Sample records for nebula photo-dissociation region

  1. The Charge State of Polycyclic Aromatic Hydrocarbons across a Reflection Nebula, an H II Region, and a Planetary Nebula

    NASA Astrophysics Data System (ADS)

    Boersma, C.; Bregman, J.; Allamandola, L. J.

    2018-05-01

    Low-resolution Spitzer-IRS spectral map data of a reflection nebula (NGC 7023), H II region (M17), and planetary nebula (NGC 40), totaling 1417 spectra, are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbon (PAH) emission is broken down into PAH charge and size subclass contributions using a database-fitting approach. The resulting charge breakdown results are combined with those derived using the traditional PAH band strength ratio approach, which interprets particular PAH band strength ratios as proxies for PAH charge. Here the 6.2/11.2 μm PAH band strength ratio is successfully calibrated against its database equivalent: the {n}PAH}+}/{n}PAH}0} ratio. In turn, this ratio is converted into the PAH ionization parameter, which relates it to the strength of the radiation field, gas temperature, and electron density. Population diagrams are used to derive the {{{H}}}2 density and temperature. The bifurcated plot of the 8.6 versus 11.2 μm PAH band strength for the northwest photo dissociation region in NGC 7023 is shown to be a robust diagnostic template for the {n}PAH}+}/{n}PAH}0} ratio in all three objects. Template spectra for the PAH charge and size subclasses are determined for each object and shown to favorably compare. Using the determined template spectra from NGC 7023 to fit the emission in all three objects yields, upon inspection of the Structure SIMilarity maps, satisfactory results. The choice of extinction curve proves to be critical. Concluding, the distinctly different astronomical environments of a reflection nebula, H II region, and planetary nebula are reflected in their PAH emission spectra.

  2. Probing the conditions within Photo-dissociation Regions with high resolution near-infrared spectroscopy of UV-excited molecular hydrogen

    NASA Astrophysics Data System (ADS)

    Kaplan, Kyle; Dinerstein, Harriet L.; Jaffe, Daniel Thomas

    2017-01-01

    UV radiation regulates the energetics, ionization, and chemistry in much of the ISM. Regions between hot ionized and cool molecular gas where non-ionizing far-UV radiation dominates the state of the gas are called Photo-Dissociation or Photon-Dominated Regions (PDRs). PDRs are found in regions of high-mass star formation, planetary nebulae, and other environments that contain strong far-UV radiation fields. Hydrogen molecules (H2) are pumped by far-UV photons into excited rotational-vibrational levels of the ground electronic state, which give rise to a rich array of transitions in the near to mid-infrared. These transitions make an excellent probe of the physical conditions within a PDR. I will present near-IR spectra taken with the Immersion GRating Infrared Spectrometer (IGRINS; Park et al. 2014, Proc. SPIE, 9147), a novel, sensitive spectrometer with high spectral resolving power (R~45000) and instantaneous broad wavelength coverage (1.45-2.45 μm). Using IGRINS, I obtained deep spectra and measured up to 100 H2 rotational-vibrational transitions in the well-studied Orion Bar PDR, four other star formation complexes, and over a dozen planetary nebulae. Measurements of many lines from a wide range of vibrational states (v=1 to 13), rotational states (J=1 to 13), and excitation energies provides leverage for constraining the overall level populations and discerning the state of and physical processes within the gas. This combination of high spectral and spatial resolution enables us to distinguish previously unresolved spatio-kinematical components with distinct intrinsic spectra and excitation mechanisms (e.g. shocks vs. radiative excitation) within some individual planetary nebulae. I use the plasma simulation code Cloudy (Ferland et al. 2013, ApJ, 757, 79) as a tool for interpreting the observed H2 line ratios. Some sources are well fit by models with a single temperature and density, consistent with emission from a narrow region of the overall PDR structure

  3. A Comparative Study of H2 Excitation and Physical Conditions in Interstellar and Circumstellar Photo-dissociation Regions

    NASA Astrophysics Data System (ADS)

    Kaplan, Kyle; Dinerstein, Harriet L.; Jaffe, Daniel Thomas

    2017-06-01

    Photo-dissociation” or “Photon-dominated” Regions (PDRs) exist in the ISM at the interfaces between photo-ionized and molecular gas, where UV radiation sets the ionization state, chemistry, and excitation at the edge of the molecular zone. In these regions, excited rotational-vibrational (“rovibrational”) states of the ground electronic state of H2 are fluorescently populated when the absorption of far-UV photons conveys the molecules into excited electronic states from which they rapidly decay. Downward transitions from the excited rovibrational states produce a rich spectrum of near-infrared emission lines. Since these quadrupole lines are generally optically thin, their fluxes scale with the populations of the upper levels of the respective transitions, providing excellent probes of the excitation and physical conditions in the emitting regions. We present and compare high resolution (R~45,000) near-infrared (1.45-2.45 μm) spectra, obtained on the 2.7 m Harlan J. Smith Telescope at McDonald Observatory with the Immersion Grating INfrared Spectrometer (IGRINS) (Park et al. 2014, SPIE, 9147, 1), for a variety of Galactic PDRs including regions of high mass star formation, reflection nebulae, and planetary nebulae. Typically a large number of transitions, up to about 100 individual lines, are seen in each source. We fit grids of Cloudy models (Ferland et al. 2013, RMxAA, 49, 137) to the observed H2 emission to constrain physical parameters such as the temperature, density, and UV field of each PDR and explore the similarities and differences between the various environments where PDRs arise.This work used the Immersion Grating INfrared Spectrometer (IGRINS), developed under a collaboration between the University of Texas at Austin and the Korea Astronomy and Space Science Institute (KASI) with the financial support of the US National Science Foundation (NSF grant AST-1229522) to the University of Texas at Austin, and the Korean GMT Project of KASI. We

  4. Laser induced fluorescence spectrum analysis of OH from photo-dissociation of water in gas phase

    NASA Astrophysics Data System (ADS)

    Li, Guohua; Ye, Jingfeng; Zhang, Zhengrong; Wang, Sheng; Hu, Zhiyun; Zhao, Xinyan

    2017-05-01

    The OH can be generated from photo-dissociation of water in the gas phase, and the generated OH has served in tagging velocimetry using the time-flight method. The hydroxyl tagging mechanism has the advantages of non-seeding, kindly flow following character, but its application in the reaction region is limited for the fluorescence interference from nascent OH. In this paper, we explored the laser induced fluorescence spectrum of OH both from burning and photodissociation. A photo-dissociation laser induced fluorescence (PD-LIF) system with optical multichannel analysis instrument (OMA) for spectrum analysis was developed. Based on multichannel mechanism, the LIF spectrum of OH from photo-dissociation and burning were acquired simultaneously. The temporal spectrum profiles of dissociation OH both in flame and air were taken by varying the pump-probe delay. The normalized emission spectrum in flame showed a process of rotational relaxation while in air the spectrum was almost not changed. The fluorescence intensity was precisely proportional to the base states population, so we can get certain states that the OH from dissociation was predominant from the fluorescence intensity ratio of OH. This result can be further utilized for hydroxyl tagging velocimetry technology (HTV) which was less affected by burning OH.

  5. VLT Images the Horsehead Nebula

    NASA Astrophysics Data System (ADS)

    2002-01-01

    Summary A new, high-resolution colour image of one of the most photographed celestial objects, the famous "Horsehead Nebula" (IC 434) in Orion, has been produced from data stored in the VLT Science Archive. The original CCD frames were obtained in February 2000 with the FORS2 multi-mode instrument at the 8.2-m VLT KUEYEN telescope on Paranal (Chile). The comparatively large field-of-view of the FORS2 camera is optimally suited to show this extended object and its immediate surroundings in impressive detail. PR Photo 02a/02 : View of the full field around the Horsehead Nebula. PR Photo 02b/02 : Enlargement of a smaller area around the Horse's "mouth" A spectacular object ESO PR Photo 02a/02 ESO PR Photo 02a/02 [Preview - JPEG: 400 x 485 pix - 63k] [Normal - JPEG: 800 x 970 pix - 896k] [Full-Res - JPEG: 1951 x 2366 pix - 4.7M] ESO PR Photo 02b/02 ESO PR Photo 02b/02 [Preview - JPEG: 400 x 501 pix - 91k] [Normal - JPEG: 800 x 1002 pix - 888k] [Full-Res - JPEG: 1139 x 1427 pix - 1.9M] Caption : PR Photo 02a/02 is a reproduction of a composite colour image of the Horsehead Nebula and its immediate surroundings. It is based on three exposures in the visual part of the spectrum with the FORS2 multi-mode instrument at the 8.2-m KUEYEN telescope at Paranal. PR Photo 02b/02 is an enlargement of a smaller area. Technical information about these photos is available below. PR Photo 02a/02 shows the famous "Horsehead Nebula" , which is situated in the Orion molecular cloud complex. Its official name is Barnard 33 and it is a dust protrusion in the southern region of the dense dust cloud Lynds 1630 , on the edge of the HII region IC 434 . The distance to the region is about 1400 light-years (430 pc). This beautiful colour image was produced from three images obtained with the multi-mode FORS2 instrument at the second VLT Unit Telescope ( KUEYEN ), some months after it had "First Light", cf. PR 17/99. The image files were extracted from the VLT Science Archive Facility and the

  6. Revisiting the Orion Nebula

    NASA Astrophysics Data System (ADS)

    2004-06-01

    ESO/MPG 2.2m telescope at La Silla, to obtain very deep images of this region. ESO PR Photo 20/04 shows a false-colour composite of images obtained in four different wavebands (see technical information below). Among others, these observations allow the astronomers to measure the rates of mass that falls onto the young stars (the mass accretion rates) and to determine if it depends on the position of the stars in the cluster. If this were the case, it would indicate that the final stages of star formation are affected by the onset of ionising radiation from the most massive stars. From a preliminary study with the Hubble Space Telescope, the astronomers found that indeed the mass accretion rates are lower in the Orion Nebula Cluster than in other, more diffuse star-forming regions. The analysis of these new WFI images should allow confirmation of this hypothesis. The astronomers also obtained images of the Orion Nebula in several narrow-band filters corresponding to emission lines - hydrogen (Halpha), oxygen ([OIII]), and sulphur ([SII]) - enabling them to probe the morphology of the nebula in these prominent lines. It is rather obvious from the image that for example some regions are redder than others, providing the astronomers with important clues on the conditions prevailing in the nebula. In the next months, a large international collaboration also led by M. Robberto will use the Hubble Space Telescope to survey with unprecedented sensitivity (23-25 mag) and spatial resolution approximately 50% of the field imaged by the present WFI observations. The astronomers expect to discover and classify an unknown but substantial population of young double stars, low mass stars and brown dwarfs.

  7. Isotope effects in photo dissociation of ozone with visible light

    NASA Astrophysics Data System (ADS)

    Früchtl, Marion; Janssen, Christof; Röckmann, Thomas

    2014-05-01

    Ozone (O3) plays a key role for many chemical oxidation processes in the Earth's atmosphere. In these chemical reactions, ozone can transfer oxygen to other trace gases. This is particularly interesting, since O3 has a very peculiar isotope composition. Following the mass dependent fractionation equation δ17O = 0.52 * δ18O, most fractionation processes depend directly on mass. However, O3 shows an offset to the mass dependent fractionation line. Processes, which show such anomalies, are termed mass independent fractionations (MIF). A very well studied example for a chemical reaction that leads to mass independent fractionation is the O3 formation reaction. To what degree O3 destruction reactions need to be considered in order to understand the isotope composition of atmospheric O3 is still not fully understood and an open question within scientific community. We set up new experiments to investigate the isotope effect resulting from photo dissociation of O3 in the Chappuis band (R1). Initial O3 is produced by an electric discharge. After photolysis O3 is collected in a cold trap at the triple point temperature of nitrogen (63K). O3 is then converted to O2 in order to measure the oxygen isotopes of O3 using isotope ratio mass spectrometry. To isolate O3 photo dissociation (R1) from O3 decomposition (R2) and secondary O3 formation (R3), we use varying amounts of carbon monoxide (CO) as O atom quencher (R4). In this way we suppress the O + O3 reaction (R3) and determine the isotope fractionation in R1 and R2 separately. We present first results on the isotope effects in O3 photo dissociation with visible light in the presence of different bath gases. Results are interpreted based on chemical kinetics modeling. (R1) O3 + hυ → O (3P) + O2 (R2) O3 + O (3P) → 2 O2 (R3) O + O2 + M → O3 + M (R4) O (3P) + CO + M → CO2 + M

  8. NICMOS PEELS AWAY LAYERS OF DUST TO SHOW INNER REGION OF DUSTY NEBULA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The revived Near Infrared Camera and Multi-Object Spectrometer (NICMOS) aboard NASA's Hubble Space Telescope has penetrated layers of dust in a star-forming cloud to uncover a dense, craggy edifice of dust and gas . This region is called the Cone Nebula (NGC 2264), so named because, in ground-based images, it has a conical shape. NICMOS enables the Hubble telescope to see in near-infrared wavelengths of light, so that it can penetrate the dust that obscures the nebula's inner regions. But the Cone is so dense that even the near-infared 'eyes' of NICMOS can't penetrate all the way through it. The image shows the upper 0.5 light-years of the nebula. The entire nebula is 7 light-years long. The Cone resides in a turbulent star-forming region, located 2,500 light-years away in the constellation Monoceros. Radiation from hot, young stars [located beyond the top of the image] has slowly eroded the nebula over millions of years. Ultraviolet light heats the edges of the dark cloud, releasing gas into the relatively empty region of surrounding space. NICMOS has peeled away the outer layers of dust to reveal even denser dust. The denser regions give the nebula a more three-dimensional structure than can be seen in the visible-light picture at left, taken by the Advanced Camera for Surveys aboard the Hubble telescope. In peering through the dusty facade to the nebula's inner regions, NICMOS has unmasked several stars [yellow dots at upper right]. Astronomers don't know whether these stars are behind the dusty nebula or embedded in it. The four bright stars lined up on the left are in front of the nebula. The human eye cannot see infrared light, so colors have been assigned to correspond with near-infrared wavelengths. The blue light represents shorter near-infrared wavelengths and the red light corresponds to longer wavelengths. The NICMOS color composite image was made by combining photographs taken in J-band, H-band, and Paschen-alpha filters. The NICMOS images were taken

  9. Exploring Molecular Complexity of the Diffuse and Translucent Gas and PhotoDissociation Regions

    NASA Astrophysics Data System (ADS)

    McCarthy, Michael

    This proposal requests funds to continue a laboratory program in close coordination with radio astronomical observations dedicated to the study of highly reactive polyatomic molecular ions in low density regions and photo-dissociation regions (PDRs). In doing so, the proposed studies will advance our understanding of the chemistry beyond light ions that have been observed so successfully in these regions with Herschel and recently extended with SOFIA, and thereby critically address a significant but unresolved question in molecular astronomy: Are larger molecules formed in a bottom-up or top-down chemistry? The rotational spectra of most new molecular ions will be detected in the laboratory in a resonant microwave cavity, followed either by microwave/millimeterwave double resonance or millimeter/THz absorption to better characterize their spectrum in bands covered by the heterodyne receivers HIFI on Herschel and GREAT on SOFIA. In collaboration with radioastronomer colleagues, we will search for the new ions in the published survey of the PDR region of the Orion Bar and archival data of other PDRs observed with the IRAM 30 m telescope; retrieve and analyze archival data from Herschel; and undertake searches for some of the new ions in PDRs and low density regions with SOFIA. This work will also have a strong bearing on proposed Early Release Science (ERS) observations of dense PDRs with the James Webb Space Telescope (JWST). The laboratory effort will build on previous work on molecular ions , specifically detection of the rotational spectra of a number of positive ions of astronomical interest such as H2NCO+, CCCH+, the cis- and trans isomers of HOSO+, HNCOH+, and H2CC(H)CNH+. We will focus our efforts on positive ions derived from closed-shell neutral molecules, radicals, and carbenes whose rotational spectra have been observed in our laboratory, and nearly all of which have also been identified in galactic molecular clouds. Examples of the ions we seek include

  10. The Extended Region Around the Planetary Nebula NGC 3242

    NASA Technical Reports Server (NTRS)

    2009-01-01

    This ultraviolet image from NASA's Galaxy Evolution Explorer shows NGC 3242, a planetary nebula frequently referred to as 'Jupiter's Ghost.'

    The unfortunate name of 'planetary nebula' for this class of celestial object is a historical legacy credited to William Herschel during the 18th century a time when telescopes where small and objects like these, at least the central region, looked very similar to gas-giant planets such as Saturn and Jupiter. In fact, NGC 3242 has no relation to Jupiter or any other planet.

    Telescopes and their detectors have dramatically improved over the past few centuries. Our understanding of what planetary nebulae truly are has improved accordingly.

    When stars with a mass similar to our sun approach the end of their lives by exhausting supplies of hydrogen and helium fuel in their cores, they swell up into cool red-giant stars. In a last gasp before death, they expel the layers of gas in their outer atmosphere. This exposes the core of the dying star, a dense hot ball of carbon and oxygen called a white dwarf. The white dwarf is so hot that it shines very brightly in the ultraviolet. The ultraviolet light from the white dwarf, in turn, ionizes the gaseous material expelled by the star causing it to glow. A planetary nebula is really the death of a low-mass star.

    Although low-mass stars like our sun live for billions of years, planetary nebulae only last for about ten thousand years. As the central white dwarf quickly cools and the ultraviolet light dwindles, the surrounding gas also cools and fades.

    In this image of NGC 3242 from the Galaxy Evolution Explorer, the extended region around the planetary nebula is shown in dramatic detail. The small circular white and blue area at the center of the image is the well-known portion of the famous planetary nebula. The precise origin and composition of the extended wispy white features is not known for certain. It is most likely material ejected during the star's red

  11. (Fe II) emission from high-density regions in the Orion Nebula

    NASA Technical Reports Server (NTRS)

    Bautista, Manuel A.; Pradhan, Anil K.; Osterbrock, Donald E.

    1994-01-01

    Direct spectroscopic evidence of high-density regions in the Orion Nebula, N(sub e) approximately equals 10(exp 5)-10(exp 7)/cu cm, is obtained from the forbidden optical and near-IR (Fe II) emission lines, using new atomic data. Calculations for level populations and line ratios are carried out using 16, 35, and 142 level collisional-radiative models for Fe II. Estimates of Fe(+) abundances derived from the near-infrared and the optical line intensities are consistent with a high density of 10(exp 6)/cu cm in the (Fe II) emitting regions. Important consequences for abundance determinations in the nebula are pointed out.

  12. A survey for PAH emission in H II regions, planetary and proto-planetary nebulae

    NASA Technical Reports Server (NTRS)

    Demuizon, M.; Cox, P.; Lequeux, J.

    1989-01-01

    The results of a systematic investigation of polycyclic aromatic hydrocarbon (PAH) emission in H II regions, planetary nebulae (PN), and proto-planetary nebulae (PNN), are reported. Data is obtained from the low resolution spectra (LRS) of IRAS. The results show that: PAHs are formed in carbon rich objects; and PAH emission is ubiquitous in general interstellar medium and requires the presence of ultraviolet photons, in planetary and proto-planetary nebulae, PAH emission is seen only where an ionizing flux is present and in carbon rich objects.

  13. Water masers and ammonia (1, 1) and (2, 2) towards six regions in the Carina Nebula

    NASA Astrophysics Data System (ADS)

    Breen, S. L.; Green, C.-E.; Cunningham, M. R.; Voronkov, M. A.; Horiuchi, S.; Green, J. A.

    2018-01-01

    We present water maser and ammonia (1, 1) and (2, 2) observations, towards six regions in the Carina Nebula, conducted with the Australia Telescope Compact Array. In total five water masers were detected within two of the target fields, and we provide their accurate positions and characteristics. These five water masers constitute all of the known masers detected towards star formation regions in the Carina Nebula and we argue, that given the evidence for active star formation, and the presence of many high-mass stars, the Carina Nebula is uncharacteristically devoid of masers. Our results are consistent with the Carina Nebula having a lack of young high-mass stars, despite the presence of older high-mass stars. Ammonia (1, 1) and (2, 2) emission was detected towards all but one of the target fields and we find that their linewidths and derived temperatures are consistent with the presence of young star formation regions.

  14. The Eagle Nebula: a spectral template for star forming regions

    NASA Astrophysics Data System (ADS)

    Flagey, Nicolas; Boulanger, Francois; Carey, Sean; Compiegne, Mathieu; Dwek, Eli; Habart, Emilie; Indebetouw, Remy; Montmerle, Thierry; Noriega-Crespo, Alberto

    2008-03-01

    IRAC and MIPS have revealed spectacular images of massive star forming regions in the Galaxy. These vivid illustrations of the interaction between the stars, through their winds and radiation, and their environment, made of gas and dust, still needs to be explained. The large scale picture of layered shells of gas components, is affected by the small scale interaction of stars with the clumpy medium that surrounds them. To understand spatial variations of physical conditions and dust properties on small scales, spectroscopic imaging observations are required on a nearby object. The iconic Eagle Nebula (M16) is one of the nearest and most observed star forming region of our Galaxy and as such, is a well suited template to obtain this missing data set. We thus propose a complete spectral map of the Eagle Nebula (M16) with the IRS/Long Low module (15-38 microns) and MIPS/SED mode (55-95 microns). Analysis of the dust emission, spectral features and continuum, and of the H2 and fine-structure gas lines within our models will provide us with constraints on the physical conditions (gas ionization state, pressure, radiation field) and dust properties (temperature, size distribution) at each position within the nebula. Only such a spatially and spectrally complete map will allow us to characterize small scale structure and dust evolution within the global context and understand the impact of small scale structure on the evolution of dusty star forming regions. This project takes advantage of the unique ability of IRS at obtaining sensitive spectral maps covering large areas.

  15. Modelling the ArH+ emission from the Crab nebula

    NASA Astrophysics Data System (ADS)

    Priestley, F. D.; Barlow, M. J.; Viti, S.

    2017-12-01

    We have performed combined photoionization and photodissociation region (PDR) modelling of a Crab nebula filament subjected to the synchrotron radiation from the central pulsar wind nebula, and to a high flux of charged particles; a greatly enhanced cosmic-ray ionization rate over the standard interstellar value, ζ0, is required to account for the lack of detected [C I] emission in published Herschel SPIRE FTS observations of the Crab nebula. The observed line surface brightness ratios of the OH+ and ArH+ transitions seen in the SPIRE FTS frequency range can only be explained with both a high cosmic-ray ionization rate and a reduced ArH+ dissociative recombination rate compared to that used by previous authors, although consistent with experimental upper limits. We find that the ArH+/OH+ line strengths and the observed H2 vibration-rotation emission can be reproduced by model filaments with nH = 2 × 104 cm-3, ζ = 107ζ0 and visual extinctions within the range found for dusty globules in the Crab nebula, although far-infrared emission from [O I] and [C II] is higher than the observational constraints. Models with nH = 1900 cm-3 underpredict the H2 surface brightness, but agree with the ArH+ and OH+ surface brightnesses and predict [O I] and [C II] line ratios consistent with observations. These models predict HeH+ rotational emission above detection thresholds, but consideration of the formation time-scale suggests that the abundance of this molecule in the Crab nebula should be lower than the equilibrium values obtained in our analysis.

  16. An IFU-view of Planetary Nebulae: Exploring NGC 6720 (Ring Nebula) with KCWI

    NASA Astrophysics Data System (ADS)

    Hoadley, Keri; Matuszewski, Matt; Hamden, Erika; Martin, Christopher; Neill, Don; Kyne, Gillian

    2018-01-01

    Studying the interaction between the ejected stellar material and interstellar clouds is important for understanding how stellar deaths influences the pollution of matter that will later form other stars. Planetary nebulae provide ideal laboratories to study such interactions. I will present on a case study of one close-by planetary nebula, the Ring Nebula (M 57, NGC 6720), to infer the abundances, temperatures, structures, and dynamics of important atomic and ionic species in two distinct regions of the nebula using a newly-commissioned integral field spectrograph (IFS) on Keck: the Keck Cosmic Web Imager (KCWI). The advantage of an IFS over traditional filter-imaging techniques is the ability to simultaneously observe the spectrum of any given pixel in the imaging area, which provides crucial information about the dynamics of the observed region. This technique is powerful for diffuse or extended astrophysical objects, and I will demonstrate the different imaging and spectral modes of KCWI used to observe the Ring Nebula.KCWI observations of the Ring Nebula focused mainly on the innermost region of the nebula, with a little coverage of the Inner Ring. We also observed the length of the Ring in one set of observations, for which we will estimate the elemental abundances, temperatures, and dynamics of the region. KCWI observations also capture an inner arc and blob that have distinctly difference characteristics than the Ring itself and may be a direct observation of either the planetary nebula ramming into an interstellar cloud projected onto the sightline or a dense interstellar cloud being illuminated by the stellar continuum from the hot central white dwarf.

  17. POLYCYCLIC AROMATIC HYDROCARBONS WITH STRAIGHT EDGES AND THE 7.6/6.2 AND 8.6/6.2 INTENSITY RATIOS IN REFLECTION NEBULAE.

    PubMed

    Ricca, Alessandra; Bauschlicher, Charles W; Roser, Joseph E; Peeters, Els

    2018-01-01

    We have investigated the mid-infrared spectral characteristics of a series of polycyclic aromatic hydrocarbons (PAHs) with straight edges and containing an even or odd number of carbons using density functional theory (DFT). For several even and odd-carbon PAHs, the 8.6/6.2 and 7.6/6.2 intensity ratios computed in emission after the absorption of a 8 eV photon match the observed ratios obtained for three reflection nebulae (RNe), namely NGC 1333, NGC 7023, and NGC 2023. Odd-carbon PAHs are favored, particularly for NGC 1333. Both cations and anions are present with the cations being predominant. Relevant PAHs span sizes ranging from 46 to 103-113 carbons for NGC 7023 and NGC 2023 and from 38 to 127 carbons for NGC 1333 and have symmetries ranging from D 2 h to C s . Our work suggests that even and odd-carbon PAHs with straight edges are viable candidates for the PAH emission seen towards irradiated Photo-Dissociation Regions (PDRs).

  18. The Orion Nebula: The Jewel in the Sword

    NASA Astrophysics Data System (ADS)

    2001-01-01

    /01 ESO PR Photo 03c/01 [Preview - JPEG: 400 x 452 pix - 57k] [Normal - JPEG: 800 x 904 pix - 488k] [Hires - JPEG: 2300 x 2600 pix - 3.3M] Caption : PR Photo 03b/01 and PR Photo 03c/01 show smaller, particularly interesting areas of PR Photo 03a/01 . Photo 03b/01 shows the traces of a massive outflow of gas from a very young object embedded in the dense molecular cloud behind the Orion Nebula. Shards of gas from the explosion create shocks and leave bow-waves as they move at speeds of up to 200 km/sec from the source. Photo 03c/01 shows the delicate tracery created at the so-called Bright Bar , as the intense UV-light and strong winds from the hot Trapezium stars eat their way into the surrounding molecular cloud. Also visible are a number of very young red objects partly hidden in the cloud, waiting to be revealed as new members of the Trapezium Cluster . Technical information about these photos is available below. Indeed, at visible wavelengths, the dense cluster of stars at the centre is drowned out by the light from the nebula and obscured by remnants of the dust in the gas from which they were formed. However, at longer wavelengths, these obscuring effects are reduced, and the cluster is revealed. In the past couple of years, several of the world's premier ground- and space-based telescopes have made new detailed infrared studies of the Orion Nebula and the Trapezium Cluster , but the VLT image shown here is the "deepest" wide-field image obtained so far. The large collecting area of the VLT and the excellent seeing of the Paranal site combined to yield this beautiful image, packed full of striking details. Powerful explosions and winds from the most massive stars in the region are evident, as well as the contours of gas sculpted by these stars, and more finely focused jets of gas flowing from the smaller stars. Sharper images from the VLT ESO PR Photo 03d/01 ESO PR Photo 03d/01 [Preview - JPEG: 400 x 490 pix - 28k] [Normal - JPEG: 800 x 980 pix - 192k] [Hi

  19. Doradus Nebula

    NASA Image and Video Library

    1999-12-01

    A panoramic view of a vast, sculpted area of gas and dust where thousands of stars are being born has been captured by NASA's Hubble Space Telescope. The image, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://hubblesite.org/newscenter/archive/releases/2001/21/image/a/. The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The photo offers an unprecedented, detailed view of the entire inner region of the fertile, star-forming 30 Doradus Nebula. The mosaic picture shows that ultraviolet radiation and high-speed material unleashed by the stars in the cluster, called R136 (the large blue blob left of center), are weaving a tapestry of creation and destruction, triggering the collapse of looming gas and dust clouds and forming pillar-like structures that incubate newborn stars. The 30 Doradus Nebula is in the Large Magellanic Cloud, a satellite galaxy of the Milky Way located 170,000 light-years from Earth. Nebulas like 30 Doradus are signposts of recent star birth. High-energy ultraviolet radiation from young, hot, massive stars in R136 causes surrounding gaseous material to glow. Previous Hubble telescope observations showed that R136 contains several dozen of the most massive stars known, each about 100 times the mass of the Sun and about 10 times as hot. These stellar behemoths formed about 2 million years ago. The stars in R136 produce intense "stellar winds," streams of material traveling at several million miles an hour. These winds push the gas away from the cluster and compress the inner regions of the surrounding gas and dust clouds (seen in the image as the pinkish material). The intense pressure triggers the collapse of parts of the clouds, producing a new star formation around the central cluster. Most stars in the nursery are not visible because they are still encased in cocoons of gas and dust. This mosaic image of 30 Doradus consists of five overlapping pictures taken between January 1994 and

  20. Hubble reveals heart of Lagoon Nebula

    NASA Image and Video Library

    2010-09-22

    Image release date September 22, 2010 To view a video of this image go here: www.flickr.com/photos/gsfc/5014452203 Caption: A spectacular new NASA/ESA Hubble Space Telescope image reveals the heart of the Lagoon Nebula. Seen as a massive cloud of glowing dust and gas, bombarded by the energetic radiation of new stars, this placid name hides a dramatic reality. The Advanced Camera for Surveys (ACS) on the NASA/ESA Hubble Space Telescope has captured a dramatic view of gas and dust sculpted by intense radiation from hot young stars deep in the heart of the Lagoon Nebula (Messier 8). This spectacular object is named after the wide, lagoon-shaped dust lane that crosses the glowing gas of the nebula. This structure is prominent in wide-field images, but cannot be seen in this close-up. However the strange billowing shapes and sandy texture visible in this image make the Lagoon Nebula’s watery name eerily appropriate from this viewpoint too. Located four to five thousand light-years away, in the constellation of Sagittarius (the Archer), Messier 8 is a huge region of star birth that stretches across one hundred light-years. Clouds of hydrogen gas are slowly collapsing to form new stars, whose bright ultraviolet rays then light up the surrounding gas in a distinctive shade of red. The wispy tendrils and beach-like features of the nebula are not caused by the ebb and flow of tides, but rather by ultraviolet radiation’s ability to erode and disperse the gas and dust into the distinctive shapes that we see. In recent years astronomers probing the secrets of the Lagoon Nebula have found the first unambiguous proof that star formation by accretion of matter from the gas cloud is ongoing in this region. Young stars that are still surrounded by an accretion disc occasionally shoot out long tendrils of matter from their poles. Several examples of these jets, known as Herbig-Haro objects, have been found in this nebula in the last five years, providing strong support for

  1. New portrait of Omega Nebula's glistening watercolours

    NASA Astrophysics Data System (ADS)

    2009-07-01

    newly released image, obtained with the EMMI instrument attached to the ESO 3.58-metre New Technology Telescope (NTT) at La Silla, Chile, shows the central region of the Omega Nebula in exquisite detail. In 2000, another instrument on the NTT, called SOFI, captured another striking image of the nebula (ESO Press Photo 24a/00) in the near-infrared, giving astronomers a penetrating view through the obscuring dust, and clearly showing many previously hidden stars. The NASA/ESA Hubble Space Telescope has also imaged small parts of this nebula (heic0305a and heic0206d) in fine detail. At the left of the image a huge and strangely box-shaped cloud of dust covers the glowing gas. The fascinating palette of subtle colour shades across the image comes from the presence of different gases (mostly hydrogen, but also oxygen, nitrogen and sulphur) that are glowing under the fierce ultraviolet light radiated by the hot young stars. More Information ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large

  2. A discussion of the H-alpha filamentary nebulae and galactic structure in the Cygnus region

    NASA Technical Reports Server (NTRS)

    Matthews, T. A.; Simonson, S. C., III

    1971-01-01

    From observation of the galactic structure in Cygnus, the system of filamentary nebulae was found to lie at a distance of roughly 1.5 kpc, in the same region as about half the thermal radio sources in Cygnus X, the supernova remnant near gamma Cygni, and the association Cygnus OB2, in the direction of which the X-ray source Cygnus XR-3 is observed. The source of excitation was probably the pulse of radiation from a supernova explosion, as proposed in the case of Gum nebula. However continuing excitation by early stars in the region of Cygnus X cannot be excluded.

  3. The Extended Region Around the Planetary Nebula NGC 3242

    NASA Image and Video Library

    2009-04-03

    This ultraviolet image from NASA Galaxy Evolution Explorer shows NGC 3242, a planetary nebula frequently referred to as Jupiter Ghost. The small circular white and blue area at the center of the image is the well-known portion of the nebula.

  4. Interrogating Seyferts with NebulaBayes: Spatially Probing the Narrow-line Region Radiation Fields and Chemical Abundances

    NASA Astrophysics Data System (ADS)

    Thomas, Adam D.; Dopita, Michael A.; Kewley, Lisa J.; Groves, Brent A.; Sutherland, Ralph S.; Hopkins, Andrew M.; Blanc, Guillermo A.

    2018-04-01

    NebulaBayes is a new Bayesian code that implements a general method of comparing observed emission-line fluxes to photoionization model grids. The code enables us to extract robust, spatially resolved measurements of abundances in the extended narrow-line regions (ENLRs) produced by Active Galactic Nuclei (AGN). We observe near-constant ionization parameters but steeply radially declining pressures, which together imply that radiation pressure regulates the ENLR density structure on large scales. Our sample includes four “pure Seyfert” galaxies from the S7 survey that have extensive ENLRs. NGC 2992 shows steep metallicity gradients from the nucleus into the ionization cones. An inverse metallicity gradient is observed in ESO 138-G01, which we attribute to a recent gas inflow or minor merger. A uniformly high metallicity and hard ionizing continuum are inferred across the ENLR of Mrk 573. Our analysis of IC 5063 is likely affected by contamination from shock excitation, which appears to soften the inferred ionizing spectrum. The peak of the ionizing continuum E peak is determined by the nuclear spectrum and the absorbing column between the nucleus and the ionized nebula. We cannot separate variation in this intrinsic E peak from the effects of shock or H II region contamination, but E peak measurements nevertheless give insights into ENLR excitation. We demonstrate the general applicability of NebulaBayes by analyzing a nuclear spectrum from the non-active galaxy NGC 4691 using a H II region grid. The NLR and H II region model grids are provided with NebulaBayes for use by the astronomical community.

  5. WISE Spies the Tarantula Nebula

    NASA Image and Video Library

    2010-07-06

    Sending chills down the spine of all arachnophobes is the Tarantula nebula, seen in this image from NASA Wide-field Infrared Survey Explorer; the nebula is the largest star-forming region known in our entire Local Group of galaxies.

  6. Interstellar gas in the Gum Nebula

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

    Wallerstein, G.; Silk, J.; Jenkins, E.B.

    1980-09-15

    We have surveyed the interstellar gas in and around the Gum Nebula by optically observing 67 stars at Ca II, 42 stars at Na I, and 14 stars in the ultraviolet with the Copernicus satellite. Velocity dispersions for gas in the Gum Nebula, excluding the region of Vela remnant filaments, are not significantly larger than in the general interstellar medium. The ionization structure is predominantly that of an H II region with moderately high ionization, i.e., strong Si III and S III, in clouds with Vertical BarV/sub LSR/Vertical Bar> or approx. =10 km s/sup -1/. Furthermore, we find an increasemore » in fine-structure excitation with increasing component LSR velocity, suggestive of ram-pressure confinement for the intermediate-velocity clouds. These denser, more highly ionized clouds appear to be concentrated toward the inner Gum Nebula, where a somewhat higher velocity dispersion is found than in the outer regions. Clouds in the Gum Nebula do not show the anomalously high ionization seen in the Vela remnant clouds. The observational data are generally consistent with a model of the Gum Nebula as an H II region ionized by OB stars and stirred up by multiple stellar winds.« less

  7. Kinematics of the Huyghenian region of the Orion Nebula.

    NASA Technical Reports Server (NTRS)

    Fischel, D.; Feibelman, W. A.

    1973-01-01

    Palomar data published by Wilson et al. (1959) on Orion Nebula wavelength 3726 and 5007 forbidden OII and OIII emission lines have been used to construct a presented pair of contour maps of isovelocities in intervals of 2.5 km/sec. The space motions of theta-1 and theta-2 Ori stars and nebula measurements are discussed.

  8. Structure and physical conditions in the Huygens region of the Orion nebula

    NASA Astrophysics Data System (ADS)

    O'Dell, C. R.; Ferland, G. J.; Peimbert, M.

    2017-02-01

    Hubble Space Telescope images, MUSE maps of emission lines, and an atlas of high velocity resolution emission-line spectra have been used to establish for the first time correlations of the electron temperature, electron density, radial velocity, turbulence, and orientation within the main ionization front of the nebula. From the study of the combined properties of multiple features, it is established that variations in the radial velocity are primarily caused by the photoevaporating ionization front being viewed at different angles. There is a progressive increase of the electron temperature and density with decreasing distance from the dominant ionizing star θ1 Ori C. The product of these characteristics (ne × Te) is the most relevant parameter in modelling a blister-type nebula like the Huygens region, where this quantity should vary with the surface brightness in Hα. Several lines of evidence indicate that small-scale structure and turbulence exist down to the level of our resolution of a few arcseconds. Although photoevaporative flow must contribute at some level to the well-known non-thermal broadening of the emission lines, comparison of quantitative predictions with the observed optical line widths indicates that it is not the major additive broadening component. Derivation of Te values for H+ from radio+optical and optical-only ionized hydrogen emission showed that this temperature is close to that derived from [N II] and that the transition from the well-known flat extinction curve which applies in the Huygens region to a more normal steep extinction curve occurs immediately outside of the Bright Bar feature of the nebula.

  9. The Boomerang Nebula - The Coldest Region of the Universe

    NASA Technical Reports Server (NTRS)

    Sahai, Raghvendra; Nyman, Lars-Ake

    1997-01-01

    In this letter, we report such observations of the Boomerang Nebula which show it to be a unique object, consisiting of an ultra-cold and extremely massive molecular envolope, expanding at very high speed. The extreeme physical characteristics of the Boomerang Nebula reported here have never been seen before in any AGB or post-AGB object, and should spur new theoretical and obesrvational efforts to understand the nature of the mass-loss processes occurring during later stellar evolution.

  10. Electronic Properties and Dissociative Photoionization of Thiocyanates, Part III. The Effect of the Group's Electronegativity in the Valence and Shallow-Core (Sulfur and Chlorine 2p) Regions of CCl3SCN and CCl2FSCN.

    PubMed

    Rodríguez Pirani, Lucas S; Della Védova, Carlos O; Geronés, Mariana; Romano, Rosana M; Cavasso-Filho, Reinaldo; Ge, Maofa; Ma, Chunping; Erben, Mauricio F

    2017-12-07

    Both photoelectron spectroscopy (PES) data and PhotoElectron-PhotoIon-Coincidence (PEPICO) spectra obtained from a synchrotron facility have been used to examine the electronic structure and the dissociative ionization of halomethyl thiocyantes in the valence and shallow-core S 2p and Cl 2p regions. Two simple and closely related molecules, namely, CCl 3 SCN and CCl 2 FSCN, have been analyzed to assess the role of halogen substitution in the electronic properties of thiocyanates. The assignment of the He(I) photoelectron spectra has been achieved with the help of quantum chemical calculations at the outer-valence Green's function (OVGF) level of approximation. The first ionization energies observed at 10.55 and 10.78 eV for CCl 3 SCN and CCl 2 FSCN, respectively, are assigned to ionization processes from the sulfur lone pair orbital [n(S)]. When these molecules are compared with CX 3 SCN (X = H, Cl, F) species, a linear relationship between the vertical first ionization energy and electronegativity of CX 3 group is observed. Irradiation of CCl 3 SCN and CCl 2 FSCN with photons in the valence energy regions leads to the formation of CCl 2 X + and CClXSCN + ions (X = Cl or F). Additionally, the achievement of the fragmentation patterns and the total ion yield spectra obtained from the PEPICO data in the S 2p and Cl 2p regions and several dissociation channels can be inferred for the core-excited species by using the triple coincidence PEPIPICO (PhotoElectron-PhotoIon-PhotoIon-Coincidence) spectra.

  11. Formation environment of cometary nuclei in the primordial solar nebula

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.

    1985-01-01

    The formation environment of comets in the primordial solar nebula is investigated from the point of view of the chemical composition of the ices of cometary nuclei. A sublimation sequence for various species of possible constituents of the nuclear ice, which would have condensed on the grain surface in the parent interstellar cloud was obtained by calculating the temperature of grains in the solar nebula. On this basis, an allowed range of the nebular temperature in the formation region of cometary nuclei is obtained from a condition for retention of the ices of the nuclear composition. Combining this result with models of the solar nebula, the region for the formation of cometary nuclei in the solar nebula is discussed. It is shown that cometary nuclei formed at least beyond the region between the formation regions of Saturn and Uranus. Finally, an upper limit is estimated for the grain temperature in the region of comet formation at an earlier stage of the solar nebula. The grain temperature is shown to be less than 60 K at this stage.

