicted greater improvements in hydraulic functioning during fog in cloud forest species relative to non-cloud forest species. Across the cloud forest ecotone, most species measured were very resistant to losses in conductivity with branch P50 values from -4.5 to -6.0 MPa, hydraulic safety margins (Ψmin - P50) >1.5 MPa and low calculated hydraulic conductivity losses. Roots had greater vulnerabilities, with P50 values ranging from -1.4 to -2.5 MPa, leading to greater predicted losses in conductivity (∼20%). Calculated values suggested strong losses of midday leaf hydraulic conductance in three of the four species, supporting the hydraulic segmentation hypothesis. In both cloud forest and hardwood species, Ψs were greater on foggy days than sunny days, demonstrating the importance of fog periods to plant water balance across fog regimes. Thus, frequent fog did not result in systemic changes in hydraulic functioning or vulnerability to embolism across our temperate cloud forest ecotone. Finally, roots functioned with lower hydraulic conductivity than branches, suggesting that they may serve as more sensitive indicators of hydraulic functioning in these mesic, foggy ecosystems. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Acanthosis Nigricans

MedlinePlus

... is a skin condition characterized by areas of dark, velvety discoloration in body folds and creases. The ... only signs of acanthosis nigricans. You'll notice dark, thickened, velvety skin in body folds and creases — ...

Cryogenic Characterization of FBK RGB-HD SiPMs

DOE PAGES

Aalseth, C. E.

2017-09-26

We report on the cryogenic characterization of Red Green Blue - High Density (RGB-HD) SiPMs developed at Fondazione Bruno Kessler (FBK) as part of the DarkSide program of dark matter searches with liquid argon time projection chambers. A dedicated setup was used to measure the primary dark noise, the correlated noise, and the gain of the SiPMs at varying temperatures. A custom-made data acquisition system and analysis software were used to precisely characterize these parameters. We demonstrate that FBK RGB-HD SiPMs with low quenching resistance (RGB-HD-LRmore » $$_q$$) can be operated from 40 K to 300 K with gains in the range $10^5$ to $10^6$ and noise rates on the order of a few Hz/mm$^2$.« less

Study to perform preliminary experiments to evaluate particle generation and characterization techniques for zero-gravity cloud physics experiments

NASA Technical Reports Server (NTRS)

Katz, U.

1982-01-01

Methods of particle generation and characterization with regard to their applicability for experiments requiring cloud condensation nuclei (CCN) of specified properties were investigated. Since aerosol characterization is a prerequisite to assessing performance of particle generation equipment, techniques for characterizing aerosol were evaluated. Aerosol generation is discussed, and atomizer and photolytic generators including preparation of hydrosols (used with atomizers) and the evaluation of a flight version of an atomizer are studied.

Parametric Simulations of the Great Dark Spots of Neptune

NASA Astrophysics Data System (ADS)

Deng, Xiaolong; Le Beau, R.

2006-09-01

Observations by Voyager II and the Hubble Space Telescope of the Great Dark Spots (GDS) of Neptune suggest that large vortices with lifespans of years are not uncommon occurrences in the atmosphere of Neptune. The variability of these features over time, in particular the complex motions of GDS-89, make them challenging candidates to simulate in atmospheric models. Previously, using the Explicit Planetary Isentropic-Coordinate (EPIC) General Circulation Model, LeBeau and Dowling (1998) simulated the GDS-like vortex features. Qualitatively, the drift, oscillation, and tail-like features of GDS-89 were recreated, although precise numerical matches were only achieved for the meridional drift rate. In 2001, Stratman et al. applied EPIC to simulate the formation of bright companion clouds to the Great Dark Spots. In 2006, Dowling et al. presented a new version of EPIC, which includes hybrid vertical coordinate, cloud physics, advanced chemistry, and new turbulence models. With the new version of EPIC, more observation results, and more powerful computers, it is the time to revisit CFD simulations of the Neptune's atmosphere and do more detailed work on GDS-like vortices. In this presentation, we apply the new version of EPIC to simulate GDS-89. We test the influences of different parameters in the EPIC model: potential vorticity gradient, wind profile, initial latitude, vortex shape, and vertical structure. The observed motions, especially the latitudinal drift and oscillations in orientation angle and aspect ratio, are used as diagnostics of these unobserved atmospheric conditions. Increased computing power allows for more refined and longer simulations and greater coverage of the parameter space than previous efforts. Improved quantitative results have been achieved, including voritices with near eight-day oscillations and comparable variations in shape to GDS-89. This research has been supported by Kentucky NASA EPSCoR.

Boreal forests, aerosols and the impacts on clouds and climate.

PubMed

Spracklen, Dominick V; Bonn, Boris; Carslaw, Kenneth S

2008-12-28

Previous studies have concluded that boreal forests warm the climate because the cooling from storage of carbon in vegetation and soils is cancelled out by the warming due to the absorption of the Sun's heat by the dark forest canopy. However, these studies ignored the impacts of forests on atmospheric aerosol. We use a global atmospheric model to show that, through emission of organic vapours and the resulting condensational growth of newly formed particles, boreal forests double regional cloud condensation nuclei concentrations (from approx. 100 to approx. 200 cm(-3)). Using a simple radiative model, we estimate that the resulting change in cloud albedo causes a radiative forcing of between -1.8 and -6.7 W m(-2) of forest. This forcing may be sufficiently large to result in boreal forests having an overall cooling impact on climate. We propose that the combination of climate forcings related to boreal forests may result in an important global homeostasis. In cold climatic conditions, the snow-vegetation albedo effect dominates and boreal forests warm the climate, whereas in warmer climates they may emit sufficiently large amounts of organic vapour modifying cloud albedo and acting to cool climate.

High resolution far-infrared observations of the evolved H II region M16

DOE Office of Scientific and Technical Information (OSTI.GOV)

McBreen, B.; Fazio, G.G.; Jaffe, D.T.

1982-03-01

M16 is an evolved, extremely density bounded H II region, which now consists only of a series of ionization fronts at molecular cloud boundaries. The source of ionization is the OB star cluster (NGC 6611) which is about 5 x 10/sup 6/ years old. We used the CFA/UA 102 cm balloon-borne telescope to map this region and detected three far-infrared (far-IR) sources embedded in an extended ridge of emission. Source I is an unresolved far-IR source embedded in a molecular cloud near a sharp ionization front. An H/sub 2/O maser is associated with this source, but no radio continuum emissionmore » has been observed. The other two far-IR sources (II and III) are associated with ionized gas-molecular cloud interfaces, with the far-IR radiation arising from dust at the boundary heated by the OB cluster. Source II is located at the southern prominent neutral intrusion with its associated bright rims and dark ''elephant trunk'' globules that delineate the current progress of the ionization front into the neutral material, and Source III arises at the interface of the northern molecular cloud fragment.« less

OH 18 cm TRANSITION AS A THERMOMETER FOR MOLECULAR CLOUDS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebisawa, Yuji; Inokuma, Hiroshi; Yamamoto, Satoshi

We have observed the four hyperfine components of the 18 cm OH transition toward the translucent cloud eastward of Heiles Cloud 2 (HCL2E), the cold dark cloud L134N, and the photodissociation region of the ρ-Ophiuchi molecular cloud with the Effelsberg 100 m telescope. We have found intensity anomalies among the hyperfine components in all three regions. In particular, an absorption feature of the 1612 MHz satellite line against the cosmic microwave background has been detected toward HCL2E and two positions of the ρ-Ophiuchi molecular cloud. On the basis of statistical equilibrium calculations, we find that the hyperfine anomalies originate frommore » the non-LTE population of the hyperfine levels, and can be used to determine the kinetic temperature of the gas over a wide range of H{sub 2} densities (10{sup 2}–10{sup 7} cm{sup −3}). Toward the center of HCL2E, the gas kinetic temperature is determined to be 53 ± 1 K, and it increases toward the cloud peripheries (∼60 K). The ortho-to-para ratio of H{sub 2} is determined to be 3.5 ± 0.9 from the averaged spectrum for the eight positions. In L134N, a similar increase of the temperature is also seen toward the periphery. In the ρ-Ophiuchi molecular cloud, the gas kinetic temperature decreases as a function of the distance from the exciting star HD 147889. These results demonstrate a new aspect of the OH 18 cm line that can be used as a good thermometer of molecular cloud envelopes. The OH 18 cm line can be used to trace a new class of warm molecular gas surrounding a molecular cloud, which is not well traced by the emission of CO and its isotopologues.« less

View of the Salinas River Valley area south of Monterey Bay, California

NASA Image and Video Library

1973-08-15

SL3-88-004 (July-September 1973) --- A vertical view of the Salinas River Valley area south of Monterey Bay, California area is seen in this Skylab 3 Earth Resources Experiments Package S190-B (five-inch Earth terrain camera) photograph taken from the Skylab space station in Earth orbit. The valley is an irrigated agricultural area, and is indicated by the dark-green and light-gray rectangular patterns in the centre of the picture. The city of Salinas is barely visible under the cloud cover at the top (north) end of the valley. The dark mass on the left (west) side of the valley is the Santa Lucia mountain range. The Big Sur area is on the left and partly covered by clouds. The Diablo Range forms the dark mass in the lower right (southeast) corner of the photograph. The town of Hollister is the gray area in the dark-green rectangular farm tracts which occupy the floor of the San Benito Valley in the upper right (northeast) corner of the photograph. The Salinas River flows northwestward toward Monterey Bay. The towns of Soledad, Greenfield and King City appear as gray areas along U.S. 101 in the Salinas Valley. The geology of the area is complex, and has been racked by several earthquakes resulting from movement along the San Andreas and subsidiary faults. Here, the surface expression of the San Andreas Fault can be traced from a point just west of Hollister at the contrast of dark brown and tan to a point about one inch left of the lower right (southeast) corner of the picture. Subsidiary faults are indicated by the curving trend of the rocks along the right side. The photograph will provide detailed information on land use patterns (Dr. R. Colwell, University of California, Berkeley) and fault tectonics (Dr. P. Merifield, Earth Science Res., Inc. and Dr. M. Abdel-Gawad, Rockwell International). Federal agencies participating with NASA on the EREP project are the Departments of Agriculture, Commerce, Interior, the Environmental Protection Agency and the Corps of Engineers. All EREP photography is available to the public through the Department of Interior’s Earth Resources Observations Systems Data Center, Sioux Falls, South Dakota, 57198. Photo credit: NASA

Quantifying and Modelling the Effect of Cloud Shadows on the Surface Irradiance at Tropical and Midlatitude Forests

NASA Astrophysics Data System (ADS)

Kivalov, Sergey N.; Fitzjarrald, David R.