  12. A New View of the Tarantula Nebula

    NASA Image and Video Library

    2012-04-17

    This composite of 30 Doradus, the Tarantula Nebula, contains data from Chandra blue, Hubble green, and Spitzer red. Located in the Large Magellanic Cloud, the Tarantula Nebula is one of the largest star-forming regions close to the Milky Way.

  13. Doradus Nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A panoramic view of a vast, sculpted area of gas and dust where thousands of stars are being born has been captured by NASA's Hubble Space Telescope.

    The image, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://oposite.stsci.edu/pubinfo/pr/2001/21 and http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    The photo offers an unprecedented, detailed view of the entire inner region of the fertile, star-forming 30 Doradus Nebula. The mosaic picture shows that ultraviolet radiation and high-speed material unleashed by the stars in the cluster, called R136 (the large blue blob left of center), are weaving a tapestry of creation and destruction, triggering the collapse of looming gas and dust clouds and forming pillar-like structures that incubate newborn stars.

    The 30 Doradus Nebula is in the Large Magellanic Cloud, a satellite galaxy of the Milky Way located 170,000 light-years from Earth. Nebulas like 30 Doradus are signposts of recent star birth. High-energy ultraviolet radiation from young, hot, massive stars in R136 causes surrounding gaseous material to glow. Previous Hubble telescope observations showed that R136 contains several dozen of the most massive stars known, each about 100 times the mass of the Sun and about 10 times as hot. These stellar behemoths formed about 2 million years ago.

    The stars in R136 produce intense 'stellar winds,' streams of material traveling at several million miles an hour. These winds push the gas away from the cluster and compress the inner regions of the surrounding gas and dust clouds (seen in the image as the pinkish material). The intense pressure triggers the collapse of parts of the clouds, producing a new star formation around the central cluster. Most stars in the nursery are not visible because they are still encased in cocoons of gas and dust.

    This mosaic image of 30 Doradus consists of five overlapping

  14. Common Envelope Shaping of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    García-Segura, Guillermo; Ricker, Paul M.; Taam, Ronald E.

    2018-06-01

    The morphology of planetary nebulae emerging from the common envelope phase of binary star evolution is investigated. Using initial conditions based on the numerical results of hydrodynamical simulations of the common envelope phase, it was found that the shapes and sizes of the resulting nebula are very sensitive to the effective temperature of the remnant core, the mass-loss rate at the onset of the common envelope phase, and the mass ratio of the binary system. These parameters are related to the efficiency of the mass ejection after the spiral-in phase, the stellar evolutionary phase (i.e., RG, AGB, or TP-AGB), and the degree of departure from spherical symmetry in the stellar wind mass-loss process itself, respectively. It was also found that the shapes are mostly bipolar in the early phase of evolution, but that they can quickly transition to elliptical and barrel-type shapes. Solutions for nested lobes are found where the outer lobes are usually bipolar and the inner lobes are elliptical, bipolar, or barrel-type, a result due to the flow of the photo-evaporated gas from the equatorial region. Also, the lobes can be produced without the need for two distinct mass ejection events. In all the computations, the bulk of the mass is concentrated in the orbital or equatorial plane, in the form of a large toroid, which can be either neutral (early phases) or photoionized (late phases), depending of the evolutionary state of the system.

  15. Polycyclic aromatic hydrocarbons and molecular hydrogen in oxygen-rich planetary nebulae: the case of NGC 6720

    PubMed Central

    Cox, N. L. J.; Pilleri, P.; Berné, O.; Cernicharo, J.; Joblin, C.

    2015-01-01

    Evolved stars are primary sources for the formation of polycyclic aromatic hydrocarbons (PAHs) and dust grains. Their circumstellar chemistry is usually designated as either oxygen-rich or carbon-rich, although dual-dust chemistry objects, whose infrared spectra reveal both silicate- and carbon-dust features, are also known. The exact origin and nature of this dual-dust chemistry is not yet understood. Spitzer-IRS mid-infrared spectroscopic imaging of the nearby, oxygen-rich planetary nebula NGC 6720 reveals the presence of the 11.3 μm aromatic (PAH) emission band. It is attributed to emission from neutral PAHs, since no band is observed in the 7–8 μm range. The spatial distribution of PAHs is found to closely follow that of the warm clumpy molecular hydrogen emission. Emission from both neutral PAHs and warm H2 is likely to arise from photo-dissociation regions associated with dense knots that are located within the main ring. The presence of PAHs together with the previously derived high abundance of free carbon (relative to CO) suggest that the local conditions in an oxygen-rich environment can also become conducive to in-situ formation of large carbonaceous molecules, such as PAHs, via a bottom-up chemical pathway. In this scenario, the same stellar source can enrich the interstellar medium with both oxygen-rich dust and large carbonaceous molecules. PMID:26924856

  16. Ionization nebulae surrounding supersoft X-ray sources

    NASA Technical Reports Server (NTRS)

    Rappaport, S.; Chiang, E.; Kallman, T.; Malina, R.

    1994-01-01

    In this work we carry out a theoretical investigation of a new type of astrophysical gaseous nebula, viz., ionized regions surrounding supersoft X-ray sources. Supersoft X-ray sources, many of which have characteristic luminosities of approximately 10(exp 37)-(10(exp 38) ergs/s and effective temperatures of approximately 4 x 10(exp 5) K, were first discovered with the Einstein Observatory. These sources have now been shown to constitute a distinct class of X-ray source and are being found in substantial numbers with ROSAT. We predict that these sources should be surrounded by regions of ionized hydrogen and helium with properties that are distinct from other astrophysical gaseous nebulae. We present caluations of the ionization and temperature structure of these ionization nebulae, as well as the expected optical line fluxes. The ionization profiles for both hydrogen and helium exhibit substantially more gradual transitions from the ionized to the unionized state than is the case for conventional H II regions. The calculated optical line intensitites are presented as absolute fluxes from sources in the Large Magellanic Cloud and as fractions of the central source luminosity. We find, in particular, that (O III) lambda 5008 and He II lambda 4686 are especially prominent in these ionization nebulae as compared to other astrophysical nebulae. We propose that searches for supersoft X-rays via their characteristic optical lines may reveal sources in regions where the soft X-rays are nearly completely absorbed by the interstellar medium.

  17. The 3-D ionization structure and evolution of NGC 7009 (Saturn Nebula)

    NASA Astrophysics Data System (ADS)

    Sabbadin, F.; Turatto, M.; Cappellaro, E.; Benetti, S.; Ragazzoni, R.

    2004-03-01

    Tomographic and 3-D analyses for extended, emission-line objects are applied to long-slit ESO NTT + EMMI high-resolution spectra of the intriguing planetary nebula NGC 7009, covered at twelve position angles. We derive the gas expansion law, the diagnostics and ionic radial profiles, the distance and the central star parameters, the nebular photo-ionization model and the spatial recovery of the plasma structure and evolution. The Saturn Nebula (distance≃1.4 kpc, age≃6000 yr, ionized mass≃0.18 M⊙) consists of several interconnected components, characterized by different morphology, physical conditions, excitation and kinematics. We identify four ``large-scale'', mean-to-high excitation sub-systems (the internal shell, the main shell, the outer shell and the halo), and as many ``small-scale'' ones: the caps (strings of low-excitation knots within the outer shell), the ansae (polar, low-excitation, likely shocked layers), the streams (high-excitation polar regions connecting the main shell with the ansae), and an equatorial, medium-to-low excitation pseudo-ring within the outer shell. The internal shell, the main shell, the streams and the ansae expand at Vexp≃4.0 × R arcsec km s-1, the outer shell, the caps and the equatorial pseudo-ring at Vexp≃3.15 × R arcsec km s-1, and the halo at Vexp≃10 km s-1. We compare the radial distribution of the physical conditions and the line fluxes observed in the eight sub-systems with the theoretical profiles coming from the photo-ionization code CLOUDY, inferring that all the spectral characteristics of NGC 7009 are explainable in terms of photo-ionization by the central star, a hot ( log T* ≃4.95) and luminous ( log L*/L⊙≃3.70) 0.60-0.61 M⊙ post-AGB star in the hydrogen-shell nuclear burning phase. The 3-D shaping of the Saturn Nebula is discussed within an evolutionary scenario dominated by photo-ionization and supported by the fast stellar wind: it begins with the superwind ejection (first isotropic, then

  18. Discovery of a Circumstellar Disk in the Lagoon Nebula

    NASA Astrophysics Data System (ADS)

    1997-04-01

    photos as tear-drop shaped, bright-rimmed areas with the cusps of the ionised regions aligned towards the exciting star. Such a region is also a very compact source of radio emission. Clearly, the harsh environment in which these disks reside does not favour planet formation. These findings were facilitated by the fact that, at a distance of `only' 1500 lightyears (about 450 parsec), the Orion Nebula is the closest site of high-mass star formation. Furthermore, many circumstellar disks around stars in this nebula are seen in silhouette against a bright and uniform background and are therefore comparatively easy to detect. The Lagoon Nebula In principle, similar phenomena should occur in any giant molecular cloud that gives rise to the birth of massive stars. However, the detection of such disks in other clouds would be very difficult, first of all because of their much larger distance. The Lagoon Nebula (M8) is located four times further away than the Orion Nebula and it is also a site of recent high-mass star formation. Its brightest part constitutes a conspicuous region of ionised hydrogen gas (an `HII-region') dubbed `The Hourglass' because of the resemblance. The gas in this area is ionised by the action of the nearby, hot star Herschel 36 (Her 36) . High-resolution radio maps show that the emission from the ionised gas peaks at 2.7 arcsec southeast of Her 36. An early explanation was that this emission is due to an unseen, massive star that is deeply embedded in the gas and dust and which is causing an ultra-compact HII-region (UCHR), catalogued as G5.97-1.17 according to its galactic coordinates. High-resolution images from ESO During a detailed investigation of such ultra-compact HII regions, Bringfried Stecklum and his colleagues found that, unlike ordinary UCHRs, this particular object is visible on optical images obtained with the HST Wide-Field Planetary Camera (HST-WFPC). This means that, contrary to the others, it is not deeply embedded in the nebula - its

  19. A Tactile Carina Nebula

    NASA Astrophysics Data System (ADS)

    Grice, Noreen A.; Mutchler, M.

    2010-01-01

    Astronomy was once considered a science restricted to fully sighted participants. But in the past two decades, accessible books with large print/Braille and touchable pictures have brought astronomy and space science to the hands and mind's eye of students, regardless of their visual ability. A new universally-designed tactile image featuring the Hubble mosaic of the Carina Nebula is being presented at this conference. The original dataset was obtained with Hubble's Advanced Camera for Surveys (ACS) hydrogen-alpha filter in 2005. It became an instant icon after being infused with additional color information from ground-based CTIO data, and released as Hubble's 17th anniversary image. Our tactile Carina Nebula promotes multi-mode learning about the entire life-cycle of stars, which is dramatically illustrated in this Hubble mosaic. When combined with descriptive text in print and Braille, the visual and tactile components seamlessly reach both sighted and blind populations. Specific touchable features of the tactile image identify the shapes and orientations of objects in the Carina Nebula that include star-forming regions, jets, pillars, dark and light globules, star clusters, shocks/bubbles, the Keyhole Nebula, and stellar death (Eta Carinae). Visit our poster paper to touch the Carina Nebula!

  20. Accidental Predissociation: A Special Case of Photo-Induced Isotope Fractionation Effect and Possible Occurrence in Nature

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Thiemens, M. H.

    2009-12-01

    light of these data, anomalous isotopic fractionations associated with accidental predissociation will be discussed for the CO and N2. These fractionations are important as VUV-photodissociation of CO and N2 have been invoked in solar nebula (self-shielding, (9-10)) to explain the observed iso-topic signatures in different solar system objects neglecting these isotope effects during photo-dissociation. References: 1. Y. L. Yung, C. E. Miller, Science 278, 1778 (1997). 2. S. Chakraborty, S. K. Bhattacharya, J. Chem. Phys. 118, 2164 (2003). 3. H. Lefebvre-Brion, R. W. Field, The Spectra and Dynamics of Diatomic Molecules. (Elsevier Academic Press, 2004). 4. A. J. Lorquet, J. C. Lorquet, Chem. Phys. Lett. 26, 138 (1974). 5. W. Ubachs, I. Velchev, P. Cacciani, J. Chem. Phys. 113, 547 (2000). 6. H. Lefebvre-Brion, R. Colin, J. Mol. Spectrosc. 65, 33 (1977). 7. S. Chakraborty, M. Ahmed, T. L. Jackson, M. H. Thiemens, Science 321, 1328 (2008). 8. S. Chakraborty, M. Ahmed, T. L. Jackson, M. H. Thiemens, Science 324, 4 (2009). 9. R. N. Clayton, Nature 415, 860 (2002). 10. J. R. Lyons, E. D. Young, Nature 435, 317 (2005).

  1. Horsehead nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Rising from a sea of dust and gas like a giant seahorse, the Horsehead nebula is one of the most photographed objects in the sky. NASA's Hubble Space Telescope took a close-up look at this heavenly icon, revealing the cloud's intricate structure. This detailed view of the horse's head is being released to celebrate the orbiting observatory's eleventh anniversary. Produced by the Hubble Heritage Project, this picture is a testament to the Horsehead's popularity. Internet voters selected this object for the orbiting telescope to view.

    The Horsehead, also known as Barnard 33, is a cold, dark cloud of gas and dust, silhouetted against the bright nebula, IC 434. The bright area at the top left edge is a young star still embedded in its nursery of gas and dust. But radiation from this hot star is eroding the stellar nursery. The top of the nebula also is being sculpted by radiation from a massive star located out of Hubble's field of view.

    Only by chance does the nebula roughly resemble the head of a horse. Its unusual shape was first discovered on a photographic plate in the late 1800s. Located in the constellation Orion, the Horsehead is a cousin of the famous pillars of dust and gas known as the Eagle nebula. Both tower-like nebulas are cocoons of young stars.

    The Horsehead nebula lies just south of the bright star Zeta Orionis, which is easily visible to the unaided eye as the left-hand star in the line of three that form Orion's Belt. Amateur astronomers often use the Horsehead as a test of their observing skills; it is known as one of the more difficult objects to see visually in an amateur-sized telescope.

    The magnificent extent of the Horsehead is best appreciated in a new wide-field image of the nebula being released today by the National Optical Astronomy Observatory, taken by Travis Rector with the National Science Foundation's 0.9 meter telescope at Kitt Peak National Observatory near Tucson, AZ.

    This popular celestial target was the clear

  2. Large-Scale Structure of the Carina Nebula.

    PubMed

    Smith; Egan; Carey; Price; Morse; Price

    2000-04-01

    Observations obtained with the Midcourse Space Experiment (MSX) satellite reveal for the first time the complex mid-infrared morphology of the entire Carina Nebula (NGC 3372). On the largest size scale of approximately 100 pc, the thermal infrared emission from the giant H ii region delineates one coherent structure: a (somewhat distorted) bipolar nebula with the major axis perpendicular to the Galactic plane. The Carina Nebula is usually described as an evolved H ii region that is no longer actively forming stars, clearing away the last vestiges of its natal molecular cloud. However, the MSX observations presented here reveal numerous embedded infrared sources that are good candidates for sites of current star formation. Several compact infrared sources are located at the heads of dust pillars or in dark globules behind ionization fronts. Because their morphology suggests a strong interaction with the peculiar collection of massive stars in the nebula, we speculate that these new infrared sources may be sites of triggered star formation in NGC 3372.

  3. The PAH Emission Characteristics of the Reflection Nebula NGC 2023

    NASA Astrophysics Data System (ADS)

    Peeters, Els; Bauschlicher, Charles W., Jr.; Allamandola, Louis J.; Tielens, Alexander G. G. M.; Ricca, Alessandra; Wolfire, Mark G.

    2017-02-01

    We present 5-20 μm spectral maps of the reflection nebula NGC 2023 obtained with the Infrared Spectrograph SL and SH modes on board the Spitzer Space Telescope, which reveal emission from polycyclic aromatic hydrocarbons (PAHs), C60, and H2 superposed on a dust continuum. We show that several PAH emission bands correlate with each other and exhibit distinct spatial distributions that reveal a spatial sequence with distance from the illuminating star. We explore the distinct morphology of the 6.2, 7.7, and 8.6 μm PAH bands and find that at least two spatially distinct components contribute to the 7-9 μm PAH emission in NGC 2023. We report that the PAH features behave independently of the underlying plateaus. We present spectra of compact, oval PAHs ranging in size from C66 to C210, determined computationally using density functional theory, and we investigate trends in the band positions and relative intensities as a function of PAH size, charge, and geometry. Based on the NASA Ames PAH database, we discuss the 7-9 μm components in terms of band assignments and relative intensities. We assign the plateau emission to very small grains with possible contributions from PAH clusters and identify components in the 7-9 μm emission that likely originate in these structures. Based on the assignments and the observed spatial sequence, we discuss the photochemical evolution of the interstellar PAH family as the PAHs are more and more exposed to the radiation field of the central star in the evaporative flows associated with the Photo-Dissociation Regions in NGC 2023.

  4. ON THE NONTHERMAL κ-DISTRIBUTED ELECTRONS IN PLANETARY NEBULAE AND H ii REGIONS: THE κ INDEX AND ITS CORRELATIONS WITH OTHER NEBULAR PROPERTIES

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

    Zhang, Yong; Zhang, Bing; Liu, Xiao-Wei, E-mail: zhangy96@hku.hk

    2016-01-20

    Recently, a suspicion arose that the free electrons in planetary nebulae (PNs) and H ii regions might have nonthermal energy distributions. In this scenario, a κ index is introduced to characterize the electron energy distributions, with smaller κ values indicating larger deviations from Maxwell–Boltzmann distributions. Assuming that this is the case, we determine the κ values for a sample of PNs and H ii regions by comparing the intensities of [O iii] collisionally excited lines and the hydrogen Balmer jump. We find the average κ indices of PNs and H ii regions to be 27 and 32, respectively. Correlations betweenmore » the resultant κ values and various physical properties of the nebulae are examined to explore the potential origin of nonthermal electrons in photoionized gaseous nebulae. However, no positive result is obtained. Thus, the current analysis does not lend support to the idea that κ-distributed electrons are present in PNs and H ii regions.« less

  5. LMC X-1: A New Spectral Analysis of the O-star in the Binary and Surrounding Nebula

    NASA Astrophysics Data System (ADS)

    Hyde, E. A.; Russell, D. M.; Ritter, A.; Filipović, M. D.; Kaper, L.; Grieve, K.; O'Brien, A. N.

    2017-09-01

    We provide new observations of the LMC X-1 O star and its extended nebula structure using spectroscopic data from VLT/UVES as well as Hα imaging from the Wide Field Imager on the Max Planck Gesellschaft/European Southern Observatory 2.2 m telescope and ATCA imaging of the 2.1 GHz radio continuum. This nebula is one of the few known to be energized by an X-ray binary. We use a new spectrum extraction technique that is superior to other methods used to obtain both radial velocities and fluxes. This provides an updated spatial velocity of ≃ 21.0 +/- 4.8 km s-1 for the O star. The slit encompasses both the photo-ionized and shock-ionized regions of the nebula. The imaging shows a clear arc-like structure reminiscent of a wind bow shock in between the ionization cone and shock-ionized nebula. The observed structure can be fit well by the parabolic shape of a wind bow shock. If an interpretation of a wind bow shock system is valid, we investigate the N159-O1 star cluster as a potential parent of the system, suggesting a progenitor mass of ˜60 M ⊙ for the black hole. We further note that the radio emission could be non-thermal emission from the wind bow shock, or synchrotron emission associated with the jet-inflated nebula. For both wind- and jet-powered origins, this would represent one of the first radio detections of such a structure.

  6. Ghost Head Nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Looking like a colorful holiday card, a new image from NASA's Hubble Space Telescope reveals a vibrant green and red nebula far from Earth.

    The image of NGC 2080, taken by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif., is available online at http://www.jpl.nasa.gov/images/wfpc . Images like this help astronomers investigate star formation in nebulas.

    NGC 2080, nicknamed 'The Ghost Head Nebula,' is one of a chain of star-forming regions lying south of the 30 Doradus nebula in the Large Magellanic Cloud. 30 Doradus is the largest star-forming complex in the local group of galaxies. This 'enhanced color' picture is composed of three narrow-band-filter images obtained by Hubble on March 28, 2000.

    The red and blue light come from regions of hydrogen gas heated by nearby stars. The green light on the left comes from glowing oxygen. The energy to illuminate the green light is supplied by a powerful stellar wind, a stream of high-speed particles coming from a massive star just outside the image. The central white region is a combination of all three emissions and indicates a core of hot, massive stars in this star-formation region. Intense emission from these stars has carved a bowl-shaped cavity in surrounding gas.

    In the white region, the two bright areas (the 'eyes of the ghost') - named A1 (left) and A2 (right) -- are very hot, glowing 'blobs' of hydrogen and oxygen. The bubble in A1 is produced by the hot, intense radiation and powerful stellar wind from one massive star. A2 contains more dust and several hidden, massive stars. The massive stars in A1 and A2 must have formed within the last 10,000 years, since their natal gas shrouds are not yet disrupted by the powerful radiation of the newborn stars.

    The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard Space Flight Center

  7. Interstellar gas in the Gum Nebula

    NASA Technical Reports Server (NTRS)

    Wallerstein, G.; Jenkins, E. B.; Silk, J.

    1980-01-01

    A survey of the interstellar gas near the Gum Nebula by optical observation of 67 stars at Ca II, 42 stars at Na I, and 14 stars in the UV with the Copernicus satellite provided radial velocities and column densities for all resolved absorption components. Velocity dispersions for gas in the Gum Nebula are not significantly larger than in the general interstellar medium; the ionization structure is predominantly that of an H II region with moderately high ionization. Denser, more highly ionized clouds are concentrated toward the Gum Nebula; these clouds do not show the anomalously high ionization observed in the Vela remnant clouds.

  8. Iridescent Glory of Nearby Helix Nebula

    NASA Image and Video Library

    2014-04-04

    This composite picture is a seamless blend of ultra-sharp NASA Hubble Space Telescope (HST) images combined with the wide view of the Mosaic Camera on the National Science Foundation's 0.9-meter telescope at Kitt Peak National Observatory, part of the National Optical Astronomy Observatory, near Tucson, Ariz. Astronomers at the Space Telescope Science Institute assembled these images into a mosaic. The mosaic was then blended with a wider photograph taken by the Mosaic Camera. The image shows a fine web of filamentary "bicycle-spoke" features embedded in the colorful red and blue gas ring, which is one of the nearest planetary nebulae to Earth. Because the nebula is nearby, it appears as nearly one-half the diameter of the full Moon. This required HST astronomers to take several exposures with the Advanced Camera for Surveys to capture most of the Helix. HST views were then blended with a wider photo taken by the Mosaic Camera. The portrait offers a dizzying look down what is actually a trillion-mile-long tunnel of glowing gases. The fluorescing tube is pointed nearly directly at Earth, so it looks more like a bubble than a cylinder. A forest of thousands of comet-like filaments, embedded along the inner rim of the nebula, points back toward the central star, which is a small, super-hot white dwarf. The tentacles formed when a hot "stellar wind" of gas plowed into colder shells of dust and gas ejected previously by the doomed star. Ground-based telescopes have seen these comet-like filaments for decades, but never before in such detail. The filaments may actually lie in a disk encircling the hot star, like a collar. The radiant tie-die colors correspond to glowing oxygen (blue) and hydrogen and nitrogen (red). Valuable Hubble observing time became available during the November 2002 Leonid meteor storm. To protect the spacecraft, including HST's precise mirror, controllers turned the aft end into the direction of the meteor stream for about half a day. Fortunately

  9. Solar nebula condensates and the composition of comets

    NASA Technical Reports Server (NTRS)

    Lunine, J. I.

    1989-01-01

    Interpretation of the volatile abundances in Halley's comet in terms of models for chemical and physical processes in the solar nebula are discussed. Key ratios of the oxidized and reduced species of nitrogen and carbon are identified which tell something of the chemical history of the environment in which cometary grains accreted to form the nucleus. Isotopic abundances are also applied to this problem. It will be shown that the abundances of methane and carbon monoxide are consistent both with models of solar nebula chemistry and chemical processing on grains in star-forming regions. Ultimately, limitations of the current data set on molecular abundances in comets and star-forming regions prevent a definitive choice between the two. Processes important to the composition of outer solar system bodies are: (1) gas phase chemistry in the solar nebula; (2) imperfect mixing in the solar nebula; (3) condensation; (4) clathration; (5) adsorption; and (6) processing of interstellar material.

  10. Mapping Excitation in the Inner Regions of the Planetary Nebula NGC 5189 Using HST WFC3 Imaging

    NASA Astrophysics Data System (ADS)

    Danehkar, Ashkbiz; Karovska, Margarita; Maksym, W. Peter; Montez, Rodolfo, Jr.

    2018-01-01

    The planetary nebula (PN) NGC 5189 around a Wolf–Rayet [WO] central star demonstrates one of the most remarkable complex morphologies among PNe with many multiscale structures, showing evidence of multiple outbursts from an asymptotic giant branch (AGB) progenitor. In this study, we use multiwavelength Hubble Space Telescope Wide Field Camera 3 observations to study the morphology of the inner 0.3 pc × 0.2 pc region surrounding the central binary that appears to be a relic of a more recent outburst of the progenitor AGB star. We applied diagnostic diagrams based on emission-line ratios of Hα λ6563, [O III] λ5007, and [S II] λ λ 6716,6731 images to identify the location and morphology of low-ionization structures within the inner nebula. We distinguished two inner, low-ionization envelopes from the ionized gas, within a radius of 55 arcsec (∼0.15 pc) extending from the central star: a large envelope expanding toward the northeast, and its smaller counterpart envelope in the opposite direction toward the southwest of the nebula. These low-ionization envelopes are surrounded by a highly ionized gaseous environment. We believe that these low-ionization expanding envelopes are a result of a powerful outburst from the post-AGB star that created shocked wind regions as they propagate through the previously expelled material along a symmetric axis. Our diagnostic mapping using high-angular resolution line-emission imaging can provide a novel approach to detection of low-ionization regions in other PNe, especially those showing a complex multiscale morphology.

  11. The PAH Emission Characteristics of the Reflection Nebula NGC 2023

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

    Peeters, Els; Bauschlicher, Charles W. Jr.; Allamandola, Louis J.

    We present 5–20 μ m spectral maps of the reflection nebula NGC 2023 obtained with the Infrared Spectrograph SL and SH modes on board the Spitzer Space Telescope, which reveal emission from polycyclic aromatic hydrocarbons (PAHs), C{sub 60}, and H{sub 2} superposed on a dust continuum. We show that several PAH emission bands correlate with each other and exhibit distinct spatial distributions that reveal a spatial sequence with distance from the illuminating star. We explore the distinct morphology of the 6.2, 7.7, and 8.6 μ m PAH bands and find that at least two spatially distinct components contribute to themore » 7–9 μ m PAH emission in NGC 2023. We report that the PAH features behave independently of the underlying plateaus. We present spectra of compact, oval PAHs ranging in size from C{sub 66} to C{sub 210}, determined computationally using density functional theory, and we investigate trends in the band positions and relative intensities as a function of PAH size, charge, and geometry. Based on the NASA Ames PAH database, we discuss the 7–9 μ m components in terms of band assignments and relative intensities. We assign the plateau emission to very small grains with possible contributions from PAH clusters and identify components in the 7–9 μ m emission that likely originate in these structures. Based on the assignments and the observed spatial sequence, we discuss the photochemical evolution of the interstellar PAH family as the PAHs are more and more exposed to the radiation field of the central star in the evaporative flows associated with the Photo-Dissociation Regions in NGC 2023.« less

  12. The size and shape of Gum's nebula

    NASA Technical Reports Server (NTRS)

    Johnson, H. M.

    1971-01-01

    The ionizing light of the supernova which produced the Gum nebula is now fossilized in the still live, though failing, H II region. The main body of the nebula suggests a hollow center or shell form, with a characteristic radius of about half the distance to the outlying fragments. The edges of the main body patches are typically sharp and often bright. The structure of the Gum nebula appears to be dependent on the event of ionization and possibly on the details of heating. It is not now an unstructured ambient medium, as it may have been before the recent ionization. Several hypotheses are presented for a structured ambient medium.

  13. Planetary nebulae with UVIT: Far ultra-violet halo around the Bow Tie nebula (NGC 40)

    NASA Astrophysics Data System (ADS)

    Kameswara Rao, N.; Sutaria, F.; Murthy, J.; Krishna, S.; Mohan, R.; Ray, A.

    2018-01-01

    Context. NGC 40 is a planetary nebula with diffuse X-ray emission, suggesting an interaction of the high-speed wind from WC8 central star (CS) with the nebula. It shows strong C IV 1550 Å emission that cannot be explained by thermal processes alone. We present here the first map of this nebula in C IV emission using broad band filters on the Ultra-Violet Imaging Telescope (UVIT). Aim. We aim to map the hot C IV-emitting gas and its correspondence with soft X-ray (0.3-8 keV) emitting regions in order to study the shock interaction between the nebula and the ISM. We also aim to illustrate the potential of UVIT for nebular studies. Methods: We carry out a morphological study of images of the nebula obtained at an angular resolution of about 1.3″ in four UVIT filter bands that include C IV 1550 Å and [C II] 2326 Å lines as well as UV continuum. We also make comparisons with X-ray, optical, and IR images from the literature. Results: The [C II] 2326 Å images show the core of the nebula with two lobes on either side of CS similar to [N II]. The C IV emission in the core shows similar morphology and extent to that of diffuse X-ray emission concentrated in nebular condensations. A surprising UVIT discovery is the presence of a large faint far UV (FUV) halo in an FUV filter with λeff of 1608 Å. The UV halo is not present in any other UV filter. The FUV halo is most likely due to UV fluorescence emission from the Lyman bands of H2 molecules. Unlike the optical and IR halo, the FUV halo trails predominantly towards the south-east side of the nebular core, opposite to the CS's proper motion direction. Conclusions: Morphological similarity of C IV 1550 Å and X-ray emission in the core suggests that it results mostly from the interaction of strong CS wind with the nebula. The FUV halo in NGC 40 highlights the extensive existence of H2 molecules in the regions even beyond the optical and IR halos. Thus UV studies are important to estimate the amount of H2, which is

  14. Dissociation in the laboratory: a comparison of strategies.

    PubMed

    Leonard, K N; Telch, M J; Harrington, P J

    1999-01-01

    Several methods for inducing dissociation in the laboratory were examined in a sample of 78 undergraduate students. Participants scoring high or low on the Dissociative Experiences Scale participated in three dissociation challenge conditions: (a) dot-staring task, (b) administration of pulsed photic and audio stimulation and (c) stimulus deprivation. Participants recorded their dissociative experiences both before and after each of the three challenge conditions. Across conditions, high DES participants reported significantly more dissociative sensations than low DES participants, even after controlling for pre-challenge dissociation. Moreover, regardless of DES status, pulsed photo and audio stimulation produced the greatest level of dissociative symptoms. The findings suggest that the induction of dissociative symptoms in a nonclinical sample is easily accomplished in the laboratory and that those who report more dissociative symptoms in their day-to-day life exhibit more pronounced dissociative symptoms when undergoing dissociative challenge in the laboratory. Implications for the study and treatment of dissociative symptoms are discussed.

  15. Planetary Nebula

    NASA Image and Video Library

    2017-12-08

    This planetary nebula's simple, graceful appearance is thought to be due to perspective: our view from Earth looking straight into what is actually a barrel-shaped cloud of gas shrugged off by a dying central star. Hot blue gas near the energizing central star gives way to progressively cooler green and yellow gas at greater distances with the coolest red gas along the outer boundary. Credit: NASA/Hubble Heritage Team ---- The Ring Nebula's distinctive shape makes it a popular illustration for astronomy books. But new observations by NASA's Hubble Space Telescope of the glowing gas shroud around an old, dying, sun-like star reveal a new twist. "The nebula is not like a bagel, but rather, it's like a jelly doughnut, because it's filled with material in the middle," said C. Robert O'Dell of Vanderbilt University in Nashville, Tenn. He leads a research team that used Hubble and several ground-based telescopes to obtain the best view yet of the iconic nebula. The images show a more complex structure than astronomers once thought and have allowed them to construct the most precise 3-D model of the nebula. "With Hubble's detail, we see a completely different shape than what's been thought about historically for this classic nebula," O'Dell said. "The new Hubble observations show the nebula in much clearer detail, and we see things are not as simple as we previously thought." The Ring Nebula is about 2,000 light-years from Earth and measures roughly 1 light-year across. Located in the constellation Lyra, the nebula is a popular target for amateur astronomers. Read more: 1.usa.gov/14VAOMk 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

  16. Hubble Space Telescope Image of Omega Nebula

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This sturning image, taken by the newly installed Advanced Camera for Surveys (ACS) aboard the Hubble Space Telescope (HST), is an image of the center of the Omega Nebula. It is a hotbed of newly born stars wrapped in colorful blankets of glowing gas and cradled in an enormous cold, dark hydrogen cloud. The region of nebula shown in this photograph is about 3,500 times wider than our solar system. The nebula, also called M17 and the Swan Nebula, resides 5,500 light-years away in the constellation Sagittarius. The Swan Nebula is illuminated by ultraviolet radiation from young, massive stars, located just beyond the upper-right corner of the image. The powerful radiation from these stars evaporates and erodes the dense cloud of cold gas within which the stars formed. The blistered walls of the hollow cloud shine primarily in the blue, green, and red light emitted by excited atoms of hydrogen, nitrogen, oxygen, and sulfur. Particularly striking is the rose-like feature, seen to the right of center, which glows in the red light emitted by hydrogen and sulfur. As the infant stars evaporate the surrounding cloud, they expose dense pockets of gas that may contain developing stars. One isolated pocket is seen at the center of the brightest region of the nebula. Other dense pockets of gas have formed the remarkable feature jutting inward from the left edge of the image. The color image is constructed from four separate images taken in these filters: blue, near infrared, hydrogen alpha, and doubly ionized oxygen. Credit: NASA, H. Ford (JHU), G. Illingworth (USCS/LO), M. Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

  17. The ionization structure of planetary nebulae. IX - NGC 1535

    NASA Technical Reports Server (NTRS)

    Barker, Timothy

    1989-01-01

    The ionization structure of planetary nebula NGC 1535 was investigated using spectrophotometric observations of emission-line intensities over the spectral range 1400-7200 A, which were carried out in five positions in this nebula. The results obtained on the ionic abundances of He, O, N, Ne, C, and Ar in NGC 1535 suggest that it is a planetary nebula that formed initially in a somewhat metal-poor region and has undergone little or no enhancement of its original abundances by mixing with nuclear-processed material.

  18. Protoplanetary Nebulae

    NASA Astrophysics Data System (ADS)

    Kwok, S.; Murdin, P.

    2000-11-01

    Protoplanetary nebulae (or pre-planetary nebulae, PPNs) are defined as objects that are in transition between the asymptotic giant branch (AGB) and planetary nebula phases of STELLAR EVOLUTION. Stars on the AGB lose mass at a high rate ((10-7-10-4)M⊙ yr-1) in the form of a stellar wind. Such mass loss eventually depletes the hydrogen envelope of the star and exposes the electron-degenerate carbon...

  19. HUBBLE SPACE TELESCOPE (HST) IMAGERY OF THE 30 DORADUS NEBULA

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Hubble Space Telescope (HST) images of the 30 Doradus Nebula show its remarkable cluster of tightly-packed young stars 160,000 light years from Earth in the large Magellanic cloud galaxy. Panel A is a portion of a image made with the HST Wide Field Planetary Camera (WFPC). WFPC photographed four adjoining sky regions simultaneously which are assembled in this mosaic. Panel B is an enlargement of the central portion of the HST image which was made in violet light. It shows the compact star cluster R136, which consists of very hot and massive young stars. The star images have bright cores that are only 0.1 arc seconds wide, allowing many more stars to be distinguished than in previous ground-based telescopic photos. Panel C is a photograph of the same region as Panel B, obtained with the Max Planck 2.2 meter telescope at the European Southern Observatory in Chile. The star images are 0.6 arc seconds wide. Panel D shows how computer processing of the HST image in Panel B has sharpened its

  20. Detection of molecular hydrogen emission from five planetary nebulae

    NASA Technical Reports Server (NTRS)

    Beckwith, S.; Gatley, I.; Persson, S. E.

    1978-01-01

    The v = 1 to 0 S(1) line of molecular hydrogen has been detected in five planetary nebulae. They are the Ring Nebula (M57, NGC 6720), BD+30 deg 3639, Hb 12, CRL 618, and CRL 2688. A region in the northeast of the Ring Nebula has been mapped in both the v = 1 to 0 S(1) molecular hydrogen line and the Brackett gamma line of atomic hydrogen. The H2 emission is not spatially correlated with the B-gamma, but is correlated with the (OI) emission as determined from interference filter photographs.

  1. Orion Nebula and Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Dufour, Reginald J.

    1998-01-01

    This report summarizes the research performed at Rice University related to NASA-Ames University consortium grant NCC2-5199 during the two year period 1996 September 1 through 1998 August 31. The research program, titled Orion Nebula and Planetary Nebulae, involved the analysis of Hubble Space Telescope (HST) imagery and spectroscopy of the Orion Nebula and of the planetary nebulae NGC 6818 and NGC 6210. In addition, we analyzed infrared spectra of the Orion Nebula taken with the Infrared Space Observatory (ISO) The primary collaborators at NASA-Ames were Drs. R. H. Rubin, A. G. C. M. Tielens, S. W. J. Colgan, and S. D. Lord (Tielens & Lord has since changed institutions). Other collaborators include Drs. P. G. Martin (CITA, Toronto), G. J. Ferland (U. KY), J. A. Baldwin (CTIO, Chile), J. J. Hester (ASU), D. K. Walter (SCSU), and P. Harrington (U. MD). In addition to the Principal Investigator, Professor Reginald J. Dufour of the Department of Space Physics & Astronomy, the research also involved two students, Mr. Matthew Browning and Mr. Brent Buckalew. Mr. Browning will be graduating from Rice in 1999 May with a B.A. degree in Physics and Mr. Buckalew continues as a graduate student in our department, having recently received a NASA GSRP research fellowship (sponsored by Ames). The collaboration was very productive, with two refereed papers already appearing in the literature, several others in preparation, numerous meeting presentations and two press releases. Some of our research accomplishments are highlighted below. Attached to the report are copies of the two major publications. Note that this research continues to date and related extensions of it recently has been awarded time with the HST for 1999-2000.

  2. 'Peony Nebula' Star Settles for Silver Medal

    NASA Technical Reports Server (NTRS)

    2008-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] Poster Version Movie

    If our galaxy, the Milky Way, were to host its own version of the Olympics, the title for the brightest known star would go to a massive star called Eta Carina. However, a new runner-up now the second-brightest star in our galaxy has been discovered in the galaxy's dusty and frenzied interior. This image from NASA's Spitzer Space Telescope shows the new silver medalist, circled in the inset above, in the central region of our Milky Way.

    Dubbed the 'Peony nebula' star, this blazing ball of gas shines with the equivalent light of 3.2 million suns. The reigning champ, Eta Carina, produces the equivalent of 4.7 million suns worth of light though astronomers say these estimates are uncertain, and it's possible that the Peony nebula star could be even brighter than Eta Carina.

    If the Peony star is so bright, why doesn't it stand out more in this view? The answer is dust. This star is located in a very dusty region jam packed with stars. In fact, there could be other super bright stars still hidden deep in the stellar crowd. Spitzer's infrared eyes allowed it to pierce the dust and assess the Peony nebula star's true brightness. Likewise, infrared data from the European Southern Observatory's New Technology Telescope in Chile were integral in calculating the Peony nebula star's luminosity.

    The Peony nebula, which surrounds the Peony nebular star, is the reddish cloud of dust in and around the white circle.

    The movie begins by showing a stretch of the dusty and frenzied central region of our Milky Way galaxy. It then zooms in to reveal the 'Peony nebula' star the new second-brightest star in the Milky Way, discovered in part by NASA's Spitzer Space Telescope.

    This is a three-color composite showing infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both

  3. 1548C27 - An interesting new cometary nebula

    NASA Technical Reports Server (NTRS)

    Craine, E. R.; Byard, P. L.; Boeshaar, G. O.

    1981-01-01

    The object 1548C27, a faint cometary nebula of classical form, discovered by an examination of early Near Infrared Photographic Sky Survey (NIPSS) data (1979) is presented. Direct imaging and polarimetric, photometric, and spectroscopic observations are reported. Early survey test photographs show that the object lies at R.A. 19h40m48s, Decl. +23 deg 17 arcmin 09 arc sec (1950) in the Vulpecula constellation in the immediate vicinity of the complex H II region and galactic cluster NGC 6820/6823. From the photographs, the nebula was estimated to be 15 m visual and of color class one. The object was observed spectroscopically in the region 5700-6800 A using an Image Dissector Scanner with a 1.8 m reflector, and the spectral scan, obtained on November 4, 1978, is presented. New information on cometary nebulae may further illuminate the evolutionary importance of the objects.

  4. Condensation Front Migration in a Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.

    2004-01-01

    Condensation front dynamics are investigated in the mid-solar nebula region. A quasi-steady model of the evolving nebula is combined with equilibrium vapor pressure curves to determine evolutionary condensation fronts for selected species. These fronts are found to migrate inwards from the far-nebula to final positions during a period of 10(exp 7) years. The physical process governing this movement is a combination of local viscous heating and luminescent heating from the central star. Two luminescent heating models are used and their effects on the ultimate radial position of the condensation front are discussed. At first the fronts move much faster than the nebular accretion velocity, but after a time the accreting gas and dust overtakes the slowing condensation front.

  5. FAST, LOW-IONIZATION EMISSION REGIONS OF THE PLANETARY NEBULA M2-42

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

    Danehkar, A.; Parker, Q. A.; Steffen, W., E-mail: ashkbiz.danehkar@cfa.harvard.edu

    Spatially resolved observations of the planetary nebula M2-42 (PN G008.2−04.8) obtained with the Wide Field Spectrograph on the Australian National University 2.3 m telescope have revealed the remarkable features of bipolar collimated jets emerging from its main structure. Velocity-resolved channel maps derived from the [N ii] λ6584 emission line disentangle different morphological components of the nebula. This information is used to develop a three-dimensional morpho-kinematic model, which consists of an equatorial dense torus and a pair of asymmetric bipolar outflows. The expansion velocity of about 20 km s{sup −1} is measured from the spectrum integrated over the main shell. However,more » the deprojected velocities of the jets are found to be in the range of 80–160 km s{sup −1} with respect to the nebular center. It is found that the mean density of the collimated outflows, 595 ± 125 cm{sup −3}, is five times lower than that of the main shell, 3150 cm{sup −3}, whereas their singly ionized nitrogen and sulfur abundances are about three times higher than those determined from the dense shell. The results indicate that the features of the collimated jets are typical of fast, low-ionization emission regions.« less

  6. Induced massive star formation in the trifid nebula?

    PubMed

    Cernicharo; Lefloch; Cox; Cesarsky; Esteban; Yusef-Zadeh; Mendez; Acosta-Pulido; Garcia Lopez RJ; Heras

    1998-10-16

    The Trifid nebula is a young (10(5) years) galactic HII region where several protostellar sources have been detected with the infrared space observatory. The sources are massive (17 to 60 solar masses) and are associated with molecular gas condensations at the edges or inside the nebula. They appear to be in an early evolutionary stage and may represent the most recent generation of stars in the Trifid. These sources range from dense, apparently still inactive cores to more evolved sources, undergoing violent mass ejection episodes, including a source that powers an optical jet. These observations suggest that the protostellar sources may have evolved by induced star formation in the Trifid nebula.

  7. A Morpho-kinematic and Spectroscopic study of Bipolar Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Clyne, Niall

    2015-09-01

    In this thesis, studies of the kinematic properties for a sample of Galactic bipolar planetary nebulae, based on optical and infrared observations, were performed using a morpho-kinematic code, optical and NIR diagnostic diagrams, and techniques using data analyses. The mechanisms that form complex bipolar planetary nebulae remain unclear, and their shapes can be generated either as a planetary or symbiotic nebula. The origin of the material ionised by the white dwarf is very different in these two scenarios, and it complicates the understanding of the morphologies of planetary nebulae. The physical properties, structure, and dynamics of the bipolar nebulae, MyCn 18, M 2-9, Mz 3, Hen 2-104, and Abell 14, are each investigated in detail with the aim of understanding their nature, shaping mechanisms, and evolutionary history. For MyCn 18, VLT infrared images, VLT ISAAC infrared spectra, and long-slit optical echelle spectra are used to investigate the inner and outer regions of the nebula. The morpho-kinematic modelling tool shape was used to firmly constrain the structure and kinematics of the source. A timescale analysis was used to help determine the kinematical age of the nebula and its main components. A spectroscopic study of MyCn 18's central region reveals the detailed make-up of its nebular composition. Molecular hydrogen, atomic helium, and Brackett gamma emission are detected in the central regions. ISAAC spectra from a slit position along the narrow waist of the nebula demonstrate that the ionised gas resides closer to the centre of the nebula than the molecular emission. A final reconstructed 3-D model of MyCn 18 was generated, providing kinematical information on the expansion velocity of its nebular components by means of position-velocity arrays (or observed long-slit spectra). A kinematical age of the nebula and its components were obtained using the position-velocity arrays and timescale analysis. For M 2-9, Mz 3, and Hen 2-104, long-slit optical

  8. Soul Nebula

    NASA Image and Video Library

    2010-04-05

    This mosaic from NASA WISE Telescope is of the Soul Nebula. It is an open cluster of stars surrounded by a cloud of dust and gas located about 6,500 light-years from Earth in the constellation Cassiopeia, near the Heart Nebula.

  9. Attosecond Coherent Control of the Photo-Dissociation of Oxygen Molecules

    NASA Astrophysics Data System (ADS)

    Sturm, Felix; Ray, Dipanwita; Wright, Travis; Shivaram, Niranjan; Bocharova, Irina; Slaughter, Daniel; Ranitovic, Predrag; Belkacem, Ali; Weber, Thorsten

    2016-05-01

    Attosecond Coherent Control has emerged in recent years as a technique to manipulate the absorption and ionization in atoms as well as the dissociation of molecules on an attosecond time scale. Single attosecond pulses and attosecond pulse trains (APTs) can coherently excite multiple electronic states. The electronic and nuclear wave packets can then be coupled with a second pulse forming multiple interfering quantum pathways. We have built a high flux extreme ultraviolet (XUV) light source delivering APTs based on HHG that allows to selectively excite neutral and ion states in molecules. Our beamline provides spectral selectivity and attosecond interferometric control of the pulses. In the study presented here, we use APTs, generated by High Harmonic Generation in a high flux extreme ultraviolet light source, to ionize highly excited states of oxygen molecules. We identify the ionization/dissociation pathways revealing vibrational structure with ultra-high resolution ion 3D-momentum imaging spectroscopy. Furthermore, we introduce a delay between IR pulses and XUV/IR pulses to constructively or destructively interfere the ionization and dissociation pathways, thus, enabling the manipulation of both the O2+and the O+ ion yields with attosecond precision. Supported by DOE under Contract No. DE-AC02-05CH11231.

  10. Trifid Nebula

    NASA Image and Video Library

    1999-12-02

    Atlas Image mosaic, covering 14.8 x 20.0 on the sky, of the Trifid Nebula, aka Messier 20 and NGC 6514. The Trifid is only about 1.5 degrees northwest on the sky of the larger Lagoon Nebula Messier 8 in the constellation Sagittarius

  11. Deuterium enrichment by selective photo-induced dissociation of an organic carbonyl compound

    DOEpatents

    Marling, John B.

    1981-01-01

    A method for producing a deuterium enriched material by photoinduced dissociation which uses as the working material a gas phase photolytically dissociable organic carbonyl compound containing at least one hydrogen atom bonded to an atom which is adjacent to a carbonyl group and consisting of molecules wherein said hydrogen atom is present as deuterium and molecules wherein said hydrogen atom is present as another isotope of hydrogen. The organic carbonyl compound is subjected to intense infrared radiation at a preselected wavelength to selectively excite and thereby induce dissociation of the deuterium containing species to yield a deuterium enriched stable molecular product. Undissociated carbonyl compound, depleted in deuterium, is preferably redeuterated for reuse.

  12. Star-Studded Strings around Cocoon Nebula

    NASA Image and Video Library

    2011-04-13

    Dense filaments of gas in the IC5146 interstellar cloud can be seen clearly in this image taken in infrared light by the Herschel space observatory. The blue region is a stellar nursery known as the Cocoon nebula.

  13. Where Do Messy Planetary Nebulae Come From?

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-03-01

    triple stellar progenitor. The primary signs the authors look for are:SymmetriesIf a planetary nebula has a strong axisymmetric or point-symmetric structure (i.e., its bipolar, elliptical, spherical, etc.), it was likely not shaped by a triple progenitor. If clear symmetries are missing, however, or if there is a departure from symmetry in specific regions, the morphology of the planetary nebula may have been shaped by the presence of stars in a close triple system.Interaction with the interstellar mediumSome asymmetries, especially local ones, can be explained by interaction of the planetary nebula with the interstellar medium. The authors look for signs of such an interaction, which decreases the likelihood that a triple stellar system need be involved to produce the morphology we observe.Examples of planetary nebulae that are extremely likely to have been shaped by a triple stellar system. They have strong departures from symmetry and dont show signs of interacting with the interstellar medium. [Bear and Soker 2017]Influential TriosFrom the images in two planetary nebulae catalogs the Planetary Nebula Image Catelog and the HASH catalog Bear and Soker find that 275 and 372 planetary nebulae are categorizable, respectively. By assigning crude probabilities to their categories, the authors estimate that the total fraction of planetary nebulae shaped by three stars in a close system is around 1321%.The authors argue that in some cases, all three stars might survive. This means that we may be able to find direct evidence of these triple stellar systems lying in the hearts of especially messy planetary nebulae.CitationEaleal Bear and Noam Soker 2017 ApJL 837 L10. doi:10.3847/2041-8213/aa611c

  14. A study of the far infrared counterparts of new candidates for planetary nebulae

    NASA Astrophysics Data System (ADS)

    Iyengar, K. V. K.

    1986-05-01

    The IRAS Point Source Catalog was searched for infrared counterparts of the fourteen new candidates for planetary nebulae of low surface brightness detected by Hartl and Tritton (1985). Five of these candidates were identified with sources in the Catalog. All five nebulae are found in regions of high cirrus flux at 100 microns, and all have both point sources and small size extended sources with numbers varying from field to field. The infrared emission from these nebulae is connected with dust temperatures of about 100 K, characteristic of planetary nebulae.

  15. The Nature of the Stingray Nebula from Radio Observations

    NASA Astrophysics Data System (ADS)

    Harvey-Smith, Lisa; Hardwick, Jennifer A.; De Marco, Orsola; Parthasarathy, Mudumba; Gonidakis, Ioannis; Akhter, Shaila; Cunningham, Maria; Green, James A.

    2018-06-01

    We have analysed the full suite of Australia Telescope Compact Array data for the Stingray planetary nebula. Data were taken in the 4- to 23-GHz range of radio frequencies between 1991 and 2016. The radio flux density of the nebula generally declined during that period, but between 2013 and 2016 it shows signs of halting that decline. We produced the first spatially resolved radio images of the Stingray nebula from data taken in 2005. A ring structure, which appears to be associated with the ring seen in HST images, was visible. In addition, we found a narrow extension to the radio emission towards the eastern and western edges of the nebula. We derived the emission measure of the nebula - this decreased between 1992 and 2011, suggesting that the nebula is undergoing recombination. The radio spectral index is broadly consistent with a free-free emission mechanism, however a single data point hints that a steeper spectral index has possibly emerged since 2013, which could indicate the presence of synchrotron emission. If a non-thermal component component has emerged, such as one associated with a region that is launching a jet or outflow, we predict that it would intensify in the years to come.

  16. Bipolar nebulae and mass loss from red giant stars

    NASA Technical Reports Server (NTRS)

    Cohen, M.

    1985-01-01

    Observations of several bipolar nebulae are used to learn something of the nature of mass loss from the probable red-giant progenitors of these nebulae. Phenomena discussed are: (1) probable GL 2688's optical molecular emissions; (2) newly discovered very high velocity knots along the axis of OH 0739 - 14, which reveal evidence for mass ejections of + or 300 km/s from the M9 III star embedded in this nebula; (3) the bipolar structure of three extreme carbon stars, and the evidence for periodic mass ejection in IRC + 30219, also at high speed (about 80 km/s); and (4) the curious cool TiO-rich region above Parsamian 13, which may represent the very recent shedding of photospheric material from a cool, oxygen-rich giant. Several general key questions about bipolar nebulae that relate to the process of mass loss from their progenitor stars are raised.

  17. Layers in the Central Orion nebula

    NASA Astrophysics Data System (ADS)

    O'Dell, C. R.

    2018-07-01

    The existence of multiple layers in the inner Orion nebula has been revealed using data from an Atlas of spectra at 2 arcsec and 12 km s-1 resolution. These data were sometimes grouped over Samples of 10 arcsec×10 arcsecto produce high signal-to-noise spectra and sometimes grouped into sequences of pseudo-slit Spectra of 12^''.8-39 arcsec width for high spatial resolution studies. Multiple velocity systems were found: V_{MIF} traces the Main Ionization Front (MIF), V_{scat} arises from back-scattering of V_{MIF} emission by particles in the background Photon Dissociation Region (PDR), V_{low} is an ionized layer in front of the MIF and if it is the source of the stellar absorption lines seen in the Trapezium stars, it must lie between the foreground Veil and those stars, V_{new,[O III] may represent ionized gas evaporating from the Veil away from the observer. There are features such as the Bright Bar where variations of velocities are due to changing tilts of the MIF, but velocity changes above about 25 arcsec arise from variations in velocity of the background PDR. In a region 25 arcsec ENE of the Orion-S Cloud one finds dramatic changes in the [OIII] components, including the signals from the V_{low,[O III] and V_{MIF,[O III] becoming equal, indicating shadowing of gas from stellar photons of >24.6 eV. This feature is also seen in areas to the west and south of the Orion-S Cloud.

  18. Layers in the Central Orion Nebula

    NASA Astrophysics Data System (ADS)

    O'Dell, C. R.

    2018-04-01

    The existence of multiple layers in the inner Orion Nebula has been revealed using data from an Atlas of spectra at 2″ and 12 km s-1 resolution. These data were sometimes grouped over Samples of 10″×10″ to produce high Signal to Noise spectra and sometimes grouped into sequences of pseudo-slit Spectra of 12{^''.}8 - 39″width for high spatial resolution studies. Multiple velocity systems were found: V_{MIF} traces the Main Ionization Front (MIF), V_{scat} arises from back-scattering of V_{MIF} emission by particles in the background Photon Dissociation Region (PDR), V_{low} is an ionized layer in front of the MIF and if it is the source of the stellar absorption lines seen in the Trapezium stars, it must lie between the foreground Veil and those stars, V_{new,[O III]} may represent ionized gas evaporating from the Veil away from the observer. There are features such as the Bright Bar where variations of velocities are due to changing tilts of the MIF, but velocity changes above about 25″ arise from variations in velocity of the background PDR. In a region 25″ ENE of the Orion-S Cloud one finds dramatic changes in the [O III] components, including the signals from the V_{low,[O III]} and V_{MIF,[O III]} becoming equal, indicating shadowing of gas from stellar photons of >24.6 eV. This feature is also seen in areas to the west and south of the Orion-S Cloud.

  19. The origin of the argonium emission discovered in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Priestley, Felix; Barlow, Mike; Viti, Serena

    2016-06-01

    We present a study of the origin of the argonium (ArH+) emission discovered by Herschel in the Crab Nebula (Barlow et al. 2013). The argonium molecule is believed to be formed principally by the reaction of singly ionised argon (Ar+) with molecular hydrogen (H2), and to be destroyed by reactions with H2 and UV photons. For the case of the argonium ground state absorption lines seen by Herschel along several interstellar sightlines (Schilke et al. 2014), those authors argued that the presence of H2 in both the formation and destruction mechanisms means that ArH+ must form in largely atomic interstellar hydrogen clouds containing only trace amounts of H2. However, In the case of the Crab Nebula the observed argonium emission might originate either from transition regions containing both Ar+ and H2, or alternatively from inside the Crab Nebula's H2 knots into which X-ray photons or charged particles from the pulsar wind nebula have penetrated to produce Ar+ and other ions. We report the results of our numerical studies that have used a combination of photoionisation and photodissociation region codes to investigate these alternative scenarios for producing ArH+ in the Crab Nebula.

  20. Radial Migration of Phyllosilicates in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Ciesla, F. J.; Lauretta, D. S.; Hood, L. L.

    2004-01-01

    It has long been recognized that the high temperatures of the inner solar nebula (within approx. 3 AU) would not have allowed water to be incorporated into solids. However, the presence of water on the surface of Earth, as well as evidence for it on the surface of an early Mars imply that water was incorporated into solid bodies in this region. How this water was delivered to the solid bodies has yet to be identified. In this abstract we explore the possibility that hydrous minerals, such as phyllosilicates, formed somewhere in the asteroid belt region of the solar nebula or beyond, and then migrated inward where they would be accreted into larger bodies.

  1. GIANT Hα NEBULA SURROUNDING THE STARBURST MERGER NGC 6240

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

    Yoshida, Michitoshi; Yagi, Masafumi; Komiyama, Yutaka

    We revealed the detailed structure of a vastly extended Hα-emitting nebula (“Hα nebula”) surrounding the starburst/merging galaxy NGC 6240 by deep narrow-band imaging observations with the Subaru Suprime-Cam. The extent of the nebula is ∼90 kpc in diameter and the total Hα luminosity amounts to L{sub Hα} ≈ 1.6 × 10{sup 42} erg s{sup −1}. The volume filling factor and the mass of the warm ionized gas are ∼10{sup −4}–10{sup −5} and ∼5 × 10{sup 8} M{sub ⊙}, respectively. The nebula has a complicated structure, which includes numerous filaments, loops, bubbles, and knots. We found that there is a tight spatial correlation between the Hαmore » nebula and the extended soft-X-ray-emitting gas, both in large and small scales. The overall morphology of the nebula is dominated by filamentary structures radially extending from the center of the galaxy. A large-scale bipolar bubble extends along the minor axis of the main stellar disk. The morphology strongly suggests that the nebula was formed by intense outflows—superwinds—driven by starbursts. We also found three bright knots embedded in a looped filament of ionized gas that show head-tail morphologies in both emission-line and continuum, suggesting close interactions between the outflows and star-forming regions. Based on the morphology and surface brightness distribution of the Hα nebula, we propose the scenario that three major episodes of starburst/superwind activities, which were initiated ∼10{sup 2} Myr ago, formed the extended ionized gas nebula of NGC 6240.« less

  2. Giant Hα Nebula Surrounding the Starburst Merger NGC 6240

    NASA Astrophysics Data System (ADS)

    Yoshida, Michitoshi; Yagi, Masafumi; Ohyama, Youichi; Komiyama, Yutaka; Kashikawa, Nobunari; Tanaka, Hisashi; Okamura, Sadanori

    2016-03-01

    We revealed the detailed structure of a vastly extended Hα-emitting nebula (“Hα nebula”) surrounding the starburst/merging galaxy NGC 6240 by deep narrow-band imaging observations with the Subaru Suprime-Cam. The extent of the nebula is ˜90 kpc in diameter and the total Hα luminosity amounts to LHα ≈ 1.6 × 1042 erg s-1. The volume filling factor and the mass of the warm ionized gas are ˜10-4-10-5 and ˜5 × 108 M⊙, respectively. The nebula has a complicated structure, which includes numerous filaments, loops, bubbles, and knots. We found that there is a tight spatial correlation between the Hα nebula and the extended soft-X-ray-emitting gas, both in large and small scales. The overall morphology of the nebula is dominated by filamentary structures radially extending from the center of the galaxy. A large-scale bipolar bubble extends along the minor axis of the main stellar disk. The morphology strongly suggests that the nebula was formed by intense outflows—superwinds—driven by starbursts. We also found three bright knots embedded in a looped filament of ionized gas that show head-tail morphologies in both emission-line and continuum, suggesting close interactions between the outflows and star-forming regions. Based on the morphology and surface brightness distribution of the Hα nebula, we propose the scenario that three major episodes of starburst/superwind activities, which were initiated ˜102 Myr ago, formed the extended ionized gas nebula of NGC 6240. Based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  3. The Tarantula Nebula

    NASA Technical Reports Server (NTRS)

    2004-01-01

    NASA's new Spitzer Space Telescope, formerly known as the Space Infrared Telescope Facility, has captured in stunning detail the spidery filaments and newborn stars of the Tarantula Nebula, a rich star-forming region also known as 30 Doradus. This cloud of glowing dust and gas is located in the Large Magellanic Cloud, the nearest galaxy to our own Milky Way, and is visible primarily from the Southern Hemisphere. This image of an interstellar cauldron provides a snapshot of the complex physical processes and chemistry that govern the birth - and death - of stars.

    At the heart of the nebula is a compact cluster of stars, known as R136, which contains very massive and young stars. The brightest of these blue supergiant stars are up to 100 times more massive than the Sun, and are at least 100,000 times more luminous. These stars will live fast and die young, at least by astronomical standards, exhausting their nuclear fuel in a few million years.

    The Spitzer Space Telescope image was obtained with an infrared array camera that is sensitive to invisible infrared light at wavelengths that are about ten times longer than visible light. In this four-color composite, emission at 3.6 microns is depicted in blue, 4.5 microns in green, 5.8 microns in orange, and 8.0 microns in red. The image covers a region that is three-quarters the size of the full moon.

    The Spitzer observations penetrate the dust clouds throughout the Tarantula to reveal previously hidden sites of star formation. Within the luminescent nebula, many holes are also apparent. These voids are produced by highly energetic winds originating from the massive stars in the central star cluster. The structures at the edges of these voids are particularly interesting. Dense pillars of gas and dust, sculpted by the stellar radiation, denote the birthplace of future generations of stars.

    The Spitzer image provides information about the composition of the material at the edges of the voids. The surface layers

  4. The Tarantula Nebula

    NASA Image and Video Library

    2004-01-13

    NASA Spitzer Space Telescope, formerly known as the Space Infrared Telescope Facility, has captured in stunning detail the spidery filaments and newborn stars of theTarantula Nebula, a rich star-forming region also known as 30 Doradus. This cloud of glowing dust and gas is located in the Large Magellanic Cloud, the nearest galaxy to our own Milky Way, and is visible primarily from the Southern Hemisphere. This image of an interstellar cauldron provides a snapshot of the complex physical processes and chemistry that govern the birth - and death - of stars. At the heart of the nebula is a compact cluster of stars, known as R136, which contains very massive and young stars. The brightest of these blue supergiant stars are up to 100 times more massive than the Sun, and are at least 100,000 times more luminous. These stars will live fast and die young, at least by astronomical standards, exhausting their nuclear fuel in a few million years. The Spitzer Space Telescope image was obtained with an infrared array camera that is sensitive to invisible infrared light at wavelengths that are about ten times longer than visible light. In this four-color composite, emission at 3.6 microns is depicted in blue, 4.5 microns in green, 5.8 microns in orange, and 8.0 microns in red. The image covers a region that is three-quarters the size of the full moon. The Spitzer observations penetrate the dust clouds throughout the Tarantula to reveal previously hidden sites of star formation. Within the luminescent nebula, many holes are also apparent. These voids are produced by highly energetic winds originating from the massive stars in the central star cluster. The structures at the edges of these voids are particularly interesting. Dense pillars of gas and dust, sculpted by the stellar radiation, denote the birthplace of future generations of stars. The Spitzer image provides information about the composition of the material at the edges of the voids. The surface layers closest to the

  5. Deuterium fractionation of water in the Solar nebula

    NASA Astrophysics Data System (ADS)

    Albertsson, Tobias; Semenov, Dmitry; Henning, Thomas

    2013-07-01

    Water evaporates in the inner regions of protoplanetary disks and is frozen onto grains in the outer regions. Therefore its presence in vast quantities on Earth is puzzling. Subsequent delivery through bombardment by primitive bodies formed in the outer icy regions is the favored mechanism. By studying water D/H ratios one hopes to understand whether the water was mainly delivered by comets or asteroids. Using an extended deuterium chemistry network coupled to a 2D chemo-dynamical disk model, we investigate the evolution of the D/H ratio of water in the young Solar nebula. We find that both the laminar and mixing Solar nebula models show the Earth's ocean water D/H ratio at 2-3 AU. In addition, the 2D-mixing model explains better the water D/H values observed in the Oort- and Jupiter-family comets.

  6. ALMA OBSERVATIONS OF THE COLDEST PLACE IN THE UNIVERSE: THE BOOMERANG NEBULA

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

    Sahai, R.; Vlemmings, W. H. T.; Huggins, P. J.

    The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of thismore » ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating.« less

  7. ALMA Observations of the Coldest Place in the Universe: The Boomerang Nebula

    NASA Astrophysics Data System (ADS)

    Sahai, R.; Vlemmings, W. H. T.; Huggins, P. J.; Nyman, L.-Å.; Gonidakis, I.

    2013-11-01

    The Boomerang Nebula is the coldest known object in the universe, and an extreme member of the class of pre-planetary nebulae, objects which represent a short-lived transitional phase between the asymptotic giant branch and planetary nebula evolutionary stages. Previous single-dish CO (J = 1-0) observations (with a 45'' beam) showed that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. Here we report the first observations of the Boomerang Nebula with ALMA in the CO J = 2-1 and J = 1-0 lines to resolve the structure of this ultra-cold nebula. We find a central hourglass-shaped nebula surrounded by a patchy, but roughly round, cold high-velocity outflow. We compare the ALMA data with visible-light images obtained with the Hubble Space Telescope and confirm that the limb-brightened bipolar lobes seen in these data represent hollow cavities with dense walls of molecular gas and dust producing both the molecular-emission-line and scattered-light structures seen at millimeter and visible wavelengths. The large diffuse biconical shape of the nebula seen in the visible wavelength range is likely due to preferential illumination of the cold, high-velocity outflow. We find a compact source of millimeter-wave continuum in the nebular waist—these data, together with sensitive upper limits on the radio continuum using observations with ATCA, indicate the presence of a substantial mass of very large (millimeter-sized) grains in the waist of the nebula. Another unanticipated result is the detection of CO emission regions beyond the ultra-cold region which indicate the re-warming of the cold gas, most likely due to photoelectric grain heating.

  8. Direct photography of the Gum Nebula

    NASA Technical Reports Server (NTRS)

    Brandt, J. C.; Roosen, R. G.; Thompson, J.; Ludden, D. J.

    1976-01-01

    The paper discusses a series of wide-angle photographs taken of the Gum Nebula in the traditional region including H-alpha with the aid of a 40-cm and an 80-cm lens in both the red and the green. The photographs support the large dimensions (75 deg in galactic longitude by 40 deg in galactic latitude) of the Gum Nebula suggested earlier, and the appearance is consistent with an origin due to photons from a supernova outburst. The relatively high-density gas has cooled and is visible on the red plates. The low-density gas has remained at a high temperature and may be visible as diffuse emission on the green plates.

  9. Preferrential Concentration of Particles in Protoplanetary Nebula Turbulence

    NASA Technical Reports Server (NTRS)

    Hartlep, Thomas; Cuzzi, Jeffrey N.

    2015-01-01

    Preferential concentration in turbulence is a process that causes inertial particles to cluster in regions of high strain (in-between high vorticity regions), with specifics depending on their stopping time or Stokes number. This process is thought to be of importance in various problems including cloud droplet formation and aerosol transport in the atmosphere, sprays, and also in the formation of asteroids and comets in protoplanetary nebulae. In protoplanetary nebulae, the initial accretion of primitive bodies from freely-floating particles remains a problematic subject. Traditional growth-by-sticking models encounter a formidable "meter-size barrier" [1] in turbulent nebulae. One scenario that can lead directly from independent nebula particulates to large objects, avoiding the problematic m-km size range, involves formation of dense clumps of aerodynamically selected, typically mm-size particles in protoplanetary turbulence. There is evidence that at least the ordinary chondrite parent bodies were initially composed entirely of a homogeneous mix of such particles generally known as "chondrules" [2]. Thus, while it is arcane, turbulent preferential concentration acting directly on chondrule size particles are worthy of deeper study. Here, we present the statistical determination of particle multiplier distributions from numerical simulations of particle-laden isotopic turbulence, and a cascade model for modeling turbulent concentration at lengthscales and Reynolds numbers not accessible by numerical simulations. We find that the multiplier distributions are scale dependent at the very largest scales but have scale-invariant properties under a particular variable normalization at smaller scales.

  10. Observations of the planetary nebula RWT 152 with OSIRIS/GTC

    NASA Astrophysics Data System (ADS)

    Aller, A.; Miranda, L. F.; Olguín, L.; Solano, E.; Ulla, A.

    2016-11-01

    RWT 152 is one of the few known planetary nebulae with an sdO central star. We present subarcsecond red tunable filter Hα imaging and intermediate-resolution, long-slit spectroscopy of RWT 152 obtained with OSIRIS/GTC (Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy/Gran Telescopio Canarias) with the goal of analysing its properties. The Hα image reveals a bipolar nebula with a bright equatorial region and multiple bubbles in the main lobes. A faint circular halo surrounds the main nebula. The nebular spectra reveal a very low excitation nebula with weak emission lines from H+, He+ and double-ionized metals, and absence of emission lines from neutral and single-ionized metals, except for an extremely faint [N II] λ6584 emission line. These spectra may be explained if RWT 152 is a density-bounded planetary nebula. Low nebular chemical abundances of S, O, Ar, N and Ne are obtained in RWT 152, which, together with the derived high peculiar velocity (˜ 92-131 km s-1), indicate that this object is a halo planetary nebula. The available data are consistent with RWT 152 evolving from a low-mass progenitor (˜1 M⊙) formed in a metal-poor environment.

  11. Horsehead Nebula

    NASA Image and Video Library

    2017-12-08

    Image released April 19, 2013. Astronomers have used NASA's Hubble Space Telescope to photograph the iconic Horsehead Nebula in a new, infrared light to mark the 23rd anniversary of the famous observatory's launch aboard the space shuttle Discovery on April 24, 1990. Looking like an apparition rising from whitecaps of interstellar foam, the iconic Horsehead Nebula has graced astronomy books ever since its discovery more than a century ago. The nebula is a favorite target for amateur and professional astronomers. It is shadowy in optical light. It appears transparent and ethereal when seen at infrared wavelengths. The rich tapestry of the Horsehead Nebula pops out against the backdrop of Milky Way stars and distant galaxies that easily are visible in infrared light. Credit: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) More on this image. 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

  12. Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

    NASA Astrophysics Data System (ADS)

    De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.; Kilcoyne, A. L. David

    2017-10-01

    Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ˜20 μm particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorly graphitized carbon (PGC). The PGC forms conformal shells around tiny 5-15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core-shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.

  13. The Twin Jet Nebula

    NASA Image and Video Library

    2015-08-26

    The Twin Jet Nebula, or PN M2-9, is a striking example of a bipolar planetary nebula. Bipolar planetary nebulae are formed when the central object is not a single star, but a binary system, Studies have shown that the nebula’s size increases with time, and measurements of this rate of increase suggest that the stellar outburst that formed the lobes occurred just 1200 years ago.

  14. A Self-Perpetuating Catalyst for the Production of Complex Organic Molecules in Protostellar Nebulae

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A.; Johnson, N. M.

    2010-01-01

    The formation of abundant carbonaceous material in meteorites is a long standing problem and an important factor in the debate on the potential for the origin of life in other stellar systems. Many mechanisms may contribute to the total organic content in protostellar nebulae, ranging from organics formed via ion-molecule and atom-molecule reactions in the cold dark clouds from which such nebulae collapse, to similar ion-molecule and atom-molecule reactions in the dark regions of the nebula far from the proto star, to gas phase reactions in sub-nebulae around growing giant planets and in the nebulae themselves. The Fischer-Tropsch-type (FTT) catalytic reduction of CO by hydrogen was once the preferred model for production of organic materials in the primitive solar nebula. The Haber-Bosch catalytic reduction of N2 by hydrogen was thought to produce the reduced nitrogen found in meteorites. However, the clean iron metal surfaces that catalyze these reactions are easily poisoned via reaction with any number of molecules, including the very same complex organics that they produce and both reactions work more efficiently in the hot regions of the nebula. We have demonstrated that many grain surfaces can catalyze both FTT and HB-type reactions, including amorphous iron and magnesium silicates, pure silica smokes as well as several minerals. Although none work as well as pure iron grains, and all produce a wide range of organic products rather than just pure methane, these materials are not truly catalysts.

  15. Observations of the Crab Nebula at energies 4.10(11)

    NASA Technical Reports Server (NTRS)

    Cawley, M. F.; Regan, D. J.; Gibbs, K.; Gorham, P. W.; Lamb, R. C.; Liebing, D. F.; Mackeown, P. K.; Porter, N. A.; Stenger, V. J.; Weekes, T. C.

    1985-01-01

    Since the development of gamma-ray astronomical telescopes, the Crab Nebula has been a prime target for observations. From 100 to 1000 MeV, the pulsar PSR0531 is the dominant source with a light-curve similar to that seen at lower energies; there is also some evidence for longterm amplitude variations but none for emission from the Nebula itself. In the very high energy gamma-ray region there have been reported detections of pulsed emission with longterm time variations from minutes to months. Recently a pulsed flux has been reported that resisted over a long time interval. The detection of a flux from the Nebula at the 3 sigma level at energies of 3x1011eV was reported; there was no evidence of periodic emissions on any time scale during the three years of observations. A new measurement of very high energy gamma rays from the Crab Nebula is reported using the imaging system on the Whipple Observatory 10m reflector.

  16. Extended halos and intracluster light using Planetary Nebulae as tracers in nearby clusters

    NASA Astrophysics Data System (ADS)

    Arnaboldi, Magda

    Since the first detection of intracluster planetary nebulae in 1996, imaging and spectroscopic surveys identified such stars to trace the radial extent and the kinematics of diffuse light in clusters. This topic of research is tightly linked with the studies of galaxy formation and evolution in dense environment, as the spatial distribution and kinematics of planetary nebulae in the outermost regions of galaxies and in the cluster cores is relevant for setting constraints on cosmological simulations. In this sense, extragalactic planetary nebulae play a very important role in the near-field cosmology, in order to measure the integrated mass as function of radius and the orbital distribution of stars in structures placed in the densest regions of the nearby universe.

  17. Ultraviolet Imaging Telescope observations of the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Hennessy, Gregory S.; O'Connell, Robert W.; Cheng, Kwang P.; Bohlin, Ralph C.; Collins, Nicholas R.; Gull, Theodore P.; Hintzen, Paul; Isensee, Joan E.; Landsman, Wayne B.; Roberts, Morton S.

    1992-01-01

    We obtained ultraviolet images of the Crab Nebula with the Ultraviolet Imaging Telescope during the Astro-1 Space Shuttle mission in 1990 December. The UV continuum morphology of the Crab is generally similar to that in the optical region, but the wispy structures are less conspicuous in the UV and X-ray. UV line emission from the thermal filaments is not strong. UV spectral index maps with a resolution of 10 arcsecs show a significant gradient across the nebula, with the outer parts being redder, as expected from synchrotron losses. The location of the bluest synchrotron continuum does not coincide with the pulsar.

  18. The Trifid Nebula

    NASA Technical Reports Server (NTRS)

    1997-01-01

    This NASA Hubble Space Telescope (HST) image of the Trifid Nebula reveals a stellar nursery being torn apart by a nearby massive star. Embryonic stars are forming within an ill-fated cloud of dust and gas, which is destined to be eaten away by the glare from the massive neighbor. The cloud is about 8 light years away from the nebula' s central star. This stellar activity is a beautiful example of how the life cycle of stars like our Sun is intimately cornected with their more powerful siblings. Residing in the constellation Sagittarius, the Trifid Nebula is about 9,000 light years from Earth.

  19. Enterprising Nebulae

    NASA Image and Video Library

    2016-09-08

    Just in time for the 50th anniversary of the TV series "Star Trek," which first aired September 8th,1966, this infrared image from NASA's Spitzer Space Telescope may remind fans of the historic show. Just as one might see the shapes of animals or other objects in clouds -- a phenomenon called pareidolia -- iconic starships from the series may seem to emerge in these nebulae./ With a little scrutiny (see Figure 1), you may see hints of the saucer and hull of the original USS Enterprise, captained by James T. Kirk, as if it were emerging from a dark nebula. To the left, its "Next Generation" successor, Jean-Luc Picard's Enterprise-D, flies off in the opposite direction. Astronomically speaking, the region pictured here falls within the disk of our Milky Way galaxy, and displays two regions of star formation that are hidden behind a haze of dust when viewed in visible light. Spitzer's ability to peer deeper into dust clouds has revealed a myriad of stellar birthplaces like these, which are officially known only by their catalog numbers, IRAS 19340+2016 and IRAS19343+2026. Trekkies, however, may prefer using the more familiar designations NCC-1701 and NCC-1701-D. This image was assembled using data from Spitzer's biggest surveys of the Milky Way, called GLIMPSE and MIPSGAL. Light with a wavelength of 3.5 microns is shown in blue, 8.0 microns is green, and 24 microns in red. The green colors highlight organic molecules in the dust clouds, illuminated by starlight. Red colors are related to thermal radiation emitted from the very hottest areas of dust. http://photojournal.jpl.nasa.gov/catalog/PIA20917

  20. STARING INTO THE WINDS OF DESTRUCTION: HST/NICMOS IMAGES OF THE PLANETARY NEBULA NGC 7027

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Hubble Space Telescope's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) has captured a glimpse of a brief stage in the burnout of NGC 7027, a medium-mass star like our sun. The infrared image (on the left) shows a young planetary nebula in a state of rapid transition. This image alone reveals important new information. When astronomers combine this photo with an earlier image taken in visible light, they have a more complete picture of the final stages of star life. NGC 7027 is going through spectacular death throes as it evolves into what astronomers call a 'planetary nebula.' The term planetary nebula came about not because of any real association with planets, but because in early telescopes these objects resembled the disks of planets. A star can become a planetary nebula after it depletes its nuclear fuel - hydrogen and helium - and begins puffing away layers of material. The material settles into a wind of gas and dust blowing away from the dying star. This NICMOS image captures the young planetary nebula in the middle of a very short evolutionary phase, lasting perhaps less than 1,000 years. During this phase, intense ultraviolet radiation from the central star lights up a region of gas surrounding it. (This gas is glowing brightly because it has been made very hot by the star's intense ultraviolet radiation.) Encircling this hot gas is a cloud of dust and cool molecular hydrogen gas that can only be seen by an infrared camera. The molecular gas is being destroyed by ultraviolet light from the central star. THE INFRARED VIEW -- The composite color image of NGC 7027 (on the left) is among the first data of a planetary nebula taken with NICMOS. This picture is actually composed of three separate images taken at different wavelengths. The red color represents cool molecular hydrogen gas, the most abundant gas in the universe. The image reveals the central star, which is difficult to see in images taken with visible light. Surrounding it is an

  1. Dynamo magnetic field-induced angular momentum transport in protostellar nebulae - The 'minimum mass' protosolar nebula

    NASA Technical Reports Server (NTRS)

    Stepinski, T. F.; Levy, E. H.

    1990-01-01

    Magnetic torques can produce angular momentum redistribution in protostellar nebulas. Dynamo magnetic fields can be generated in differentially rotating and turbulent nebulas and can be the source of magnetic torques that transfer angular momentum from a protostar to a disk, as well as redistribute angular momentum within a disk. A magnetic field strength of 100-1000 G is needed to transport the major part of a protostar's angular momentum into a surrounding disk in a time characteristic of star formation, thus allowing formation of a solar-system size protoplanetary nebula in the usual 'minimum-mass' model of the protosolar nebula. This paper examines the possibility that a dynamo magnetic field could have induced the needed angular momentum transport from the proto-Sun to the protoplanetary nebula.

  2. In the Blackest Night, a Green Ring Nebula

    NASA Image and Video Library

    2011-06-15

    This glowing emerald nebula seen by NASA Spitzer Space Telescope is named RCW 120; this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius.

  3. The VISTA Carina Nebula Survey . I. Introduction and source catalog

    NASA Astrophysics Data System (ADS)

    Preibisch, T.; Zeidler, P.; Ratzka, T.; Roccatagliata, V.; Petr-Gotzens, M. G.

    2014-12-01

    Context. The Carina Nebula is one of the most massive and active star-forming regions in our Galaxy and has been studied with numerous multiwavelength observations in the past five years. However, most of these studies were restricted to the inner parts (≲1 square-degree) of the nebula, and thus covered only a small fraction of the whole cloud complex. Aims: Our aim was to conduct a near-infrared survey that covers the full spatial extent (~5 square-degrees) of the Carina Nebula complex and is sensitive enough to detect all associated young stars through extinctions of up to AV ≈ 6 mag. Methods: We used the 4m Visible and Infrared Survey Telescope for Astronomy (VISTA) of ESO to map an area of 6.7 square-degrees around the Carina Nebula in the near-infrared J-, H-, Ks-bands. Results: The analysis of our VISTA data revealed 4 840 807 individual near-infrared sources, 3 951 580 of which are detected in at least two bands. The faintest S/N ≥ 3 detections have magnitudes of J ≈ 21.2, H ≈ 19.9, and Ks ≈ 19.3. For objects at the distance of the Carina Nebula (2.3 kpc), our catalog is estimated to be complete down to stellar masses of ≈0.1 M⊙ for young stars with extinctions of AV ≈ 5 mag; for regions in the brightest parts of the central nebula with particularly strong diffuse emission, the completeness limit is at slightly higher stellar masses. We describe the photometric calibration, the characteristics, and the quality of these data. VISTA images of several newly detected or yet rarely studied clusters in the outer parts of the Carina Nebula complex are presented. Finally, a list of stars with high proper motions that were discovered in our analysis is provided in an appendix. Conclusions: Our catalog represents by far the most comprehensive deep near-infrared catalog of the Carina Nebula complex. It provides a new basis for spatially complete investigations of the young stellar population in this important star-forming complex. Based on

  4. Evidence for Reduced, Carbon-rich Regions in the Solar Nebula from an Unusual Cometary Dust Particle

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

    De Gregorio, Bradley T.; Stroud, Rhonda M.; Nittler, Larry R.