2018-02-01

Cloud shadows lead to alternating light and dark periods at the surface, with the most abrupt changes occurring in the presence of low-level forced cumulus clouds. We examine multiyear irradiance time series observed at a research tower in a midlatitude mixed deciduous forest (Harvard Forest, Massachusetts, USA: 42.53{°}N, 72.17{°}W) and one made at a similar tower in a tropical rain forest (Tapajós National Forest, Pará, Brazil: 2.86{°}S, 54.96{°}W). We link the durations of these periods statistically to conventional meteorological reports of sky type and cloud height at the two forests and present a method to synthesize the surface irradiance time series from sky-type information. Four classes of events describing distinct sequential irradiance changes at the transition from cloud shadow and direct sunlight are identified: sharp-to-sharp, slow-to-slow, sharp-to-slow, and slow-to-sharp. Lognormal and the Weibull statistical distributions distinguish among cloudy-sky types. Observers' qualitative reports of `scattered' and `broken' clouds are quantitatively distinguished by a threshold value of the ratio of mean clear to cloudy period durations. Generated synthetic time series based on these statistics adequately simulate the temporal "radiative forcing" linked to sky type. Our results offer a quantitative way to connect the conventional meteorological sky type to the time series of irradiance experienced at the surface.

Characterizing synoptic and cloud variability in the northern atlantic using self-organizing maps

NASA Astrophysics Data System (ADS)

Fish, Carly

Low-level clouds have a significant influence on the Earth's radiation budget and it is thus imperative to understand their behavior within the marine boundary layer (MBL). The cloud properties in the Northeast Atlantic region are highly variable in space and time and are a research focus for many atmospheric scientists. Characterizing the synoptic patterns in the region through the implementation of self-organizing maps (SOMs) enables a climatological grasp of cloud and atmospheric fields. ERA -- Interim and MODIS provide the platform to explore the variability in the Northeast Atlantic for over 30 years of data. Station data comes from CAP -- MBL on Graciosa Island in the Azores, which lies in a strong gradient of cloud and other atmospheric fields, offer an opportunity to incorporate an observational aspect for the years of 2009 and 2010.

Analyzing the Effect of Intraseasonal Meteorological Variability and Land Cover on Aerosol-Cloud Interactions During the Amazonian Biomass Burning Season

NASA Technical Reports Server (NTRS)

TenHoeve, J. E.; Remer, L. A.; Jacobson, M. Z.

2010-01-01

High resolution aerosol, cloud, water vapor, and atmospheric profile data from the Moderate Resolution Imaging Spectroradiometer (MODIS) are utilized to examine the impact of aerosols on clouds during the Amazonian biomass burning season in Rondnia, Brazil. It is found that increasing background column water vapor (CWV) throughout this transition season between the Amazon dry and wet seasons exerts a strong effect on cloud properties. As a result, aerosol-cloud correlations should be stratified by column water vapor to achieve a more accurate assessment of the effect of aerosols on clouds. Previous studies ignored the systematic changes to meteorological factors during the transition season, leading to possible misinterpretation of their results. Cloud fraction is shown generally to increase with aerosol optical depth (AOD) for both low and high values of column water vapor, whereas the relationship between cloud optical depth (COD) and AOD exhibits a different relationship. COD increases with AOD until AOD approx. 0.25 due to the first indirect (microphysical) effect. At higher values of AOD, COD is found to decrease with increasing AOD, which may be due to: (1) the inhibition of cloud development by absorbing aerosols (radiative effect) and/or (2) a retrieval artifact in which the measured reflectance in the visible is less than expected from a cloud top either from the darkening of clouds through the addition of carbonaceous biomass burning aerosols or subpixel dark surface contamination in the measured cloud reflectance. If (1) is a contributing mechanism, as we suspect, then a linear relationship between the indirect effect and increasing AOD, assumed in a majority of GCMs, is inaccurate since these models do not include treatment of aerosol absorption in and around clouds. The effect of aerosols on both column water vapor and clouds over varying land surface types is also analyzed. The study finds that the difference in column water vapor between forest and pasture is not correlated with aerosol loading, supporting the assumption that temporal variation of column water vapor is primarily a function of the larger-scale meteorology. However, a difference in the response of cloud fraction to increasing AOD is observed between forest and pasture. This suggests that dissimilarities between other meteorological factors, such as atmospheric stability, are likely to have an impact on aerosol-cloud correlations between different land-cover types.

SCUBA and HIRES Results for Protostellar Cores in the MON OB1 Dark Cloud

NASA Astrophysics Data System (ADS)

Wolf-Chase, G.; Moriarty-Schieven, G.; Fich, M.; Barsony, M.

1999-05-01

We have used HIRES-processing of IRAS data and point-source modelling techniques (Hurt & Barsony 1996; O'Linger 1997; Barsony et al. 1998), together with submillimeter continuum imaging using the Submillimeter Common-User Bolometer Array (SCUBA) on the 15-meter James Clerk Maxwell Telescope (JCMT), to search CS cores in the Mon OB1 dark cloud (Wolf-Chase, Walker, & Lada 1995; Wolf-Chase & Walker 1995) for deeply embedded sources. These observations, as well as follow-up millimeter photometry at the National Radio Astronomy Observatory (NRAO) 12-meter telescope on Kitt Peak, have lead to the identification of two Class 0 protostellar candidates, which were previously unresolved from two brighter IRAS point sources (IRAS 06382+0939 & IRAS 06381+1039) in this cloud. Until now, only one Class 0 object had been confirmed in Mon OB1; the driving source of the highly-collimated outflow NGC 2264 G (Ward-Thompson, Eiroa, & Casali 1995; Margulis et al. 1990; Lada & Fich 1996), which lies well outside the extended CS cores. One of the new Class 0 candidates may be an intermediate-mass source associated with an H_2O maser, and the other object is a low-mass source which may be associated with a near-infrared jet, and possibly with a molecular outflow. We report accurate positions for the new Class 0 candidates, based on the SCUBA images, and present new SEDs for these sources, as well as for the brighter IRAS point sources. A portion of this work was performed while GWC held a President's Fellowship from the University of California. MB and GWC gratefully acknowledge financial support from MB's NSF CAREER Grant, AST97-9753229.

Core Emergence in a Massive Infrared Dark Cloud: A Comparison between Mid-IR Extinction and 1.3 mm Emission

NASA Astrophysics Data System (ADS)

Kong, Shuo; Tan, Jonathan C.; Arce, Héctor G.; Caselli, Paola; Fontani, Francesco; Butler, Michael J.

2018-03-01

Stars are born from dense cores in molecular clouds. Observationally, it is crucial to capture the formation of cores in order to understand the necessary conditions and rate of the star formation process. The Atacama Large Millimeter/submillimeter Array (ALMA) is extremely powerful for identifying dense gas structures, including cores, at millimeter wavelengths via their dust continuum emission. Here, we use ALMA to carry out a survey of dense gas and cores in the central region of the massive (∼105 M ⊙) infrared dark cloud (IRDC) G28.37+0.07. The observation consists of a mosaic of 86 pointings of the 12 m array and produces an unprecedented view of the densest structures of this IRDC. In this first Letter about this data set, we focus on a comparison between the 1.3 mm continuum emission and a mid-infrared (MIR) extinction map of the IRDC. This allows estimation of the “dense gas” detection probability function (DPF), i.e., as a function of the local mass surface density, Σ, for various choices of thresholds of millimeter continuum emission to define “dense gas.” We then estimate the dense gas mass fraction, f dg, in the central region of the IRDC and, via extrapolation with the DPF and the known Σ probability distribution function, to the larger-scale surrounding regions, finding values of about 5% to 15% for the fiducial choice of threshold. We argue that this observed dense gas is a good tracer of the protostellar core population and, in this context, estimate a star formation efficiency per free-fall time in the central IRDC region of ɛ ff ∼ 10%, with approximately a factor of two systematic uncertainties.

The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice Mantles

NASA Astrophysics Data System (ADS)

Pauly, Tyler; Garrod, Robin T.

2016-02-01

Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface-gas interactions.

In Orbit Performance of Si Avalanche Photodiode Single Photon Counting Modules in the Geoscience Laser Altimeter System on ICESat

NASA Technical Reports Server (NTRS)

Sun, X.; Jester, P. L.; Palm, S. P.; Abshire, J. B.; Spinhime, J. D.; Krainak, M. A.

2006-01-01

Si avalanche photodiode (APD) single photon counting modules (SPCMs) are used in the Geoscience Laser Altimeter System (GLAS) on Ice, Cloud, anti land Elevation Satellite (ICESat), currently in orbit measuring Earth surface elevation and atmosphere backscattering. These SPCMs are used to measure cloud and aerosol backscatterings to the GLAS laser light at 532-nm wavelength with 60-70% quantum efficiencies and up to 15 millions/s maximum count rates. The performance of the SPCMs has been closely monitored since ICESat launch on January 12, 2003. There has been no measurable change in the quantum efficiency, as indicated by the average photon count rates in response to the background light from the sunlit earth. The linearity and the afterpulsing seen from the cloud and surface backscatterings profiles have been the same as those during ground testing. The detector dark count rates monitored while the spacecraft was in the dark side of the globe have increased almost linearly at about 60 counts/s per day due to space radiation damage. The radiation damage appeared to be independent of the device temperature and power states. There was also an abrupt increase in radiation damage during the solar storm in 28-30 October 2003. The observed radiation damage is a factor of two to three lower than the expected and sufficiently low to provide useful atmosphere backscattering measurements through the end of the ICESat mission. To date, these SPCMs have been in orbit for more than three years. The accumulated operating time to date has reached 290 days (7000 hours). These SPCMs have provided unprecedented receiver sensitivity and dynamic range in ICESat atmosphere backscattering measurements.

Distinguishing Clouds from Ice over the East Siberian Sea, Russia

NASA Technical Reports Server (NTRS)

2002-01-01

As a consequence of its capability to retrieve cloud-top elevations, stereoscopic observations from the Multi-angle Imaging SpectroRadiometer (MISR) can discriminate clouds from snow and ice. The central portion of Russia's East Siberian Sea, including one of the New Siberian Islands, Novaya Sibir, are portrayed in these views from data acquired on May 28, 2002.

The left-hand image is a natural color view from MISR's nadir camera. On the right is a height field retrieved using automated computer processing of data from multiple MISR cameras. Although both clouds and ice appear white in the natural color view, the stereoscopic retrievals are able to identify elevated clouds based on the geometric parallax which results when they are observed from different angles. Owing to their elevation above sea level, clouds are mapped as green and yellow areas, whereas land, sea ice, and very low clouds appear blue and purple. Purple, in particular, denotes elevations very close to sea level. The island of Novaya Sibir is located in the lower left of the images. It can be identified in the natural color view as the dark area surrounded by an expanse of fast ice. In the stereo map the island appears as a blue region indicating its elevation of less than 100 meters above sea level. Areas where the automated stereo processing failed due to lack of sufficient spatial contrast are shown in dark gray. The northern edge of the Siberian mainland can be found at the very bottom of the panels, and is located a little over 250 kilometers south of Novaya Sibir. Pack ice containing numerous fragmented ice floes surrounds the fast ice, and narrow areas of open ocean are visible.