    Geochemical indicators in meteorites imply that most formed under relatively oxidizing conditions. However, some planetary materials, such as the enstatite chondrites, aubrite achondrites, and Mercury, were produced in reduced nebular environments. Because of large-scale radial nebular mixing, comets and other Kuiper Belt objects likely contain some primitive material related to these reduced planetary bodies. Here, we describe an unusual assemblage in a dust particle from comet 81P/Wild 2 captured in silica aerogel by the NASA Stardust spacecraft. The bulk of this ∼20 μ m particle is comprised of an aggregate of nanoparticulate Cr-rich magnetite, containing opaque sub-domains composed of poorlymore » graphitized carbon (PGC). The PGC forms conformal shells around tiny 5–15 nm core grains of Fe carbide. The C, N, and O isotopic compositions of these components are identical within errors to terrestrial standards, indicating a formation inside the solar system. Magnetite compositions are consistent with oxidation of reduced metal, similar to that seen in enstatite chondrites. Similarly, the core–shell structure of the carbide + PGC inclusions suggests a formation via FTT reactions on the surface of metal or carbide grains in warm, reduced regions of the solar nebula. Together, the nanoscale assemblage in the cometary particle is most consistent with the alteration of primary solids condensed from a C-rich, reduced nebular gas. The nanoparticulate components in the cometary particle provide the first direct evidence from comets of reduced, carbon-rich regions that were present in the solar nebula.« less

  5. An investigation of the Carina Nebula

    NASA Astrophysics Data System (ADS)

    Brooks, Kate J.

    2000-10-01

    It is well known that the radiation fields and stellar winds of massive stars can drastically affect the physical conditions, structure and chemistry of the giant molecular cloud (GMC) from which they formed. It is also thought that massive stars are at least partly responsible for triggering further star formation within a GMC. The details of this interaction, however, are not well understood and additional detailed study of massive star-forming regions is needed. This study has focused on a multi-wavelength investigation of the Carina Nebula. This is a spectacular massive star-forming region that contains two of the most massive star clusters in our galaxy, Trumpler 14 and Trumpler 16, and one of the most massive stars known -- η Car. The goal of this study has been to obtain information on the molecular gas, ionized gas and photodissociation regions (PDRs) from a collection of instruments which have the highest angular resolution and sensitivity available to date. The Mopra Telescope and the Swedish-ESO Submillimeter Telescope (SEST) were used to obtain a series of molecular line observations of the GMC between 150 and 230 GHz. Observations of H110α recombination-line emission at 4.874 GHz and the related continuum emission were obtained with the Australia Telescope Compact Array and used to study the ionized gas associated with the two HII regions, Car I and Car II. H2 1--0 S(1) (2.12 microns) and Brγ (2.16 microns) observations using the University of New South Wales Infrared Fabry-Perot (UNSWIRF) and 3.29 micron narrow-band observations obtained with the SPIREX/Abu thermal infrared camera were used to study the PDRs on the surface of molecular clumps in the Keyhole region, a dark optical feature in the vicinity of η Car. The results of these observations provide detailed information on the excitation conditions, kinematics and morphology of regions within the HII region/molecular cloud complex of the Carina Nebula. In addition, the results confirm that

  6. 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.

  7. The Trifid Nebula: Stellar Sibling Rivalry

    NASA Technical Reports Server (NTRS)

    2001-01-01

    A zoom into the Trifid Nebula starts with ground-based observations and ends with a Hubble Space Telescope (HST) image. Another HST image shows star formation in the nebula and the video concludes with a ground-based image of the Trifid Nebula.

  8. Nucleosynthesis of intermediate mass stars: inferences from the observed abundances in photoionized nebulae of the Local Group

    NASA Astrophysics Data System (ADS)

    Maciel, W. J.; Costa, R. D. D.; Cavichia, O.

    2018-01-01

    Photoionized nebulae, comprising HII regions and planetary nebulae, are excellent laboratories to investigate the nucleosynthesis and chemical evolution of several elements in the Galaxy and other galaxies of the Local Group. Our purpose in this investigation is threefold: (i) to compare the abundances of HII regions and planetary nebulae in each system in order to investigate the differences derived from the age and origin of these objects, (ii) to compare the chemical evolution in different systems, such as the Milky Way, the Magellanic Clouds, and other galaxies of the Local Group, and (iii) to investigate to what extent the nucleosynthesis contributions from the progenitor stars affect the observed abundances in planetary nebulae, especially for oxygen and neon, which places constraints on the amount of these elements that can be produced by intermediate mass stars.

  9. Nature versus Nurture: Luminous Blue Variable Nebulae in and near Massive Stellar Clusters at the Galactic Center

    NASA Astrophysics Data System (ADS)

    Lau, R. M.; Herter, T. L.; Morris, M. R.; Adams, J. D.

    2014-04-01

    Three luminous blue variables (LBVs) are located in and near the Quintuplet Cluster at the Galactic center: the Pistol Star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs, obtained with SOFIA using FORCAST. We argue that Pistol and G0.120-0.048 are identical "twins" that exhibit contrasting nebulae due to the external influence of their different environments. Our images reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, no detection of hot dust associated with qF362 is made. Dust and gas composing the Pistol nebula are primarily heated and ionized by the nearby Quintuplet Cluster stars. The northern region of the Pistol nebula is decelerated due to the interaction with the high-velocity (2000 km s-1) winds from adjacent Wolf-Rayet Carbon (WC) stars. From fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEM code we determine that the Pistol nebula is composed of a distribution of very small, transiently heated grains (10 to ~ 35 Å) having a total dust mass of 0.03 M ⊙, and that it exhibits a gradient of decreasing grain size from south to north due to differential sputtering by the winds from the WC stars. The total IR luminosity of the Pistol nebula is 5.2 × 105 L ⊙. Dust in the G0.120-0.048 nebula is primarily heated by the central star; however, the nebular gas is ionized externally by the Arches Cluster. Unlike the Pistol nebula, the G0.120-0.048 nebula is freely expanding into the surrounding medium. A grain size distribution identical to that of the non-sputtered region of the Pistol nebula satisfies the constraints placed on the G0.120-0.048 nebula from DustEM model fits to its SED and implies a total dust mass of 0.021 M ⊙. The total IR luminosity of the G0.120-0.048 nebula is ~105 L ⊙. From

  10. Photographs of Stars, Star-Clusters and Nebulae 2 Volume Paperback Set

    NASA Astrophysics Data System (ADS)

    Roberts, Isaac

    2010-10-01

    Volume 1: Preface; Isaac Roberts' observatory, Crowborough Hill; Isaac Roberts' telescopes; List of the plates; List of the abbreviations; 1. The negatives; 2. Arrangement of the photographs; 3. Epoch of the Fiducial stars (A.D. 1900); 4. A table for converting measurements in right ascensions into intervals of time; 5. Illustrations of the method for determining the right ascensions and declinations of the stars; 6. Introduction; Utility of the photographic charts; 7. Refractors and reflectors as photo-instruments; 8. Requirements and adjustments of a reflector for celestial photography; 9. Collimation of the mirror; 10. Essentials of a photo-telescope; 11. Method for testing the stability of a photo-instrument; 12. Photographic plates: their exposures and development; 13. Description of the photographs and references concerning them; 14. Deductions from the photographs. Volume 2: Preface; List of the plates; Instruments; List of abbreviations adopted in this work; 1. The negatives; 2. Epoch of the Fiducial stars, A.D. 1900; 3. Table for converting the measured right ascensions; 4. Deterioration of the negatives; 5. Effects of atmospheric glare and of diffraction upon the films of photographic plates; 6. Arrangement of the plates; 7. Method for micro-puncturing the photographic discs of stars on plates; 8. Star catalogues and photographic charts; 9. Duration of the effective exposures given to photographic plates in the 20-inch reflector; 10. Are the millions of stars and the numerous nebulosities limited in number and extent; 11. The evolution of stellar systems; 12. Inferences suggested by examination of the photographs; 13. Description of the photographs; 14. M.31. Andromedae; 15. M.99 Virginis; 16. M.51 Canum Venaticorum; 17. Region of 7 Cassiopeiae; 18. Nebulae in the Pleiades; 19. M.42. Orionis; 20. General conclusions concerning the evolution of stellar systems.

  11. On planetary nebulae as sources of carbon dust: Infrared emission from planetary nebulae of the galactic halo

    NASA Technical Reports Server (NTRS)

    Dinerstein, Harriet L.; Lester, Daniel F.

    1990-01-01

    Planetary nebulae of the galactic disk are generally seen to emit a thermal continuum due to dust grains heated by stellar and nebular photons. This continuum typically peaks between 25 and 60 micron m, so that the total power emitted by the dust is sampled well by the broad-band measurements made by IRAS. Researchers examine here the characteristics of the infrared emission from the four planetary nebulae which are believed on the basis of their low overall metallicities to belong to the halo population. These nebulae are of particular interest because they are the most metal-poor ionized nebulae known in our Galaxy, and offer the opportunity to probe possible dependences of the dust properties on nebular composition. Researchers present fluxes extracted from co-addition of the IRAS data, as well as ground-based near infrared measurements. Each of the four halo objects, including the planetary nebula in the globular cluster M15, is detected in at least one infrared band. Researchers compare the estimated infrared excesses of these nebulae (IRE, the ratio of measured infrared power to the power available in the form of resonantly-trapped Lyman alpha photons) to those of disk planetary nebulae with similar densities but more normal abundances. Three of the halo planetaries have IRE values similar to those of the disk nebulae, despite the fact that their Fe- and Si-peak gas phase abundances are factors of 10 to 100 lower. However, these halo nebulae have normal or elevated C/H ratios, due to nuclear processing and mixing in their red giant progenitors. Unlike the other halo planetaries, DDDM1 is deficient in carbon as well as in the other light metals. This nebula has a substantially lower IRE than the other halo planetaries, and may be truly dust efficient. Researchers suggest that the deficiency is due to a lack of the raw material for producing carbon-based grains, and that the main bulk constituent of the dust in these planetary nebulae is carbon.

  12. Physics and chemistry of the solar nebula.

    PubMed

    Lunine, J I

    1997-06-01

    The solar system is thought to have begun in a flattened disk of gas and dust referred to traditionally as the solar nebula. Such a construct seems to be a natural product of the collapse of dense parts of giant molecular clouds, the vast star-forming regions that pepper the Milky Way and other galaxies. Gravitational, magnetic and thermal forces within the solar nebula forced a gradual evolution of mass toward the center (where the sun formed) and angular momentum (borne by a small fraction of the mass) toward the outer more distant regions of the disk. This evolution was accompanied by heating and a strong temperature contrast from the hot, inner regions to the cold, more remote parts of the disk. The resulting chemistry in the disk determined the initial distribution of organic matter in the planets; most of the reduced carbon species, in condensed form, were located beyond the asteroid belt (the 'outer' solar system). The Earth could have received much of its inventory of pre-biological material from comets and other icy fragments of the process of planetary formation in the outer solar system.

  13. The Orion Nebula in the Far-Infrared: High-J CO and fine-structure lines mapped by FIFI-LS/SOFIA

    NASA Astrophysics Data System (ADS)

    Klein, Randolf; Looney, Leslie W.; Cox, Erin; Fischer, Christian; Iserlohe, Christof; Krabbe, Alfred

    2017-03-01

    The Orion Nebula is the closest massive star forming region allowing us to study the physical conditions in such a region with high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the atomic and molecular gas in the Orion Nebula at medium spectral resolution. The large maps obtained with FIFI-LS cover the nebula from the BN/KL-object to the bar in several fine structure lines. They allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud with unprecedented detail. Another investigation targeted the molecular gas in the BN/KL region of the Orion Nebula, which is stirred up by a violent explosion about 500 years ago. The explosion drives a wide angled molecular outflow. We present maps of several high-J CO observations, allowing us to analyze the heated molecular gas.

  14. Planetary Nebula NGC 7293 also Known as the Helix Nebula

    NASA Image and Video Library

    2005-05-05

    This ultraviolet image from NASA Galaxy Evolution Explorer is of the planetary nebula NGC 7293 also known as the Helix Nebula. It is the nearest example of what happens to a star, like our own Sun, as it approaches the end of its life when it runs out of fuel, expels gas outward and evolves into a much hotter, smaller and denser white dwarf star. http://photojournal.jpl.nasa.gov/catalog/PIA07902

  15. THE NATURE AND FREQUENCY OF OUTFLOWS FROM STARS IN THE CENTRAL ORION NEBULA CLUSTER

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

    O’Dell, C. R.; Ferland, G. J.; Henney, W. J.

    Recent Hubble Space Telescope images have allowed the determination with unprecedented accuracy of motions and changes of shocks within the inner Orion Nebula. These originate from collimated outflows from very young stars, some within the ionized portion of the nebula and others within the host molecular cloud. We have doubled the number of Herbig–Haro objects known within the inner Orion Nebula. We find that the best-known Herbig–Haro shocks originate from relatively few stars, with the optically visible X-ray source COUP 666 driving many of them. While some isolated shocks are driven by single collimated outflows, many groups of shocks aremore » the result of a single stellar source having jets oriented in multiple directions at similar times. This explains the feature that shocks aligned in opposite directions in the plane of the sky are usually blueshifted because the redshifted outflows pass into the optically thick photon-dominated region behind the nebula. There are two regions from which optical outflows originate for which there are no candidate sources in the SIMBAD database.« less

  16. Rossby Waves in the Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Sheehan, Daniel P.

    1998-01-01

    Fluid waves and instabilities are considered critical to the evolution of protoplanetary nebulae, particularly for their roles in mass, angular momentum, and energy transport. A number have been identified, however, notably absent, is an influential wave commonly found in planetary atmospheres and oceans: the planetary Rossby wave (PRW). Since, in the Earth's atmosphere, the PRW is of primary importance in shaping large-scale meteorological phenomena, it is reasonable to consider whether it might have similar importance in the protoplanetary nebula. The thrust of the research project this summer (1998) was to determine whether a nebular analog to the PRW is viable, a so-called nebular Rossby wave (NRW), and if so, to explore possible ramifications of this wave to the evolution of the nebula. This work was carried out primarily by S. Davis, J. Cuzzi and me, with significant discussions with P. Cassen. We believe we have established a good case for the NRW and as a result believe we have opened up a new and possibly interesting line of research in regard to the nebular development, in particular with regard to zonal jet formation, a potent accretion mechanism, and possible ties to vortex formation. The standard model of the protoplanetary nebula consists of a large disk of gas with about 1% entrained dust gravitationally bound to a large central mass, m(sub c) i.e., the protostar. The planet-forming region of the disk extends to roughly 100 A.U. in radius. Disk thickness, H, is believed to be on the order of 10-100 times less than disk radius. Disk lifetime is on the order of a million years.

  17. The Formation of a Planetary Nebula.

    ERIC Educational Resources Information Center

    Harpaz, Amos

    1991-01-01

    Proposes a scenario to describe the formation of a planetary nebula, a cloud of gas surrounding a very hot compact star. Describes the nature of a planetary nebula, the number observed to date in the Milky Way Galaxy, and the results of research on a specific nebula. (MDH)

  18. Do stellar and nebular abundances in the Cocoon nebula agree?

    NASA Astrophysics Data System (ADS)

    García-Rojas, J.; Simón-Díaz, S.; Esteban, C.

    2015-05-01

    The Cocoon nebula is an apparently spherical Galactic HII region ionized by a single star (BD+46 3474). This nebula seems to be appropriate to investigate the chemical behavior of oxygen and other heavy elements from two different points of view: a detailed analysis of the chemical content of the ionized gas through nebular spectrophotometry and a detailed spectroscopic analysis of the spectrum of the ionizing star using the state-of-the-art stellar atmosphere modelling. In this poster we present the results from a set of high-quality observations, from 2m-4m class telescopes, including the optical spectrum of the ionizing star BD+46 3474, along with long-slit spatially resolved spectroscopy of the nebula. We have used state-of-the-art stellar atmosphere codes to determine stellar parameters and the chemical content of several heavy elements. Traditional nebular techniques along with updated atomic data have been used to compute gaseous abundances of O, N and S in the Cocoon nebula. Thanks to the low ionization degree of the nebula, we could determine total abundances directly from observable ions (no ionization correction factors were needed) for three of the analyzed elements (O, S, and N). The derived stellar and nebular abundances are compared and the influence of the possible presence of the so-called temperature fluctuations on the nebula is discussed. The results of this study are presented in more detail in García-Rojas, Simón-Díaz & Esteban 2014, A&A, 571, A93.

  19. A Starfish Preplanetary Nebula: IRAS 19024+0044

    NASA Astrophysics Data System (ADS)

    Sahai, Raghvendra; Sánchez Contreras, Carmen; Morris, Mark

    2005-02-01

    Using the Hubble Space Telescope, we have imaged the OH/IR star IRAS 19024+0044 (I19024) at 0.6, 0.8, 1.1, and 1.6 μm, as part of our surveys of candidate preplanetary nebulae. The images show a multipolar nebula of size ~3.7"×2.3", with at least six elongated lobes emanating from the center of the nebula. Two of the lobes show limb-brightened tips having point-symmetric structure with respect to the expected location of the central star. The central region shows two dark bands southwest and northeast of a central shallow maximum that may be either two inclined dusty toroidal structures or the dense parts of a single wide, inhomogeneous, toroid. A very faint, surface brightness-limited, diffuse halo surrounds the lobes. Long-slit/echelle optical spectroscopy obtained at the Mount Palomar and Keck observatories shows a spatially compact source of Hα emission; the Hα line shows a strong, narrow, central core with very broad (+/-1000 km s-1), weak wings, and a narrower blueshifted absorption feature signifying the presence of a ~100 km s-1 outflow. The spectrum is characterized by a strong, relatively featureless, continuum and lacks the strong forbidden emission lines characteristic of planetary nebulae, confirming that IRAS 19024 is a preplanetary nebula; the spectral type for the central star, although uncertain, is most likely early G. Interferometric observations of the CO J=1-0 line emission with the Owens Valley Radio Interferometer show a marginally resolved molecular envelope (size 5.5"×4.4") with an expansion velocity of 13 km s-1, resulting from the asymptotic giant granch (AGB) progenitor's dense, slow wind. We derive a kinematic distance of 3.5 kpc to I19024, based on its radial velocity. The bolometric flux is 7.3×10-9 ergs s-1 cm-2, and the luminosity 2850 Lsolar. The relatively low luminosity of I19024, in comparison with stellar evolutionary models, indicates that the initial mass of its central star was ~1-1.5 Msolar. The lobes, which appear to

  20. The population of planetary nebulae near the Galactic Centre: chemical abundances

    NASA Astrophysics Data System (ADS)

    Mollá, M.; Cavichia, O.; Costa, R. D. D.; Maciel, W. J.

    2017-10-01

    In this work, we report physical parameters and abundances derived for a sample of 15 high extinction planetary nebulae located in the inner 2° of the Galactic bulge, based on low dispersion spectroscopy secured at the SOAR telescope using the Goodman spectrograph. The new data allow us to extend our database including older, weaker objects that are at the faint end of the planetary nebulae luminosity function. The data provide chemical compositions for PNe located in this region of the bulge to explore the chemical enrichment history of the central region of the Galactic bulge. The results show that the abundances of our sample are skewed to higher metallicities than previous data in the outer regions of the bulge. This can indicate a faster chemical enrichment taking place at the Galactic centre.

  1. Frontal and occipital perfusion changes in dissociative identity disorder.

    PubMed

    Sar, Vedat; Unal, Seher N; Ozturk, Erdinc

    2007-12-15

    The aim of the study was to investigate if there were any characteristics of regional cerebral blood flow (rCBF) in dissociative identity disorder. Twenty-one drug-free patients with dissociative identity disorder and nine healthy volunteers participated in the study. In addition to a clinical evaluation, dissociative psychopathology was assessed using the Structured Clinical Interview for DSM-IV Dissociative Disorders, the Dissociative Experiences Scale and the Clinician-Administered Dissociative States Scale. A semi-structured interview for borderline personality disorder, the Hamilton Depression Rating Scale, and the Childhood Trauma Questionnaire were also administered to all patients. Normal controls had to be without a history of childhood trauma and without any depressive or dissociative disorder. Regional cerebral blood flow (rCBF) was studied with single photon emission computed tomography (SPECT) with Tc99m-hexamethylpropylenamine (HMPAO) as a tracer. Compared with findings in the control group, the rCBF ratio was decreased among patients with dissociative identity disorder in the orbitofrontal region bilaterally. It was increased in median and superior frontal regions and occipital regions bilaterally. There was no significant correlation between rCBF ratios of the regions of interest and any of the psychopathology scale scores. An explanation for the neurophysiology of dissociative psychopathology has to invoke a comprehensive model of interaction between anterior and posterior brain regions.

  2. Kinematic and chemical study of planetary nebulae and H II regions in NGC 3109

    NASA Astrophysics Data System (ADS)

    Flores-Durán, S. N.; Peña, M.; Ruiz, M. T.

    2017-05-01

    Aims: We present high-resolution spectroscopy of a number of planetary nebulae (PNe) and H II regions distributed along the dwarf irregular galaxy NGC 3109 and compare their kinematical behavior with that of H I data. We aim to determine if there is a kinematical connection among these objects. We also aim to determine the chemical composition of some PNe and H II regions in this galaxy and discuss it in comparison with stellar evolution models. Methods: Data for eight PNe and one H II region were obtained with the high-resolution spectrograph Magellan Inamori Kyocera Echelle (MIKE) at Las Campanas Observatory, Chile. Data for three PNe, six compact H II regions, and nine knots or clumps in extended H II regions were obtained with the high-resolution spectrograph Manchester Echelle Spectrometer (MES) attached to the 2.1m telescope at the Observatorio Astronómico Nacional, SPM, B.C., Mexico. An additional object was obtained from The SPM Catalogue of Extragalactic Planetary Nebulae. Thus, in total we have high-quality data for nine of the 20 PNe detected in this galaxy, and many H II regions. In the wavelength calibrated spectra, the heliocentric radial velocities were measured with a precision better than 7.8 km s-1. Data for blue supergiant stars were collected from the literature to be included in the analysis. The heliocentric radial velocities of the different objects were compared to the velocities of the H I disk at the same position. Physical conditions and ionic abundances of PNe and H II regions were obtained from the emission lines, and we used recent ionization correction factors to derive the total chemical abundances. Results: From the analysis of radial velocities we found that H II regions in NGC 3109 share the kinematics of the H I disk at the same projected position with very low dispersion in velocities. Blue supergiant stars and PNe rotate in the same direction as the H I disk but these objects have much larger dispersion; this larger dispersion

  3. Part 1: Physical studies of distant comets. Part 2: Morphologies of planetary nebulae

    NASA Astrophysics Data System (ADS)

    Jewitt, D. C.

    Broadband observations of comets P/Stephan-Oterma (1980g), Bowell (1980b) and Panther (1980u) in the visual and infrared wavelength regions are reported together with measurements in the 1.5 to 2.4 microns wavelength range having 5% spectral resolution. Ice grain halos are detected around P/Stephan-Oterma and Panther. The spatial distribution of (Cl)(3)P to (1)D line emission in NGC 6720 is reported. The emission emanates from small filaments in which the carbon neutral fraction may approach 10%. It is proposed that the Cl is present in regions which are shielded from direct stellar photons, possibly by H2 blobs. A CCD survey of planetary nebulae reveals numerous faint halos around the primary nebulae. About 2/3 of the 44 objects observed show halos. (Sll) electron density measurements show the halo mass in some nebulae. Possible origins of the halos are discussed.

  4. Lightning in the Protoplanetary Nebula?

    NASA Technical Reports Server (NTRS)

    Love, Stanley G.

    1997-01-01

    Lightning in the protoplanetary nebula has been proposed as a mechanism for creating meteoritic chondrules: enigmatic mm-sized silicate spheres formed in the nebula by the brief melting of cold precursors.

  5. Forming Planets in the Hostile Carina Nebula

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-07-01

    Can protoplanetary disks form and be maintained around low-mass stars in the harsh environment of a highly active, star-forming nebula? A recent study examines the Carina nebula to answer this question.Crowded ClustersStars are often born in clusters that contain both massive and low-mass stars. The most massive stars in these clusters emit far-ultraviolet and extreme-ultraviolet light that irradiates the region around them, turning the surrounding area into a hostile environment for potential planet formation.Planet formation from protoplanetary disks typically requires timescales of at least 12 million years. Could the harsh radiation from massive stars destroy the protoplanetary disks around low-mass stars by photoevaporation before planets even have a chance to form?Artists impression of a protoplanetary disk. Such disks can be photoevaporated by harsh ultraviolet light from nearby massive stars, causing the disk to be destroyed before planets have a chance to form within them. [ESO/L. Calada]Turning ALMA Toward CarinaA perfect case study for exploring hostile environments is the Carina nebula, located about 7500 lightyears away and home to nearly 100 O-type stars as well as tens of thousands of lower-mass young stars. The Carina population is ~14 Myr old: old enough to form planets within protoplanetary disks, but also old enough that photoevaporation could already have wreaked havoc on those disks.Due to the dense stellar populations in Carinas clusters, this is a difficult region to explore, but the Atacama Large Millimeter-submillimeter Array (ALMA) is up to the task. In a recent study, a team of scientists led by Adal Mesa-Delgado (Pontifical Catholic University of Chile) made use of ALMAs high spatial resolution to image four regions spaced throughout Carina, searching for protoplanetary disks.Detections and Non-DetectionsTwo evaporating gas globules in the Carina nebula, 104-593 and 105-600, that each contain a protoplanetary disk. The top panels are

  6. Nature versus nurture: Luminous blue variable nebulae in and near massive stellar clusters at the galactic center

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

    Lau, R. M.; Herter, T. L.; Adams, J. D.

    Three luminous blue variables (LBVs) are located in and near the Quintuplet Cluster at the Galactic center: the Pistol Star, G0.120-0.048, and qF362. We present imaging at 19, 25, 31, and 37 μm of the region containing these three LBVs, obtained with SOFIA using FORCAST. We argue that Pistol and G0.120-0.048 are identical 'twins' that exhibit contrasting nebulae due to the external influence of their different environments. Our images reveal the asymmetric, compressed shell of hot dust surrounding the Pistol Star and provide the first detection of the thermal emission from the symmetric, hot dust envelope surrounding G0.120-0.048. However, nomore » detection of hot dust associated with qF362 is made. Dust and gas composing the Pistol nebula are primarily heated and ionized by the nearby Quintuplet Cluster stars. The northern region of the Pistol nebula is decelerated due to the interaction with the high-velocity (2000 km s{sup –1}) winds from adjacent Wolf-Rayet Carbon (WC) stars. From fits to the spectral energy distribution (SED) of the Pistol nebula with the DustEM code we determine that the Pistol nebula is composed of a distribution of very small, transiently heated grains (10 to ∼ 35 Å) having a total dust mass of 0.03 M {sub ☉}, and that it exhibits a gradient of decreasing grain size from south to north due to differential sputtering by the winds from the WC stars. The total IR luminosity of the Pistol nebula is 5.2 × 10{sup 5} L {sub ☉}. Dust in the G0.120-0.048 nebula is primarily heated by the central star; however, the nebular gas is ionized externally by the Arches Cluster. Unlike the Pistol nebula, the G0.120-0.048 nebula is freely expanding into the surrounding medium. A grain size distribution identical to that of the non-sputtered region of the Pistol nebula satisfies the constraints placed on the G0.120-0.048 nebula from DustEM model fits to its SED and implies a total dust mass of 0.021 M {sub ☉}. The total IR luminosity of the G0

  7. Star Formation in the Eagle Nebula

    NASA Astrophysics Data System (ADS)

    Oliveira, J. M.

    2008-12-01

    M16 (the Eagle Nebula) is a striking star forming region, with a complex morphology of gas and dust sculpted by the massive stars in NGC 6611. Detailed studies of the famous ``elephant trunks'' dramatically increased our understanding of the massive star feedback into the parent molecular cloud. A rich young stellar population (2-3 Myr) has been identified, from massive O-stars down to substellar masses. Deep into the remnant molecular material, embedded protostars, Herbig-Haro objects and maser sources bear evidence of ongoing star formation in the nebula, possibly triggered by the massive cluster members. M 16 is a excellent template for the study of star formation under the hostile environment created by massive O-stars. This review aims at providing an observational overview not only of the young stellar population but also of the gas remnant of the star formation process.

  8. Processing NASA Earth Science Data on Nebula Cloud

    NASA Technical Reports Server (NTRS)

    Chen, Aijun; Pham, Long; Kempler, Steven

    2012-01-01

    Three applications were successfully migrated to Nebula, including S4PM, AIRS L1/L2 algorithms, and Giovanni MAPSS. Nebula has some advantages compared with local machines (e.g. performance, cost, scalability, bundling, etc.). Nebula still faces some challenges (e.g. stability, object storage, networking, etc.). Migrating applications to Nebula is feasible but time consuming. Lessons learned from our Nebula experience will benefit future Cloud Computing efforts at GES DISC.

  9. A study of the neutral hydrogen in direction to the GUM nebula

    NASA Astrophysics Data System (ADS)

    Dubner, G.; Giacani, E.; Cappa de Nicolau, C.; Reynoso, E.

    1992-12-01

    This paper presents 44 gray-scale maps at constant velocity of the distribution of H I in the direction of the Gum nebula. It is shown that there is no H I shell with a size comparable to the 36 deg diameter optical nebulosities and that there is a thick H I shell, about 7 deg in radius, shifted from the center of the optical nebula by more than 10 deg. The observations are consistent with a model in which the Gum nebula is the remnant of a supernova explosion that occurred about 2.6 million yr ago. The presence of two new H I bubbles associated with SWR 12 and 14, plus a possible one around WR 13, are disclosed from analysis of the H I gas distribution around the four WR star located beyond the Gum nebula. These H I bubbles have characteristics similar to those previously observed. Three shell-like objects probably related to OB stars and H II regions are also described.

  10. Water Splitting Using Porous Silicon Photo-electrodes for Hydrogen Production

    NASA Astrophysics Data System (ADS)

    Ali, M.; Starkov, V. V.; Gosteva, E. A.; Druzhinin, A. V.; Sattar, S.

    2017-11-01

    This paper presents the efficiency study results of using gradient-porous silicon structures with different morphology, as photo-anodes for photo-electrochemical dissociation of water. The results of a study of the physicochemical properties of gradient-porous silicon structures show the relatively low cost and simplicity of the technological process, as well as the possibility of forming structures with predefined properties, allow the creation of effective devices for artificial photosynthesis based on porous silicon for subsequent use in hydrogen energy.

  11. Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

    NASA Technical Reports Server (NTRS)

    Pendleton, Yvonne J.; Cruikshank, Dale P.

    2014-01-01

    The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pe 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the fo planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoeb open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cass Phoebe (mean diameter 213 km) is a former TNO now orbiting Saturn. VIMS spectral maps of Phoebe's surface reveal a complex consisting of prominent aromatic (CH) and aliphatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 µm). Phoebe is the source encircling Saturn, and from which particles (5-20 µm size) spiral inward toward Saturn. They encounter Iapetus and Hyperion wh blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aroma abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, com carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis o itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 4, which is larger than the value found in the di as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inv understanding the content and degree of processing of that nebular material. There are other Phoebe-like TNOs that are presently b in the organic spectral region, but JWST will open that possibility for a number of objects. We now need to explore and understand organic-bearing Solar System material to the solar nebula and the inventory of ISM materials incorporated therein.

  12. Utilitarian models of the solar nebula

    NASA Technical Reports Server (NTRS)

    Cassen, Patrick

    1994-01-01

    Models of the primitive solar nebula based on a combination of theory, observations of T Tauri stars, and global conservation laws are presented. The models describe the motions of nebular gas, mixing of interstellar material during the formation of the nebula, and evolution of thermal structure in terms of several characteristic parameters. The parameters describe key aspects of the protosolar cloud (its rotation rate and collapse rate) and the nebula (its mass relative to the Sun, decay time, and density distribution). For most applications, the models are heuristic rather than predicted. Their purpose is to provide a realistic context for the interpretation of solar system data, and to distinquish those nebular characteristics that can be specified with confidence, independently of the assumtions of particular models, form those that are poorly constrained. It is demonstrated that nebular gas typically experienced large radial excursions during the evolution of the nebula and that both inward and outward mean radial velocities on the order of meters per second occured in the terrestrial planet region, with inward velocities predominant for most ofthe evolution. However, the time history of disk size, surface density, and radial velocities are sensitive to the total angular momentun of the protosolar cloud, which cannot be constrained by purely theoretical considerations.It is shown that a certain amount of 'formational' mixing of interstellar material was an inevitable consequenc of nebular mass and angular momentum transport during protostellar collapse, regardless of the specific transport mechanisms invloved. Even if the protosolar cloud was initially homogeneous, this mixing was important because it had the effect of mingling presolar material that had experienced different degrees of thermal processing during collapse and passage through the accertion shock. Nebular thermal structure is less sensitive to poorly constrained parameters than is dynamical

  13. The Gum nebula and related problems

    NASA Technical Reports Server (NTRS)

    Maran, S. P.; Brandt, J. C.; Stecher, T. P.

    1971-01-01

    Papers were presented in conference sessions on the Gum nebula, the Vela X remnant, the hot stars gamma Velorum and zeta Puppis, the B associations in the Vela-Puppis complex, and pulsars. Ground-based optical and radio astronomy; rocket and satellite observations in the radio, visible, ultraviolet, and X-ray regions; and theoretical problems in the physical state of the interstellar medium, stellar evolution, and runaway star dynamics were considered.

  14. A nitrogen-rich nebula

    NASA Image and Video Library

    2015-06-29

    This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4000 light-years away in the southern constellation of Scorpius (The Scorpion). The faint blue haze across the frame shows what remains of a star like the Sun after it has depleted most of its fuel. When this happens, the outer layers of the star are ejected, and get excited and ionised by the energetic ultraviolet light emitted by the bright hot core of the star, forming the nebula. NGC 6153 is a planetary nebula that is elliptical in shape, with an extremely rich network of loops and filaments, shown clearly in this Hubble image. However, this is not what makes this planetary nebula so interesting for astronomers. Measurements show that NGC 6153 contains large amounts of neon, argon, oxygen, carbon and chlorine — up to three times more than can be found in the Solar System. The nebula contains a whopping five times more nitrogen than the Sun! Although it may be that the star developed higher levels of these elements as it grew and evolved, it is more likely that the star originally formed from a cloud of material that already contained lots more of these elements. A version of this image was entered into the Hubble’s Hidden Treasures image processing competition by contestant Matej Novak. Links Matej Novak’s image on Flickr

  15. IUE observations of stars in the neighborhood of the Lambda Orionis nebula

    NASA Technical Reports Server (NTRS)

    Bergoffen, Martin J.; Van Buren, Dave

    1988-01-01

    Results are presented from an IUE archive study of five stars along the line of sight towards the Lambda Ori H II region. H I, Fe II, Si II, and Mn II column densities have been found using a profile-fitting technique for H I and the curve-of-growth method for the ions. HD 36861 and HD 36822 lie at or near the center of the H II region, while HD 35468 and HD 37490 are imbedded in the dense neutral shell surrounding the H II region. HD 38899 is a foreground star. The depletion factors in the gas of this nebula are indicative of some shock processing of the material along these lines of sight. This processing probably occurred in the early stages of the nebula's evolution.

  16. Discovery of interstellar circular polarization in the direction of the Crab Nebula.

    NASA Technical Reports Server (NTRS)

    Martin, P. G.; Illing, R.; Angel, J. R. P.

    1972-01-01

    A search in many small regions of the Crab Nebula has resulted in the detection of a small component of circular polarization. The variation of the sign and magnitude with position in the Nebula indicates that the polarization is of interstellar origin. On the basis of the polarity, strength, and colour dependence, it is concluded that the composition of the aligned grains causing this polarization is dielectric. Metallic particles are clearly ruled out. Some stars have also been observed with negative results.

  17. Discovery of a Pulsar Wind Nebula Candidate in the Cygnus Loop

    NASA Technical Reports Server (NTRS)

    Katsuda, Satoru; Tsunemi, Hiroshi; Mori, Koji; Uchida, Hiroyuki; Petre, Robert; Yamada, Shin'ya; Tamagawa, Toru

    2012-01-01

    We report on a discovery of a diffuse nebula containing a point-like source in the southern blowout region of the Cygnus Loop supernova remnant, based on Suzaku and XMM-Newton observations. The X-ray spectra from the nebula and the point-like source are well represented by an absorbed power-law model with photon indices of 2.2+/-0.1 and 1.6+/-0.2, respectively. The photon indices as well as the flux ratio of F(sub nebula)/F(sub point-like) approx. 4 lead us to propose that the system is a pulsar wind nebula, although pulsations have not yet been detected. If we attribute its origin to the Cygnus Loop supernova, then the 0.5-8 keV luminosity of the nebula is computed to be 2.1x10(exp 31)(d/540pc)(exp 2)ergss/2, where d is the distance to the Loop. This implies a spin-down loss-energy E approx. 2.6x10(exp 35)(d/540pc)(exp 2)ergs/s. The location of the neutron star candidate, approx.2deg away from the geometric center of the Loop, implies a high transverse velocity of approx.1850(theta/2deg)(d/540pc)(t/10kyr)/k/s assuming the currently accepted age of the Cygnus Loop.

  18. Planetesimal Formation in the Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Mrad, Susan (Technical Monitor)

    1998-01-01

    In this talk we will address two distinct phases of planetesimal formation, each of which is fundamentally dependent upon the coupled interactions of particles and turbulent nebula gas. It has been shown both numerically and experimentally that 3-D (three dimensional) turbulence concentrates aerodynamically size-selected particles by orders of magnitude. In a previous review chapter we illustrated the initial predictions of Turbulent Concentration (TC) as applied to the solar nebula. We predicted the particle size which will be most effectively concentrated by turbulence; it is the particle which has a gas drag stopping time equal to the overturn time of the smallest (Kolmogorov scale) eddy. The primary uncertainty is the level of nebula turbulence, or Reynolds number Re, which can be expressed in terms of the standard nebula eddy viscosity parameter alpha = Rev(sub m)/cH, where v(sub m) is molecular viscosity, c is sound speed, and H is vertical scale height. Several studies, and observed lifetimes of circumstellar disks, have suggested that the level of nebula turbulence can be described by alpha = 10(exp -2) - 10(exp -4). There is some recent concern about how energy is provided to maintain this turbulence, but the issue remains open. We adopt a canonical minimum mass nebula with a range of alpha is greater than 0. We originally showed that chondrule-sized particles are selected for concentration in the terrestrial planet region if alpha = 10(exp -3) - 10(exp -4). In addition, Paque and Cuzzi found that the size distribution of chondrules is an excellent match for theoretical predictions. One then asks by what concentration factor C these particles can be concentrated; our early numerical results indicated an increase of C with alpha, and were supported by simple scaling arguments, but the extrapolation range was quite large and the predictions (C is approximately equal to 10(exp 5) - 10(exp 6) not unlikely) uncertain. The work presented here, which makes use of

  19. Ant nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    A new Hubble Space Telescope image of a celestial object called the Ant Nebula may shed new light on the future demise of our Sun. The image is available at http://www.jpl.nasa.gov/pictures/wfpc .

    The nebula, imaged on July 20, 1997, and June 30, 1998, by Hubble's Wide Field and Planetary Camera 2, was observed by Drs. Raghvendra Sahai and John Trauger of NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Bruce Balick of the University of Washington in Seattle; and Vincent Icke of Leiden University in the Netherlands. JPL designed and built the camera.

    The Ant Nebula, whose technical name is Mz3, resembles the head and thorax of an ant when observed with ground-based telescopes. The new Hubble image, with 10 times the resolution revealing 100 times more detail, shows the 'ant's' body as a pair of fiery lobes protruding from a dying, Sun- like star. The Ant Nebula is located between 3,000 and 6,000 light years from Earth in the southern constellation Norma.

    The image challenges old ideas about what happens to dying stars. This observation, along with other pictures of various remnants of dying stars called planetary nebulae, shows that our Sun's fate will probably be much more interesting, complex and dramatic than astronomers previously believed.

    Although the ejection of gas from the dying star in the Ant Nebula is violent, it does not show the chaos one might expect from an ordinary explosion, but instead shows symmetrical patterns. One possibility is that the central star has a closely orbiting companion whose gravitational tidal forces shape the outflowing gas. A second possibility is that as the dying star spins, its strong magnetic fields are wound up into complex shapes like spaghetti in an eggbeater. Electrically charged winds, much like those in our Sun's solar wind but millions of times denser and moving at speeds up to 1,000 kilometers per second (more than 600 miles per second) from the star, follow the twisted field lines on their way

  20. Millimeter-wave Molecular Line Observations of the Tornado Nebula

    NASA Astrophysics Data System (ADS)

    Sakai, D.; Oka, T.; Tanaka, K.; Matsumura, S.; Miura, K.; Takekawa, S.