The East Siberian Sea is part of the Arctic Ocean and is ice-covered most of the year. The New Siberian Islands are almost always covered by snow and ice, and tundra vegetation is very scant. Despite continuous sunlight from the end of April until the middle of August, the ice between the island and the mainland typically remains until August or September.

The Multi-angle Imaging SpectroRadiometer views almost the entire Earth every 9 days. These images were acquired during Terra orbit 12986 and cover an area of about 380 kilometers x 1117 kilometers. They utilize data from blocks 24 to 32 within World Reference System-2 path 117.

MISR was built and is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Office of Earth Science, Washington, DC. The Terra satellite is managed by NASA's Goddard Space Flight Center, Greenbelt, MD. JPL is a division of the California Institute of Technology.

Comparison View of Mars Cloud Cover

NASA Technical Reports Server (NTRS)

1997-01-01

These color and black and white pictures of Mars were taken by NASA's Hubble Space Telescope just two weeks after Earth made its closest approach to the Red Planet during the 1997 opposition. When the Hubble pictures were taken Mars was at a distance of 62 million miles (100 million kilometers) and the resolution at the center of the disk is 13.5 miles/pixel (22 kilometers/pixel). Both images were made with the Wide Field and Planetary Camera 2. The color composite (left image) is constructed from three images taken in red (673 nanometers), green (502 nm) and blue (410 nm) light. The right image, in blue light only, brings out details in the cloud structure and is remarkably similar to weather satellite pictures taken of Earth. A planetary-scale wave curls around the north pole, similar in behavior to high latitude cold fronts which descend over North America and Europe during springtime.

The picture was taken when Mars was near aphelion, its farthest point from the Sun. The faint sunlight results in cold atmospheric conditions which stimulate the formation of water ice clouds. The clouds themselves further reduce atmospheric temperatures. Atmospheric heating, resulting when sunlight is absorbed by the dust, is reduced when ice forms around the dust particles and causes the dust to gravitationally settle to the ground.

These images of Mars are centered at approximately 94 degrees longitude and 23 degrees N latitude (oriented with north up). The four largest Tharsis Montes (massive extinct volcanoes) are visible as dark spots extending through the clouds. The vast canyon system, Valles Marineris, stretches across the eastern (lower right) half of the image; the Pathfinder landing site is near the eastern edge of the image. It is early summer in the northern hemisphere, and the North polar cap has retreated to about 80 degrees N latitude; the 'residual' summer cap, which is composed of water ice, is about one-third the size of the 'seasonal' winter cap, which consists mostly of carbon-dioxide frost (dry ice) condensed on the surface. The polar cap is surrounded by a 'sand sea' made up of dark sand dunes. A distinct belt of water-ice clouds extends over much of this hemisphere.

This image and other images and data received from the Hubble Space Telescope are posted on the World Wide Web on the Space Telescope Science Institute home page at URL http://oposite.stsci.edu/pubinfo/

COMPARISON VIEW OF MARS CLOUD COVER

NASA Technical Reports Server (NTRS)

2002-01-01

These color and black and white pictures of Mars were taken by NASA's Hubble Space Telescope just two weeks after Earth made its closest approach to the Red Planet during the 1997 opposition. When the Hubble pictures were taken Mars was at a distance of 62 million miles (100 million kilometers) and the resolution at the center of the disk is 13.5 miles/pixel (22 kilometers/pixel). Both images were made with the Wide Field and Planetary Camera 2. The color composite (left image) is constructed from three images taken in red (673 nanometers), green (502 nm) and blue (410 nm) light. The right image, in blue light only, brings out details in the cloud structure and is remarkably similar to weather satellite pictures taken of Earth. A planetary-scale wave curls around the north pole, similar in behavior to high latitude cold fronts which descend over North America and Europe during springtime. The picture was taken when Mars was near aphelion, its farthest point from the Sun. The faint sunlight results in cold atmospheric conditions which stimulate the formation of water ice clouds. The clouds themselves further reduce atmospheric temperatures. Atmospheric heating, resulting when sunlight is absorbed by the dust, is reduced when ice forms around the dust particles and causes the dust to gravitationally settle to the ground. These images of Mars are centered at approximately 94 degrees longitude and 23 degrees N latitude (oriented with north up). The four largest Tharsis Montes (massive extinct volcanoes) are visible as dark spots extending through the clouds. The vast canyon system, Valles Marineris, stretches across the eastern (lower right) half of the image; the Pathfinder landing site is near the eastern edge of the image. It is early summer in the northern hemisphere, and the North polar cap has retreated to about 80 degrees N latitude; the 'residual' summer cap, which is composed of water ice, is about one-third the size of the 'seasonal' winter cap, which consists mostly of carbon-dioxide frost (dry ice) condensed on the surface. The polar cap is surrounded by a 'sand sea' made up of dark sand dunes. A distinct belt of water-ice clouds extends over much of this hemisphere. Credit: Phil James (Univ. Toledo), Todd Clancy (Space Science Inst., Boulder, CO), Steve Lee (Univ. Colorado), and NASA Image files in GIF and JPEG format and captions may be accessed on the Internet via anonymous ftp from oposite.stsci.edu in /pubinfo.

The dark side of Venus - Near-infrared images and spectra from the Anglo-Australian Observatory

NASA Technical Reports Server (NTRS)

Crisp, D.; Allen, D. A.; Grinspoon, D. H.; Pollack, J. B.

1991-01-01

Near-IR images and spectra of the night side of Venus taken at the Anglo-Australian Telescope during February 1990 reveal four new thermal emission windows at 1.10, 1.18, 1.27, and 1.31 microns, in addition to the previously discovered windows at 1.74 and 2.3 microns. Images of the Venus night side show similar bright and dark markings in all windows, but their contrast is much lower at short wavelengths. The 1.27-micron window includes a bright, high-altitude O2 airglow feature in addition to a thermal contribution from the deep atmosphere. Simulations of the 1.27- and 2.3-micron spectra indicate water vapor mixing ratios near 40 + or - 20 ppm by volume between the surface and the cloud base.

CLOTHES AS A SOURCE OF PARTICLES CONTRIBUTING TO THE "PERSONAL CLOUD"

EPA Science Inventory

Previous studies such as EPA's PTEAM Study have documented increased personal exposures to particles compared to either indoor or outdoor concentrations--a finding that bas been characterized as a "personal cloud." The sources of the personal cloud are unknown, but co...

Characterization of hydrometeors and precipitation over the Indian monsoon region using aircraft measurements

NASA Astrophysics Data System (ADS)

Maheskumar, R. S.; Padmakumari, B.; Konwar, Mahen; Morwal, S. B.; Deshpande, C. G.

2018-06-01

In-situ observations of cloud microphysical properties, carried out over different parts of Indian sub-continent using an instrumented research aircraft during Phase-I of Cloud Aerosol Interaction and Precipitation Enhancement EXperiment (CAIPEEX) from June to September 2009, were studied. Different cloud probes were used to characterize the hydrometeor and precipitation types in the monsoon clouds. The results revealed that all liquid phase hydrometeors were present at temperatures -12 °C to 15 °C. Most of the presence of rain drops were found in the liquid water content (LWC) range from 0.5 to 2 g/m3. In general, rain drops are initiated when the droplet effective radius (Re) exceeded 12 μm. Rain dominated at the tops of young growing convective clouds even at temperatures colder than -10 °C. Mixed phase hydrometeors were present at temperatures from -2 °C to -18 °C. The cases where mixed phase precipitation occurred at temperatures warmer than about -7 °C were associated with influx of transported dust aerosol at the upper (supercooled) region of these cloud systems. Ice only hydrometeors were found at temperatures extending from -10 °C to -22 °C. Most of the monsoon rain is produced by warm and cold cloud/mixed-phase processes in the cloud. The combined Re from two different cloud probes is useful for validation of satellite derived cloud microphysical parameter.

Neutral hydrogen self-absorption in the Milky Way Galaxy

NASA Astrophysics Data System (ADS)

Kavars, Dain William

2006-06-01

To develop a better understanding of the cold neutral medium phase of the interstellar medium, we present a detailed analysis of neutral hydrogen self- absorption (HISA) clouds in the Milky Way Galaxy. These HISA clouds are in the Southern Galactic Plane Survey (SGPS), spanning the region l = 253°--358° and | b | <= 1.3°, and in the VLA Galactic Plane Survey (VGPS), spanning the region l = 18°--67° and | b | <= 1.3°--2.3°. The SGPS and VGPS have an angular resolution of ~1 arcminute and a velocity channel spacing of 0.82 km s -1 . With the recent completion of these surveys, we can study HISA features across the Galaxy at a much better resolution and sensitivity than any previous work. To analyze HISA in detail, catalogs of clouds of all sizes, including those undetectable by eye alone, are required. We present an automated search routine to detect all HISA clouds in the SGPS. We compare HISA to CO data and find some HISA clouds associated with CO, but others have no associated CO. This suggests that HISA clouds are in a transition between molecular and atomic gas, bridging the gap between dense molecular clouds and warmer, diffuse atomic clouds. HISA thus plays an important role in the overall evolution of the Galaxy. To study this transition further, we present observations of the OH molecule toward a select sample of HISA clouds in the VGPS, using the Green Bank Telescope (GBT). We present an analysis of the molecular properties of this sample, including a derivation of an OH to H 2 conversion factor and H 2 to H I abundance ratios. We discuss the complex relationship between H I, OH, 12 CO, and 13 CO emission. Finally we present a statistical analysis comparing HISA with infrared data from the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) project. The GLIMPSE data reveal a large number of compact, dark infrared clouds believed to be in the early stages of star formation. If GLIMPSE clouds are associated with HISA, they provide valuable information on the evolution of HISA clouds.

Saturn Methane Image

NASA Image and Video Library

2004-03-05

NASA's Cassini narrow angle camera took this image of Saturn on Feb. 16, 2004, from a distance of 66.1 million kilometers (41.1 million miles) in a special filter which reveals clouds and haze high in the atmosphere. The image scale is 397 kilometers (247 miles) per pixel. The MT2 spectral filter samples a near-infrared region of the electromagnetic spectrum where methane gas absorbs light at a wavelength of 727 nanometers. In the image, methane gas is uniformly mixed with hydrogen, the main gas in Saturn's atmosphere. Dark locales are places of strong methane absorption, relatively free of high clouds; the bright areas are places with high, thick clouds which shield the methane below. Image details reveal a high, thick equatorial cloud and a relatively deep or thin haze encircling the pole, as well as several distinct latitude bands with different cloud height attributes. It also shows a high atmospheric disturbance, just south of the equator, which has persisted throughout the 1990s in images returned by NASA's Hubble Space Telescope. Four of Saturn's moons are visible (clockwise from above right): Enceladus (499 kilometers, or 310 miles across); Mimas (396 kilometers, or 245 miles across); Tethys (1,060 kilometers, or 659 miles across); and Rhea (1,528 kilometers, or 949 miles across). The imaging team enhanced the brightness of Mimas and Enceladus by a factor of three. http://photojournal.jpl.nasa.gov/catalog/PIA05381

GOT C+: Galactic Plane Survey of the 1.9 THz [CII] Line

NASA Astrophysics Data System (ADS)

Langer, William

2012-01-01

The ionized carbon [CII] 1.9 THz fine structure line is a major gas coolant in the interstellar medium (ISM) and controls the thermal conditions in diffuse gas clouds and Photodissociation Regions (PDRs). The [CII] line is also an important tracer of the atomic gas and atomic to molecular transition in diffuse clouds throughout the Galaxy. I will review some of the results from the recently completed Galactic Observations of Terahertz C+ (GOT C+) survey. This Herschel Open Time Key Project is a sparse, but uniform volume sample survey of [CII] line emission throughout the Galactic disk using the HIFI heterodyne receiver. HIFI observations, with their high spectral resolution, isolate and locate individual clouds in the Galaxy and provide excitation information on the gas. I will present [CII] position-velocity maps that reveal the distribution and motion of the clouds in the inner Galaxy and discuss results on the physical properties of the gas using spectral observations of [CII] and ancillary HI and 12CO, 13CO, and C18O J=1-0 data. The [CII] emission is also a useful tracer of the "Dark H2 Gas", and I will discuss its distribution in a sample of interstellar clouds. This research was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

Constructing a Merged Cloud-Precipitation Radar Dataset for Tropical Convective Clouds during the DYNAMO/AMIE Experiment at Addu Atoll

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Zhe; McFarlane, Sally A.; Schumacher, Courtney

2014-05-16

To improve understanding of the convective processes key to the Madden-Julian-Oscillation (MJO) initiation, the Dynamics of the MJO (DYNAMO) and Atmospheric Radiation Measurement MJO Investigation Experiment (AMIE) collected four months of observations from three radars, the S-band Polarization Radar (S-Pol), the C-band Shared Mobile Atmospheric Research & Teaching Radar (SMART-R), and Ka-band Zenith Radar (KAZR) on Addu Atoll in the tropical Indian Ocean. This study compares the measurements from the S-Pol and SMART-R to those from the more sensitive KAZR in order to characterize the hydrometeor detection capabilities of the two scanning precipitation radars. Frequency comparisons for precipitating convective cloudsmore » and non-precipitating high clouds agree much better than non-precipitating low clouds for both scanning radars due to issues in ground clutter. On average, SMART-R underestimates convective and high cloud tops by 0.3 to 1.1 km, while S-Pol underestimates cloud tops by less than 0.4 km for these cloud types. S-Pol shows excellent dynamic range in detecting various types of clouds and therefore its data are well suited for characterizing the evolution of the 3D cloud structures, complementing the profiling KAZR measurements. For detecting non-precipitating low clouds and thin cirrus clouds, KAZR remains the most reliable instrument. However, KAZR is attenuated in heavy precipitation and underestimates cloud top height due to rainfall attenuation 4.3% of the time during DYNAMO/AMIE. An empirical method to correct the KAZR cloud top heights is described, and a merged radar dataset is produced to provide improved cloud boundary estimates, microphysics and radiative heating retrievals.« less

Using High-Resolution Airborne Remote Sensing to Study Aerosol Near Clouds

NASA Technical Reports Server (NTRS)

Levy, Robert; Munchak, Leigh; Mattoo, Shana; Marshak, Alexander; Wilcox, Eric; Gao, Lan; Yorks, John; Platnick, Steven

2016-01-01

The horizontal space in between clear and cloudy air is very complex. This so-called twilight zone includes activated aerosols that are not quite clouds, thin cloud fragments that are not easily observable, and dying clouds that have not quite disappeared. This is a huge challenge for satellite remote sensing, specifically for retrieval of aerosol properties. Identifying what is cloud versus what is not cloud is critically important for attributing radiative effects and forcings to aerosols. At the same time, the radiative interactions between clouds and the surrounding media (molecules, surface and aerosols themselves) will contaminate retrieval of aerosol properties, even in clear skies. Most studies on aerosol cloud interactions are relevant to moderate resolution imagery (e.g. 500 m) from sensors such as MODIS. Since standard aerosol retrieval algorithms tend to keep a distance (e.g. 1 km) from the nearest detected cloud, it is impossible to evaluate what happens closer to the cloud. During Studies of Emissions, Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS), the NASA ER-2 flew with the enhanced MODIS Airborne Simulator (eMAS), providing MODIS-like spectral observations at high (50 m) spatial resolution. We have applied MODIS-like aerosol retrieval for the eMAS data, providing new detail to characterization of aerosol near clouds. Interpretation and evaluation of these eMAS aerosol retrievals is aided by independent MODIS-like cloud retrievals, as well as profiles from the co-flying Cloud Physics Lidar (CPL). Understanding aerosolcloud retrieval at high resolution will lead to better characterization and interpretation of long-term, global products from lower resolution (e.g.MODIS) satellite retrievals.

Hayman Fire, Colorado

NASA Image and Video Library

2002-06-18

The Hayman forest fire, started on June 8, is continuing to burn in the Pike National Forest, 57 km (35 miles) south-southwest of Denver. According to the U.S. Forest Service, the fire has consumed more than 90,000 acres and has become Colorado's worst fire ever. In this ASTER image, acquired Sunday, June 16, 2002 at 10:30 am MST, the dark blue area is burned vegetation and the green areas are healthy vegetation. Red areas are active fires, and the blue cloud at the top center is smoke. Meteorological clouds are white. The image covers an area of 32.2 x 35.2 km (20.0 x 21.8 miles), and displays ASTER bands 8-3-2 in red, green and blue. http://photojournal.jpl.nasa.gov/catalog/PIA03499

East African Rift Valley, Kenya

NASA Technical Reports Server (NTRS)

1990-01-01

This rare, cloud free view of the East African Rift Valley, Kenya (1.5N, 35.5E) shows a clear view of the Turkwell River Valley, an offshoot of the African REift System. The East African Rift is part of a vast plate fracture which extends from southern Turkey, through the Red Sea, East Africa and into Mozambique. Dark green patches of forests are seen along the rift margin and tea plantations occupy the cooler higher ground.

Fall's Changing Colors

NASA Technical Reports Server (NTRS)

2002-01-01

As the clouds allowed during the past two months, the Sea-viewing Wide field-of-View Sensor (SeaWiFS) recorded the changing colors of eastern U.S. and Canadian vegetation. This series of true-color images from the fall of 2000 shows the deciduous forests of the region change from dark green to bright red and orange, and begin to drop their leaves. Image provided by the SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE

The Collection 6 'dark-target' MODIS Aerosol Products

NASA Technical Reports Server (NTRS)

Levy, Robert C.; Mattoo, Shana; Munchak, Leigh A.; Kleidman, Richard G.; Patadia, Falguni; Gupta, Pawan; Remer, Lorraine

2013-01-01

Aerosol retrieval algorithms are applied to Moderate resolution Imaging Spectroradiometer (MODIS) sensors on both Terra and Aqua, creating two streams of decade-plus aerosol information. Products of aerosol optical depth (AOD) and aerosol size are used for many applications, but the primary concern is that these global products are comprehensive and consistent enough for use in climate studies. One of our major customers is the international modeling comparison study known as AEROCOM, which relies on the MODIS data as a benchmark. In order to keep up with the needs of AEROCOM and other MODIS data users, while utilizing new science and tools, we have improved the algorithms and products. The code, and the associated products, will be known as Collection 6 (C6). While not a major overhaul from the previous Collection 5 (C5) version, there are enough changes that there are significant impacts to the products and their interpretation. In its entirety, the C6 algorithm is comprised of three sub-algorithms for retrieving aerosol properties over different surfaces: These include the dark-target DT algorithms to retrieve over (1) ocean and (2) vegetated-dark-soiled land, plus the (3) Deep Blue (DB) algorithm, originally developed to retrieve over desert-arid land. Focusing on the two DT algorithms, we have updated assumptions for central wavelengths, Rayleigh optical depths and gas (H2O, O3, CO2, etc.) absorption corrections, while relaxing the solar zenith angle limit (up to 84) to increase pole-ward coverage. For DT-land, we have updated the cloud mask to allow heavy smoke retrievals, fine-tuned the assignments for aerosol type as function of season location, corrected bugs in the Quality Assurance (QA) logic, and added diagnostic parameters such as topographic altitude. For DT-ocean, improvements include a revised cloud mask for thin-cirrus detection, inclusion of wind speed dependence in the retrieval, updates to logic of QA Confidence flag (QAC) assignment, and additions of important diagnostic information. At the same time as we have introduced algorithm changes, we have also accounted for upstream changes including: new instrument calibration, revised land-sea masking, and changed cloud masking. Upstream changes also impact the coverage and global statistics of the retrieved AOD. Although our responsibility is to the DT code and products, we have also added a product that merges DT and DB product over semi-arid land surfaces to provide a more gap-free dataset, primarily for visualization purposes. Preliminary validation shows that compared to surface-based sunphotometer data, the C6, Level 2 (along swath) DT-products compare at least as well as those from C5. C6 will include new diagnostic information about clouds in the aerosol field, including an aerosol cloud mask at 500 m resolution, and calculations of the distance to the nearest cloud from clear pixels. Finally, we have revised the strategy for aggregating and averaging the Level 2 (swath) data to become Level 3 (gridded) data. All together, the changes to the DT algorithms will result in reduced global AOD (by 0.02) over ocean and increased AOD (by 0.02) over land, along with changes in spatial coverage. Changes in calibration will have more impact to Terras time series, especially over land. This will result in a significant reduction in artificial differences in the Terra and Aqua datasets, and will stabilize the MODIS data as a target for AEROCOM studie

Variability of cirrus clouds in a convective outflow during the Hibiscus campaign

NASA Astrophysics Data System (ADS)

Fierli, F.; di Donfrancesco, G.; Cairo, F.; Marécal, V.; Zampieri, M.; Orlandi, E.; Durry, G.

2008-08-01

Light-weight microlidar and water vapour measurements were taken on-board a stratospheric balloon during the HIBISCUS 2004 campaign, held in Bauru, Brazil (49° W, 22° S). Cirrus clouds were observed throughout the flight between 12 and 15 km height with a high mesoscale variability in optical and microphysical properties. It was found that the cirrus clouds were composed of different layers characterized by marked differences in height, thickness and optical properties. Simultaneous water vapour observations show that the different layers are characterized by different values of the saturation with respect to ice. A mesoscale simulation and a trajectory analysis clearly revealed that the clouds had formed in the outflow of a large and persistent convective region and that the observed variability of the optical properties and of the cloud structure is likely linked to the different residence times of the convectively-processed air in the upper troposphere.