    2014-08-01

    We report the results of millimeter-wave molecular line observations of the Tornado Nebula (G357.7-0.1), which is a bright radio source behind the Galactic center region. A 15' × 15' area was mapped in the J = 1-0 lines of CO, 13CO, and HCO+ with the Nobeyama Radio Observatory 45 m telescope. The Very Large Array archival data of OH at 1720 MHz were also reanalyzed. We found two molecular clouds with separate velocities, V LSR = -14 km s-1 and +5 km s-1. These clouds show rough spatial anti-correlation. Both clouds are associated with OH 1720 MHz emissions in the area overlapping with the Tornado Nebula. The spatial and velocity coincidence indicates violent interaction between the clouds and the Tornado Nebula. Modestly excited gas prefers the position of the Tornado "head" in the -14 km s-1 cloud, also suggesting the interaction. Virial analysis shows that the +5 km s-1 cloud is more tightly bound by self-gravity than the -14 km s-1 cloud. We propose a formation scenario for the Tornado Nebula; the +5 km s-1 cloud collided into the -14 km s-1 cloud, generating a high-density layer behind the shock front, which activates a putative compact object by Bondi-Hoyle-Lyttleton accretion to eject a pair of bipolar jets.

  1. Solar Nebula Magnetohydrodynamic Dynamos: Kinematic Theory, Dynamical Constraints, and Magnetic Transport of Angular Momentum

    NASA Technical Reports Server (NTRS)

    Stepinski, Tomasz F.; Reyes-Ruiz, Mauricio; Vanhala, Harri A. T.

    1993-01-01

    A hydromagnetic dynamo provides the best mechanism for contemporaneously producing magnetic fields in a turbulent solar nebula. We investigate the solar nebula in the framework of a steady-state accretion disk model and establish the criteria for a viable nebular dynamo. We have found that typically a magnetic gap exists in the nebula, the region where the degree of ionization is too small for the magnetic field to couple to the gas. The location and width of this gap depend on the particular model; the supposition is that gaps cover different parts of the nebula at different evolutionary stages. We have found, from several dynamical constraints, that the generated magnetic field is likely to saturate at a strength equal to equipartition with the kinetic energy of turbulence. Maxwell stress arising from a large-scale magnetic field may significantly influence nebular structure, and Maxwell stress due to small-scale fields can actually dominate other stresses in the inner parts of the nebula. We also argue that the bulk of nebular gas, within the scale height from the midplane, is stable against Balbus-Hawley instability.

  2. The Gum Nebula.

    NASA Technical Reports Server (NTRS)

    Maran, S. P.

    1971-01-01

    A historical review of observations on the Gum Nebula is given together with a survey of knowledge on its size, emission features, and dynamics of expansion. The ultraviolet spectrum of Zeta Puppis is examined in terms of features caused by various absorption lines, and radio emission from Vela X is analyzed, together with the effects of nebular plasma on the propagation of radio pulses from pulsars in the Nebula. The density distribution and the possibility of being produced by the Vela X supernova are discussed.

  3. The spectrophotometry and chemical composition of the oxygen-poor bipolar nebula NGC 6164-5

    NASA Technical Reports Server (NTRS)

    Dufour, Reginald J.; Parker, Robert A. R.; Henize, Karl G.

    1988-01-01

    The paper presents new ground-based and IUE spectrophotometry of several positions in NGC 6164-5 surrounding the Population I Of star HD 148937. Electron temperatures, densities, and abundances are derived for the various positions in the nebula using spectral line information. For all of the regions observed, Ne/H is depleted by an amount comparable to O/H, while S/H and Ar/H have normal values. The results suggest that the nebula consists partly of material ejected from inner shell-burning regions of the Of star. In effect, HD 148937 is older and more advanced than what was previously thought.

  4. Spectroscopy of Planetary Nebulae at the Bright End of the Luminosity Function

    NASA Astrophysics Data System (ADS)

    Rilinger, Anneliese; Kwitter, Karen B.; Balick, Bruce; Corradi, R. L. M.; Galera Rosillo, Rebeca; Jacoby, George H.; Shaw, Richard A.

    2017-01-01

    We have obtained spectra of 8 luminous planetary nebulae (PNe) in M31 and 4 in the Large Magellanic Cloud with the goal of understanding their properties and those of their progenitor stars. These PNe are at or near the M* region (the most luminous PNe) in their respective galaxies. M31 PNe were observed at the Gran Telescopio Canarias using the OSIRIS spectrograph; LMC PNe were observed with the FORS2 spectrograph at the Very Large Telescope. Line intensities were measured in IRAF. Using our n-level atom program, ELSA (Johnson, et.al, 2006, Planetary Nebulae in our Galaxy and Beyond, 234, 439), we determined temperature, density, and elemental abundances for each nebula. We then modeled the nebulae and central stars with Cloudy (Ferland, et al. 1998, PASP, 110, 761). We plan to use these models of the central stars to estimate the masses and ages of the progenitor stars. We hope to discover whether the progenitor stars of M* PNe exhibit consistently different characteristics from those of other PNe progenitors.

  5. NGC 7293, the Helix Nebula

    NASA Image and Video Library

    2012-05-16

    NGC 7293, better known as the Helix nebula, displays its ultraviolet glow courtesy of NASA GALEX. The Helix is the nearest example of a planetary nebula, which is the eventual fate of a star, like our own Sun, as it approaches the end of its life.

  6. BY POPULAR DEMAND: HUBBLE OBSERVES THE HORSEHEAD NEBULA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Rising from a sea of dust and gas like a giant seahorse, the Horsehead nebula is one of the most photographed objects in the sky. NASA's Hubble Space Telescope took a close-up look at this heavenly icon, revealing the cloud's intricate structure. This detailed view of the horse's head is being released to celebrate the orbiting observatory's eleventh anniversary. Produced by the Hubble Heritage Project, this picture is a testament to the Horsehead's popularity. Internet voters selected this object for the orbiting telescope to view. The Horsehead, also known as Barnard 33, is a cold, dark cloud of gas and dust, silhouetted against the bright nebula, IC 434. The bright area at the top left edge is a young star still embedded in its nursery of gas and dust. But radiation from this hot star is eroding the stellar nursery. The top of the nebula also is being sculpted by radiation from a massive star located out of Hubble's field of view. Only by chance does the nebula roughly resemble the head of a horse. Its unusual shape was first discovered on a photographic plate in the late 1800s. Located in the constellation Orion, the Horsehead is a cousin of the famous pillars of dust and gas known as the Eagle nebula. Both tower-like nebulas are cocoons of young stars. The Horsehead nebula lies just south of the bright star Zeta Orionis, which is easily visible to the unaided eye as the left-hand star in the line of three that form Orion's Belt. Amateur astronomers often use the Horsehead as a test of their observing skills; it is known as one of the more difficult objects to see visually in an amateur-sized telescope. The magnificent extent of the Horsehead is best appreciated in a new wide-field image of the nebula being released today by the National Optical Astronomy Observatory, taken by Travis Rector with the National Science Foundation's 0.9 meter telescope at Kitt Peak National Observatory near Tucson, AZ. This popular celestial target was the clear winner among more

  7. Gamma-ray flares from the Crab Nebula.

    PubMed

    Abdo, A A; Ackermann, M; Ajello, M; Allafort, A; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Bechtol, K; Bellazzini, R; Berenji, B; Blandford, R D; Bloom, E D; Bonamente, E; Borgland, A W; Bouvier, A; Brandt, T J; Bregeon, J; Brez, A; Brigida, M; Bruel, P; Buehler, R; Buson, S; Caliandro, G A; Cameron, R A; Cannon, A; Caraveo, P A; Casandjian, J M; Çelik, Ö; Charles, E; Chekhtman, A; Cheung, C C; Chiang, J; Ciprini, S; Claus, R; Cohen-Tanugi, J; Costamante, L; Cutini, S; D'Ammando, F; Dermer, C D; de Angelis, A; de Luca, A; de Palma, F; Digel, S W; do Couto e Silva, E; Drell, P S; Drlica-Wagner, A; Dubois, R; Dumora, D; Favuzzi, C; Fegan, S J; Ferrara, E C; Focke, W B; Fortin, P; Frailis, M; Fukazawa, Y; Funk, S; Fusco, P; Gargano, F; Gasparrini, D; Gehrels, N; Germani, S; Giglietto, N; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I A; Grondin, M-H; Grove, J E; Guiriec, S; Hadasch, D; Hanabata, Y; Harding, A K; Hayashi, K; Hayashida, M; Hays, E; Horan, D; Itoh, R; Jóhannesson, G; Johnson, A S; Johnson, T J; Khangulyan, D; Kamae, T; Katagiri, H; Kataoka, J; Kerr, M; Knödlseder, J; Kuss, M; Lande, J; Latronico, L; Lee, S-H; Lemoine-Goumard, M; Longo, F; Loparco, F; Lubrano, P; Madejski, G M; Makeev, A; Marelli, M; Mazziotta, M N; McEnery, J E; Michelson, P F; Mitthumsiri, W; Mizuno, T; Moiseev, A A; Monte, C; Monzani, M E; Morselli, A; Moskalenko, I V; Murgia, S; Nakamori, T; Naumann-Godo, M; Nolan, P L; Norris, J P; Nuss, E; Ohsugi, T; Okumura, A; Omodei, N; Ormes, J F; Ozaki, M; Paneque, D; Parent, D; Pelassa, V; Pepe, M; Pesce-Rollins, M; Pierbattista, M; Piron, F; Porter, T A; Rainò, S; Rando, R; Ray, P S; Razzano, M; Reimer, A; Reimer, O; Reposeur, T; Ritz, S; Romani, R W; Sadrozinski, H F-W; Sanchez, D; Saz Parkinson, P M; Scargle, J D; Schalk, T L; Sgrò, C; Siskind, E J; Smith, P D; Spandre, G; Spinelli, P; Strickman, M S; Suson, D J; Takahashi, H; Takahashi, T; Tanaka, T; Thayer, J B; Thompson, D J; Tibaldo, L; Torres, D F; Tosti, G; Tramacere, A; Troja, E; Uchiyama, Y; Vandenbroucke, J; Vasileiou, V; Vianello, G; Vitale, V; Wang, P; Wood, K S; Yang, Z; Ziegler, M

    2011-02-11

    A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (10(15) electron volts) electrons in a region smaller than 1.4 × 10(-2) parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.

  8. Gamma-Ray Flares from the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Brandt, T. J.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Casandjian, J. M.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Costamante, L.; Cutini, S.; D'Ammando, F.; Dermer, C. D.; de Angelis, A.; de Luca, A.; de Palma, F.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Hanabata, Y.; Harding, A. K.; Hayashi, K.; Hayashida, M.; Hays, E.; Horan, D.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Khangulyan, D.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Marelli, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Ray, P. S.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Romani, R. W.; Sadrozinski, H. F.-W.; Sanchez, D.; Parkinson, P. M. Saz; Scargle, J. D.; Schalk, T. L.; Sgrò, C.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Troja, E.; Uchiyama, Y.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Wang, P.; Wood, K. S.; Yang, Z.; Ziegler, M.

    2011-02-01

    A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega-electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta-electron-volt (1015 electron volts) electrons in a region smaller than 1.4 × 10-2 parsecs. These are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.

  9. Spectroscopy and CCD-photography of extended red emission in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Witt, A. N.; Schild, R. E.

    1986-01-01

    Recent spectrographic studies of extended red emission (ERE) seen in the 0.6 to 0.9 micron spectral region in many reflection nebulae have shown fluorescence by amorphous hydrogenated carbon to be the most probable cause of the ERE. Spectrographic observations were performed on the nebulae NGC 2023 and NGC 7023, using the intensified Reticon scanner (IRS) of Kitt Peak National Observatory on the N0-2 0.9 mm telescope. Charge coupled device (CCD) images of NGC2023 and NGC 7023 were obtained with the CfA CCD detector on the 0.6 mm telescope of the Whipple Observatory. Results are discussed.

  10. Probabilistic graphlet transfer for photo cropping.

    PubMed

    Zhang, Luming; Song, Mingli; Zhao, Qi; Liu, Xiao; Bu, Jiajun; Chen, Chun

    2013-02-01

    As one of the most basic photo manipulation processes, photo cropping is widely used in the printing, graphic design, and photography industries. In this paper, we introduce graphlets (i.e., small connected subgraphs) to represent a photo's aesthetic features, and propose a probabilistic model to transfer aesthetic features from the training photo onto the cropped photo. In particular, by segmenting each photo into a set of regions, we construct a region adjacency graph (RAG) to represent the global aesthetic feature of each photo. Graphlets are then extracted from the RAGs, and these graphlets capture the local aesthetic features of the photos. Finally, we cast photo cropping as a candidate-searching procedure on the basis of a probabilistic model, and infer the parameters of the cropped photos using Gibbs sampling. The proposed method is fully automatic. Subjective evaluations have shown that it is preferred over a number of existing approaches.

  11. Anatomy of the Photodissociation Region in the Orion Bar

    NASA Technical Reports Server (NTRS)

    Tielens, A. G. G. M.; Meixner, M. M.; vanderWerf, P. P.; Bregman, J.; Tauber, J. A.; Stutzki, J.; Rank, D.

    1993-01-01

    Much of the interstellar gas resides in photodissociation regions whose chemistry and energy balance is controlled by the flux of far-ultraviolet radiation upon them. These photons can ionize and dissociate molecules and heat the gas through the photoelectric effect working on dust grains. These regions have been extensively modeled theoretically, but detailed observational studies are few. Mapping of the prominent Orion Bar photo-dissociation region at wavelengths corresponding to the carbon-hydrogen stretching mode of polycyclic aromatic hydrocarbons, the 1-0 S(l) line of molecular hydrogen, and the J = 1-0 rotational line of carbon monoxide allows the penetration of the far-ultraviolet radiation into the cloud to be traced. The results strongly support the theoretical models and show conclusively that the incident far-ultraviolet radiation field, not shocks as has sometimes been proposed, is responsible for the emission in the Orion Bar.

  12. Coherent control of D2/H2 dissociative ionization by a mid-infrared two-color laser field

    NASA Astrophysics Data System (ADS)

    Wanie, Vincent; Ibrahim, Heide; Beaulieu, Samuel; Thiré, Nicolas; Schmidt, Bruno E.; Deng, Yunpei; Alnaser, Ali S.; Litvinyuk, Igor V.; Tong, Xiao-Min; Légaré, François

    2016-01-01

    Steering the electrons during an ultrafast photo-induced process in a molecule influences the chemical behavior of the system, opening the door to the control of photochemical reactions and photobiological processes. Electrons can be efficiently localized using a strong laser field with a well-designed temporal shape of the electric component. Consequently, many experiments have been performed with laser sources in the near-infrared region (800 nm) in the interest of studying and enhancing the electron localization. However, due to its limited accessibility, the mid-infrared (MIR) range has barely been investigated, although it allows to efficiently control small molecules and even more complex systems. To push further the manipulation of basic chemical mechanisms, we used a MIR two-color (1800 and 900 nm) laser field to ionize H2 and D2 molecules and to steer the remaining electron during the photo-induced dissociation. The study of this prototype reaction led to the simultaneous control of four fragmentation channels. The results are well reproduced by a theoretical model solving the time-dependent Schrödinger equation for the molecular ion, identifying the involved dissociation mechanisms. By varying the relative phase between the two colors, asymmetries (i.e., electron localization selectivity) of up to 65% were obtained, corresponding to enhanced or equivalent levels of control compared to previous experiments. Experimentally easier to implement, the use of a two-color laser field leads to a better electron localization than carrier-envelope phase stabilized pulses and applying the technique in the MIR range reveals more dissociation channels than at 800 nm.

  13. A Smoking Gun in the Carina Nebula

    NASA Technical Reports Server (NTRS)

    Hamaguchi, Kenji; Corcoran, Michael F.; Ezoe, Yuichiro; Townsley, Leisa; Broos, Patrick; Gruendl, Robert; Vaidya, Kaushar; White, Stephen M.; Petre, Rob; Chu, You-Hua

    2009-01-01

    The Carina Nebula is one of thc youngest, most active sites of massive star formation in our Galaxy. In this nebula, we have discovered a bright X-ray source that has persisted for approx.30 years. The soft X-ray spectrum. consistent with kT approx.130 eV blackbody radiation with mild extinction, and no counterpart in the near- and mid-infrared wavelengths indicate that it is a, approx. 10(exp 6)-year-old neutron star housed in the Carina Nebula. Current star formation theory does not suggest that the progenitor of the neutron star and massive stars in the Carina Nebula, in particular (eta)Car, are coeval. This result demonstrates that the Carina Nebula experienced at least two major episodes of massive star formation. The neutron star would be responsible for remnants of high energy activity seen in multiple wavelengths.

  14. Model nebulae and determination of the chemical composition of the Magellanic Clouds

    PubMed Central

    Aller, L. H.; Keyes, C. D.; Czyzak, S. J.

    1979-01-01

    An analysis of previously presented photoelectric spectrophotometry of HII regions (emission-line diffuse nebulae) in the two Magellanic Clouds is carried out with the aid of theoretical nebular models, which are used primarily as interpolation devices. Some advantages and limitations of such theoretical models are discussed. A comparison of the finally obtained chemical compositions with those found by other observers shows generally a good agreement, suggesting that it is possible to obtain reliable chemical compositions from low excitation gaseous nebulae in our own galaxy as well as in distant stellar systems. PMID:16592633

  15. Near-infrared and ultraviolet spectrophotometry of the young planetary nebula Hubble 12

    NASA Technical Reports Server (NTRS)

    Rudy, Richard J.; Rossano, George S.; Erwin, Peter; Puetter, R. C.; Feibelman, Walter A.

    1993-01-01

    The young planetary nebula Hubble 12 is observed using near-IR and UV spectrophotometry. The brightness of the O I lines, which is greater than in any other planetary nebula yet measured, indicates that fluorescent excitation by stellar continuum is the principal mechanism generating these lines. Extinction, electron density, and electron temperature are determined using infrared measurements combined with UV data and published optical observations. The range in extinction, density, and temperature implies that, within the ionized region, pockets of emission with distinctly different conditions exist. Logarithmic abundances for helium, oxygen, and sulfur are presented.

  16. Particle acceleration in explosive relativistic reconnection events and Crab Nebula gamma-ray flares

    NASA Astrophysics Data System (ADS)

    Lyutikov, Maxim; Komissarov, Serguei; Sironi, Lorenzo

    2018-04-01

    We develop a model of gamma-ray flares of the Crab Nebula resulting from the magnetic reconnection events in a highly magnetised relativistic plasma. We first discuss physical parameters of the Crab Nebula and review the theory of pulsar winds and termination shocks. We also review the principle points of particle acceleration in explosive reconnection events [Lyutikov et al., J. Plasma Phys., vol. 83(6), p. 635830601 (2017a); J. Plasma Phys., vol. 83(6), p. 635830602 (2017b)]. It is required that particles producing flares are accelerated in highly magnetised regions of the nebula. Flares originate from the poleward regions at the base of the Crab's polar outflow, where both the magnetisation and the magnetic field strength are sufficiently high. The post-termination shock flow develops macroscopic (not related to the plasma properties on the skin-depth scale) kink-type instabilities. The resulting large-scale magnetic stresses drive explosive reconnection events on the light-crossing time of the reconnection region. Flares are produced at the initial stage of the current sheet development, during the X-point collapse. The model has all the ingredients needed for Crab flares: natural formation of highly magnetised regions, explosive dynamics on the light travel time, development of high electric fields on macroscopic scales and acceleration of particles to energies well exceeding the average magnetic energy per particle.

  17. Interstellar Organics, the Solar Nebula, and Saturn's Satellite Phoebe

    NASA Technical Reports Server (NTRS)

    Pendleton, Y. J.; Cruikshank, D. P.

    2014-01-01

    The diffuse interstellar medium inventory of organic material (Pendleton et al. 1994, Pendleton & Allamandola 2002) was likely incorporated into the molecular cloud in which the solar nebula condensed. This provided the feedstock for the formation of the Sun, major planets, and the smaller icy bodies in the region outside Neptune's orbit (transneptunian objects, or TNOs). Saturn's satellites Phoebe, Iapetus, and Hyperion open a window to the composition of one class of TNO as revealed by the near-infrared mapping spectrometer (VIMS) on the Cassini spacecraft at Saturn. Phoebe (mean diameter 213 km) is a former TNO now orbiting Saurn. VIMS spaectral maps of PHoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and alophatic hydrocarbon (CH2, CH3) absorption bands (3.2-3.6 micrometers). Phoebe is the source of a huge debris ring encircling Saturn, and from which particles (approximately 5-20 micrometer size) spiral inward toward Saturn. They encounter Iapetus and Hperion where they mix with and blanket the native H2O ice of those two bodies. Quantitative analysis of the hydrocarbon bands on Iapetus demonstrates that aromatic CH is approximately 10 times as abundant as aliphatic CH2+CH3, significantly exceeding the strength of the aromatic signature in interplanetary dust particles, comet particles, ad in carbonaceous meteorites (Cruikshank et al. 2013). A similar excess of aromatics over aliphatics is seen in the qualitative analysis of Hyperion and Phoebe itself (Dalle Ore et al. 2012). The Iapetus aliphatic hydrocarbons show CH2/CH3 approximately 4, which is larger than the value found in the diffuse ISM (approximately 2-2.5). In so far as Phoebe is a primitive body that formed in the outer regions of the solar nebula and has preserved some of the original nebula inventory, it can be key to understanding the content and degree of procesing of the nebular material. There are other Phoebe-like TNOs that are presently

  18. Atoms, Stars, and Nebulae

    NASA Astrophysics Data System (ADS)

    Aller, Lawrence H.

    1991-09-01

    1. Introducing stars and nebulae; 2. Stellar rainbows; 3. Atoms and molecules; 4. The climate in a stellar atmosphere; 5. Analysing the stars; 6. Dwarfs, giants, and supergiants; 7. What makes a star shine?; 8. The youth and middle age of a common star; 9. Wind, dust and pulsations; 10. A star's last hurray?; 11. The interstellar medium and gaseous nebulae; 12. Uncommon stars and their sometimes violent behaviour; 13. High energy astronomy.

  19. Trigonometric Parallaxes of Central Stars of Planetary Nebulae

    DTIC Science & Technology

    2007-02-01

    is a large nebula with a larger outer halo (Hewett et al. 2003; Rauch et al. 2004). Frew& Parker (2006) find that the nebula may be ionized ISM. 3...TRIGONOMETRIC PARALLAXES OF CENTRAL STARS OF PLANETARY NEBULAE Hugh C. Harris,1 Conard C. Dahn, Blaise Canzian, Harry H. Guetter, S. K. Leggett,2...parallaxes of 16 nearby planetary nebulae are presented, including reduced errors for seven objects with previous initial results and results for six new

  20. X-Ray Outburst from Young Star in McNeil's Nebula

    NASA Astrophysics Data System (ADS)

    2004-07-01

    Observations with NASA's Chandra X-ray Observatory captured an X-ray outburst from a young star, revealing a probable scenario for the intermittent brightening of the recently discovered McNeil's Nebula. It appears the interaction between the young star's magnetic field and an orbiting disk of gas can cause dramatic, episodic increases in the light from the star and disk, illuminating the surrounding gas. "The story of McNeil's Nebula is a wonderful example of the importance of serendipity in science," said Joel Kastner of the Rochester Institute of Technology in Rochester, New York, lead author of a paper in the July 22 issue of Nature describing the X-ray results. "Visible-light images were made of this region several months before Jay McNeil made his discovery, so it could be determined approximately when and by how much the star flared up to produce McNeil's Nebula." The small nebula, which lies in the constellation Orion about 1300 light years from Earth, was discovered with a 3-inch telescope by McNeil, an amateur astronomer from Paducah, Kentucky, in January 2004. In November 2002, a team led by Ted Simon of the Institute for Astronomy in Hawaii had observed the star-rich region with Chandra in search of young, X-ray emitting stars, and had detected several objects. Optical and infrared astronomers had, as part of independent surveys, also observed the region about a year later, in 2003. After the announcement of McNeil's discovery, optical, infrared and X-ray astronomers rushed to observe the region again. They found that a young star buried in the nebula had flared up, and was illuminating the nebula. This star was coincident with one of the X-ray sources discovered earlier by Simon. Chandra observations obtained by Kastner's group just after the optical outburst showed that the source had brightened fifty-fold in X-rays when compared to Simon's earlier observation. The visible-light eruption provides evidence that the cause of the X-ray outburst is the

  1. The complete Einstein Observatory X-ray survey of the Orion Nebula region.

    NASA Technical Reports Server (NTRS)

    Gagne, Marc; Caillault, Jean-Pierre

    1994-01-01

    We have analyzed archival Einstein Observatory images of a roughly 4.5 square degree region centered on the Orion Nebula. In all, 245 distinct X-ray sources have been detected in six High Resolution Imager (HRI) and 17 Imaging Proportional Counter (IPC) observations. An optical database of over 2700 stars has been assembled to search for candidate counterparts to the X-ray sources. Roughly half the X-ray sources are identified with a single Orion Nebula cluster member. The 10 main-sequence O6-B5 cluster stars detected in Orion have X-ray activity levels comparable to field O and B stars. X-ray emission has also been detected in the direction of four main-sequence late-B and early-A type stars. Since the mechanisms producing X-rays in late-type coronae and early-type winds cannot operate in the late-B and early-A type atmospheres, we argue that the observed X-rays, with L(sub X) approximately = 3 x 10(exp 30) ergs/s, are probably produced in the coronae of unseen late-type binary companions. Over 100 X-ray sources have been associated with late-type pre-main sequence stars. The upper envelope of X-ray activity rises sharply from mid-F to late-G, with L(sub x)/L(sub bol) in the range 10(exp -4) to 2 x 10(exp -3) for stars later than approximately G7. We have looked for variability of the late-type cluster members on timescales of a day to a year and find that 1/4 of the stars show significantly variable X-ray emission. A handful of the late-type stars have published rotational periods and spectroscopic rotational velocities; however, we see no correlation between X-ray activity and rotation. Thus, for this sample of pre-main-sequence stars, the large dispersion in X-ray activity does not appear to be caused by the dispersion in rotation, in contrast with results obtained for low-mass main-sequence stars in the Pleiades and pre-main-sequence stars in Taurus-Auriga.

  2. THE TRIFID NEBULA: STELLAR SIBLING RIVALRY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    previously in the Eagle Nebula, another star-forming region photographed by Hubble. The stalk has survived because at its tip there is a knot of gas that is dense enough to resist being eaten away by the powerful radiation. Reflected starlight at the tip of the EGG may be due to light from the Trifid's central star, or from a young stellar object buried within the EGG. Similarly, a tiny spike of emission pointing outward from the EGG looks like a small stellar jet. Hubble astronomers are tentatively interpreting this jet as the last gasp from a star that was cut off from its supply lines 100,000 years ago. The images were taken Sept. 8, 1997 through filters that isolate emission from hydrogen atoms, ionized sulfur atoms, and doubly ionized oxygen atoms. The images were combined in a single color composite picture. While the resulting picture is not true color, it is suggestive of what a human eye might see. Credits: NASA and Jeff Hester (Arizona State University)

  3. The SPM Kinematic Catalogue of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    López, J. A.; Richer, M. G.; Riesgo, H.; Steffen, W.; García-Segura, G.; Meaburn, J.; Bryce, M.

    The San Pedro Mártir Kinematic Catalogue of Planetary Nebulae aims at providing detailed kinematic information for galactic planetary nebulae (PNe) and bright PNe in the Local Group. The database provides long-slit, Echelle spectra and images where the location of the slits on the nebula are indicated. As a tool to help interpret the 2D line profiles or position-velocity data, an atlas of synthetic emission line spectra accompanies the Catalogue. The atlas has been produced with the code SHAPE and contains synthetic spectra for all the main morphological groups for a wide range of spatial orientations and slit locations over the nebula.

  4. A Herschel study of NGC 650

    NASA Astrophysics Data System (ADS)

    van Hoof, P. A. M.; Van de Steene, G. C.; Exter, K. M.; Barlow, M. J.; Ueta, T.; Groenewegen, M. A. T.; Gear, W. K.; Gomez, H. L.; Hargrave, P. C.; Ivison, R. J.; Leeks, S. J.; Lim, T. L.; Olofsson, G.; Polehampton, E. T.; Swinyard, B. M.; Van Winckel, H.; Waelkens, C.; Wesson, R.

    2013-12-01

    As part of the Herschel guaranteed time key project Mass loss of Evolved StarS (MESS) we have imaged a sample of planetary nebulae. In this paper we present the Photodetector Array Camera and Spectrometer (PACS) and Spectral and Photometric Imaging Receiver (SPIRE) images of the classical bipolar planetary nebula NGC 650. We used these images to derive a temperature map of the dust. We also constructed a photoionization and dust radiative transfer model using the spectral synthesis code Cloudy. To constrain this model, we used the PACS and SPIRE fluxes and combined them with hitherto unpublished International Ultraviolet Explorer (IUE) and Spitzer InfraRed Spectrograph (IRS) spectra as well as various other data from the literature. A temperature map combined with a photoionization model were used to study various aspects of the central star, the nebula, and in particular the dust grains in the nebula. The central star parameters are determined to be Teff = 208 kK and L = 261 L⊙ assuming a distance of 1200 pc. The stellar temperature is much higher than previously published values. We confirm that the nebula is carbon-rich with a C/O ratio of 2.1. The nebular abundances are typical for a type IIa planetary nebula. With the photoionization model we determined that the grains in the ionized nebula are large (assuming single-sized grains, they would have a radius of 0.15 μm). Most likely these large grains were inherited from the asymptotic giant branch phase. The PACS 70/160 μm temperature map shows evidence of two radiation components heating the grains. The first component is direct emission from the central star, while the second component is diffuse emission from the ionized gas (mainly Lyα). We show that previous suggestions of a photo-dissociation region surrounding the ionized region are incorrect. The neutral material resides in dense clumps inside the ionized region. These may also harbor stochastically heated very small grains in addition to the large

  5. The chromosomal association/dissociation of the chromatin insulator protein Cp190 of Drosophila melanogaster is mediated by the BTB/POZ domain and two acidic regions.

    PubMed

    Oliver, Daniel; Sheehan, Brian; South, Heather; Akbari, Omar; Pai, Chi-Yun

    2010-12-31

    Chromatin insulators or boundary elements are a class of functional elements in the eukaryotic genome. They regulate gene transcription by interfering with promoter-enhancer communication. The Cp190 protein of Drosophila melanogaster is essential to the function of at least three-types of chromatin insulator complexes organized by Su(Hw), CTCF and BEAF32. We mapped functional regions of Cp190 in vivo and identified three domains that are essential for the insulator function and for the viability of flies: the BTB/POZ domain, an aspartic acid-rich (D-rich) region and a C-terminal glutamic acid-rich (E-rich) region. Other domains including the centrosomal targeting domain and the zinc fingers are dispensable. The N-terminal CP190BTB-D fragment containing the BTB/POZ domain and the D-rich region is sufficient to mediate association with all three types of insulator complexes. The fragment however is not sufficient for insulator activity or viability. The Cp190 and CP190BTB-D are regulated differently in cells treated with heat-shock. The Cp190 dissociated from chromosomes during heat-shock, indicating that dissociation of Cp190 with chromosomes can be regulated. In contrast, the CP190BTB-D fragment didn't dissociate from chromosomes in the same heat-shocked condition, suggesting that the deleted C-terminal regions have a role in regulating the dissociation of Cp190 with chromosomes. The N-terminal fragment of Cp190 containing the BTB/POZ domain and the D-rich region mediates association of Cp190 with all three types of insulator complexes and that the E-rich region of Cp190 is required for dissociation of Cp190 from chromosomes during heat-shock. The heat-shock-induced dissociation is strong evidence indicating that dissociation of the essential insulator protein Cp190 from chromosomes is regulated. Our results provide a mechanism through which activities of an insulator can be modulated by internal and external cues.

  6. NASA Satellites Find High-Energy Surprises in 'Constant' Crab Nebula

    NASA Image and Video Library

    2011-01-12

    NASA image release January 12, 2010 NASA's Chandra X-ray Observatory reveals the complex X-ray-emitting central region of the Crab Nebula. This image is 9.8 light-years across. Chandra observations were not compatible with the study of the nebula's X-ray variations. To read more go to: geeked.gsfc.nasa.gov/?p=4945 Credit: NASA/CXC/SAO/F. Seward et al. 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 Join us on Facebook

  7. Gamma-Ray Flares from the Crab Nebula

    DOE PAGES

    Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

    2010-01-06

    A young and energetic pulsar powers the well-known Crab Nebula. Here, we describe two separate gamma-ray (photon energy greater than 100 mega–electron volts) flares from this source detected by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. The first flare occurred in February 2009 and lasted approximately 16 days. The second flare was detected in September 2010 and lasted approximately 4 days. During these outbursts, the gamma-ray flux from the nebula increased by factors of four and six, respectively. The brevity of the flares implies that the gamma rays were emitted via synchrotron radiation from peta–electron-volt (10more » 15 electron volts) electrons in a region smaller than 1.4 × 10 -2 parsecs. In conclusion, these are the highest-energy particles that can be associated with a discrete astronomical source, and they pose challenges to particle acceleration theory.« less

  8. The Orion Nebula in the Far-Infrared: high-J CO and fine-structure lines mapped by FIFI-LS/SOFIA

    NASA Astrophysics Data System (ADS)

    Klein, Randolf; Looney, Leslie; Cox, Erin; Fischer, Christian; Iserlohe, Christof; Krabbe, Alfred

    2015-08-01

    The Orion Nebula is the closest massive star forming region allowing us to study the physical conditions in such a region with high spatial resolution. We used the far infrared integral-field spectrometer, FIFI-LS, on-board the airborne observatory SOFIA to study the atomic and molecular gas in the Orion Nebula at medium spectral resolution.The large maps obtained with FIFI-LS cover the nebula from the BN/KL-object to the bar in several fine structure lines. These spectral maps are the largest and highest spatially resolved to date. They allow us to study the conditions of the photon-dominated region and the interface to the molecular cloud with unprecedented detail.Another investigation targeted the molecular gas in the BN/KL region of the Orion Nebula, which is stirred up by a violent explosion about 500 years ago. The explosion drives a wide angled molecular outflow. We present maps of several high-J CO observations (J in the range of 10 to 30), allowing us to analyse of the heated molecular gas.The observations were taken during the commissioning of FIFI-LS last year and as recent as this March. The results are still preliminary as the data reduction and calibration is still under development.

  9. Weighing in on the Dumbbell Nebula

    NASA Image and Video Library

    2011-08-10

    The Dumbbell nebula, also known as Messier 27, pumps out infrared light in this image from NASA Spitzer Space Telescope. Planetary nebulae are now known to be the remains of stars that once looked a lot like our sun.

  10. Hypersonic Boundary Layer Transition Measurements Using NO2 approaches NO Photo-dissociation Tagging Velocimetry

    NASA Technical Reports Server (NTRS)

    Bathel, Brett F.; Johansen, Craig T.; Danehy, Paul M.; Inman, Jennifer A.; Jones, Stephen B.; Goyne, Christopher P.

    2011-01-01

    Measurements of instantaneous and mean streamwise velocity profiles in a hypersonic laminar boundary layer as well as a boundary layer undergoing laminar-to-turbulent transition were obtained over a 10-degree half-angle wedge model. A molecular tagging velocimetry technique consisting of a NO2 approaches?NO photo-dissociation reaction and two subsequent excitations of NO was used. The measurement of the transitional boundary layer velocity profiles was made downstream of a 1-mm tall, 4-mm diameter cylindrical trip along several lines lying within a streamwise measurement plane normal to the model surface and offset 6-mm from the model centerline. For laminar and transitional boundary layer measurements, the magnitudes of streamwise velocity fluctuations are compared. In the transitional boundary layer the fluctuations were, in general, 2-4 times larger than those in the laminar boundary layer. Of particular interest were fluctuations corresponding to a height of approximately 50% of the laminar boundary layer thickness having a magnitude of nearly 30% of the mean measured velocity. For comparison, the measured fluctuations in the laminar boundary layer were approximately 5% of the mean measured velocity at the same location. For the highest 10% signal-to-noise ratio data, average single-shot uncertainties using a 1 ?Es and 50 ?Es interframe delay were 115 m/s and 3 m/s, respectively. By averaging single-shot measurements of the transitional boundary layer, uncertainties in mean velocity as low as 39 m/s were obtained in the wind tunnel. The wall-normal and streamwise spatial resolutions were 0.14-mm (2 pixel) and 0.82-mm (11 pixels), respectively. These measurements were performed in the 31-inch Mach 10 Air Wind Tunnel at the NASA Langley Research Center.

  11. Dissociable parietal regions facilitate successful retrieval of recently learned and personally familiar information.

    PubMed

    Elman, Jeremy A; Cohn-Sheehy, Brendan I; Shimamura, Arthur P

    2013-03-01

    In fMRI analyses, the posterior parietal cortex (PPC) is particularly active during the successful retrieval of episodic memory. To delineate the neural correlates of episodic retrieval more succinctly, we compared retrieval of recently learned spatial locations (photographs of buildings) with retrieval of previously familiar locations (photographs of familiar campus buildings). Episodic retrieval of recently learned locations activated a circumscribed region within the ventral PPC (anterior angular gyrus and adjacent regions in the supramarginal gyrus) as well as medial PPC regions (posterior cingulated gyrus and posterior precuneus). Retrieval of familiar locations activated more posterior regions in the ventral PPC (posterior angular gyrus, LOC) and more anterior regions in the medial PPC (anterior precuneus and retrosplenial cortex). These dissociable effects define more precisely PPC regions involved in the retrieval of recent, contextually bound information as opposed to regions involved in other processes, such as visual imagery, scene reconstruction, and self-referential processing. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Rotten Egg Nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Violent gas collisions that produced supersonic shock fronts in a dying star are seen in a new, detailed image from NASA's Hubble Space Telescope.

    The picture, taken by Hubble's Wide Field and Planetary Camera 2, is online at http://www.jpl.nasa.gov/images/wfpc . The camera was designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif.

    Stars like our Sun will eventually die and expel most of their material outward into shells of gas and dust. These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae.

    'This new image gives us a rare view of the early death throes of stars like our Sun. For the first time, we can see phenomena leading to the formation of planetary nebulae. Until now, this had only been predicted by theory, but had never been seen directly,' said Dr. Raghvendra Sahai, research scientist and member of the science team at JPL for the Wide Field and Planetary Camera 2.

    The object is sometimes called the Rotten Egg Nebula, because it contains a lot of sulphur, which would produce an awful odor if one could smell in space. The object is also known as the Calabash Nebula or by the technical name OH231.8+4.2.

    The densest parts of the nebula are composed of material ejected recently by the central star and accelerated in opposite directions. This material, shown as yellow in the image, is zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Most of the star's original mass is now contained in these bipolar gas structures.

    A team of Spanish and American astronomers used NASA's Hubble Space Telescope to study how the gas stream rams into the surrounding material, shown in blue. They believe that such interactions dominate the formation process in planetary nebulae. Due to the high speed of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and

  13. Near-Infrared Polarimetry of the Eagle Nebula (M 16)

    NASA Astrophysics Data System (ADS)

    Sugitani, Koji; Watanabe, Makoto; Tamura, Motohide; Kandori, Ryo; Hough, James H.; Nishiyama, Shogo; Nakajima, Yasushi; Kusakabe, Nobuhiko; Hashimoto, Jun; Nagayama, Takahiro; Nagashima, Chie; Kato, Daisuke; Fukuda, Naoya

    2007-06-01

    We carried out deep and wide (˜ 8 × 8) JHKs imaging polarimetry in the southern region of the Eagle Nebula (M 16). The polarization intensity map reveals that two YSOs with near-IR reflection nebulae are located at the tips of two famous molecular pillars (Pillars 1 and 2) facing toward the exciting stars of M 16. The centrosymmetric polarization pattern are consistent with those around Class I objects having circumstellar envelopes, confirming that star formation is now taking place at the two tips of the pillars under the influence of UV radiation from the exciting stars. Polarization measurements of point sources show that magnetic fields are aligned along some of the pillars, but in a direction that is quite different to the global structure in M 16.

  14. Turbulent Concentration of MM-Size Particles in the Protoplanetary Nebula: Scaled-Dependent Multiplier Functions

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Hartlep, Thomas; Weston, B.; Estremera, Shariff Kareem

    2014-01-01

    The initial accretion of primitive bodies (asteroids and TNOs) from freely-floating nebula particles remains problematic. Here we focus on the asteroids where constituent particle (read "chondrule") sizes are observationally known; similar arguments will hold for TNOs, but the constituent particles in those regions will be smaller, or will be fluffy aggregates, and are unobserved. Traditional growth-bysticking models encounter a formidable "meter-size barrier" [1] (or even a mm-cm-size barrier [2]) in turbulent nebulae, while nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids [3]. Even if growth by sticking could somehow breach the meter size barrier, other obstacles are encountered through the 1-10km size range [4]. Another clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids [5]; scenarios leading directly from independent nebula particulates to this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios [6-8]. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. The typical sizes of planetesimals and the rate of their formation [7,8] are determined by a statistical model with properties inferred from large numerical simulations of turbulence [9]. Nebula turbulence can be described by its Reynolds number Re = L/eta sup(4/3), where L = ETA alpha sup (1/2) the largest eddy scale, H is the nebula gas vertical scale height, and a the nebula turbulent viscosity parameter, and ? is the Kolmogorov or smallest scale in turbulence (typically about 1km), with eddy turnover time t?. In the nebula, Re is far larger than any numerical simulation can

  15. Temporal Profiles Dissociate Regional Extracellular Ethanol versus Dopamine Concentrations

    PubMed Central

    2015-01-01

    In vivo monitoring of dopamine via microdialysis has demonstrated that acute, systemic ethanol increases extracellular dopamine in regions innervated by dopaminergic neurons originating in the ventral tegmental area and substantia nigra. Simultaneous measurement of dialysate dopamine and ethanol allows comparison of the time courses of their extracellular concentrations. Early studies demonstrated dissociations between the time courses of brain ethanol concentrations and dopaminergic responses in the nucleus accumbens (NAc) elicited by acute ethanol administration. Both brain ethanol and extracellular dopamine levels peak during the first 5 min following systemic ethanol administration, but the dopamine response returns to baseline while brain ethanol concentrations remain elevated. Post hoc analyses examined ratios of the dopamine response (represented as a percent above baseline) to tissue concentrations of ethanol at different time points within the first 25–30 min in the prefrontal cortex, NAc core and shell, and dorsomedial striatum following a single intravenous infusion of ethanol (1 g/kg). The temporal patterns of these “response ratios” differed across brain regions, possibly due to regional differences in the mechanisms underlying the decline of the dopamine signal associated with acute intravenous ethanol administration and/or to the differential effects of acute ethanol on the properties of subpopulations of midbrain dopamine neurons. This Review draws on neurochemical, physiological, and molecular studies to summarize the effects of acute ethanol administration on dopamine activity in the prefrontal cortex and striatal regions, to explore the potential reasons for the regional differences observed in the decline of ethanol-induced dopamine signals, and to suggest directions for future research. PMID:25537116

  16. Millimeter-wave molecular line observations of the Tornado nebula

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

    Sakai, D.; Oka, T.; Tanaka, K.