Cosmology with interaction in the dark sector

DOE Office of Scientific and Technical Information (OSTI.GOV)

Costa, F. E. M.; Barboza, E. M. Jr.; Alcaniz, J. S.

2009-06-15

Unless some unknown symmetry in nature prevents or suppresses a nonminimal coupling in the dark sector, the dark energy field may interact with the pressureless component of dark matter. In this paper, we investigate some cosmological consequences of a general model of interacting dark matter-dark energy characterized by a dimensionless parameter {epsilon}. We derive a coupled scalar field version for this general class of scenarios and carry out a joint statistical analysis involving type Ia supernovae data (Legacy and Constitution sets), measurements of baryon acoustic oscillation peaks at z=0.20 (2dFGRS) and z=0.35 (SDSS), and measurements of the Hubble evolution H(z).more » For the specific case of vacuum decay (w=-1), we find that, although physically forbidden, a transfer of energy from dark matter to dark energy is favored by the data.« less

Limb darkening in Venus night-side disk as viewed from Akatsuki IR2

NASA Astrophysics Data System (ADS)

Satoh, Takehiko; Nakakushi, Takashi; Sato, Takao M.; Hashimoto, George L.

2017-10-01

Night-side hemisphere of Venus exhibits dark and bright regions as a result of spatially inhomogeneous cloud opacity which is illuminated by infrared radiation from deeper atmosphere. The 2-μm camera (IR2) onboard Akatsuki, Japan's Venus Climate Orbiter, is equipped with three narrow-band filters (1.735, 2.26, and 2.32 μm) to image Venus night-side disk in well-known transparency windows of CO2 atmosphere (Allen and Crawford 1984). In general, a cloud feature appears brightest when it is in the disk center and becomes darker as the zenith angle of emergent light increases. Such limb darkening was observed with Galileo/NIMS and mathematically approximated (Carlson et al., 1993). Limb-darkening correction helps to identify branches, in a 1.74-μm vs. 2.3-μm radiances scatter plot, each of which corresponds to a group of aerosols with similar properties. We analyzed Akatsuki/IR2 images to characterize the limb darkening for three night-side filters.There is, however, contamination from the intense day-side disk blurred by IR2's point spread function (PSF). It is found that infrared light can be multiplly reflected within the Si substrate of IR2 detector (1024x1024 pixels PtSi array), causing elongated tail in the actual PSF. We treated this in two different ways. One is to mathematically approximate the PSF (with a combination of modified Lorentz functions) and another is to differentiate 2.26-μm image from 2.32-μm image so that the blurred light pattern can directly be obtained. By comparing results from these two methods, we are able to reasonablly clean up the night-side images and limb darkening is extracted. Physical interpretation of limb darkening, as well as "true" time variations of cloud brightness will be presented/discussed.

Whole Sky Imager Characterization of Sky Obscuration by Clouds for the Starfire Optical Range

DTIC Science & Technology

2010-01-11

9.3 Further Algorithm Development and Evaluation 58 9.4 Analysis of the Data Base 58 10.0 DISCUSSION OF CONTRACT REQUIREMENTS 59 10.1...clouds, Site 5 Feb 14 2008 0900 28 21 Transmittance map, Moonlight , clear sky, Site 5 Feb 3 2008 0700 28 22 Transmittance map, Moonlight , thin...clouds, Site 5 Feb 8 2008 1200 29 23 Transmittance map, Moonlight , broken clouds, Site 5 Feb 2 2008 0800 29 24 Cloud Algorithm Results, Moonlight

The Spectral Energy Distribution of the Earliest Phases of Massive Star Formation from the Spizter and Herschel Archives

NASA Astrophysics Data System (ADS)

Klein, Randolf; Looney, Leslie; Henning, Thomas; Chakrabarti, Sukanya; Shenoy, Sachin

2015-08-01

Infrared Dark Clouds (IRDCs) are very good candidates for the earliest phases of massive star formation, but can only be found in regions with high infrared background. We have searched for early phases among cold and massive (M>100M⊙) cloud cores by selecting cores from millimeter continuum surveys (Faundez et al. 2004, Sridharan et al. 2005, Klein et al. 2005, Beltran et al. 2006) without associations at short wavelengths. We compared the millimeter continuum peak positions with IR and radio catalogs (2MASS, MSX, IRAS, and NVSS) and excluded cores that had sources associated with the cores' peaks. We compiled a list of 173 cores in over 117 regions that are candidates for very early phases of Massive Star Formation (MSF). Now with the Spitzer and Herschel archives, these cores can be characterized further. The GLIMPSE and MIPSGAL programs alone covered 86 of these regions. The Herschel Archive adds even longer wavelengths. We are compiling this data set to construct the complete spectral energy distribution (SED) in the mid- and far-infrared with good spatial resolution and broad spectral coverage. This allow us to disentangle the complex regions and model the SED of the deeply embedded protostars/clusters.We will be presenting the IR properties of all cores and their embedded source, attempt a characterization, and order the cores in an evolutionary sequence. The resulting properties can be compared to e.g. IRDCs, a class of objects suggested to be the earliest stages of MSF. With the relative large number of cores, we can try to answer questions like: How homogeneous or diverse are our regions in terms of their evolutionary stage? Where do our embedded sources fit in the evolutionary sequence of IRDCs, hot molecular cores, ultra-compact HII regions, etc? How is the MSF shaping the environment and vice versa? Can we extrapolate to the initial conditions of MSF using our evolutionary sequence?

The New Progress of the Starry Sky Project of China

NASA Astrophysics Data System (ADS)

Wang, Xiaohua

2015-08-01

Since the 28th General Assembly of IAU, the SSPC team made new progress:1. Enhanced the function of the SSPC team-- Established the contact with IAU C50, IUCN Dark Skies Advisory Group, AWB and IDA,and undertakes the work of the IDA Beijing Chapter.-- Got supports from China’s National Astronomical Observatories, Beijing Planetarium, and Shanghai Science and Technology Museum.-- Signed cooperation agreements with Lighting Research Center, English Education Group and law Firm; formed the team force.2. Put forward a proposal to national top institutionThe SSPC submitted the first proposal about dark sky protection to the Chinese People’s Political Consultative Conference.3. Introduced the Criteria and Guideline of dark sky protectionThe SSPC team translated 8 documents of IDA, and provided a reference basis for Chinese dark sky protection.4. Actively establish dark sky places-- Plan a Dark Sky Reserve around Ali astronomical observatory (5,100m elevation) in Tibet. China’s Xinhua News Agency released the news.-- Combining with Hangcuo Lake, a National Natural Reserve and Scenic in Tibet, to plan and establish the Dark Sky Park.-- Cooperated with Shandong Longgang Tourism Group to construct the Dream Sky Theme Park in the suburbs of Jinan city.In the IYL 2015, the SSPC is getting further development:First, make dark sky protection enter National Ecological Strategy of “Beautiful China”. We call on: “Beautiful China” needs “Beautiful Night Sky” China should care the shared starry sky, and left this resource and heritage for children.Second, hold “Cosmic Light” exhibition in Shanghai Science and Technology Museum on August.Third, continue to establish Dark Sky Reserve, Park and Theme Park. We want to make these places become the bases of dark sky protection, astronomical education and ecological tourism, and develop into new cultural industry.Fourth, actively join international cooperation.Now, “Blue Sky, White Cloud and Starry Sky “have become the common pursuit of Chinese society. In order to obtain this goal, the SSPC team would like to pay more efforts.

The 27-28 October 1986 FIRE IFO Cirrus Case Study: Cirrus Parameter Relationships Derived from Satellite and Lidar Data

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Young, David F.; Sassen, Kenneth; Alvarez, Joseph M.; Grund, Christian J.

1996-01-01

Cirrus cloud radiative and physical characteristics are determined using a combination of ground based, aircraft, and satellite measurements taken as part of the First ISCCP Region Experiment (FIRE) cirrus intensive field observations (IFO) during October and November 1986. Lidar backscatter data are used with rawinsonde data to define cloud base, center and top heights and the corresponding temperatures. Coincident GOES-4 4-km visible (0.65 micrometer) and 8-km infrared window (11.5 micrometer) radiances are analyzed to determine cloud emittances and reflectances. Infrared optical depth is computed from the emittance results. Visible optical depth is derived from reflectance using a theoretical ice crystal scattering model and an empirical bidirectional reflectance model. No clouds with visible optical depths greater than 5 or infrared optical depths less than 0.1 were used in the analysis. Average cloud thickness ranged from 0.5 km to 8.0 km for the 71 scenes. Mean vertical beam emittances derived from cloud-center temperatures were 062 for all scenes compared to 0.33 for the case study (27-28 October) reflecting the thinner clouds observed for the latter scenes. Relationships between cloud emittance , extinction coefficients, and temperature for the case study are very similar to those derived from earlier surface-based studies. The thicker clouds seen during the other IFO days yield different results. Emittances derived using cloud-top temperature wer ratioed to those determined from cloud-center temperature. A nearly linear relationship between these ratios and cloud-center temperature holds promise for determining actual cloud-top temperature and cloud thickness from visible and infrared radiance pairs. The mean ratio of the visible scattering optical depth to the infrared absorption optical depth was 2.13 for these data. This scattering efficiency ratio shows a significant dependence on cloud temperature. Values of mean scattering efficiency as high as 2.6 suggest the presence of small ice particles at temperatures below 230 K. the parameterization of visible reflectance in terms of cloud optical depth and clear sky reflectance shows promise as a simplified method for interpreting visible satellite data reflected from cirrus clouds. Large uncertainties in the optical parameters due to cloud reflectance anisotropy and shading were found by analyzing data for various solar zenith angles and for simultaneous advanced very high resolution radiometer (AVHRR) data. Inhomogeneities in the cloud fields result in uneven cloud shading that apparently causes the occurrence of anomalously dark, cloud pixels in the GOES data. These shading effects complicate the interpretation of the satellite data. The results highlight the need for additional study or cirrus cloud scattering processes and remote sensing techniques.

E4 True and false color hot spot mosaic

NASA Technical Reports Server (NTRS)

1997-01-01

True and false color views of Jupiter from NASA's Galileo spacecraft show an equatorial 'hotspot' on Jupiter. These images cover an area 34,000 kilometers by 11,000 kilometers (about 21,100 by 6,800 miles). The top mosaic combines the violet and near infrared continuum filter images to create an image similar to how Jupiter would appear to human eyes. Differences in coloration are due to the composition and abundances of trace chemicals in Jupiter's atmosphere. The bottom mosaic uses Galileo's three near-infrared wavelengths displayed in red, green, and blue) to show variations in cloud height and thickness. Bluish clouds are high and thin, reddish clouds are low, and white clouds are high and thick. The dark blue hotspot in the center is a hole in the deep cloud with an overlying thin haze. The light blue region to the left is covered by a very high haze layer. The multicolored region to the right has overlapping cloud layers of different heights. Galileo is the first spacecraft to distinguish cloud layers on Jupiter.

North is at the top. The mosaic covers latitudes 1 to 10 degrees and is centered at longitude 336 degrees west. The smallest resolved features are tens of kilometers in size. These images were taken on December 17, 1996, at a range of 1.5 million kilometers (about 930,000 miles) by the Solid State Imaging camera system aboard Galileo. The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at: http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at: http:/ /www.jpl.nasa.gov/galileo/sepo.

The Distribution of Mass Surface Densities in a High-mass Protocluster

NASA Astrophysics Data System (ADS)

Lim, Wanggi; Tan, Jonathan C.; Kainulainen, Jouni; Ma, Bo; Butler, Michael J.

2016-09-01

We study the probability distribution function (PDF) of mass surface densities, Σ, of infrared dark cloud (IRDC) G028.37+00.07 and its surrounding giant molecular cloud. This PDF constrains the physical processes, such as turbulence, magnetic fields, and self-gravity, that are expected to be controlling cloud structure and star formation activity. The chosen IRDC is of particular interest since it has almost 100,000 solar masses within a radius of 8 pc, making it one of the most massive, dense molecular structures known and is thus a potential site for the formation of a “super star cluster.” We study Σ in two ways. First, we use a combination of NIR and MIR extinction maps that are able to probe the bulk of the cloud structure up to Σ ˜ 1 g cm-2(A V ≃ 200 mag). Second, we study the FIR and submillimeter dust continuum emission from the cloud utilizing Herschel-PACS and SPIRE images and paying careful attention to the effects of foreground and background contamination. We find that the PDFs from both methods, applied over a ˜20‧(30 pc)-sized region that contains ≃1.5 × 105 M ⊙ and enclosing a minimum closed contour with Σ ≃ 0.013 g cm-2 (A V ≃ 3 mag), shows a lognormal shape with the peak measured at Σ ≃ 0.021 g cm-2 (A V ≃ 4.7 mag). There is tentative evidence for the presence of a high-Σ power-law tail that contains from ˜3% to 8% of the mass of the cloud material. We discuss the implications of these results for the physical processes occurring in this cloud.

Jupiter's Northern Hemisphere in Violet Light (Time Set 3)

NASA Technical Reports Server (NTRS)

1997-01-01

Mosaic of Jupiter's northern hemisphere between 10 and 50 degrees latitude. Jupiter's atmospheric circulation is dominated by alternating eastward and westward jets from equatorial to polar latitudes. The direction and speed of these jets in part determine the color and texture of the clouds seen in this mosaic. Also visible are several other common Jovian cloud features, including large white ovals, bright spots, dark spots, interacting vortices, and turbulent chaotic systems. The north-south dimension of each of the two interacting vortices in the upper half of the mosaic is about 3500 kilometers. Light at 410 nanometers is affected by the sizes and compositions of cloud particles, as well as the trace chemicals that give Jupiter's clouds their colors. This mosaic shows the features of Jupiter's main visible cloud deck and the hazy cloud layer above it.

North is at the top. The images are projected on a sphere, with features being foreshortened towards the north. The planetary limb runs along the right edge of the mosaic. Cloud patterns appear foreshortened as they approach the limb. The smallest resolved features are tens of kilometers in size. These images were taken on April 3, 1997, at a range of 1.4 million kilometers by the Solid State Imaging system (CCD) on NASA's Galileo spacecraft.

The Jet Propulsion Laboratory, Pasadena, CA manages the mission for NASA's Office of Space Science, Washington, DC.

This image and other images and data received from Galileo are posted on the World Wide Web, on the Galileo mission home page at URL http://galileo.jpl.nasa.gov. Background information and educational context for the images can be found at URL http://www.jpl.nasa.gov/galileo/sepo

A Comparison between Airborne and Mountaintop Cloud Microphysics

NASA Astrophysics Data System (ADS)

David, R.; Lowenthal, D. H.; Hallar, A. G.; McCubbin, I.; Avallone, L. M.; Mace, G. G.; Wang, Z.

2014-12-01

Complex terrain has a large impact on cloud dynamics and microphysics. Several studies have examined the microphysical details of orographically-enhanced clouds from either an aircraft or from a mountain top location. However, further research is needed to characterize the relationships between mountain top and airborne microphysical properties. During the winter of 2011, an airborne study, the Colorado Airborne Mixed-Phase Cloud Study (CAMPS), and a ground-based field campaign, the Storm Peak Lab (SPL) Cloud Property Validation Experiment (StormVEx) were conducted in the Park Range of the Colorado Rockies. The CAMPS study utilized the University of Wyoming King Air (UWKA) to provide airborne cloud microphysical and meteorological data on 29 flights totaling 98 flight hours over the Park Range from December 15, 2010 to February 28, 2011. The UWKA was equipped with instruments that measured both cloud droplet and ice crystal size distributions, liquid water content, total water content (vapor, liquid, and ice), and 3-dimensional wind speed and direction. The Wyoming Cloud Radar and Lidar were also deployed during the campaign. These measurements are used to characterize cloud structure upwind and above the Park Range. StormVEx measured cloud droplet, ice crystal, and aerosol size distributions at SPL, located on the west summit of Mt. Werner at 3220m MSL. The observations from SPL are used to determine mountain top cloud microphysical properties at elevations lower than the UWKA was able to sample in-situ. Comparisons showed that cloud microphysics aloft and at the surface were consistent with respect to snow growth processes while small crystal concentrations were routinely higher at the surface, suggesting ice nucleation near cloud base. The effects of aerosol concentrations and upwind stability on mountain top and downwind microphysics are considered.

The 27-28 October 1986 FIRE IFO Cirrus Case Study: Cirrus Parameter Relationships Derived from Satellite and Lidar Data

NASA Technical Reports Server (NTRS)

Minnis, Patrick; Young, David F.; Sassen, Kenneth; Alvarez, Joseph M.; Grund, Christian J.

1990-01-01

Cirrus cloud radiative and physical characteristics are determined using a combination of ground-based, aircraft, and satellite measurements taken as part of the FIRE Cirrus Intensive Field Observations (IFO) during October and November 1986. Lidar backscatter data are used with rawinsonde data to define cloud base, center, and top heights and the corresponding temperatures. Coincident GOES 4-km visible (0.65 micro-m) and 8-km infrared window (11.5 micro-m) radiances are analyzed to determine cloud emittances and reflectances. Infrared optical depth is computed from the emittance results. Visible optical depth is derived from reflectance using a theoretical ice crystal scattering model and an empirical bidirectional reflectance model. No clouds with visible optical depths greater than 5 or infrared optical depths less than 0.1 were used in the analysis. Average cloud thickness ranged from 0.5 km to 8.0 km for the 71 scenes. Mean vertical beam emittances derived from cloud-center temperatures were 0.62 for all scenes compared to 0.33 for the case study (27-28 October) reflecting the thinner clouds observed for the latter scenes. Relationships between cloud emittance, extinction coefficients, and temperature for the case study are very similar to those derived from earlier surface- based studies. The thicker clouds seen during the other IFO days yield different results. Emittances derived using cloud-top temperature were ratioed to those determined from cloud-center temperature. A nearly linear relationship between these ratios and cloud-center temperature holds promise for determining actual cloud-top temperatures and cloud thicknesses from visible and infrared radiance pairs. The mean ratio of the visible scattering optical depth to the infrared absorption optical depth was 2.13 for these data. This scattering efficiency ratio shows a significant dependence on cloud temperature. Values of mean scattering efficiency as high as 2.6 suggest the presence of small ice particles at temperatures below 230 K. The parameterization of visible reflectance in terms of cloud optical depth and clear-sky reflectance shows promise as a simplified method for interpreting visible satellite data reflected from cirrus clouds. Large uncertainties in the optical parameters due to cloud reflectance anisotropy and shading were found by analyzing data for various solar zenith angles and for simultaneous AVHRR data. Inhomogeneities in the cloud fields result in uneven cloud shading that apparently causes the occurrence of anomalously dark, cloudy pixels in the GOES data. These shading effects complicate the interpretation of the satellite data. The results highlight the need for additional study of cirrus cloud scattering processes and remote sensing techniques.

Probing dark matter physics with galaxy clusters

NASA Astrophysics Data System (ADS)

Dalal, Neal

2016-10-01

We propose a theoretical investigation of the effects of a class of dark matter (DM) self-interactions on the properties of galaxy clusters and their host dark matter halos. Recent work using HST has claimed the detection of a particular form of DM self-interaction, which can lead to observable displacements between satellite galaxies within clusters and the DM subhalos hosting them. This form of self-interaction is highly anisotropic, favoring forward scattering with low momentum transfer, unlike isotropically scattering self-interacting dark matter (SIDM) models. This class of models has not been simulated numerically, clouding the interpretation of the claimed offsets between galaxies and lensing peaks observed by HST. We propose to perform high resolution simulations of cosmological structure formation for this class of SIDM model, focusing on three observables accessible to existing HST observations of clusters. First, we will quantify the extent to which offsets between baryons and DM can arise in these models, as a function of the cross section. Secondly, we will also quantify the effects of this type of DM self-interaction on halo concentrations, to determine the range of cross-sections allowed by existing stringent constraints from HST. Finally we will compute the so-called splashback feature in clusters, specifically focusing on whether SIDM can resolve the current discrepancy between observed values of splashback radii in clusters compared to theoretical predictions for CDM. The proposed investigations will add value to all existing deep HST observations of galaxy clusters by allowing them to probe dark matter physics in three independent ways.