    We report the results of millimeter-wave molecular line observations of the Tornado Nebula (G357.7-0.1), which is a bright radio source behind the Galactic center region. A 15' × 15' area was mapped in the J = 1-0 lines of CO, {sup 13}CO, and HCO{sup +} with the Nobeyama Radio Observatory 45 m telescope. The Very Large Array archival data of OH at 1720 MHz were also reanalyzed. We found two molecular clouds with separate velocities, V{sub LSR} = –14 km s{sup –1} and +5 km s{sup –1}. These clouds show rough spatial anti-correlation. Both clouds are associated with OH 1720more » MHz emissions in the area overlapping with the Tornado Nebula. The spatial and velocity coincidence indicates violent interaction between the clouds and the Tornado Nebula. Modestly excited gas prefers the position of the Tornado 'head' in the –14 km s{sup –1} cloud, also suggesting the interaction. Virial analysis shows that the +5 km s{sup –1} cloud is more tightly bound by self-gravity than the –14 km s{sup –1} cloud. We propose a formation scenario for the Tornado Nebula; the +5 km s{sup –1} cloud collided into the –14 km s{sup –1} cloud, generating a high-density layer behind the shock front, which activates a putative compact object by Bondi-Hoyle-Lyttleton accretion to eject a pair of bipolar jets.« less

  17. A Photometrically and Morphologically Variable Infrared Nebula IN L483

    NASA Astrophysics Data System (ADS)

    Connelley, Michael S.; Hodapp, Klaus W.; Fuller, Gary A.

    2009-03-01

    We present narrow and broad K-band observations of the Class 0/I source IRAS 18148-0440 that span 17 years. The infrared nebula associated with this protostar in the L483 dark cloud is both morphologically and photometrically variable on a timescale of only a few months. This nebula appears to be an infrared analog to other well known optically visible variable nebulae associated with young stars, such as Hubble's Variable Nebula. Along with Cepheus A, this is one of the first large variable nebulae to be found that is only visible in the infrared. The variability of this nebula is most likely due to changing illumination of the cloud rather than any motion of the structure in the nebula. Both morphological and photometric changes are observed on a timescale only a few times longer than the light crossing time of the nebula, suggesting very rapid intrinsic changes in the illumination of the nebula. Our narrowband observations also found that H2 knots are found nearly twice as far to the east of the source as to its west, and that H2 emission extends farther east of the source than the previously known CO outflow.

  18. The Gum Nebula and Related Problems

    NASA Technical Reports Server (NTRS)

    1973-01-01

    Proceedings of a symposium concerning the Gum Nebula (GN) and related topics are reported. Papers presented include: Colin Gum and the discovery of the GN; identification of the GN as the fossil Stromgren sphere of Vela X Supernova; size and shape of GN; formation of giant H-2 regions following supernova explosions; radio astronomy Explorer 1 observations of GN; cosmic ray effects in the GN; low intensity H beta emission from the interstellar medium; and how to recognize and analyze GN. Astronomical charts and diagrams are included.

  19. Radio astronomy Explorer-1 observations of the Gum nebula

    NASA Technical Reports Server (NTRS)

    Alexander, J. K.

    1971-01-01

    Complicating factors in the spectrum analysis of the Gum nebula are discussed. These include accounting for the spectrum of supernova remnants in the direction of the nebula, the different absorption laws for radiation from beyond and within the nebula, and the Razin effect. This last results in a low frequency cutoff to the spectrum of synchrotron radiation by particles in a thermal plasma. These factors cause the observer to overestimate the amount of absorption occurring in the nebula. Data from the Explorer 38 satellite are presented for 3.93 and 6.55 MHz. Average optical depth for the nebula at 4 MHz was calculated.

  20. The "Water-Fountain Nebula" IRAS 16342-3814: Hubble Space Telescope/Very Large Array Study of a Bipolar Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Sahal, Raghvendra; teLintelHekkert, Peter; Morris, Mark; Zijlstra, Albert; Likkel, Lauren

    1999-01-01

    We present Hubble Space Telescope (HST) Wide-Field Planetary Camera 2 images and VLA OH maser emission-line maps of the cold infrared object IRAS 16342-3814, believed to be a protoplanetary nebula. The HST images show an asymmetrical bipolar nebula, with the lobes separated by a dark equatorial waist. The two bright lobes and the dark waist are simply interpreted as bubble-like reflection nebulae illuminated by starlight escaping through polar holes in a dense, flattened, optically thick cocoon of dust, which completely obscures the central star. A faint halo can be seen surrounding each of the lobes. The bubbles are likely to have been created by a fast outflow (evidenced by H2O emission) plowing into a surrounding dense, more slowly expanding, circumstellar envelope of the progenitor asymptotic giant-branch (AGB) star (evidenced by the halo). The IRAS fluxes indicate a circumstellar mass of about 0.7 solar mass (D/2 kpc) and an AGB mass-loss rate of about 10(exp -4) solar mass/yr (V(sub exp)/15 km/s)(D/2 kpc)(sup 2) (assuming a gas-to-dust ratio of 200). OH features with the largest redshifted and blueshifted velocities are concentrated around the bright eastern and western polar lobes, respectively, whereas intermediate-velocity features generally occur at low latitudes, in the dark waist region. We critically examine evidence for the post-AGB classification of IRAS 16342-3814.

  1. Far-ultraviolet imagery of the Barnard Loop Nebula

    NASA Technical Reports Server (NTRS)

    Carruthers, G. R.; Opal, C. B.

    1977-01-01

    An electrographic Schmidt camera carried on a sounding rocket has yielded far-ultraviolet (1050-2000 A and 1230-2000 A) images of the Barnard Loop Nebula and of the general background in the Orion region due to scattering of ultraviolet starlight by interstellar dust particles. The total intensity in the Barnard Loop region agrees well with OAO-2 measurements, but the discrete Loop structure contributes only some 15% of the total. The measurements are consistent with a relatively high albedo for the dust grains in the far-ultraviolet.

  2. Pulsar wind nebulae created by fast-moving pulsars

    NASA Astrophysics Data System (ADS)

    Kargaltsev, O.; Pavlov, G. G.; Klingler, N.; Rangelov, B.

    2017-10-01

    We review multiwavelength properties of pulsar wind nebulae created by supersonically moving pulsars and the effects of pulsar motion on the pulsar wind nebulae morphologies and the ambient medium. Supersonic pulsar wind nebulae are characterized by bow-shaped shocks around the pulsar and/or cometary tails filled with the shocked pulsar wind. In the past several years significant advances in supersonic pulsar wind nebula studies have been made in deep observations with the Chandra and XMM-Newton X-ray observatories and the Hubble Space Telescope. In particular, these observations have revealed very diverse supersonic pulsar wind nebula morphologies in the pulsar vicinity, different spectral behaviours of long pulsar tails, the presence of puzzling outflows misaligned with the pulsar velocity and far-UV bow shocks. Here we review the current observational status focusing on recent developments and their implications.

  3. THE 'SPIROGRAPH' NEBULA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    THE 'SPIROGRAPH' NEBULA Glowing like a multi-faceted jewel, the planetary nebula IC 418 lies about 2,000 light-years from Earth in the direction of the constellation Lepus. This photograph is one of the latest from NASA's Hubble Space Telescope, obtained with the Wide Field Planetary Camera 2. A planetary nebula represents the final stage in the evolution of a star similar to our Sun. The star at the center of IC 418 was a red giant a few thousand years ago, but then ejected its outer layers into space to form the nebula, which has now expanded to a diameter of about 0.1 light-year. The stellar remnant at the center is the hot core of the red giant, from which ultraviolet radiation floods out into the surrounding gas, causing it to fluoresce. Over the next several thousand years, the nebula will gradually disperse into space, and then the star will cool and fade away for billions of years as a white dwarf. Our own Sun is expected to undergo a similar fate, but fortunately this will not occur until some 5 billion years from now. The Hubble image of IC 418 is shown in a false-color representation, based on Wide Field Planetary Camera 2 exposures taken in February and September, 1999 through filters that isolate light from various chemical elements. Red shows emission from ionized nitrogen (the coolest gas in the nebula, located furthest from the hot nucleus), green shows emission from hydrogen, and blue traces the emission from ionized oxygen (the hottest gas, closest to the central star). The remarkable textures seen in the nebula are newly revealed by the Hubble telescope, and their origin is still uncertain. Credit: NASA and The Hubble Heritage Team (STScI/AURA) Acknowledgment: Dr. Raghvendra Sahai (JPL) and Dr. Arsen R. Hajian (USNO). EDITOR'S NOTE: For additional information, please contact Dr. Raghvendra Sahai, Jet Propulsion Laboratory, MS 183-900, 4800 Oak Grove Drive, Pasadena, CA 91109, (phone) 818-354-0452, (fax) 818-393-9088, (e-mail) sahai@bb8.jpl

  4. Circumstantial Starbirth in Starbursts: Systematic Variations in the Stellar and Nebular Content of Giant HII Regions in the Local Group Galaxy M33

    NASA Astrophysics Data System (ADS)

    Waller, W. H.; Murphy, E. J.; Gherz, R. D.; Polomski, E.; Woodward, C. E.; Fazio, G. G.; Rieke, G. H.; Spitzer/M33 Research Team

    2005-12-01

    From the Orion Nebula to the Hubble Deep Field, starburst activity can be seen transforming galaxian clouds of gas into populous clusters of stars. The pyrotechnics and chemical enrichment associated with this activity have led to outcomes as ubiquitous as interstellar dust and as exquisite as life on Earth. In this talk, I will focus on the circumstances of star formation in the environmental context of ongoing starburst activity. I begin with the premises that (1) the formation of a single star takes time, (2) the formation of a populous cluster takes even more time, and (3) ''stuff'' happens in the interim. Hubble images of the Orion Nebula and Eagle Nebula show how hot stars can excavate neighboring clouds of gas and photoevaporate the star-forming cores that are exposed. Hubble observations of giant HII regions in M33 reveal a significant variation in the stellar populations, such that the most metal-rich HII regions contain the greatest proportions of the most massive stars. ISO and Spitzer observations of these same HII regions reveal corresponding variations in the nebular content. These multi-wavelength diagnostics of the stellar-nebular feedback in galaxian starbursts suggest a star-forming mechanism which is subject to photo-evaporative ablation -- an erosive process that is systematically mediated by the metal abundance and corresponding amounts of protective dust in the starbursting environment.

  5. Multispectral Observations and Analysis of the Rosette Nebula

    NASA Astrophysics Data System (ADS)

    Huber, Jeremy

    The Rosette nebula is a large, ring-shaped emission nebula with a distinctive central cavity excavated by its central cluster of OB stars. Toward understanding the three dimensional structure and fundamental physical processes of this object, we have acquired ux-calibrated, 4-degree field, deep exposures of the Rosette region through 3 nm bandwidth Halpha (656.3 nm) as well as Hbeta (486.1nm), [OIII] (500.7 nm) and [SII] (671.6 nm) filters with 4.5 nm bandwidth. The 4 arcsec/pixel images are supplemented with 4 degree field slit spectra and combined with archival data from the Galactic Evolution Explorer satellite (GALEX), Akari, the Infrared Astronomical Satellite (IRAS), the Midcourse Space Experiment (MSX), the Wide-field Infrared Survey Explorer (WISE), the Wilkinson Microwave Anisotropy Probe (WMAP) and the Planck mission, along with published single dish radio data of the hydrogen continuum at 1410, 2700, and 4750 MHz. These disparate sources have been converted to the same flux and spatial scale as our own wide field data to create a multispectral data cube which allows comparative analysis across the electromagnetic spectrum. Using ratios of data cube slices, spatial maps of extinction and ionization have been constructed to explore the spatial variation of these parameters across the nebula. Comparison of emission in different wavelengths across the data cube allows generation of a spectral energy distribution (SED) to probe dust temperature and geometry. A radial profile analysis of emission from the Rosette in each band supports a spherical shell model of three dimensional structure, and visual representations of this model have been generated in both Python and Javascript/GLSL. An investigation of anomalous dust emission in the center of the nebula via supplemental spectroscopy, conducted on the Anglo-Australian Telescope, is also presented.

  6. Functional (dissociative) retrograde amnesia.

    PubMed

    Markowitsch, H J; Staniloiu, A

    2016-01-01

    Retrograde amnesia is described as condition which can occur after direct brain damage, but which occurs more frequently as a result of a psychiatric illness. In order to understand the amnesic condition, content-based divisions of memory are defined. The measurement of retrograde memory is discussed and the dichotomy between "organic" and "psychogenic" retrograde amnesia is questioned. Briefly, brain damage-related etiologies of retrograde amnesia are mentioned. The major portion of the review is devoted to dissociative amnesia (also named psychogenic or functional amnesia) and to the discussion of an overlap between psychogenic and "brain organic" forms of amnesia. The "inability of access hypothesis" is proposed to account for most of both the organic and psychogenic (dissociative) patients with primarily retrograde amnesia. Questions such as why recovery from retrograde amnesia can occur in retrograde (dissociative) amnesia, and why long-term new learning of episodic-autobiographic episodes is possible, are addressed. It is concluded that research on retrograde amnesia research is still in its infancy, as the neural correlates of memory storage are still unknown. It is argued that the recollection of episodic-autobiographic episodes most likely involves frontotemporal regions of the right hemisphere, a region which appears to be hypometabolic in patients with dissociative amnesia. © 2016 Elsevier B.V. All rights reserved.

  7. Spatial variation of the cooling lines in the reflection nebula NGC 7023

    NASA Astrophysics Data System (ADS)

    Bernard-Salas, J.; Habart, E.; Köhler, M.; Abergel, A.; Arab, H.; Lebouteiller, V.; Pinto, C.; van der Wiel, M. H. D.; White, G. J.; Hoffmann, M.

    2015-02-01

    Context. The north-west photo-dissociation region (PDR) in the reflection nebula NGC 7023 displays a complex structure. Filament-like condensations at the edge of the cloud can be traced via the emission of the main cooling lines, offering a great opportunity to study the link between the morphology and energetics of these regions. Aims: We study the spatial variation of the far-infrared fine-structure lines of [C ii] (158 μm) and [O i] (63 and 145 μm). These lines trace the local gas conditions across the PDR. We also compare their emission with molecular tracers including rotational and ro-vibrational lines of H2 and high-rotational lines of CO. Methods: We used observations from the Herschel/PACS instrument to map the spatial distribution of these fine-structure lines. The observed region covers a square area of about 110″ × 110″ with an angular resolution that varies from 4'' to 11''. We compared this emission with ground-based and Spitzer observations of H2 lines, Herschel/SPIRE observations of CO lines, and Spitzer/IRAC 3.6 μm images that trace the emission of polycyclic aromatic hydrocarbons. We used a PDR code to model the [O i]145 μm line and infer the physical conditions in the region. Results: The [C ii] (158 μm) and [O i] (63 and 145 μm) lines arise from the warm cloud surface where the PDR is located and the gas is warm, cooling the region. We find that although the relative contribution to the cooling budget over the observed region is dominated by [O i]63 μm (>30%), H2 contributes significantly in the PDR (~35%), as does [C ii]158 μm outside the PDR (30%). Other species contribute little to the cooling ([O i]145 μm 9%, and CO 4%). Enhanced emission of these far-infrared atomic lines trace the presence of condensations, where high-excitation CO rotational lines and dust emission in the submillimetre are detected as well. The [O i] maps resolve these condensations into two structures and show that the peak of [O i] is slightly displaced

  8. Horsehead Nebula

    NASA Image and Video Library

    1999-12-01

    Rising from a sea of dust and gas like a giant seahorse, the Horsehead nebula is one of the most photographed objects in the sky. NASA Hubble Space Telescope took a close-up look at this heavenly icon, revealing the cloud intricate structure.

  9. Hydroxyl Emission in the Westbrook Nebula

    NASA Astrophysics Data System (ADS)

    Strack, Angelica; Araya, Esteban; Ghosh, Tapasi; Arce, Hector G.; Lebron, Mayra E.; Salter, Christopher J.; Minchin, Robert F.; Pihlstrom, Ylva; Kurtz, Stan; Hofner, Peter; Olmi, Luca

    2016-06-01

    CRL 618, also known as the Westbrook Nebula, is a carbon-rich pre-planetary nebula. Hydroxyl (OH) transitions are typically not detected in carbon-rich late-type stellar objects, however observations conducted with the 305m Arecibo Telescope in 2008 resulted in the detection of 4765 MHz OH emission in CRL 618. We present results of observations carried out a few months after the original detection that confirm the line. This is the first detection of 4765 MHz OH emission (most likely a maser) in a pre-planetary nebula. Follow up observations conducted in 2015 resulted in non-detection of the 4765 MHz OH transition. This behavior is consistent with the high level of variability of excited OH lines that have been detected toward a handful of other pre-planetary nebulae. Our work supports that excited OH masers are short-lived during the pre-planetary nebula phase. We also conducted a search for other OH transitions from 1612 MHz to 8611 MHz with the Arecibo Telescope; we report no other detections at rms levels of ~5 mJy.This work has made use of the computational facilities donated by Frank Rodeffer to the WIU Astrophysics Research Laboratory. We also acknowledge support from M. & C. Wong RISE scholarships and a grant from the WIU College of Arts and Sciences.

  10. Organic photovoltaics: elucidating the ultra-fast exciton dissociation mechanism in disordered materials.

    PubMed

    Heitzer, Henry M; Savoie, Brett M; Marks, Tobin J; Ratner, Mark A

    2014-07-14

    Organic photovoltaics (OPVs) offer the opportunity for cheap, lightweight and mass-producible devices. However, an incomplete understanding of the charge generation process, in particular the timescale of dynamics and role of exciton diffusion, has slowed further progress in the field. We report a new Kinetic Monte Carlo model for the exciton dissociation mechanism in OPVs that addresses the origin of ultra-fast (<1 ps) dissociation by incorporating exciton delocalization. The model reproduces experimental results, such as the diminished rapid dissociation with increasing domain size, and also lends insight into the interplay between mixed domains, domain geometry, and exciton delocalization. Additionally, the model addresses the recent dispute on the origin of ultra-fast exciton dissociation by comparing the effects of exciton delocalization and impure domains on the photo-dynamics.This model provides insight into exciton dynamics that can advance our understanding of OPV structure-function relationships. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. OVERTURNING THE CASE FOR GRAVITATIONAL POWERING IN THE PROTOTYPICAL COOLING LYα NEBULA

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

    Prescott, Moire K. M.; Fynbo, Johan P. U.; Momcheva, Ivelina

    The Nilsson et al. Lyα nebula has often been cited as the most plausible example of an Lyα nebula powered by gravitational cooling. In this paper, we bring together new data from the Hubble Space Telescope and the Herschel Space Observatory as well as comparisons to recent theoretical simulations in order to revisit the questions of the local environment and most likely power source for the Lyα nebula. In contrast to previous results, we find that this Lyα nebula is associated with six nearby galaxies and an obscured AGN that is offset by ∼4″ ≈ 30 kpc from the Lyαmore » peak. The local region is overdense relative to the field, by a factor of ∼10, and at low surface brightness levels the Lyα emission appears to encircle the position of the obscured AGN, highly suggestive of a physical association. At the same time, we confirm that there is no compact continuum source located within ∼2–3″ ≈ 15–23 kpc of the Lyα peak. Since the latest cold accretion simulations predict that the brightest Lyα emission will be coincident with a central growing galaxy, we conclude that this is actually a strong argument against, rather than for, the idea that the nebula is gravitationally powered. While we may be seeing gas within cosmic filaments, this gas is primarily being lit up, not by gravitational energy, but due to illumination from a nearby buried AGN.« less

  12. DIFFERENTIAL PROPER-MOTION MEASUREMENTS OF THE CYGNUS EGG NEBULA: THE PRESENCE OF EQUATORIAL OUTFLOWS

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

    Ueta, Toshiya; Tomasino, Rachael L.; Ferguson, Brian A.

    2013-08-01

    We present the results of differential proper-motion analyses of the Egg Nebula (RAFGL 2688, V1610 Cyg) based on the archived two-epoch optical data taken with the Hubble Space Telescope. First, we determined that the polarization characteristics of the Egg Nebula are influenced by the higher optical depth of the central regions of the nebula (i.e., the 'dustsphere' of {approx}10{sup 3} AU radius), causing the nebula to illuminate in two steps-the direct starlight is first channeled into bipolar cavities and then scattered off to the rest of the nebula. We then measured the amount of motion of local structures and themore » signature concentric arcs by determining their relative shifts over the 7.25 yr interval. Based on our analysis, which does not rely on the single-scattering assumption, we concluded that the lobes have been excavated by a linear expansion along the bipolar axis for the past {approx}400 yr, while the concentric arcs have been generated continuously and moving out radially at about 10 km s{sup -1} for the past {approx}5500 yr, and there appears to be a colatitudinally increasing trend in the radial expansion velocity field of the concentric arcs. Numerical investigations into the mass-loss modulation by the central binary system exist, which predict such a colatitudinally increasing expansion velocity field in the spiral-shock trails of the mass-loss ejecta. Therefore, the Egg Nebula may represent a rare edge-on case of the binary-modulated circumstellar environs, corroborating the previous theoretical predictions.« less

  13. Ultraviolet spectra of planetary nebulae. X - Physical conditions in the compact planetary nebula Sw St 1

    NASA Technical Reports Server (NTRS)

    Flower, D. R.; Goharji, A.; Cohen, M.

    1984-01-01

    Photoelectric visual and ultraviolet observations of the compact planetary nebula Sw St 1 are analyzed. The electron density, determined from the C III 1907/1909 A line ratio, is N(e) = (1.1 + or - 0.1) x 10 to the 5th/cu cm, consistent with the high emission measure and high critical frequency determined from observations of the thermal radio emission. The C/O abundance ratio in the nebula is found to be N(C)/N(O) = 0.72 + or - 0.1, i.e. the envelope is oxygen-rich, as suggested by the identification of the silicate feature in the 8-13 micron infrared spectrum. Difficulties remain in accurately determining the reddening constant to the nebula and its electron temperature.

  14. A morpho-kinematic and spectroscopic study of the bipolar nebulae: M 2-9, Mz 3, and Hen 2-104

    NASA Astrophysics Data System (ADS)

    Clyne, N.; Akras, S.; Steffen, W.; Redman, M. P.; Gonçalves, D. R.; Harvey, E.

    2015-10-01

    Context. Complex bipolar shapes can be generated either as a planetary nebula or a symbiotic system. The origin of the material ionised by the white dwarf is very different in these two scenarios, and it complicates the understanding of the morphologies of planetary nebulae. Aims: The physical properties, structure, and dynamics of the bipolar nebulae, M 2-9, Mz 3, and Hen 2-104, are investigated in detail with the aim of understanding their nature, shaping mechanisms, and evolutionary history. Both a morpho-kinematic study and a spectroscopic analysis, can be used to more accurately determine the kinematics and nature of each nebula. Methods: Long-slit optical echelle spectra are used to investigate the morpho-kinematics of M 2-9, Mz 3, and Hen 2-104. The morpho-kinematic modelling software SHAPE is used to constrain both the morphology and kinematics of each nebula by means of detailed 3D models. Near-infrared (NIR) data, as well as optical, spectra are used to separate Galactic symbiotic-type nebulae from genuine planetary nebulae by means of a 2MASS J-H/H-Ks diagram and a λ4363/Hγ vs. λ5007/Hβ diagnostic diagram, respectively. Results: The best-fitted 3D models for M 2-9, Mz 3, and Hen 2-104 provide invaluable kinematical information on the expansion velocity of its nebular components by means of synthetic spectra. The observed spectra match up very well with the synthetic spectra for each model, thus showing that each model is tightly constrained both morphologically and kinematically. Kinematical ages of the different structures of M 2-9 and Mz 3 have also been determined. Both diagnostic diagrams show M 2-9 and Hen 2-104 to fall well within the category of having a symbiotic source, whereas Mz 3 borders the region of symbiotic and young planetary nebulae in the optical diagram but is located firmly in the symbiotic region of the NIR colour-colour diagram. The optical diagnostic diagram is shown to successfully separate the two types of nebulae, however

  15. Into the Depths of the Lagoon Nebula

    NASA Image and Video Library

    2011-09-16

    Swirling dust clouds and bright newborn stars dominate the view in this image of the Lagoon nebula from NASA Spitzer Space Telescope. The nebula lies in the general direction of the center of our galaxy in the constellation Sagittarius.

  16. A Broad 22 Micron Emission Feature in the Carina Nebula H ii Region.

    PubMed

    Chan; Onaka

    2000-04-10

    We report the detection of a broad 22 µm emission feature in the Carina Nebula H ii region by the Infrared Space Observatory (ISO) short-wavelength spectrometer. The feature shape is similar to that of the 22 µm emission feature of newly synthesized dust observed in the Cassiopeia A supernova remnant. This finding suggests that both of the features are arising from the same carrier and that supernovae are probably the dominant production sources of this new interstellar grain. A similar broad emission dust feature is also found in the spectra of two starburst galaxies from the ISO archival data. This new dust grain could be an abundant component of interstellar grains and can be used to trace the supernova rate or star formation rate in external galaxies. The existence of the broad 22 µm emission feature complicates the dust model for starburst galaxies and must be taken into account correctly in the derivation of dust color temperature. Mg protosilicate has been suggested as the carrier of the 22 µm emission dust feature observed in Cassiopeia A. The present results provide useful information in studies on the chemical composition and emission mechanism of the carrier.

  17. Direct measurement of exciton dissociation energy in polymers

    NASA Astrophysics Data System (ADS)

    Toušek, J.; Toušková, J.; Chomutová, R.; Paruzel, B.; Pfleger, J.

    2017-01-01

    Exciton dissociation energy was obtained based on the comparison of thickness of the space charge region estimated from the measurement of capacitance of prepared Schottky diode and from the measurement of photovoltage spectra. While the capacitance measurements provide information about the total width of the space charge region (SCR) the surface photovoltaic effect brings information only about the part of the SCR where electric field is sufficiently high to cause dissociation. For determination of the dissociation energy it is sufficient to find the electric potential in the SCR where the process starts.

  18. HUBBLE FINDS AN HOURGLASS NEBULA AROUND A DYING STAR

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is an image of MyCn18, a young planetary nebula located about 8,000 light-years away, taken with the Wide Field and Planetary Camera 2 (WFPC2) aboard NASA's Hubble Space Telescope (HST). This Hubble image reveals the true shape of MyCn18 to be an hourglass with an intricate pattern of 'etchings' in its walls. This picture has been composed from three separate images taken in the light of ionized nitrogen (represented by red), hydrogen (green), and doubly-ionized oxygen (blue). The results are of great interest because they shed new light on the poorly understood ejection of stellar matter which accompanies the slow death of Sun-like stars. In previous ground-based images, MyCn18 appears to be a pair of large outer rings with a smaller central one, but the fine details cannot be seen. According to one theory for the formation of planetary nebulae, the hourglass shape is produced by the expansion of a fast stellar wind within a slowly expanding cloud which is more dense near its equator than near its poles. What appears as a bright elliptical ring in the center, and at first sight might be mistaken for an equatorially dense region, is seen on closer inspection to be a potato shaped structure with a symmetry axis dramatically different from that of the larger hourglass. The hot star which has been thought to eject and illuminate the nebula, and therefore expected to lie at its center of symmetry, is clearly off center. Hence MyCn18, as revealed by Hubble, does not fulfill some crucial theoretical expectations. Hubble has also revealed other features in MyCn18 which are completely new and unexpected. For example, there is a pair of intersecting elliptical rings in the central region which appear to be the rims of a smaller hourglass. There are the intricate patterns of the etchings on the hourglass walls. The arc-like etchings could be the remnants of discrete shells ejected from the star when it was younger (e.g. as seen in the Egg Nebula), flow instabilities, or

  19. EXTERNAL PHOTOEVAPORATION OF THE SOLAR NEBULA: JUPITER's NOBLE GAS ENRICHMENTS

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

    Monga, Nikhil; Desch, Steven

    We present a model explaining the elemental enrichments in Jupiter's atmosphere, particularly the noble gases Ar, Kr, and Xe. While He, Ne, and O are depleted, seven other elements show similar enrichments (∼3 times solar, relative to H). Being volatile, Ar is difficult to fractionate from H{sub 2}. We argue that external photoevaporation by far-ultraviolet (FUV) radiation from nearby massive stars removed H{sub 2}, He, and Ne from the solar nebula, but Ar and other species were retained because photoevaporation occurred at large heliocentric distances where temperatures were cold enough (≲ 30 K) to trap them in amorphous water ice. Asmore » the solar nebula lost H, it became relatively and uniformly enriched in other species. Our model improves on the similar model of Guillot and Hueso. We recognize that cold temperatures alone do not trap volatiles; continuous water vapor production is also necessary. We demonstrate that FUV fluxes that photoevaporated the disk generated sufficient water vapor in regions ≲ 30 K to trap gas-phase species in amorphous water ice in solar proportions. We find more efficient chemical fractionation in the outer disk: whereas the model of Guillot and Hueso predicts a factor of three enrichment when only <2% of the disk mass remains, we find the same enrichments when 30% of the disk mass remains. Finally, we predict the presence of ∼0.1 M {sub ⊕} of water vapor in the outer solar nebula and protoplanetary disks in H II regions.« less

  20. An Introduction to Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Nishiyama, Jason J.

    2018-05-01

    In this book we will look at what planetary nebulae are, where they come from and where they go. We will discuss what mechanisms cause these beautiful markers of stellar demise as well as what causes them to form their variety of shapes. How we measure various aspects of planetary nebulae such as what they are made of will also be explored. Though we will give some aspects of planetary nebulae mathematical treatment, the main points should be accessible to people with only a limited background in mathematics. A short glossary of some of the more arcane astronomical terms is at the end of the book to help in understanding. Included at the end of each chapter is an extensive bibliography to the peer reviewed research on these objects and I would encourage the reader interested in an even deeper understanding to read these articles.

  1. The Making of a Pre-Planetary Nebula

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-07-01

    The gas expelled by dying stars gets twisted into intricate shapes and patterns as nebulae form. Now a team of researchers might have some answers about how this happens.Whats a Pre-Planetary Nebula?This H-R diagram for the globular cluster M5 shows where AGB stars lie: they are represented by blue markers here. The AGB is one of the final stages in a low- to intermediate-mass stars lifetime. [Lithopsian]When a low- to intermediate-mass star approaches the end of its lifetime, it moves onto the Asymptotic Giant Branch (AGB) in the Herzsprung-Russell diagram. As the star exhausts its fuel here, it shrugs off its outer layers. These layers of gas then encase the stars core, which is not yet hot enough to ionize the gas and cause it to glow.Instead, during this time the gas is relatively cool and dark, faintly reflecting light from the star and emitting only very dim infrared emission of its own. At this stage, the gas represents a pre-planetary nebula. Only later when the stellar core contracts enough to heat up and emit ionizing radiation does the nebula begin to properly glow, at which point it qualifies as a full planetary nebula.Images of OH231 in optical light (top) and 12CO (bottom) taken from the literature. [See Balick et al. 2017 for full credit]Unexpected ShapesPre-planetary nebulae are a very short-lived evolutionary stage, so weve observed only a few hundred of them which has left many unanswered questions about these objects.One particular mystery is that of their shapes: if these nebulae are formed by stars expelling their outer layers, we would naively expect them to be simple spherical shells and yet we observe pre-planetary nebulae to have intricate shapes and patterns. How does the star create these asymmetric shapes? A team of scientists led by Bruce Balick (University of Washington, Seattle) has now used simulations to address this question.Injecting MassBalick and collaborators use 3D hydrodynamic simulations to model one particular pre

  2. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, Charles G. [Pleasanton, CA

    1978-08-29

    A method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, .sup.235 UF.sub.6 is separated from a UF.sub.6 mixture by selective excitation followed by dissociative electron capture into .sup.235 UF.sub.5 - and F.

  3. Is the dissociation of coronene in stellar winds a source of molecular hydrogen? application to the HD 44179 nebula

    NASA Astrophysics Data System (ADS)

    Champeaux, J.-P.; Moretto-Capelle, P.; Cafarelli, P.; Deville, C.; Sence, M.; Casta, R.

    2014-06-01

    The physical interactions of polycyclic aromatic hydrocarbons (PAHs) with stellar particular radiation are key to understanding the life cycle of PAHs, their abundance and their role in the complex astrochemistry of the interstellar medium. In this context, we present experimental results on the ionization/fragmentation of isolated coronene by a 100-keV proton, reproducing interactions between stellar winds and PAH molecules in the star's environment. In particular, we show, without ambiguity, that such ionization/fragmentation induces intense dehydrogenation processes for which the loss of even numbers of hydrogen atoms and the detection of CH_2+ cations as a possible H2 precursor strongly suggest the formation of H2 neutral molecules along a scenario revealed by a quantum chemical calculation. We have evaluated the H2 emission cross-section from the coronene/proton interaction at 100 and 1.6 keV to be 2.97 × 10-16 and 3.3 × 10-16 cm2, respectively. A qualitative discussion on the formation rate of H2 in the HD 44179 Red Rectangle (RR) nebula leads to the conclusion that such processes could be very efficient, especially inside planetary nebulae rich in PAH molecules interacting with high proton mass-loss rate stars (such as post-asymptotic giant branch stars) or high velocity jets produced by an accretion disc.

  4. Hubble Space Telescope observations of Orion Nebula, Helix Nebula, and NGC 6822

    NASA Technical Reports Server (NTRS)

    Spitzer, Lyman; Fitzpatrick, Ed

    1999-01-01

    This grant covered the major part of the work of the Principal Investigator and his collaborators as a Guaranteed Time Observer on the Hubble Space Telescope. The work done naturally divided itself into two portions the first being study of nebular objects and the second investigation of the interstellar medium between stars. The latter investigation was pursued through a contract with Princeton University, with Professor Lyman Spitzer as the supervising astronomer, assisted by Dr. Ed Fitzpatrick. Following the abrupt death of Professor Spitzer, his responsibilities were shifted to Dr. Fitzpatrick. When Dr. Fitzpatrick relocated to Villanova University the concluding work on that portion of this grant was concluded under a direct service arrangement. This program has been highly successful and the resulting publications in scientific journals are listed below. To the scientist, this is the bottom line, so that I shall simply try to describe the general nature of what was accomplished. There were three nebular programs conducted, one on the Orion Nebula, the second on the Helix Nebula, and the third on NGC 6822. The largest program was that on the Orion Nebula. This involved both HST observations and supporting groundbased observations obtained with a variety of instruments, including the Coude Feed Telescope at the Kitt Peak National observatory in Arizona, the Cerro Tololo observatory in Chile, and the Keck Observatory on Mauna Kea, Hawaii. Moreover, considerable theoretical modeling was done and all of the data analysis was performed at the Rice University in Houston, except for the PI's period of sabbatical leave (6-96 through 7-97) when he was based at the Max Planck Institute for Astronomy in Heidelberg, Germany. The Orion Nebula program was the most productive part, resulting in numerous papers, but more important in the discovery of a new class of objects, for which we coined the name "proplyds". The proplyds are protoplanetary disks surrounding very young

  5. Near infrared photography with a vacuum-cold camera. [Orion nebula observation

    NASA Technical Reports Server (NTRS)

    Rossano, G. S.; Russell, R. W.; Cornett, R. H.

    1980-01-01

    Sensitized cooled plates have been obtained of the Orion nebula region and of Sh2-149 in the wavelength ranges 8000 A-9000 A and 9,000 A-11,000 A with a recently designed and constructed vacuum-cold camera. Sensitization procedures are described and the camera design is presented.

  6. Monitoring the Crab Nebula with LOFT

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.

    2012-01-01

    From 2008-2010, the Crab Nebula was found to decline by 7% in the 15-50 keV band, consistently in Fermi GBM, INTEGRAL IBIS, SPI, and JEMX, RXTE PCA, and Swift BAT. From 2001-2010, the 15-50 keV flux from the Crab Nebula typically varied by about 3.5% per year. Analysis of RXTE PCA data suggests possible spectral variations correlated with the flux variations. I will present estimates of the LOFT sensitivity to these variations. Prior to 2001 and since 2010, the observed flux variations have been much smaller. Monitoring the Crab with the LOFT WFM and LAD will provide precise measurements of flux variations in the Crab Nebula if it undergoes a similarly active episode.

  7. The carbon budget in the outer solar nebula

    NASA Technical Reports Server (NTRS)

    Simonelli, Damon P.; Pollack, James B.; Mckay, Christopher P.; Reynolds, Ray T.; Summers, Audrey L.

    1989-01-01

    The compositional contrast between the giant-planet satellites and the significantly rockier Pluto/Charon system is indicative of different formation mechanisms; cosmic abundance calculations, in conjunction with an assumption of the Pluto/Charon system's direct formation from solar nebula condensates, strongly suggest that most of the carbon in the outer solar nebula was in CO form, in keeping with both the inheritance from the dense molecular clouds in the interstellar medium, and/or the Lewis and Prinn (1980) kinetic-inhibition model of solar nebula chemistry. Laboratory studies of carbonaceous chondrites and Comet Halley flyby studies suggest that condensed organic material, rather than elemental carbon, is the most likely candidate for the small percentage of the carbon-bearing solid in the outer solar nebula.

  8. NIF Discovery Science Eagle Nebula

    NASA Astrophysics Data System (ADS)

    Kane, Jave; Martinez, David; Pound, Marc; Heeter, Robert; Casner, Alexis; Villette, Bruno; Mancini, Roberto

    2017-10-01

    The University of Maryland and and LLNL are investigating the origin and dynamics of the famous Pillars of the Eagle Nebula and similar parsec-scale structures at the boundaries of HII regions in molecular hydrogen clouds. The National Ignition Facility (NIF) Discovery Science program Eagle Nebula has performed NIF shots to study models of pillar formation. The shots feature a new long-duration x-ray source, in which multiple hohlraums mimicking a cluster of stars are driven with UV light in series for 10 to 15 ns each to create a 30 to 60 ns output x-ray pulse. The source generates deeply nonlinear hydrodynamics in the Eagle science package, a structure of dense plastic and foam mocking up a molecular cloud containing a dense core. Omega EP and NIF shots have validated the source concept, showing that earlier hohlraums do not compromise later ones by preheat or by ejecting ablated plumes that deflect later beams. The NIF shots generated radiographs of shadowing-model pillars, and also showed evidence that cometary structures can be generated. The velocity and column density profiles of the NIF shadowing and cometary pillars have been compared with observations of the Eagle Pillars made at the millimeter-wave BIMA and CARMA observatories. Prepared by LLNL under Contract DE-AC52-07NA27344.

  9. Interlocked Photo-degradable Macrocycles Allow One-Off Photo-triggerable Gelation of Organo- and Hydrogelators.

    PubMed

    Tung, Shun-Te; Cheng, Hung-Te; Inthasot, Alex; Hsueh, Fang-Che; Gu, Ting-Jia; Yan, Pei-Cong; Lai, Chien-Chen; Chiu, Sheng-Hsien

    2018-02-01

    [2]Rotaxanes displaying one-off photo-triggerable gelation properties have been synthesized through the "clipping" of photo-degradable macrocycles around the amide or urea functionalities of organo- and hydrogelators. Irradiation with UV-light cleaved the photo-labile macrocyclic components from the [2]rotaxanes, resulting in the free gelators being released into solution and, thereafter, forming gels. When the rate of gelation was sufficiently rapid, selective gelation of specific regions of the solution-and, indeed, photo-patterning of the solution-was possible. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. CO self-shielding as the origin of oxygen isotope anomalies in the early solar nebula.