Stratocumulus Precipitation and Entrainment Experiment (SPEE) Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albrecht, Bruce; Ghate, Virendra; CADeddu, Maria

2016-06-01

The scientific focus of this project was to examine precipitation and entrainment processes in marine stratocumulus clouds. The entrainment studies focused on characterizing cloud turbulence at cloud top using Doppler cloud radar observations. The precipitation studies focused on characterizing the precipitation and the macroscopic properties (cloud thickness, and liquid water path) of the clouds. This project will contribute to the U.S. Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Climate Research Facility’s overall objective of providing the remote-sensing observations needed to improve the representation of key cloud processes in climate models. It will be of direct relevance to the componentsmore » of ARM dealing with entrainment and precipitation processes in stratiform clouds. Further, the radar observing techniques that will be used in this study were developed using ARM Southern Great Plains (SGP) facility observations under Atmospheric System Research (ASR) support. The observing systems operating automatously from a site located just north of the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) aircraft hangar in Marina, California during the period of 1 May to 4 November 2015 included: 1. Microwave radiometer: ARM Microwave Radiometer, 3-Channel (MWR3C) with channels centered at 23.834, 30, and 89 GHz; supported by Dr. Maria Cadeddu. 2. Cloud Radar: CIRPAS 95 GHz Frequency Modulated Continuous Wave (FMCW) Cloud Radar (Centroid Frequency Chirp Rate [CFCR]); operations overseen by Drs. Ghate and Albrecht. 3. Ceilometer: Vaisala CK-14; operations overseen by Drs. Ghate and Albrecht.« less

Aerosol partitioning between the interstitial and the condensed phase in mixed-phase clouds

NASA Astrophysics Data System (ADS)

Verheggen, Bart; Cozic, Julie; Weingartner, Ernest; Bower, Keith; Mertes, Stephan; Connolly, Paul; Gallagher, Martin; Flynn, Michael; Choularton, Tom; Baltensperger, Urs

2007-12-01

The partitioning of aerosol particles between the cloud and the interstitial phase (i.e., unactivated aerosol) has been investigated during several Cloud and Aerosol Characterization Experiments (CLACE-3, CLACE-3? and CLACE-4) conducted in winter and summer 2004 and winter 2005 at the high alpine research station Jungfraujoch (3580 m altitude, Switzerland). Ambient air was sampled using different inlets in order to determine the activated fraction of aerosol particles, FN, defined as the fraction of the total aerosol number concentration (with particle diameter dp > 100 nm) that has been incorporated into cloud particles. The liquid and ice water content of mixed-phase clouds were characterized by analyzing multiple cloud probes. The dependence of the activated fraction on several environmental factors is discussed on the basis of more than 900 h of in-cloud observations and parameterizations for key variables are given. FN is found to increase with increasing liquid water content and to decrease with increasing particle number concentration in liquid clouds. FN also decreases with increasing cloud ice mass fraction and with decreasing temperature from 0 to -25°C. The Wegener-Bergeron-Findeisen process probably contributed to this trend, since the presence of ice crystals causes liquid droplets to evaporate, thus releasing the formerly activated particles back into the interstitial phase. Ice nucleation could also have prevented additional cloud condensation nuclei from activating. The observed activation behavior has significant implications for our understanding of the indirect effect of aerosols on climate.

Searching for Galactic hidden gas through interstellar scintillation: results from a test with the NTT-SOFI detector

NASA Astrophysics Data System (ADS)

Habibi, F.; Moniez, M.; Ansari, R.; Rahvar, S.

2011-01-01

Aims: Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected at a longer time scale when the light of remote stars crosses an interstellar molecular cloud, but it has never been observed at optical wavelength. In a favorable case, the light of a background star can be subject to stochastic fluctuations on the order of a few percent at a characteristic time scale of a few minutes. Our ultimate aim is to discover or exclude these scintillation effects to estimate the contribution of molecular hydrogen to the Galactic baryonic hidden mass. This feasibility study is a pathfinder toward an observational strategy to search for scintillation, probing the sensitivity of future surveys and estimating the background level. Methods: We searched for scintillation induced by molecular gas in visible dark nebulae as well as by hypothetical halo clumpuscules of cool molecular hydrogen (H2-He) during two nights. We took long series of 10 s infrared exposures with the ESO-NTT telescope toward stellar populations located behind visible nebulae and toward the Small Magellanic Cloud (SMC). We therefore searched for stars exhibiting stochastic flux variations similar to what is expected from the scintillation effect. According to our simulations of the scintillation process, this search should allow one to detect (stochastic) transverse gradients of column density in cool Galactic molecular clouds of order of ~ 3 × 10-5 g/cm2/10 000 km. Results: We found one light-curve that is compatible with a strong scintillation effect through a turbulent structure characterized by a diffusion radius Rdiff < 100 km in the B68 nebula. Complementary observations are needed to clarify the status of this candidate, and no firm conclusion can be established from this single observation. We can also infer limits on the existence of turbulent dense cores (of number density n > 109 cm-3) within the dark nebulae. Because no candidate is found toward the SMC, we are also able to establish upper limits on the contribution of gas clumpuscules to the Galactic halo mass. Conclusions: The limits set by this test do not seriously constrain the known models, but we show that the short time-scale monitoring for a few 106 star × hour in the visible band with a >4 m telescope and a fast readout camera should allow one to quantify the contribution of turbulent molecular gas to the Galactic halo. The LSST (Large Synoptic Survey Telescope) is perfectly suited for this search. This work is based on observations made at the European Southern Observatory, La Silla, Chile.

Grain Growth and Silicates in Dense Clouds

NASA Technical Reports Server (NTRS)

Pendeleton, Yvonne J.; Chiar, J. E.; Ennico, K.; Boogert, A.; Greene, T.; Knez, C.; Lada, C.; Roellig, T.; Tielens, A.; Werner, M.;

Characterizing the boundary lateral to the shear direction of deformation twins in magnesium

DOE PAGES

Liu, Y.; Li, N.; Shao, S.; ...

2016-06-01

The three-dimensional nature of twins, especially the atomic structures and motion mechanisms of the boundary lateral to the shear direction of the twin, has never been characterized at the atomic level, because such boundary is, in principle, crystallographically unobservable. We thus refer to it here as the dark side of the twin. Here, using high-resolution transmission electron microscopy and atomistic simulations, we characterize the dark side of {101 ⁻2} deformation twins in magnesium. It is found that the dark side is serrated and comprised of {101 ⁻2} coherent twin boundaries and semi-coherent twist prismatic–prismatic {211 ⁻0} boundaries that control twinmore » growth. The conclusions we find in this work apply to the same twin mode in other hexagonal close-packed materials, and the conceptual ideas discussed here should hold for all twin modes in crystalline materials.« less

CALIS—A CALibration Insertion System for the DarkSide-50 dark matter search experiment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.

This paper describes the design, fabrication, commissioning and use of a CALibration source Insertion System (CALIS) in the DarkSide-50 direct dark matter search experiment. CALIS deploys radioactive sources into the liquid scintillator veto to characterize the detector response and detection efficiency of the DarkSide-50 Liquid Argon Time Projection Chamber, and the surrounding 30 t organic liquid scintillator neutron veto. It was commissioned in September 2014 and has been used successfully in several gamma and neutron source campaigns since then. A description of the hardware and an excerpt of calibration analysis results are given below.

CALIS—A CALibration Insertion System for the DarkSide-50 dark matter search experiment

NASA Astrophysics Data System (ADS)

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; Alton, A. K.; Asner, D. M.; Back, H. O.; Baldin, B.; Biery, K.; Bocci, V.; Bonfini, G.; Bonivento, W.; Bossa, M.; Bottino, B.; Brigatti, A.; Brodsky, J.; Budano, F.; Bussino, S.; Cadeddu, M.; Cadonati, L.; Cadoni, M.; Calaprice, F.; Canci, N.; Candela, A.; Caravati, M.; Cariello, M.; Carlini, M.; Catalanotti, S.; Cavalcante, P.; Chepurnov, A.; Cicalò, C.; Cocco, A. G.; Covone, G.; D'Angelo, D.; D'Incecco, M.; Davini, S.; De Cecco, S.; De Deo, M.; De Vincenzi, M.; Derbin, A.; Devoto, A.; Di Eusanio, F.; Di Pietro, G.; Dionisi, C.; Edkins, E.; Empl, A.; Fan, A.; Fiorillo, G.; Fomenko, K.; Forster, G.; Franco, D.; Gabriele, F.; Galbiati, C.; Giagu, S.; Giganti, C.; Giovanetti, G. K.; Goretti, A. M.; Granato, F.; Grandi, L.; Gromov, M.; Guan, M.; Guardincerri, Y.; Hackett, B. R.; Herner, K.; Hughes, D.; Humble, P.; Hungerford, E. V.; Ianni, Al.; Ianni, An.; James, I.; Johnson, T. N.; Jollet, C.; Keeter, K.; Kendziora, C. L.; Koh, G.; Korablev, D.; Korga, G.; Kubankin, A.; Li, X.; Lissia, M.; Loer, B.; Lombardi, P.; Longo, G.; Ma, Y.; Machado, A. A.; Machulin, I. N.; Mandarano, A.; Mari, S. M.; Maricic, J.; Marini, L.; Martoff, C. J.; Meregaglia, A.; Meyers, P. D.; Milincic, R.; Miller, J. D.; Montanari, D.; Monte, A.; Mount, B. J.; Muratova, V. N.; Musico, P.; Napolitano, J.; Navrer Agasson, A.; Odrowski, S.; Orsini, M.; Ortica, F.; Pagani, L.; Pallavicini, M.; Pantic, E.; Parmeggiano, S.; Pelczar, K.; Pelliccia, N.; Pocar, A.; Pordes, S.; Pugachev, D. A.; Qian, H.; Randle, K.; Ranucci, G.; Razeti, M.; Razeto, A.; Reinhold, B.; Renshaw, A. L.; Rescigno, M.; Riffard, Q.; Romani, A.; Rossi, B.; Rossi, N.; Rountree, D.; Sablone, D.; Saggese, P.; Saldanha, R.; Sands, W.; Savarese, C.; Schlitzer, B.; Segreto, E.; Semenov, D. A.; Shields, E.; Singh, P. N.; Skorokhvatov, M. D.; Smirnov, O.; Sotnikov, A.; Stanford, C.; Suvorov, Y.; Tartaglia, R.; Tatarowicz, J.; Testera, G.; Tonazzo, A.; Trinchese, P.; Unzhakov, E. V.; Verducci, M.; Vishneva, A.; Vogelaar, B.; Wada, M.; Walker, S.; Wang, H.; Wang, Y.; Watson, A. W.; Westerdale, S.; Wilhelmi, J.; Wojcik, M. M.; Xiang, Xi.; Xiao, X.; Xu, J.; Yang, C.; Zec, A.; Zhong, W.; Zhu, C.; Zuzel, G.

2017-12-01

This paper describes the design, fabrication, commissioning and use of a CALibration source Insertion System (CALIS) in the DarkSide-50 direct dark matter search experiment. CALIS deploys radioactive sources into the liquid scintillator veto to characterize the detector response and detection efficiency of the DarkSide-50 Liquid Argon Time Projection Chamber, and the surrounding 30 t organic liquid scintillator neutron veto. It was commissioned in September 2014 and has been used successfully in several gamma and neutron source campaigns since then. A description of the hardware and an excerpt of calibration analysis results are given below.

CALIS—A CALibration Insertion System for the DarkSide-50 dark matter search experiment

DOE PAGES

Agnes, P.; Albuquerque, I. F. M.; Alexander, T.; ...

2017-12-18

This paper describes the design, fabrication, commissioning and use of a CALibration source Insertion System (CALIS) in the DarkSide-50 direct dark matter search experiment. CALIS deploys radioactive sources into the liquid scintillator veto to characterize the detector response and detection efficiency of the DarkSide-50 Liquid Argon Time Projection Chamber, and the surrounding 30 t organic liquid scintillator neutron veto. It was commissioned in September 2014 and has been used successfully in several gamma and neutron source campaigns since then. A description of the hardware and an excerpt of calibration analysis results are given below.