    PubMed

    Lyons, J R; Young, E D

    2005-05-19

    The abundances of oxygen isotopes in the most refractory mineral phases (calcium-aluminium-rich inclusions, CAIs) in meteorites have hitherto defied explanation. Most processes fractionate isotopes by nuclear mass; that is, 18O is twice as fractionated as 17O, relative to 16O. In CAIs 17O and 18O are nearly equally fractionated, implying a fundamentally different mechanism. The CAI data were originally interpreted as evidence for supernova input of pure 16O into the solar nebula, but the lack of a similar isotope trend in other elements argues against this explanation. A symmetry-dependent fractionation mechanism may have occurred in the inner solar nebula, but experimental evidence is lacking. Isotope-selective photodissociation of CO in the innermost solar nebula might explain the CAI data, but the high temperatures in this region would have rapidly erased the signature. Here we report time-dependent calculations of CO photodissociation in the cooler surface region of a turbulent nebula. If the surface were irradiated by a far-ultraviolet flux approximately 10(3) times that of the local interstellar medium (for example, owing to an O or B star within approximately 1 pc of the protosun), then substantial fractionation of the oxygen isotopes was possible on a timescale of approximately 10(5) years. We predict that similarly irradiated protoplanetary disks will have H2O enriched in 17O and 18O by several tens of per cent relative to CO.

  11. Detection of a noble gas molecular ion, 36ArH+, in the Crab Nebula.

    PubMed

    Barlow, M J; Swinyard, B M; Owen, P J; Cernicharo, J; Gomez, H L; Ivison, R J; Krause, O; Lim, T L; Matsuura, M; Miller, S; Olofsson, G; Polehampton, E T

    2013-12-13

    Noble gas molecules have not hitherto been detected in space. From spectra obtained with the Herschel Space Observatory, we report the detection of emission in the 617.5- and 1234.6-gigahertz J = 1-0 and 2-1 rotational lines of (36)ArH(+) at several positions in the Crab Nebula, a supernova remnant known to contain both molecular hydrogen and regions of enhanced ionized argon emission. Argon-36 is believed to have originated from explosive nucleosynthesis in massive stars during core-collapse supernova events. Its detection in the Crab Nebula, the product of such a supernova event, confirms this expectation. The likely excitation mechanism for the observed (36)ArH(+) emission lines is electron collisions in partially ionized regions with electron densities of a few hundred per centimeter cubed.

  12. Cat's Eye Nebula

    NASA Image and Video Library

    2017-12-08

    The Cat's Eye Nebula, one of the first planetary nebulae discovered, also has one of the most complex forms known to this kind of nebula. Eleven rings, or shells, of gas make up the Cat's Eye. The full beauty of the Cat's Eye Nebula is revealed in this detailed view from NASA's Hubble Space Telescope. The image from Hubble's Advanced Camera for Surveys (ACS) shows a bull's eye pattern of eleven or even more concentric rings, or shells, around the Cat's Eye. Each 'ring' is actually the edge of a spherical bubble seen projected onto the sky -- that's why it appears bright along its outer edge. Observations suggest the star ejected its mass in a series of pulses at 1,500-year intervals. These convulsions created dust shells, each of which contain as much mass as all of the planets in our solar system combined (still only one percent of the Sun's mass). These concentric shells make a layered, onion-skin structure around the dying star. The view from Hubble is like seeing an onion cut in half, where each skin layer is discernible. The bull's-eye patterns seen around planetary nebulae come as a surprise to astronomers because they had no expectation that episodes of mass loss at the end of stellar lives would repeat every 1,500 years. Several explanations have been proposed, including cycles of magnetic activity somewhat similar to our own Sun's sunspot cycle, the action of companion stars orbiting around the dying star, and stellar pulsations. Another school of thought is that the material is ejected smoothly from the star, and the rings are created later on due to formation of waves in the outflowing material. Credit: NASA, ESA, HEIC, and The Hubble Heritage Team (STScI/AURA) Acknowledgment: R. Corradi (Isaac Newton Group of Telescopes, Spain) and Z. Tsvetanov (NASA) The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science

  13. Hubble Space Telescope images and follow-up spectroscopy of the Orion nebula

    NASA Technical Reports Server (NTRS)

    O'Dell, C. R.; Wen, Zheng; Hester, J. J.

    1991-01-01

    Recently published HST images of the Orion nebula reveal elephant-trunk structures, an apparent jet of material, and fine-scale structure in the Herbig-Haro object HH2, which is located at the base of an elephant trunk. High-resolution spectroscopy shows that the apparent jet is actually an ionization front seen edge-on. HH2 shows a complex structure in the several stages of ionization observed. There seem to be two velocity systems characterized by a bright central region and an accompanying shell-like emission. These two systems are most likely to be the result of a bow shock and corresponding Mach disk formed from the interaction of a collimated jet and the ambient gas of the nebula.

  14. Detection of C60 and C70 in a young planetary nebula.

    PubMed

    Cami, Jan; Bernard-Salas, Jeronimo; Peeters, Els; Malek, Sarah Elizabeth

    2010-09-03

    In recent decades, a number of molecules and diverse dust features have been identified by astronomical observations in various environments. Most of the dust that determines the physical and chemical characteristics of the interstellar medium is formed in the outflows of asymptotic giant branch stars and is further processed when these objects become planetary nebulae. We studied the environment of Tc 1, a peculiar planetary nebula whose infrared spectrum shows emission from cold and neutral C60 and C70. The two molecules amount to a few percent of the available cosmic carbon in this region. This finding indicates that if the conditions are right, fullerenes can and do form efficiently in space.

  15. Far-ultraviolet imagery of the Orion Nebula

    NASA Technical Reports Server (NTRS)

    Carruthers, G. R.; Opal, C. B.

    1977-01-01

    Two electrographic cameras carried on a sounding rocket have yielded useful-resolution far-ultraviolet (1000-2000 A) imagery of the Orion Nebula. The brightness distribution in the images is consistent with a primary source which is due to scattering of starlight by dust grains, although an emission-line contribution, particularly in the fainter outer regions, is not ruled out. The results are consistent with an albedo of the dust grains that is high in the far-ultraviolet and which increases toward shorter wavelengths below 1230 A.

  16. Absolute Single Photoionization Cross Sections of Se^3+ For the Determination of Elemental Abundances in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Esteves, David; Sterling, Nicholas; Aguilar, Alex; Kilcoyne, A. L. David; Phaneuf, Ronald; Bilodeau, Rene; Red, Eddie; McLaughlin, Brendan; Norrington, Patrick; Balance, Connor

    2009-05-01

    Numerical simulations show that derived elemental abundances in astrophysical nebulae can be uncertain by factors of two or more due to atomic data uncertainties alone, and of these uncertainties, absolute photoionization cross sections are the most important. Absolute single photoionization cross sections for Se^3+ ions have been measured from 42 eV to 56 eV at the ALS using the merged beams photo-ion technique. Theoretical photoionization cross section calculations were also performed for these ions using the state-of-the-art fully relativistic Dirac R-matrix code (DARC). The calculations show encouraging agreement with the experimental measurements.

  17. The effects of mass and metallicity upon planetary nebula formation

    NASA Astrophysics Data System (ADS)

    Papp, K. A.; Purton, C. R.; Kwok, S.

    1983-05-01

    A parameterized function is constructed which describes the possible dependence of planetary nebula formation upon metal abundance and stellar mass. Data on galaxies in the Local Group compared with predictions made from the parameterized function indicate that heavy element abundance is the principal agent influencing the formation of planetary nebulae; stars which are rich in heavy elements are the progenitors of planetary nebulae. This analysis, when compared with the observations, argues for a modest degree of pre-enrichment in a few of the sample galaxies. The heavy element dependence of planetary nebula formation also accounts for the deficit of planetary nebulae in the nuclei of NGC 221 and NGC 224, and in the bulge of our Galaxy.

  18. Dusty globules in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Grenman, T.; Gahm, G. F.; Elfgren, E.

    2017-03-01

    Context. Dust grains are widespread in the Crab Nebula. A number of small, dusty globules, are visible as dark spots against the background of continuous synchrotron emission in optical images. Aims: Our aim is to catalogue such dusty globules and investigate their properties. Methods: From existing broad-band images obtained with the Hubble Space Telescope, we located 92 globules, for which we derived positions, dimensions, orientations, extinctions, masses, proper motions, and their distributions. Results: The globules have mean radii ranging from 400 to 2000 AU and are not resolved in current infrared images of the nebula. The extinction law for dust grains in these globules matches a normal interstellar extinction law. Derived masses of dust range from 1 to 60 × 10-6M⊙, and the total mass contained in globules constitute a fraction of approximately 2% or less of the total dust content of the nebula. The globules are spread over the outer part of the nebula, and a fraction of them coincide in position with emission filaments, where we find elongated globules that are aligned with these filaments. Only 10% of the globules are coincident in position with the numerous H2-emitting knots found in previous studies. All globules move outwards from the centre with transversal velocities of 60 to 1600 km s-1, along with the general expansion of the remnant. We discuss various hypotheses for the formation of globules in the Crab Nebula. Based on observations collected with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute.

  19. The appearance of the Gum nebula

    NASA Technical Reports Server (NTRS)

    Bok, B. J.

    1971-01-01

    The dimensions of the Gum nebula complex appear to be overestimated. The distance of 460 parsecs to the central pulsar is rather on the large side, and likely contributions from gamma Velorum and zeta Puppis were underestimated. The multiorigin character of the Gum nebula is reaffirmed. The parts produced by traditional ultraviolet thermal radiation and by processes directly related to the supernova outburst must be defined.

  20. The carbon budget in the outer solar nebula.

    PubMed

    Simonelli, D P; Pollack, J B; McKay, C P; Reynolds, R T; Summers, A L

    1989-01-01

    Detailed models of the internal structures of Pluto and Charon, assuming rock and water ice as the only constituents, indicate that the mean silicate mass fraction of this two-body system is on the order of 0.7; thus the Pluto/Charon system is significantly "rockier" than the satellites of the giant planets (silicate mass fraction approximately 0.55). This compositional contrast reflects different formation mechanisms: it is likely that Pluto and Charon formed directly from the solar nebula, while the circumplanetary nebulae that produced the giant planet satellites were derived from envelopes that surrounded the forming giant planets (envelopes in which icy planetesimals dissolved more readily than rocky planetesimals). Simple cosmic abundance calculations, and the assumption that the Pluto/Charon system formed directly from solar nebula condensates, strongly suggest that the majority of the carbon in the outer solar nebula was in the form of carbon monoxide; these results are consistent with (1) inheritance from the dense molecular clouds in the interstellar medium (where CH4/CO < 10(-2) in the gas phase) and/or (2) of the Lewis and Prinn kinetic inhibition model of solar nebula chemistry. Theoretical predictions of the C/H enhancements in the atmospheres of the giant planets, when compared to the actual observed enhancements, suggest that 10%, or slightly more, of the carbon in the outer solar nebula was in the form of condensed materials (although the amount of condensed C may have dropped slightly with increasing heliocentric distance). Strict compositional limits computed for the Pluto/Charon system using the densities of CH4 and CO ices indicate that these pure ices are at best minor components in the interiors of these bodies, and imply that CH4 and CO ices were not the dominant C-bearing solids in the outer nebula. Clathrate-hydrates could not have appropriated enough CH4 or CO to be the major form of condensed carbon, although such clathrates may be

  1. A Study of Planetary Nebulae using the Faint Object Infrared Camera for the SOFIA Telescope

    NASA Technical Reports Server (NTRS)

    Davis, Jessica

    2012-01-01

    A planetary nebula is formed following an intermediate-mass (1-8 solar M) star's evolution off of the main sequence; it undergoes a phase of mass loss whereby the stellar envelope is ejected and the core is converted into a white dwarf. Planetary nebulae often display complex morphologies such as waists or torii, rings, collimated jet-like outflows, and bipolar symmetry, but exactly how these features form is unclear. To study how the distribution of dust in the interstellar medium affects their morphology, we utilize the Faint Object InfraRed CAmera for the SOFIA Telescope (FORCAST) to obtain well-resolved images of four planetary nebulae--NGC 7027, NGC 6543, M2-9, and the Frosty Leo Nebula--at wavelengths where they radiate most of their energy. We retrieve mid infrared images at wavelengths ranging from 6.3 to 37.1 micron for each of our targets. IDL (Interactive Data Language) is used to perform basic analysis. We select M2-9 to investigate further; analyzing cross sections of the southern lobe reveals a slight limb brightening effect. Modeling the dust distribution within the lobes reveals that the thickness of the lobe walls is higher than anticipated, or rather than surrounding a vacuum surrounds a low density region of tenuous dust. Further analysis of this and other planetary nebulae is needed before drawing more specific conclusions.

  2. The 3-D ionization structure of the planetary nebula NGC 6565

    NASA Astrophysics Data System (ADS)

    Turatto, M.; Cappellaro, E.; Ragazzoni, R.; Benetti, S.; Sabbadin, F.

    2002-03-01

    A detailed study of the planetary nebula NGC 6565 has been carried out on long-slit echellograms (lambda /Delta lambda =60 000, spectral range = lambda lambda 3900-7750 Å) at six, equally spaced position angles. The expansion velocity field, the c(Hβ ) distribution and the radial profile of the physical conditions (electron temperature and density) are obtained. The distance, radius, mass and filling factor of the nebula and the temperature and luminosity of the central star are derived. The radial ionization structure is analyzed using both the classical method and the photo-ionization code CLOUDY. Moreover, we present the spatial structure in a series of images from different directions, allowing the reader to ``see'' the nebula in 3-D. NGC 6565 results to be a young (2000-2500 years), patchy, optically thick triaxial ellipsoid (a=10.1 arcsec, a/b=1.4, a/c=1.7) projected almost pole-on. The matter close to major axis was swept-up by some accelerating agent (fast wind? ionization? magnetic fields?), forming two faint and asymmetric polar cups. A large cocoon of almost neutral gas completely embeds the ionized nebula. NGC 6565 is in a recombination phase, because of the luminosity drop of the massive powering star, which is reaching the white dwarf domain (log T* =~ 5.08 K; log L*/Lsun =~ 2.0). The stellar decline started about 1000 years ago, but the main nebula remained optically thin for other 600 years before the recombination phase occurred. In the near future the ionization front will re-grow, since the dilution factor due to the expansion will prevail on the slower and slower stellar decline. NGC 6565 is at a distance of 2.0 (+/-0.5) kpc and can be divided into three radial zones: the ``fully ionized'' one, extending up to 0.029-0.035 pc at the equator (0.050 pc at the poles), the ``transition'' one, up to 0.048-0.054 pc (0.080 pc), the ``halo'', detectable up to 0.110 pc. The ionized mass ( =~ 0.03 Msun) is only a fraction of the total mass (>= 0.15 Msun

  3. Crab Nebula from Five Observatories

    NASA Image and Video Library

    2017-05-10

    In the summer of the year 1054 AD, Chinese astronomers saw a new "guest star," that appeared six times brighter than Venus. So bright in fact, it could be seen during the daytime for several months. This "guest star" was forgotten about until 700 years later with the advent of telescopes. Astronomers saw a tentacle-like nebula in the place of the vanished star and called it the Crab Nebula. Today we know it as the expanding gaseous remnant from a star that self-detonated as a supernova, briefly shining as brightly as 400 million suns. The explosion took place 6,500 light-years away. If the blast had instead happened 50 light-years away it would have irradiated Earth, wiping out most life forms. In the late 1960s astronomers discovered the crushed heart of the doomed star, an ultra-dense neutron star that is a dynamo of intense magnetic field and radiation energizing the nebula. Astronomers therefore need to study the Crab Nebula across a broad range of electromagnetic radiation, from X-rays to radio waves. This image combines data from five different telescopes: the VLA (radio) in red; Spitzer Space Telescope (infrared) in yellow; Hubble Space Telescope (visible) in green; XMM-Newton (ultraviolet) in blue; and Chandra X-ray Observatory (X-ray) in purple. More images and an animation are available at https://photojournal.jpl.nasa.gov/catalog/PIA21474

  4. Isotope separation by photoselective dissociative electron capture

    DOEpatents

    Stevens, C.G.

    1978-08-29

    Disclosed is a method of separating isotopes based on photoselective electron capture dissociation of molecules having an electron capture cross section dependence on the vibrational state of the molecule. A molecular isotope source material is irradiated to selectively excite those molecules containing a desired isotope to a predetermined vibrational state having associated therewith an electron capture energy region substantially non-overlapping with the electron capture energy ranges associated with the lowest vibration states of the molecules. The isotope source is also subjected to electrons having an energy corresponding to the non-overlapping electron capture region whereby the selectively excited molecules preferentially capture electrons and dissociate into negative ions and neutrals. The desired isotope may be in the negative ion product or in the neutral product depending upon the mechanism of dissociation of the particular isotope source used. The dissociation product enriched in the desired isotope is then separated from the reaction system by conventional means. Specifically, [sup 235]UF[sub 6] is separated from a UF[sub 6] mixture by selective excitation followed by dissociative electron capture into [sup 235]UF[sub 5]- and F. 2 figs.

  5. Hubble Images Searchlight Beams from a Preplanetary Nebula

    NASA Image and Video Library

    2017-12-08

    NASA image release April 27, 2012 The NASA/ESA Hubble Space Telescope has been at the cutting edge of research into what happens to stars like our sun at the ends of their lives. One stage that stars pass through as they run out of nuclear fuel is called the preplanetary or protoplanetary nebula stage. This Hubble image of the Egg Nebula shows one of the best views to date of this brief but dramatic phase in a star’s life. The preplanetary nebula phase is a short period in the cycle of stellar evolution, and has nothing to do with planets. Over a few thousand years, the hot remains of the aging star in the center of the nebula heat it up, excite the gas, and make it glow as a subsequent planetary nebula. The short lifespan of preplanetary nebulae means there are relatively few of them in existence at any one time. Moreover, they are very dim, requiring powerful telescopes to be seen. This combination of rarity and faintness means they were only discovered comparatively recently. The Egg Nebula, the first to be discovered, was first spotted less than 40 years ago, and many aspects of this class of object remain shrouded in mystery. At the center of this image, and hidden in a thick cloud of dust, is the nebula’s central star. While we can’t see the star directly, four searchlight beams of light coming from it shine out through the nebula. It is thought that ring-shaped holes in the thick cocoon of dust, carved by jets coming from the star, let the beams of light emerge through the otherwise opaque cloud. The precise mechanism by which stellar jets produce these holes is not known for certain, but one possible explanation is that a binary star system, rather than a single star, exists at the center of the nebula. The onion-like layered structure of the more diffuse cloud surrounding the central cocoon is caused by periodic bursts of material being ejected from the dying star. The bursts typically occur every few hundred years. The distance to the Egg Nebula is

  6. A Radio-Polarisation and Rotation Measure Study of the Gum Nebula and Its Environment

    NASA Astrophysics Data System (ADS)

    Purcell, C. R.; Gaensler, B. M.; Sun, X. H.; Carretti, E.; Bernardi, G.; Haverkorn, M.; Kesteven, M. J.; Poppi, S.; Schnitzeler, D. H. F. M.; Staveley-Smith, L.

    2015-05-01

    The Gum Nebula is 36°-wide shell-like emission nebula at a distance of only ˜450 pc. It has been hypothesized to be an old supernova remnant, fossil H ii region, wind-blown bubble, or combination of multiple objects. Here we investigate the magneto-ionic properties of the nebula using data from recent surveys: radio-continuum data from the NRAO VLA and S-band Parkes All Sky Surveys, and H α data from the Southern H-Alpha Sky Survey Atlas. We model the upper part of the nebula as a spherical shell of ionized gas expanding into the ambient medium. We perform a maximum-likelihood Markov chain Monte Carlo fit to the NVSS rotation measure data, using the H α data to constrain average electron density in the shell ne. Assuming a latitudinal background gradient in rotation measure, we find {{n}e}=1.3-0.4+0.4 c{{m}-3}, angular radius {{φ }outer}=22\\buildrel{\\circ}\\over{.} 7-0.1+0.1, shell thickness dr=18.5-1.4+1.5 pc, ambient magnetic field strength {{B}0}=3.9-2.2+4.9 μ G, and warm gas filling factor f=0.3-0.1+0.3. We constrain the local, small-scale (˜260 pc) pitch-angle of the ordered Galactic magnetic field to +7{}^\\circ ≲ \\wp ≲ +44{}^\\circ , which represents a significant deviation from the median field orientation on kiloparsec scales (˜-7.°2). The moderate compression factor X=6.0-2.5+5.1 at the edge of the H α shell implies that the “old supernova remnant” origin is unlikely. Our results support a model of the nebula as a H ii region around a wind-blown bubble. Analysis of depolarization in 2.3 GHz S-PASS data is consistent with this hypothesis and our best-fitting values agree well with previous studies of interstellar bubbles.

  7. Laser-induced dissociation processes of protonated glucose: dehydration reactions vs cross-ring dissociation

    NASA Astrophysics Data System (ADS)

    Dyakov, Y. A.; Kazaryan, M. A.; Golubkov, M. G.; Gubanova, D. P.; Bulychev, N. A.; Kazaryan, S. M.

    2018-04-01

    Studying the processes occurring in biological systems under irradiation is critically important for understanding the principles of working of biological systems. One of the main problems, which stimulate interest to the processes of photo-induced excitation and ionization of biomolecules, is the necessity of their identification by various mass spectrometry (MS) methods. While simple analysis of small molecules became a standard MS technique long time ago, recognition of large molecules, especially carbohydrates, is still a difficult problem, and requires sophisticated techniques and complicated computer analysis. Due to the large variety of substances in the samples, as far as the complexity of the processes occurring after excitation/ionization of the molecules, the recognition efficiency of MS technique in terms of carbohydrates is still not high enough. Additional theoretical and experimental analysis of ionization and dissociation processes in various kinds of polysaccharides, beginning from the simplest ones, is necessary. In our work, we extent previous theoretical and experimental studies of saccharides, and concentrate our attention to protonated glucose. In this article we paid the most attention to the cross-ring dissociation and water loss reactions due to their importance for identification of various isomers of hydrocarbon molecules (for example, distinguish α- and β-glucose).

  8. Planetary Nebulae and their parent stellar populations. Tracing the mass assembly of M87 and Intracluster light in the Virgo cluster core

    NASA Astrophysics Data System (ADS)

    Arnaboldi, Magda; Longobardi, Alessia; Gerhard, Ortwin

    2016-08-01

    The diffuse extended outer regions of galaxies are hard to study because they are faint, with typical surface brightness of 1% of the dark night sky. We can tackle this problem by using resolved star tracers which remain visible at large distances from the galaxy centers. This article describes the use of Planetary Nebulae as tracers and the calibration of their properties as indicators of the star formation history, mean age and metallicity of the parent stars in the Milky Way and Local Group galaxies. We then report on the results from a deep, extended, planetary nebulae survey in a 0.5 deg2 region centered on the brightest cluster galaxy NGC 4486 (M87) in the Virgo cluster core, carried out with SuprimeCam@Subaru and FLAMES-GIRAFFE@VLT. Two planetary nebulae populations are identified out to 150 kpc distance from the center of M87. One population is associated with the M87 halo and the second one with the intracluster light in the Virgo cluster core. They have different line-of-sight velocity and spatial distributions, as well as different planetary nebulae specific frequencies and luminosity functions. The intracluster planetary nebulae in the surveyed region correspond to a luminosity of four times the luminosity of the Large Magellanic Cloud. The M87 halo planetary nebulae trace an older, more metal-rich, parent stellar population. A substructure detected in the projected phase-space of the line-of-sight velocity vs. major axis distance for the M87 halo planetary nebulae provides evidence for the recent accretion event of a satellite galaxy with luminosity twice that of M33. The satellite stars were tidally stripped about 1 Gyr ago, and reached apocenter at a major axis distance of 60-90 kpc from the center of M87. The M87 halo is still growing significantly at the distances where the substructure is detected.

  9. Two different sources of water for the early solar nebula.

    PubMed

    Kupper, Stefan; Tornow, Carmen; Gast, Philipp

    2012-06-01

    Water is essential for life. This is a trivial fact but has profound implications since the forming of life on the early Earth required water. The sources of water and the related amount of delivery depend not only on the conditions on the early Earth itself but also on the evolutionary history of the solar system. Thus we ask where and when water formed in the solar nebula-the precursor of the solar system. In this paper we explore the chemical mechanics for water formation and its expected abundance. This is achieved by studying the parental cloud core of the solar nebula and its gravitational collapse. We have identified two different sources of water for the region of Earth's accretion. The first being the sublimation of the icy mantles of dust grains formed in the parental cloud. The second source is located in the inner region of the collapsing cloud core - the so-called hot corino with a temperature of several hundred Kelvin. There, water is produced efficiently in the gas phase by reactions between neutral molecules. Additionally, we analyse the dependence of the production of water on the initial abundance ratio between carbon and oxygen.

  10. Really Hot Stars

    NASA Astrophysics Data System (ADS)

    2003-04-01

    nebular emission. The reproduced brightness is proportional to the square-root of the actual intensity; this increases the "dynamical range" of the image, i.e. it shows better areas of very different brightness. PR Photo 09b/03 is a similar reproduction of the sky area with the nebula near the Wolf-Rayet (WR) star BAT99-2 in the LMC. The filters are the same, but the exposure times were 60, 5 and 5 min for the blue, green and red exposures, respectively. PR Photo 09c/03 shows, in the same way, the nebula around the hot double star BAT99-49 in the LMC. The filters are the same, but the exposure times were 45, 5 and 5 min for the blue, green and red exposures, respectively. Finally, PR Photo 09d/03 shows the N44C nebula in the LMC, photographed through the same optical filters with exposure times of 20, 5 and 5 min for the blue, green and red exposures, respectively. The sky field measures 208 x 208 arcsec2. The above collection of impressive VLT colour photos is unique. They show some of the highest excitation nebulae in the Magellanic Clouds (MCs), two satellite galaxies of our own Milky Way. They may be enjoyed for their beauty alone. However, each of them also carries a message about the depicted objects, their properties and evolutionary state. In fact, they represent the spectacular and visible result of a dedicated research programme begun by an international team of astronomers from Belgium and the United States of America [1], and aimed at unravelling the secrets of unsually hot nebulae. What makes them shine? From where come the enormous energies needed to make these nebulae glow in the light of ionized helium atoms? Emission nebulae Nebulae are huge clouds of gas and dust, the cosmic material from which stars and planets form, cf. the Appendix. Many of them emit their own light, and are then called emission nebulae. Astronomers distinguish between Planetary Nebulae (PNe), Supernova Remnants (SNRs) and "normal" emission nebulae or "HII regions" (pronounced "Eitch

  11. Perceptually Guided Photo Retargeting.

    PubMed

    Xia, Yingjie; Zhang, Luming; Hong, Richang; Nie, Liqiang; Yan, Yan; Shao, Ling

    2016-04-22

    We propose perceptually guided photo retargeting, which shrinks a photo by simulating a human's process of sequentially perceiving visually/semantically important regions in a photo. In particular, we first project the local features (graphlets in this paper) onto a semantic space, wherein visual cues such as global spatial layout and rough geometric context are exploited. Thereafter, a sparsity-constrained learning algorithm is derived to select semantically representative graphlets of a photo, and the selecting process can be interpreted by a path which simulates how a human actively perceives semantics in a photo. Furthermore, we learn the prior distribution of such active graphlet paths (AGPs) from training photos that are marked as esthetically pleasing by multiple users. The learned priors enforce the corresponding AGP of a retargeted photo to be maximally similar to those from the training photos. On top of the retargeting model, we further design an online learning scheme to incrementally update the model with new photos that are esthetically pleasing. The online update module makes the algorithm less dependent on the number and contents of the initial training data. Experimental results show that: 1) the proposed AGP is over 90% consistent with human gaze shifting path, as verified by the eye-tracking data, and 2) the retargeting algorithm outperforms its competitors significantly, as AGP is more indicative of photo esthetics than conventional saliency maps.

  12. POPULATION I WOLF-RAYET RUNAWAY STARS: THE CASE OF WR124 AND ITS EXPANDING NEBULA M1-67

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

    Marchenko, S. V.; Moffat, A. F. J.; Crowther, P. A., E-mail: sergey.marchenko@ssaihq.co, E-mail: moffat@astro.umontreal.c, E-mail: Paul.Crowther@sheffield.ac.u

    2010-11-20

    In 1997 and 2008 we used the WFPC2 camera on board the Hubble Space Telescope to obtain two sets of narrow-band H{alpha} images of the runaway Wolf-Rayet (WR) star WR 124 surrounded by its nebula M1-67. This two-epoch imaging provides an expansion parallax and thus a practically assumption-free geometric distance to the nebula, d = 3.35 {+-} 0.67 kpc. Combined with the global velocity distribution in the ejected nebula, this confirms the extreme runaway status of WR 124. WR stars embedded within such ejection nebulae at the point of core collapse would produce different supernova characteristics from those expected formore » stars surrounded by wind-filled cavities. In galaxies with extremely low ambient metallicity, Z {<=} 10{sup -3} Z {sub sun}, {gamma}-ray bursts originating from fast-moving runaway WR stars may produce afterglows which appear to be coming from regions with a relatively homogeneous circumburst medium.« less

  13. The Dual Role of Disorder on the Dissociation of Interfacial Charge Transfer Excitons

    NASA Astrophysics Data System (ADS)

    Shi, Liang; Lee, Chee-Kong; Willard, Adam

    In organic-based photovoltaics (OPV), dissociation of neutral photo-excitations (i.e., Frenkel excitons) into free charge carriers requires the excitons to overcome binding energy that can significantly exceed thermal energies. The inability of bound charges to overcome this large binding energy has been implicated as a primary source of efficiency loss in OPVs. Despite the potential impact on the performance of organic solar cells much remains to be understood about the microscopic mechanism of exciton dissociation in OPV materials. Here we explore the role of static molecular disorder in mediating this charge dissociation process. Using a simple lattice model of exciton dynamics we demonstrate that random spatial variations in the energetic landscape can mitigate the effects of the exciton binding energy by lowering the free energy barrier. By considering the competition between this thermodynamic effect and the disorder-induced slowing of dissociation kinetics we demonstrate that exciton dissociation yields are expected to depend non-monotonically on the degree of static disorder. We conclude that a certain amount of molecular-scale disorder is desirable in order to optimize the performance of organic photovoltaic materials.

  14. VizieR Online Data Catalog: MIPS 24um nebulae (Gvaramadze+, 2010)

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.; Fabrika, S.

    2011-03-01

    Massive evolved stars lose a large fraction of their mass via copious stellar wind or instant outbursts. During certain evolutionary phases, they can be identified by the presence of their circumstellar nebulae. In this paper, we present the results of a search for compact nebulae (reminiscent of circumstellar nebulae around evolved massive stars) using archival 24um data obtained with the Multiband Imaging Photometer for Spitzer. We have discovered 115 nebulae, most of which bear a striking resemblance to the circumstellar nebulae associated with luminous blue variables (LBVs) and late WN-type (WNL) Wolf-Rayet (WR) stars in the Milky Way and the Large Magellanic Cloud (LMC). (1 data file).

  15. Very bright optical transient near the Trifid and Lagoon Nebulae

    NASA Astrophysics Data System (ADS)

    Dunsby, Peter

    2018-03-01

    Peter Dunsby (University of Cape Town) reports the detection of a very bright optical transient in the region between the Lagoon and Trifid Nebulae based on observations obtained from Cape Town on 20 March 2018, between 01:00 and 03:45 UT. The object was visible throughout the full duration of the observations and not seen when this field was observed previously (08 March 2018).

  16. Hot Gas in the Wolf-Rayet Nebula NGC 3199

    NASA Astrophysics Data System (ADS)

    Toalá, J. A.; Marston, A. P.; Guerrero, M. A.; Chu, Y.-H.; Gruendl, R. A.

    2017-09-01

    The Wolf-Rayet (WR) nebula NGC 3199 has been suggested to be a bow shock around its central star, WR 18, which is presumably a runaway star, because optical images of the nebula show a dominating arc of emission southwest of the star. We present the XMM-Newton detection of extended X-ray emission from NGC 3199, unveiling the powerful effect of the fast wind from WR 18. The X-ray emission is brighter in the region southeast of the star and an analysis of the spectral properties of the X-ray emission reveals abundance variations: (I) regions close to the optical arc present nitrogen-rich gas enhanced by the stellar wind from WR 18 and (II) gas at the eastern region exhibits abundances close to those reported for the nebular abundances derived from optical studies, which is a signature of an efficient mixing of the nebular material with the stellar wind. The dominant plasma temperature and electron density are estimated to be T ≈ 1.2 × 106 K and n e = 0.3 cm-3 with an X-ray luminosity in the 0.3-3.0 keV energy range of L X = 2.6 × 1034 erg s-1. Combined with information derived from Herschel and the recent Gaia first data release, we conclude that WR 18 is not a runaway star and that the formation, chemical variations, and the shape of NGC 3199 depend on the initial configuration of the interstellar medium.

  17. The Pacman Nebula

    NASA Image and Video Library

    2011-09-28

    This composite image of the star cluster NGC 28 contains X-ray data from Chandra, in purple, with infrared observations from Spitzer, in red, green, blue. NGC 281 is known informally as the Pacman Nebula because of its appearance in optical images.

  18. Integral field spectroscopy of M1-67. A Wolf-Rayet nebula with luminous blue variable nebula appearance

    NASA Astrophysics Data System (ADS)

    Fernández-Martín, A.; Vílchez, J. M.; Pérez-Montero, E.; Candian, A.; Sánchez, S. F.; Martín-Gordón, D.; Riera, A.

    2013-06-01

    Aims: This work aims to disentangle the morphological, kinematic, and chemical components of the nebula M1-67 to shed light on its process of formation around the central Wolf-Rayet (WR) star WR124. Methods: We have carried out integral field spectroscopy observations over two regions of M1-67, covering most of the nebula in the optical range. Maps of electron density, line ratios, and radial velocity were created to perform a detailed analysis of the two-dimensional structure. We studied the physical and chemical properties by means of integrated spectra selected over the whole nebula. Photoionization models were performed to confirm the empirical chemical results theoretically. In addition, we obtained and analysed infrared spectroscopic data and the MIPS 24 μm image of M1-67 from Spitzer. Results: We find that the ionized gas of M1-67 is condensed in knots aligned in a preferred axis along the NE-SW direction, like a bipolar structure. Both electron density and radial velocity decrease in this direction when moving away from the central star. From the derived electron temperature, Te ~ 8200 K, we have estimated chemical abundances, obtaining that nitrogen appears strongly enriched and oxygen depleted. From the last two results, we infer that this bipolarity is the consequence of an ejection of an evolved stage of WR124 with material processed in the CNO cycle. Furthermore, we find two regions placed outside of the bipolar structure with different spectral and chemical properties. The infrared study has revealed that the bipolar axis is composed of ionized gas with a low ionization degree that is well mixed with warm dust and of a spherical bubble surrounding the ejection at 24 μm. Taking the evolution of a 60 M⊙ star and the temporal scale of the bipolar ejection into account, we propose that the observed gas was ejected during an eruption in the luminous blue variable stage. The star has entered the WR phase recently without apparent signs of interaction

  19. DNA Microcapsule for Photo-Triggered Drug Release Systems.

    PubMed

    Kamiya, Yukiko; Yamada, Yoshinobu; Muro, Takahiro; Matsuura, Kazunori; Asanuma, Hiroyuki

    2017-12-19

    In this study we constructed spherical photo-responsive microcapsules composed of three photo-switchable DNA strands. These strands first formed a three-way junction (TWJ) motif that further self-assembled to form microspheres through hybridization of the sticky-end regions of each branch. To serve as the photo-switch, multiple unmodified azobenzene (Azo) or 2,6-dimethyl-4-(methylthio)azobenzene (SDM-Azo) were introduced into the sticky-end regions via a d-threoninol linker. The DNA capsule structure deformed upon trans-to-cis isomerization of Azo or SDM-Azo induced by specific light irradiation. In addition, photo-triggered release of encapsulated small molecules from the DNA microcapsule was successfully achieved. Moreover, we demonstrated that photo-triggered release of doxorubicin caused cytotoxicity to cultured cells. This biocompatible photo-responsive microcapsule has potential application as a photo-controlled drug-release system. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Disentangling the outflow and protostars in HH 900 in the Carina Nebula

    NASA Astrophysics Data System (ADS)

    Reiter, Megan; Smith, Nathan; Kiminki, Megan M.; Bally, John; Anderson, Jay

    2015-04-01

    HH 900 is a peculiar protostellar outflow emerging from a small, tadpole-shaped globule in the Carina Nebula. Previous Hα imaging with Hubble Space Telescope (HST)/Advanced Camera for Surveys showed an ionized outflow with a wide opening angle that is distinct from the highly collimated structures typically seen in protostellar jets. We present new narrowband near-IR [Fe II] images taken with the Wide Field Camera 3 on the HST that reveal a remarkably different structure than Hα. In contrast to the unusual broad Hα outflow, the [Fe II] emission traces a symmetric, collimated bipolar jet with the morphology and kinematics that are more typical of protostellar jets. In addition, new Gemini adaptive optics images reveal near-IR H2 emission coincident with the Hα emission, but not the [Fe II]. Spectra of these three components trace three separate and distinct velocity components: (1) H2 from the slow, entrained molecular gas, (2) Hα from the ionized skin of the accelerating outflow sheath, and (3) [Fe II] from the fast, dense, and collimated protostellar jet itself. Together, these data require a driving source inside the dark globule that remains undetected behind a large column density of material. In contrast, Hα and H2 emission trace the broad outflow of material entrained by the jet, which is irradiated outside the globule. As it get dissociated and ionized, it remains visible for only a short time after it is dragged into the H II region.

  1. Featured Image: A Detailed Look at the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-07-01

    Planning on watching fireworks tomorrow? Heres an astronomical firework to help you start the celebrations! A new study has stunningly detailed the Crab Nebula (click for a closer look), a nebula 6,500 light-years away thought to have been formedby a supernova explosion and the subsequent ultrarelativistic wind emitted by the pulsar at its heart. Led by Gloria Dubner (University of Buenos Aires), the authors of this study obtained new observations of the Crab Nebula from five different telescopes. They compiled these observations to compare the details of the nebulas structure across different wavelengths, which allowedthem to learnabout the sources of various features within the nebula. In the images above, thetop left shows the 3 GHz data from the Very Large Array (radio). Moving clockise, the radio data (shown in red) is composited with: infrared data from Spitzer Space Telescope, optical continuum from Hubble Space Telescope, 500-nm optical datafrom Hubble, and ultraviolet data from XMM-Newton. The final two images are of the nebula center, and they are composites of the radio imagewith X-ray data from Chandra and near-infrared data from Hubble. To read more about what Dubner and collaborators learned (and to see more spectacular images!), check out the paper below.CitationG. Dubner et al 2017 ApJ 840 82. doi:10.3847/1538-4357/aa6983

  2. Distinguishing between symbiotic stars and planetary nebulae

    NASA Astrophysics Data System (ADS)

    Iłkiewicz, K.; Mikołajewska, J.

    2017-10-01

    Context. The number of known symbiotic stars (SySt) is still significantly lower than their predicted population. One of the main problems in finding the total population of SySt is the fact that their spectrum can be confused with other objects, such as planetary nebulae (PNe) or dense H II regions. This problem is reinforced by the fact that in a significant fraction of established SySt the emission lines used to distinguish them from other objects are not present. Aims: We aim at finding new diagnostic diagrams that could help separate SySt from PNe. Additionally, we examine a known sample of extragalactic PNe for candidate SySt. Methods: We employed emission line fluxes of known SySt and PNe from the literature. Results: We found that among the forbidden lines in the optical region of spectrum, only the [O III] and [N II] lines can be used as a tool for distinguishing between SySt and PNe, which is consistent with the fact that they have the highest critical densities. The most useful diagnostic that we propose is based on He I lines, which are more common and stronger in SySt than forbidden lines. All these useful diagnostic diagrams are electron density indicators that better distinguish PNe and ionized symbiotic nebulae. Moreover, we found six new candidate SySt in the Large Magellanic Cloud and one in M 81. If confirmed, the candidate in M 81 would be the farthest known SySt thus far.

  3. Solar nebula chemistry - Implications for volatiles in the solar system

    NASA Technical Reports Server (NTRS)

    Fegley, Bruce, Jr.; Prinn, Ronald G.

    1989-01-01

    Current theoretical models of solar nebula chemistry which take into account the interplay between chemistry and dynamics are presented for the abundant reactive volatile elements including hydrogen, carbon, nitrogen, oxygen, and sulfur. Results of these models indicate that, in the solar nebula, the dominant carbon and nitrogen gases were CO and NO, whereas, in giant planet subnebulae, the dominant carbon and nitrogen gases were CH4 and NH3; in the solar nebula, the Fe metal grains catalyzed the formation of organic compounds from CO and H2 via the Fischer-Tropsch-type reaction. It was also found that, in solar nebula, bulk FeS formation was kinetically favorable, while FeO incorporation into silicates and bulk Fe3O4 formation were kinetically inhibited. Furthermore, clathrate formation was kinetically inhibited in the solar nebula, while it was kinetically favorable in giant planet subnebulae.