Evaluation and Applications of Cloud Climatologies from CALIOP

NASA Technical Reports Server (NTRS)

Winker, David; Getzewitch, Brian; Vaughan, Mark

2008-01-01

Clouds have a major impact on the Earth radiation budget and differences in the representation of clouds in global climate models are responsible for much of the spread in predicted climate sensitivity. Existing cloud climatologies, against which these models can be tested, have many limitations. The CALIOP lidar, carried on the CALIPSO satellite, has now acquired over two years of nearly continuous cloud and aerosol observations. This dataset provides an improved basis for the characterization of 3-D global cloudiness. Global average cloud cover measured by CALIOP is about 75%, significantly higher than for existing cloud climatologies due to the sensitivity of CALIOP to optically thin cloud. Day/night biases in cloud detection appear to be small. This presentation will discuss detection sensitivity and other issues associated with producing a cloud climatology, characteristics of cloud cover statistics derived from CALIOP data, and applications of those statistics.

Cassini First-Look Images of Jupiter

NASA Image and Video Library

2000-10-05

This image of Jupiter was taken by the Cassini Imaging Science narrow angle camera through the blue filter (centered at 445 nanometers) on October 1, 2000, 15:26 UTC at a distance of 84.1million km from Jupiter. The smallest features that can be seen are 500 kilometers across. The contrast between bright and dark features in this region of the spectrum is determined by the different light absorbing properties of the particles composing Jupiter's clouds. Ammonia ice particles are white, reflecting all light that falls on them. But some particles are red, and absorb mostly blue light. The composition of these red particles and the processes which determine their distribution are two of the long-standing mysteries of Jovian meteorology and chemistry. Note that the Great Red Spot contains a dark core of absorbing particles. http://photojournal.jpl.nasa.gov/catalog/PIA02666

Eruption of Alaska volcano breaks historic pattern

USGS Publications Warehouse

Larsen, Jessica; Neal, Christina A.; Webley, Peter; Freymueller, Jeff; Haney, Matthew; McNutt, Stephen; Schneider, David; Prejean, Stephanie; Schaefer, Janet; Wessels, Rick L.

2009-01-01

In the late morning of 12 July 2008, the Alaska Volcano Observatory (AVO) received an unexpected call from the U.S. Coast Guard, reporting an explosive volcanic eruption in the central Aleutians in the vicinity of Okmok volcano, a relatively young (~2000-year-old) caldera. The Coast Guard had received an emergency call requesting assistance from a family living at a cattle ranch on the flanks of the volcano, who reported loud "thunder," lightning, and noontime darkness due to ashfall. AVO staff immediately confirmed the report by observing a strong eruption signal recorded on the Okmok seismic network and the presence of a large dark ash cloud above Okmok in satellite imagery. Within 5 minutes of the call, AVO declared the volcano at aviation code red, signifying that a highly explosive, ash-rich eruption was under way.

Eruption of Alaska Volcano Breaks Historic Pattern

NASA Astrophysics Data System (ADS)

Larsen, Jessica; Neal, Christina; Webley, Peter; Freymueller, Jeff; Haney, Matthew; McNutt, Stephen; Schneider, David; Prejean, Stephanie; Schaefer, Janet; Wessels, Rick

2009-05-01

In the late morning of 12 July 2008, the Alaska Volcano Observatory (AVO) received an unexpected call from the U.S. Coast Guard, reporting an explosive volcanic eruption in the central Aleutians in the vicinity of Okmok volcano, a relatively young (˜2000-year-old) caldera. The Coast Guard had received an emergency call requesting assistance from a family living at a cattle ranch on the flanks of the volcano, who reported loud “thunder,” lightning, and noontime darkness due to ashfall. AVO staff immediately confirmed the report by observing a strong eruption signal recorded on the Okmok seismic network and the presence of a large dark ash cloud above Okmok in satellite imagery. Within 5 minutes of the call, AVO declared the volcano at aviation code red, signifying that a highly explosive, ash-rich eruption was under way.

Abstract Art or Arbiters of Energy?

NASA Technical Reports Server (NTRS)

2002-01-01

More than just the idle stuff of daydreams, clouds help control the flow of radiant energy around our world. Clouds are plentiful and widespread throughout Earth's atmosphere-covering up to 75 percent of our planet at any given time-so they play a dominant role in determining how much sunlight reaches the surface, how much sunlight is reflected back into space, how and where warmth is spread around the globe, and how much heat escapes from the surface and atmosphere back into space. Clouds are also highly variable. Clouds' myriad variations through time and space make them one of the greatest areas of uncertainty in scientists' understanding and predictions of climate change. In short, they play a central role in our world's climate system. The false-color image above shows a one-month composite of cloud optical thickness measured by the Moderate-resolution Imaging Spectroradiometer (MODIS) and averaged globally for April 2001. Optical thickness is a measure of how much solar radiation is not allowed to travel through a column of atmosphere. Areas colored red and yellow indicate very cloudy skies, on average, while areas colored green and light blue show moderately cloudy skies. Dark blue regions show where there is little or no cloud cover. This data product is an important new tool for helping scientists understand the roles clouds play in our global climate system. MODIS gives scientists new capabilities for measuring the structure and composition of clouds. MODIS observes the entire Earth almost every day in 36 spectral bands ranging from visible to thermal infrared wavelengths, enabling it to quantify a wide suite of clouds' physical and radiative properties. Specifically, MODIS can determine whether a cloud is composed of ice or water particles (or some combination of the two), it can measure the effective radius of the particles within a cloud, it can determine the temperature and altitude of cloud tops, and it can observe how much sunlight passes through a cloud. MODIS is one of five sensors flying aboard NASA's Terra satellite, the flagship in NASA's Earth Observing System, launched in December 1999. For more information about this and other new MODIS products, read NASA Unveils Spectacular Suite of New Global Data Products from MODIS. Image courtesy MODIS Atmosphere Group, NASA GSFC

High spectral resolution observations of HNC3 and HCCNC in the L1544 pre-stellar core

NASA Astrophysics Data System (ADS)

Vastel, C.; Kawaguchi, K.; Quénard, D.; Ohishi, M.; Lefloch, B.; Bachiller, R.; Müller, H. S. P.

2018-02-01

HCCNC and HNC3 are less commonly found isomers of cyanoacetylene, HC3N, a molecule that is widely found in diverse astronomical sources. We want to know if HNC3 is present in sources other than the dark cloud TMC-1 and how its abundance is relative to that of related molecules. We used the Astrochemical Studies At IRAM unbiased spectral survey at IRAM 30 m towards the prototypical pre-stellar core L1544 to search for HNC3 and HCCNC which are by-product of the HC3NH+ recombination, previously detected in this source. We performed a combined analysis of published HNC3 microwave rest frequencies with thus far unpublished millimetre data because of issues with available rest frequency predictions. We determined new spectroscopic parameters for HNC3, produced new predictions and detected it towards L1544. We used a gas-grain chemical modelling to predict the abundances of N-species and compare with the observations. The modelled abundances are consistent with the observations, considering a late stage of the evolution of the pre-stellar core. However, the calculated abundance of HNC3 was found 5-10 times higher than the observed one. The HC3N, HNC3, and HCCNC versus HC3NH+ ratios are compared in the TMC-1 dark cloud and the L1544 pre-stellar core.

The EOS CERES Global Cloud Mask

NASA Technical Reports Server (NTRS)

Berendes, T. A.; Welch, R. M.; Trepte, Q.; Schaaf, C.; Baum, B. A.

1996-01-01

To detect long-term climate trends, it is essential to produce long-term and consistent data sets from a variety of different satellite platforms. With current global cloud climatology data sets, such as the International Satellite Cloud Climatology Experiment (ISCCP) or CLAVR (Clouds from Advanced Very High Resolution Radiometer), one of the first processing steps is to determine whether an imager pixel is obstructed between the satellite and the surface, i.e., determine a cloud 'mask.' A cloud mask is essential to studies monitoring changes over ocean, land, or snow-covered surfaces. As part of the Earth Observing System (EOS) program, a series of platforms will be flown beginning in 1997 with the Tropical Rainfall Measurement Mission (TRMM) and subsequently the EOS-AM and EOS-PM platforms in following years. The cloud imager on TRMM is the Visible/Infrared Sensor (VIRS), while the Moderate Resolution Imaging Spectroradiometer (MODIS) is the imager on the EOS platforms. To be useful for long term studies, a cloud masking algorithm should produce consistent results between existing (AVHRR) data, and future VIRS and MODIS data. The present work outlines both existing and proposed approaches to detecting cloud using multispectral narrowband radiance data. Clouds generally are characterized by higher albedos and lower temperatures than the underlying surface. However, there are numerous conditions when this characterization is inappropriate, most notably over snow and ice of the cloud types, cirrus, stratocumulus and cumulus are the most difficult to detect. Other problems arise when analyzing data from sun-glint areas over oceans or lakes over deserts or over regions containing numerous fires and smoke. The cloud mask effort builds upon operational experience of several groups that will now be discussed.

Cloud Properties under Different Synoptic Circulations: Comparison of Radiosonde and Ground-Based Active Remote Sensing Measurements

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Jinqiang; Li, Jun; Xia, Xiangao

In this study, long-term (10 years) radiosonde-based cloud data are compared with the ground-based active remote sensing product under six prevailing large-scale synoptic patterns, i.e., cyclonic center (CC), weak pressure pattern (WP), the southeast bottom of cyclonic center (CB), cold front (CF), anticyclone edge (AE) and anticyclone center (AC) over the Southern Great Plains (SGP) site. The synoptic patterns are generated by applying the self-organizing map weather classification method to the daily National Centers for Environmental Protection mean sea level pressure records from the North American Regional Reanalysis. It reveals that the large-scale synoptic circulations can strongly influence the regionalmore » cloud formation, and thereby have impact on the consistency of cloud retrievals from the radiosonde and ground-based cloud product. The total cloud cover at the SGP site is characterized by the least in AC and the most in CF. The minimum and maximum differences between the two cloud methods are 10.3% for CC and 13.3% for WP. Compared to the synoptic patterns characterized by scattered cloudy and clear skies (AE and AC), the agreement of collocated cloud boundaries between the two cloud approaches tends to be better under the synoptic patterns dominated by overcast and cloudy skies (CC, WP and CB). The rainy and windy weather conditions in CF synoptic pattern influence the consistency of the two cloud retrieval methods associated with the limited capabilities inherent to the instruments. As a result, the cloud thickness distribution from the two cloud datasets compares favorably with each other in all synoptic patterns, with relative discrepancy of ≤0.3 km.« less