  4. Bidirectional Regulation of Amyloid Precursor Protein-Induced Memory Defects by Nebula/DSCR1: A Protein Upregulated in Alzheimer's Disease and Down Syndrome

    PubMed Central

    Shaw, Jillian L.; Zhang, Shixing

    2015-01-01

    Aging individuals with Down syndrome (DS) have an increased risk of developing Alzheimer's disease (AD), a neurodegenerative disorder characterized by impaired memory. Memory problems in both DS and AD individuals usually develop slowly and progressively get worse with age, but the cause of this age-dependent memory impairment is not well understood. This study examines the functional interactions between Down syndrome critical region 1 (DSCR1) and amyloid-precursor protein (APP), proteins upregulated in both DS and AD, in regulating memory. Using Drosophila as a model, we find that overexpression of nebula (fly homolog of DSCR1) initially protects against APP-induced memory defects by correcting calcineurin and cAMP signaling pathways but accelerates the rate of memory loss and exacerbates mitochondrial dysfunction in older animals. We report that transient upregulation of Nebula/DSCR1 or acute pharmacological inhibition of calcineurin in aged flies protected against APP-induced memory loss. Our data suggest that calcineurin dyshomeostasis underlies age-dependent memory impairments and further imply that chronic Nebula/DSCR1 upregulation may contribute to age-dependent memory impairments in AD in DS. SIGNIFICANCE STATEMENT Most Down syndrome (DS) individuals eventually develop Alzheimer's disease (AD)-like dementia, but mechanisms underlying this age-dependent memory impairment remain poorly understood. This study examines Nebula/Down syndrome critical region 1 (DSCR1) and amyloid-precursor protein (APP), proteins upregulated in both DS and AD, in regulating memory. We uncover a previously unidentified role for Nebula/DSCR1 in modulating APP-induced memory defects during aging. We show that upregulation of Nebula/DSCR1, an inhibitor of calcineurin, rescues APP-induced memory defects in young flies but enhances memory loss of older flies. Excitingly, transient Nebula/DSCR1 overexpression or calcineurin inhibition in aged flies ameliorates APP-mediated memory

  5. Bidirectional Regulation of Amyloid Precursor Protein-Induced Memory Defects by Nebula/DSCR1: A Protein Upregulated in Alzheimer's Disease and Down Syndrome.

    PubMed

    Shaw, Jillian L; Zhang, Shixing; Chang, Karen T

    2015-08-12

    Aging individuals with Down syndrome (DS) have an increased risk of developing Alzheimer's disease (AD), a neurodegenerative disorder characterized by impaired memory. Memory problems in both DS and AD individuals usually develop slowly and progressively get worse with age, but the cause of this age-dependent memory impairment is not well understood. This study examines the functional interactions between Down syndrome critical region 1 (DSCR1) and amyloid-precursor protein (APP), proteins upregulated in both DS and AD, in regulating memory. Using Drosophila as a model, we find that overexpression of nebula (fly homolog of DSCR1) initially protects against APP-induced memory defects by correcting calcineurin and cAMP signaling pathways but accelerates the rate of memory loss and exacerbates mitochondrial dysfunction in older animals. We report that transient upregulation of Nebula/DSCR1 or acute pharmacological inhibition of calcineurin in aged flies protected against APP-induced memory loss. Our data suggest that calcineurin dyshomeostasis underlies age-dependent memory impairments and further imply that chronic Nebula/DSCR1 upregulation may contribute to age-dependent memory impairments in AD in DS. Most Down syndrome (DS) individuals eventually develop Alzheimer's disease (AD)-like dementia, but mechanisms underlying this age-dependent memory impairment remain poorly understood. This study examines Nebula/Down syndrome critical region 1 (DSCR1) and amyloid-precursor protein (APP), proteins upregulated in both DS and AD, in regulating memory. We uncover a previously unidentified role for Nebula/DSCR1 in modulating APP-induced memory defects during aging. We show that upregulation of Nebula/DSCR1, an inhibitor of calcineurin, rescues APP-induced memory defects in young flies but enhances memory loss of older flies. Excitingly, transient Nebula/DSCR1 overexpression or calcineurin inhibition in aged flies ameliorates APP-mediated memory problems. These results

  6. Generation of dynamo magnetic fields in the primordial solar nebula

    NASA Technical Reports Server (NTRS)

    Stepinski, Tomasz F.

    1992-01-01

    The present treatment of dynamo-generated magnetic fields in the primordial solar nebula proceeds in view of the ability of the combined action of Keplerian rotation and helical convention to generate, via alpha-omega dynamo, large-scale magnetic fields in those parts of the nebula with sufficiently high, gas-and magnetic field coupling electrical conductivity. Nebular gas electrical conductivity and the radial distribution of the local dynamo number are calculated for both a viscous-accretion disk model and the quiescent-minimum mass nebula. It is found that magnetic fields can be easily generated and maintained by alpha-omega dynamos occupying the inner and outer parts of the nebula.

  7. Family ties of WR to LBV nebulae yielding clues for stellar evolution

    NASA Astrophysics Data System (ADS)

    Weis, K.

    Luminous Blue Variables (LBVs) are stars is a transitional phase massive stars may enter while evolving from main-sequence to Wolf-Rayet stars. The to LBVs intrinsic photometric variability is based on the modulation of the stellar spectrum. Within a few years the spectrum shifts from OB to AF type and back. During their cool phase LBVs are close to the Humphreys-Davidson (equivalent to Eddington/Omega-Gamma) limit. LBVs have a rather high mass loss rate, with stellar winds that are fast in the hot and slower in the cool phase of an LBV. These alternating wind velocities lead to the formation of LBV nebulae by wind-wind interactions. A nebula can also be formed in a spontaneous giant eruption in which larger amounts of mass are ejected. LBV nebulae are generally small (< 5 pc) mainly gaseous circumstellar nebulae, with a rather large fraction of LBV nebulae being bipolar. After the LBV phase the star will turn into a Wolf-Rayet star, but note that not all WR stars need to have passed the LBV phase. Some follow from the RSG and the most massive directly from the MS phase. In general WRs have a large mass loss and really fast stellar winds. The WR wind may interact with winds of earlier phases (MS, RSG) to form WR nebulae. As for WR with LBV progenitors the scenario might be different, here no older wind is present but an LBV nebula! The nature of WR nebulae are therefore manifold and in particular the connection (or family ties) of WR to LBV nebulae is important to understand the transition between these two phases, the evolution of massive stars, their winds, wind-wind and wind-nebula interactions. Looking at the similarities and differences of LBV and WR nebula, figuring what is a genuine LBV and WR nebula are the basic question addressed in the analysis presented here.

  8. The Removal of Terrestrial Dissolved Organic Matter in Coastal Regions by Photo-Flocculation Process

    NASA Astrophysics Data System (ADS)

    Abdulla, H. A.; Mopper, K.

    2015-12-01

    The fate of terrestrial dissolved organic matter (tDOM) as it moves to open ocean was the focus of many studies for the last three decades, most of these studies were focused on three major removal processes: 1) Photochemical mineralization of tDOM (conversion to inorganic forms); 2) Microbial oxidation; and 3) Mixing-induced flocculation. Based on recent estimations, the combination of theses removal processes accounts for ~20-35% of the loss of tDOM in estuaries and coastal regions; which is far from closing the gap between the riverine fluxes of tDOM and the amount of tDOM detected in the open ocean. In a preliminary experiment to determine if photo-flocculation indeed occurs at pH values and ionic strengths found in estuaries. A 0.1-μm filtered riverine was diluted 1:1 with artificial seawater and MilliQ water to yield final salinities ranging from 0 - 15; the pH of the saline samples was ranged from 6-8. Photo-flocculation was observed for all salinities, with particles organic carbon (POC) values ranged from 3.2 to 8.5% of the original DOC. Interestingly, the composition of the Photo-flocculated particles in the saline samples was markedly different from the zero salinity samples as shown in their FT-IR spectra. The photo-flocculated particles that formed in the saline samples appear to be rich in carbohydrate and amide functionalities (protein-like), while containing insignificant deprotonated carboxylate. While the flocs that formed in freshwater (salinity zero) are richer in deprotonated carboxyl groups, and relatively depleted in carbohydrate functionality.

  9. Waiting in the Wings: Reflected X-ray Emission from the Homunculus Nebula

    NASA Technical Reports Server (NTRS)

    Corcoran, M. F.; Hamaguchi, K.; Gull, T.; Davidson, K.; Petre, R.; Hillier, D. J.; Smith, N.; Damineli, A.; Morse, J. A.; Walborn, N. R.

    2004-01-01

    We report the first detection of X-ray emission associated with the Homunculus Nebula which surrounds the supermassive star eta Carinae. The emission is characterized by a temperature in excess of 100 MK, and is consistent with scattering of the time-delayed X-ray flux associated with the star. The nebular emission is bright in the northwestern lobe and near the central regions of the Homunculus, and fainter in the southeastern lobe. We also report the detection of an unusually broad Fe K fluorescent line, which may indicate fluorescent scattering off the wind of a companion star or some other high velocity outflow. The X-ray Homunculus is the nearest member of the small class of Galactic X-ray reflection nebulae, and the only one in which both the emitting and reflecting sources are distinguishable.

  10. Direct simulation with vibration-dissociation coupling

    NASA Technical Reports Server (NTRS)

    Hash, David B.; Hassan, H. A.

    1992-01-01

    The majority of implementations of the Direct Simulation Monte Carlo (DSMC) method of Bird do not account for vibration-dissociation coupling. Haas and Boyd have proposed the vibrationally-favored dissociation model to accomplish this task. This model requires measurements of induction distance to determine model constants. A more general expression has been derived that does not require any experimental input. The model is used to calculate one-dimensional shock waves in nitrogen and the flow past a lunar transfer vehicle (LTV). For the conditions considered in the simulation, the influence of vibration-dissociation coupling on heat transfer in the stagnation region of the LTV can be significant.

  11. N44C nebula

    NASA Image and Video Library

    1999-12-03

    Resembling the hair in Botticelli famous portrait of the birth of Venus, an image from NASA Hubble Space Telescope has captured softly glowing filaments streaming from hot young stars in a nearby nebula.

  12. IRAS surface brightness maps of reflection nebulae in the Pleiades

    NASA Technical Reports Server (NTRS)

    Castelaz, Michael W.; Werner, M. W.; Sellgren, K.

    1987-01-01

    Surface brightness maps at 12, 25, 60, and 100 microns were made of a 2.5 deg x 2.5 deg area of the reflection nebulae in the Pleiades by coadding IRAS scans of this region. Emission is seen surrounding 17 Tau, 20 Tau, 23 Tau, and 25 Tau in all four bands, coextensive with the visible reflection nebulosity, and extending as far as 30 arcminutes from the illuminating stars. The infrared energy distributions of the nebulae peak in the 100 micron band, but up to 40 percent of the total infrared power lies in the 12 and 25 micron bands. The brightness of the 12 and 25 micron emission and the absence of temperature gradients at these wavelengths are inconsistent with the predictions of equilibrium thermal emission models. The emission at these wavelengths appears to be the result of micron nonequilibrium emission from very small grains, or from molecules consisting of 10-100 carbon atoms, which have been excited by ultraviolet radiation from the illuminating stars.

  13. Magneto-photo-acoustic imaging

    PubMed Central

    Qu, Min; Mallidi, Srivalleesha; Mehrmohammadi, Mohammad; Truby, Ryan; Homan, Kimberly; Joshi, Pratixa; Chen, Yun-Sheng; Sokolov, Konstantin; Emelianov, Stanislav

    2011-01-01

    Magneto-photo-acoustic imaging, a technique based on the synergy of magneto-motive ultrasound, photoacoustic and ultrasound imaging, is introduced. Hybrid nanoconstructs, liposomes encapsulating gold nanorods and iron oxide nanoparticles, were used as a dual-contrast agent for magneto-photo-acoustic imaging. Tissue-mimicking phantom and macrophage cells embedded in ex vivo porcine tissue were used to demonstrate that magneto-photo-acoustic imaging is capable of visualizing the location of cells or tissues labeled with dual-contrast nanoparticles with sufficient contrast, excellent contrast resolution and high spatial resolution in the context of the anatomical structure of the surrounding tissues. Therefore, magneto-photo-acoustic imaging is capable of identifying the nanoparticle-labeled pathological regions from the normal tissue, providing a promising platform to noninvasively diagnose and characterize pathologies. PMID:21339883

  14. Nebula--a web-server for advanced ChIP-seq data analysis.

    PubMed

    Boeva, Valentina; Lermine, Alban; Barette, Camille; Guillouf, Christel; Barillot, Emmanuel

    2012-10-01

    ChIP-seq consists of chromatin immunoprecipitation and deep sequencing of the extracted DNA fragments. It is the technique of choice for accurate characterization of the binding sites of transcription factors and other DNA-associated proteins. We present a web service, Nebula, which allows inexperienced users to perform a complete bioinformatics analysis of ChIP-seq data. Nebula was designed for both bioinformaticians and biologists. It is based on the Galaxy open source framework. Galaxy already includes a large number of functionalities for mapping reads and peak calling. We added the following to Galaxy: (i) peak calling with FindPeaks and a module for immunoprecipitation quality control, (ii) de novo motif discovery with ChIPMunk, (iii) calculation of the density and the cumulative distribution of peak locations relative to gene transcription start sites, (iv) annotation of peaks with genomic features and (v) annotation of genes with peak information. Nebula generates the graphs and the enrichment statistics at each step of the process. During Steps 3-5, Nebula optionally repeats the analysis on a control dataset and compares these results with those from the main dataset. Nebula can also incorporate gene expression (or gene modulation) data during these steps. In summary, Nebula is an innovative web service that provides an advanced ChIP-seq analysis pipeline providing ready-to-publish results. Nebula is available at http://nebula.curie.fr/ Supplementary data are available at Bioinformatics online.

  15. The Surface Density Distribution in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Davis, Sanford S.

    2004-01-01

    The commonly used minimum mass power law representation of the pre-solar nebula is reanalyzed using a new cumulative-mass-model. This model predicts a smoother surface density approximation compared with methods based on direct computation of surface density. The density is quantified using two independent analytical formulations. First, a best-fit transcendental function is applied directly to the basic planetary data. Next a solution to the time-dependent disk evolution equation is parametrically adapted to the solar nebula data. The latter model is shown to be a good approximation to the finite-size early Solar Nebula, and by extension to other extra solar protoplanetary disks.

  16. Comets Kick up Dust in Helix Nebula

    NASA Technical Reports Server (NTRS)

    2007-01-01

    This infrared image from NASA's Spitzer Space Telescope shows the Helix nebula, a cosmic starlet often photographed by amateur astronomers for its vivid colors and eerie resemblance to a giant eye.

    The nebula, located about 700 light-years away in the constellation Aquarius, belongs to a class of objects called planetary nebulae. Discovered in the 18th century, these colorful beauties were named for their resemblance to gas-giant planets like Jupiter.

    Planetary nebulae are the remains of stars that once looked a lot like our sun. When sun-like stars die, they puff out their outer gaseous layers. These layers are heated by the hot core of the dead star, called a white dwarf, and shine with infrared and visible colors. Our own sun will blossom into a planetary nebula when it dies in about five billion years.

    In Spitzer's infrared view of the Helix nebula, the eye looks more like that of a green monster's. Infrared light from the outer gaseous layers is represented in blues and greens. The white dwarf is visible as a tiny white dot in the center of the picture. The red color in the middle of the eye denotes the final layers of gas blown out when the star died.

    The brighter red circle in the very center is the glow of a dusty disk circling the white dwarf (the disk itself is too small to be resolved). This dust, discovered by Spitzer's infrared heat-seeking vision, was most likely kicked up by comets that survived the death of their star. Before the star died, its comets and possibly planets would have orbited the star in an orderly fashion. But when the star blew off its outer layers, the icy bodies and outer planets would have been tossed about and into each other, resulting in an ongoing cosmic dust storm. Any inner planets in the system would have burned up or been swallowed as their dying star expanded.

    So far, the Helix nebula is one of only a few dead-star systems in which evidence for comet survivors has been found.

    This image

  17. The population of TeV pulsar wind nebulae in the H.E.S.S. Galactic Plane Survey

    NASA Astrophysics Data System (ADS)

    H. E. S. S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Bregeon, J.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Capasso, M.; Carr, J.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I. D.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hadasch, D.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; de Oña Wilhelmi, E.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tuffs, R.; Uchiyama, Y.; Valerius, K.; van der Walt, D. J.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.

    2018-04-01

    The nine-year H.E.S.S. Galactic Plane Survey (HGPS) has yielded the most uniform observation scan of the inner Milky Way in the TeV gamma-ray band to date. The sky maps and source catalogue of the HGPS allow for a systematic study of the population of TeV pulsar wind nebulae found throughout the last decade. To investigate the nature and evolution of pulsar wind nebulae, for the first time we also present several upper limits for regions around pulsars without a detected TeV wind nebula. Our data exhibit a correlation of TeV surface brightness with pulsar spin-down power Ė. This seems to be caused both by an increase of extension with decreasing Ė, and hence with time, compatible with a power law RPWN(Ė) Ė-0.65±0.20, and by a mild decrease of TeV gamma-ray luminosity with decreasing Ė, compatible with L1-10 TeV Ė0.59±0.21. We also find that the offsets of pulsars with respect to the wind nebula centre with ages around 10 kyr are frequently larger than can be plausibly explained by pulsar proper motion and could be due to an asymmetric environment. In the present data, it seems that a large pulsar offset is correlated with a high apparent TeV efficiency L1-10 TeV/Ė. In addition to 14 HGPS sources considered firmly identified pulsar wind nebulae and 5 additional pulsar wind nebulae taken from literature, we find 10 HGPS sources that are likely TeV pulsar wind nebula candidates. Using a model that subsumes the present common understanding of the very high-energy radiative evolution of pulsar wind nebulae, we find that the trends and variations of the TeV observables and limits can be reproduced to a good level, drawing a consistent picture of present-day TeV data and theory.

  18. WISE Catches the Lagoon Nebula in Center of Action

    NASA Image and Video Library

    2011-01-06

    This colorful picture is a mosaic of Messier 8, or the Lagoon nebula, taken by NASA Wide-field Infrared Survey Explorer. This nebula is composed of clouds of gas and dust in which new stars are forming.

  19. Psychiatric symptoms and dissociation in conversion, somatization and dissociative disorders.

    PubMed

    Espirito-Santo, Helena; Pio-Abreu, Jose Luis

    2009-03-01

    Conversion, dissociation and somatization are historically related in the long established concept of hysteria. Somewhere along the way they were separated due to the Cartesian dualistic view. The aim of the present study was to compare these pathologies and investigate whether symptoms of these pathologies overlap in their clinical appearance in a Portuguese sample. Twenty-six patients with conversion disorder, 38 with dissociative disorders, 40 with somatization disorder, and a comparison group of 46 patients having other psychiatric disorders answered questions about dissociation (Dissociative Experiences Scale), somatoform dissociation (Somatoform Dissociation Questionnaire), and psychopathological symptoms (Brief Symptom Inventory). Dissociative and somatoform symptoms were significantly more frequent in dissociative and conversion disorder than in somatization disorder and controls. There were no significant differences between dissociative and conversion patients. Conversion disorder is closely related to dissociative disorders. These results support the ICD-10 categorization of conversion disorder among dissociative disorders and the hypothesis of analogous psychopathological processes in conversion and dissociative disorders versus somatization disorder.

  20. Bi-Abundance Ionisation Structure of the Wolf-Rayet Planetary Nebula PB 8

    NASA Astrophysics Data System (ADS)

    Danehkar, A.

    2018-01-01

    The planetary nebula PB 8 around a [WN/WC]-hybrid central star is one of planetary nebulae with moderate abundance discrepancy factors (ADFs 2-3), which could be an indication of a tiny fraction of metal-rich inclusions embedded in the nebula (bi-abundance). In this work, we have constructed photoionisation models to reproduce the optical and infrared observations of the planetary nebula PB 8 using a non-LTE stellar model atmosphere ionising source. A chemically homogeneous model initially used cannot predict the optical recombination lines. However, a bi-abundance model provides a better fit to most of the observed optical recombination lines from N and O ions. The metal-rich inclusions in the bi-abundance model occupy 5.6% of the total volume of the nebula, and are roughly 1.7 times cooler and denser than the mean values of the surrounding nebula. The N/H and O/H abundance ratios in the metal-rich inclusions are 1.0 and 1.7 dex larger than the diffuse warm nebula, respectively. To reproduce the Spitzer spectral energy distribution of PB 8, dust grains with a dust-to-gas ratio of 0.01 (by mass) were also included. It is found that the presence of metal-rich inclusions can explain the heavy element optical recombination lines, while a dual-dust chemistry with different grain species and discrete grain sizes likely produces the infrared continuum of this planetary nebula. This study demonstrates that the bi-abundance hypothesis, which was examined in a few planetary nebulae with large abundance discrepancies (ADFs > 10), could also be applied to those typical planetary nebulae with moderate abundance discrepancies.

  1. The remarkably high excitation planetary nebula GC 6537

    PubMed Central

    Aller, Lawrence H.; Hung, Siek; Feibelman, Walter A.

    1999-01-01

    NGC 6537 is an unusually high excitation point symmetric planetary nebula with a rich spectrum. Its kinematical structures are of special interest. We are here primarily concerned with the high resolution spectrum as revealed by the Hamilton echelle Spectrograph at Lick Observatory (resolution ≈ 0.2 Å) and supplemented by UV and near-UV data. These extensive data permit a determination of interstellar extinction, plasma diagnostics, and ionic concentrations. The photoionization models that have been used successfully for many planetary nebulae are not entirely satisfactory here. The plasma electron temperature of a photoionization model cannot much exceed 20,000 K, but plasma diagnostics show that regions emitting radiation of highly ionized atoms such as [Neiv] and [Nev] are much hotter, showing that shock excitation must be important, as suggested by the remarkable kinematics of this object. Hence, instead of employing a strict photoionization model, we are guided by the nebular diagnostics, which reveal how electron temperature varies with ionization potential and accommodates density effects. The predictions of the photoionization model may be useful in estimating ionization correction factor. In effect, we have estimated the chemical composition by using both photoionization and shock considerations. PMID:10318889

  2. The remarkably high excitation planetary nebula GC 6537.

    PubMed

    Aller, L H; Hung, S; Feibelman, W A

    1999-05-11

    NGC 6537 is an unusually high excitation point symmetric planetary nebula with a rich spectrum. Its kinematical structures are of special interest. We are here primarily concerned with the high resolution spectrum as revealed by the Hamilton echelle Spectrograph at Lick Observatory (resolution approximately 0.2 A) and supplemented by UV and near-UV data. These extensive data permit a determination of interstellar extinction, plasma diagnostics, and ionic concentrations. The photoionization models that have been used successfully for many planetary nebulae are not entirely satisfactory here. The plasma electron temperature of a photoionization model cannot much exceed 20,000 K, but plasma diagnostics show that regions emitting radiation of highly ionized atoms such as [NeIV] and [NeV] are much hotter, showing that shock excitation must be important, as suggested by the remarkable kinematics of this object. Hence, instead of employing a strict photoionization model, we are guided by the nebular diagnostics, which reveal how electron temperature varies with ionization potential and accommodates density effects. The predictions of the photoionization model may be useful in estimating ionization correction factor. In effect, we have estimated the chemical composition by using both photoionization and shock considerations.

  3. Evolution of the Solar Nebula. II. Thermal Structure during Nebula Formation

    NASA Astrophysics Data System (ADS)

    Boss, Alan P.

    1993-11-01

    " Keplerian disk, with surface density σ ∝ r-1/2, surrounded by a much lower density "halo" infalling onto the disk. This initial condition produced Mṡs → 0 and Mṡd ˜ 10-6 to 10-5 Msun yr-1, as desired. The resulting nebula temperature distributions show that midplane temperatures of at least 1000 K inside 2.5 AU, falling to around 100 K outside 5 AU, are to be expected during the formation phase of a minimum mass nebula containing ˜0.02 Msun within 10 AU. This steady state temperature distribution appears to be consistent with cosmochemical evidence which has been interpreted as implying a phase of relatively high temperatures in the inner nebula. The temperature distribution also implies that the nebula would be cool enough outside 5 AU to allow ices to accumulate into planetesimals even at this relatively early phase of nebula evolution.

  4. ISO Spectroscopy of Proto-Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Hrivnak, Bruce J.

    2000-01-01

    The goal of this program was to determine the chemical properties of the dust shells around protoplanetary nebulae (PPNs) through a study of their short-wavelength (6-45 micron) infrared spectra. PPNs are evolved stars in transition from the asymptotic giant branch to the planetary nebula stages. Spectral features in the 10 to 20 gm region indicate the chemical nature (oxygen- or carbon-rich), and the strengths of the features relate to the physical properties of the shells. A few bright carbon-rich PPNs have been observed to show PAH features and an unidentified 21 micron emission feature. We used the Infrared Space Observatory (ISO) to observe a sample of IRAS sources that have the expected properties of PPNs and for which we have accurate positions. Some of these have optical counterparts (proposal SWSPPN01) and some do not (SWSPPN02). We had previously observed these from the ground with near-infrared photometry and, for those with visible counterparts, visible photometry and spectroscopy, which we have combined with these new ISO data in the interpretation of the spectra. We have completed a study of the unidentified emission feature at 21 micron in eight sources. We find the shape of the feature to be the same in all of the sources, with no evidence of any substructure. The ratio of the emission peak to continuum ranges from 0.13 to 1.30. We have completed a study of seven PPNs and two other carbon-rich objects for which we had obtained ISO 2-45 micron observations. The unidentified emission features at 21 and 30 micron were detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature was resolved and found to consist of a broad feature peaking at 27.2 micron (the "30 micron" feature) and a narrower feature peaking at 25.5 micron (the "26 micron" feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229+6208 and 16594-4656. The unidentified

  5. Broad Halpha Wing Formation in the Planetary Nebula IC 4997.

    PubMed

    Lee; Hyung

    2000-02-10

    The young and compact planetary nebula IC 4997 is known to exhibit very broad wings with a width exceeding 5000 km s-1 around Halpha. We propose that the broad wings are formed through Rayleigh-Raman scattering that involves atomic hydrogen, by which Lybeta photons with a velocity width of a few 102 km s-1 are converted to optical photons and fill the Halpha broad wing region. The conversion efficiency reaches 0.6 near the line center, where the scattering optical depth is much larger than 1, and rapidly decreases in the far wings. Assuming that close to the central star there exists an unresolved inner compact core of high density, nH approximately 109-1010 cm-3, we use the photoionization code "CLOUDY" to show that sufficient Lybeta photons for scattering are produced. Using a top-hat-incident profile for the Lybeta flux and a scattering region with a H i column density NHi=2x1020 cm-2 and a substantial covering factor, we perform a profile-fitting analysis in order to obtain a satisfactory fit to the observed flux. We briefly discuss the astrophysical implications of the Rayleigh-Raman processes in planetary nebulae and other emission objects.

  6. The near-infrared continuum emission of visual reflection nebulae

    NASA Technical Reports Server (NTRS)

    Sellgren, K.

    1984-01-01

    In the past, reflection nebulae have provided an astrophysical laboratory well suited for the study of the reflection properties of interstellar dust grains at visual and ultraviolet wavelengths. The present investigation is concerned with observations which were begun with the objective to extend to near-infrared wavelengths the study of grains in reflection. Observations of three classical visual reflection nebulae were conducted in the wavelength range from 1.25 to 2.2 microns, taking into account NGC 7023, 2023, and 2068. All three nebulae were found to have similar near-infrared colors, despite widely different colors of their illuminating stars. The brightness level shown by two of the nebulae at 2.2 microns was too high to be easily accounted for on the basis of reflected light. Attention is given to a wide variety of possible emission mechanisms.

  7. Neutral carbon in the Egg Nebula (AFGL 2688)

    NASA Technical Reports Server (NTRS)

    Beichman, C. A.; Keene, J.; Phillips, T. G.; Huggins, P. J.; Wooten, H. A.; Masson, C.; Frerking, M. A.

    1983-01-01

    A search for sub-mm C I emission from seven stars that are surrounded by dense molecular gas shells led to the detection, in the case of the "Egg Nebula' (AFGL 2688), of an 0.9 K line implying a C I/CO value greater than 5. The material surrounding this star must be extremely carbon-rich, and it is suggested that the apparently greater extent of the C I emission region may be due to the effects of the galactic UV field on the shell's chemistry, as suggested by Huggins and Glassgold (1982).

  8. Irradiated interfaces in the Ara OB1, Carina, Eagle Nebula, and Cyg OB2 massive star formation regions

    DOE PAGES

    Hartigan, P.; Palmer, J.; Cleeves, L. I.

    2012-09-05

    Regions of massive star formation offer some of the best and most easily-observed examples of radiation hydrodynamics. Boundaries where fully-ionized H II regions transition to neutral/molecular photodissociation regions (PDRs) are of particular interest because marked temperature and density contrasts across the boundaries lead to evaporative flows and fluid dynamical instabilities that can evolve into spectacular pillar-like structures. Furthermore, when detached from their parent clouds, pillars become ionized globules that often harbor one or more young stars. H2 molecules at the interface between a PDR and an H II region absorb ultraviolet light from massive stars, and the resulting fluoresced infraredmore » emission lines are an ideal way to trace this boundary independent of obscuring dust. This paper presents H2 images of four regions of massive star formation that illustrate different types of PDR boundaries. The Ara OB1 star formation region contains a striking long wall that has several wavy structures which are present in H2, but the emission is not particularly bright because the ambient UV fluxes are relatively low. In contrast, the Carina star formation region shows strong H2 fluorescence both along curved walls and at the edges of spectacular pillars that in some cases have become detached from their parent clouds. The less-spectacular but more well-known Eagle Nebula has two regions that have strong fluorescence in addition to its pillars. And while somewhat older than the other regions, Cyg OB2 has the highest number of massive stars of the regions surveyed and contains many isolated, fluoresced globules that have head–tail morphologies which point towards the sources of ionizing radiation. Our images provide a collection of potential astrophysical analogs that may relate to ablated interfaces observed in laser experiments of radiation hydrodynamics.« less

  9. Hot Gas in the Wolf–Rayet Nebula NGC 3199

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

    Toalá, J. A.; Chu, Y.-H.; Marston, A. P.

    The Wolf–Rayet (WR) nebula NGC 3199 has been suggested to be a bow shock around its central star, WR 18, which is presumably a runaway star, because optical images of the nebula show a dominating arc of emission southwest of the star. We present the XMM-Newton detection of extended X-ray emission from NGC 3199, unveiling the powerful effect of the fast wind from WR 18. The X-ray emission is brighter in the region southeast of the star and an analysis of the spectral properties of the X-ray emission reveals abundance variations: (i) regions close to the optical arc present nitrogen-richmore » gas enhanced by the stellar wind from WR 18 and (ii) gas at the eastern region exhibits abundances close to those reported for the nebular abundances derived from optical studies, which is a signature of an efficient mixing of the nebular material with the stellar wind. The dominant plasma temperature and electron density are estimated to be T ≈ 1.2 × 10{sup 6} K and n {sub e} = 0.3 cm{sup −3} with an X-ray luminosity in the 0.3–3.0 keV energy range of L {sub X} = 2.6 × 10{sup 34} erg s{sup −1}. Combined with information derived from Herschel and the recent Gaia first data release, we conclude that WR 18 is not a runaway star and that the formation, chemical variations, and the shape of NGC 3199 depend on the initial configuration of the interstellar medium.« less

  10. Dissociation and psychosis in dissociative identity disorder and schizophrenia.

    PubMed

    Laddis, Andreas; Dell, Paul F

    2012-01-01

    Dissociative symptoms, first-rank symptoms of schizophrenia, and delusions were assessed in 40 schizophrenia patients and 40 dissociative identity disorder (DID) patients with the Multidimensional Inventory of Dissociation (MID). Schizophrenia patients were diagnosed with the Structured Clinical Interview for the DSM-IV Axis I Disorders; DID patients were diagnosed with the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised. DID patients obtained significantly (a) higher dissociation scores; (b) higher passive-influence scores (first-rank symptoms); and (c) higher scores on scales that measure child voices, angry voices, persecutory voices, voices arguing, and voices commenting. Schizophrenia patients obtained significantly higher delusion scores than did DID patients. What is odd is that the dissociation scores of schizophrenia patients were unrelated to their reports of childhood maltreatment. Multiple regression analyses indicated that 81% of the variance in DID patients' dissociation scores was predicted by the MID's Ego-Alien Experiences Scale, whereas 92% of the variance in schizophrenia patients' dissociation scores was predicted by the MID's Voices Scale. We propose that schizophrenia patients' responses to the MID do not index the same pathology as do the responses of DID patients. We argue that neither phenomenological definitions of dissociation nor the current generation of dissociation instruments (which are uniformly phenomenological in nature) can distinguish between the dissociative phenomena of DID and what we suspect are just the dissociation-like phenomena of schizophrenia.

  11. HUBBLE SEES SUPERSONIC EXHAUST FROM NEBULA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    2-9 is a striking example of a 'butterfly' or a bipolar planetary nebula. Another more revealing name might be the 'Twin Jet Nebula.' If the nebula is sliced across the star, each side of it appears much like a pair of exhausts from jet engines. Indeed, because of the nebula's shape and the measured velocity of the gas, in excess of 200 miles per second, astronomers believe that the description as a super-super-sonic jet exhaust is quite apt. Ground-based studies have shown that the nebula's size increases with time, suggesting that the stellar outburst that formed the lobes occurred just 1,200 years ago. The central star in M2-9 is known to be one of a very close pair which orbit one another at perilously close distances. It is even possible that one star is being engulfed by the other. Astronomers suspect the gravity of one star pulls weakly bound gas from the surface of the other and flings it into a thin, dense disk which surrounds both stars and extends well into space. The disk can actually be seen in shorter exposure images obtained with the Hubble telescope. It measures approximately 10 times the diameter of Pluto's orbit. Models of the type that are used to design jet engines ('hydrodynamics') show that such a disk can successfully account for the jet-exhaust-like appearance of M2-9. The high-speed wind from one of the stars rams into the surrounding disk, which serves as a nozzle. The wind is deflected in a perpendicular direction and forms the pair of jets that we see in the nebula's image. This is much the same process that takes place in a jet engine: The burning and expanding gases are deflected by the engine walls through a nozzle to form long, collimated jets of hot air at high speeds. M2-9 is 2,100 light-years away in the constellation Ophiucus. The observation was taken Aug. 2, 1997 by the Hubble telescope's Wide Field and Planetary Camera 2. In this image, neutral oxygen is shown in red, once-ionized nitrogen in green, and twice-ionized oxygen in

  12. On the peculiar shapes of some pulsar bow-shock nebulae

    NASA Astrophysics Data System (ADS)

    Bandiera, Rino

    Pulsar bow-shock nebulae are pulsar-wind nebulae formed by the direct interaction of pulsar relativistic winds with the interstellar medium. The bow-shock morphology, well outlined in Hα for some objects, is an effect of the supersonic pulsar motion with respect to the ambient medium. However, in a considerable fraction of cases (e.g. the nebulae associated to PSR B2224+65, PSR B0740-28, PSR J2124-3358) clear deviations from the classical bow shock shape are observed. Such deviations are usually interpreted as due to ambient density gradients and/or to pulsar-wind anisotropies. Here I present a different interpretation, aiming at explaining deviations from the standard morphology as signs of the peculiar physical conditions present in these objects. Using dimensional arguments, I show that, unlike normal pulsar-wind nebulae, in pulsar bow-shock nebulae the mean free path of the highest-energy particles may be comparable with the bow-shock head. I then investigate whether this may affect the shape of the bow-shock; for instance, whether a conical bow shock (like that observed in the "Guitar", the nebula associated to PSR B2224+65) does really imply an ambient density gradient. Finally, I discuss some other possible signatures of these high-energy, long mean-free-path particles.

  13. The Gum nebula

    NASA Technical Reports Server (NTRS)

    Brandt, J. C.

    1972-01-01

    The distance from the sun to the center of the star, Gamma Velorium, is determined in an effort to draw a physical model and identify the ionized energy source of the Gum nebula. The distance is calculated from the local hydrogen density of radio astronomy studies and the hydrogen measure.

  14. Content-aware photo collage using circle packing.

    PubMed

    Yu, Zongqiao; Lu, Lin; Guo, Yanwen; Fan, Rongfei; Liu, Mingming; Wang, Wenping

    2014-02-01

    In this paper, we present a novel approach for automatically creating the photo collage that assembles the interest regions of a given group of images naturally. Previous methods on photo collage are generally built upon a well-defined optimization framework, which computes all the geometric parameters and layer indices for input photos on the given canvas by optimizing a unified objective function. The complex nonlinear form of optimization function limits their scalability and efficiency. From the geometric point of view, we recast the generation of collage as a region partition problem such that each image is displayed in its corresponding region partitioned from the canvas. The core of this is an efficient power-diagram-based circle packing algorithm that arranges a series of circles assigned to input photos compactly in the given canvas. To favor important photos, the circles are associated with image importances determined by an image ranking process. A heuristic search process is developed to ensure that salient information of each photo is displayed in the polygonal area resulting from circle packing. With our new formulation, each factor influencing the state of a photo is optimized in an independent stage, and computation of the optimal states for neighboring photos are completely decoupled. This improves the scalability of collage results and ensures their diversity. We also devise a saliency-based image fusion scheme to generate seamless compositive collage. Our approach can generate the collages on nonrectangular canvases and supports interactive collage that allows the user to refine collage results according to his/her personal preferences. We conduct extensive experiments and show the superiority of our algorithm by comparing against previous methods.

  15. On the formation of runaway stars BN and x in the Orion Nebula Cluster

    NASA Astrophysics Data System (ADS)

    Farias, J. P.; Tan, J. C.

    2018-05-01

    We explore scenarios for the dynamical ejection of stars BN and x from source I in the Kleinmann-Low nebula of the Orion Nebula Cluster (ONC), which is important because it is the closest region of massive star formation. This ejection would cause source I to become a close binary or a merger product of two stars. We thus consider binary-binary encounters as the mechanism to produce this event. By running a large suite of N-body simulations, we find that it is nearly impossible to match the observations when using the commonly adopted masses for the participants, especially a source I mass of 7 M⊙. The only way to recreate the event is if source I is more massive, that is, 20 M⊙. However, even in this case, the likelihood of reproducing the observed system is low. We discuss the implications of these results for understanding this important star-forming region.

  16. Interaction of planetary nebulae with the interstellar medium

    NASA Technical Reports Server (NTRS)

    Borkowski, Kazimierz J.; Sarazin, Craig L.; Soker, Noam

    1990-01-01

    The interaction of a moving planetary nebula (PN) with the interstellar medium is considered. The PN shell is compressed first in the direction of the stellar motion. This produces a dipole asymmetry in the surface brightness of the nebula, typically at a nebular density of about 40/cu cm if the nebula is located in the Galactic plane. In the later stages of the interaction, this part of the shell is significantly decelerated with respect to the central star, and the PN becomes strongly asymmetric in shape. This distortion and the subsequent stripping of the nebular gas away from the central star typically occurs at a low nebular density of about 6/cu cm. The morphology of PNs with central stars whose proper motions exceed 0.015 arcsec/yr was examined, and it was found that many of the extended nebulae are interacting with the interstellar medium (ISM). The sample doubles the number of known PNs interacting with the ISM. The morphology of nearby PNs was examined, and a number of strongly asymmetric nebuale were found.

  17. SULFURIZATION OF IRON IN THE DYNAMIC SOLAR NEBULA AND IMPLICATIONS FOR PLANETARY COMPOSITIONS

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

    Ciesla, Fred J., E-mail: fciesla@uchicago.edu

    One explanation for the enhanced ratio of volatiles to hydrogen in Jupiter’s atmosphere compared to a a gas of solar composition is that the planet accreted volatile-bearing clathrates during its formation. Models, however, suggest that S would be over abundant if clathrates were the primary carrier of Jupiter’s volatiles. This led to the suggestion that S was depleted in the outer nebula due to the formation troilite (FeS). Here, this depletion is quantitatively explored by modeling the coupled dynamical and chemical evolution of Fe grains in the solar nebula. It is found that disks that undergo rapid radial expansion frommore » an initially compact state may allow sufficient production of FeS and carry H{sub 2}S-depleted gas outward where ices would form, providing the conditions needed for S-depleted clathrates to form. However, this expansion would also carry FeS grains to this region, which could also be incorporated into planetesimals. Thus for clathrates to be a viable source of volatiles, models must account for the presence of both H{sub 2}S in FeS in the outer solar nebula.« less

  18. Hubble View of a Nitrogen-Rich Nebula

    NASA Image and Video Library

    2015-06-26

    This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4,000 light-years away in the southern constellation of Scorpius (The Scorpion). The faint blue haze across the frame shows what remains of a star like the sun after it has depleted most of its fuel. When this happens, the outer layers of the star are ejected, and get excited and ionized by the energetic ultraviolet light emitted by the bright hot core of the star, forming the nebula. NGC 6153 is a planetary nebula that is elliptical in shape, with an extremely rich network of loops and filaments, shown clearly in this Hubble image. However, this is not what makes this planetary nebula so interesting for astronomers. Measurements show that NGC 6153 contains large amounts of neon, argon, oxygen, carbon and chlorine — up to three times more than can be found in the solar system. The nebula contains a whopping five times more nitrogen than our sun! Although it may be that the star developed higher levels of these elements as it grew and evolved, it is more likely that the star originally formed from a cloud of material that already contained a lot more of these elements. Text credit: European Space Agency Image credit: ESA/Hubble & NASA, Acknowledgement: Matej Novak 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

  19. OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT

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

    Loll, A. M.; Desch, S. J.; Scowen, P. A.

    2013-03-10

    We present the first Hubble Space Telescope Wide Field Planetary Camera-2 imaging survey of the entire Crab Nebula, in the filters F502N ([O III] emission), F673N ([S II]), F631N ([O I]), and F547M (continuum). We use our mosaics to characterize the pulsar wind nebula (PWN) and its three-dimensional structure, the ionizational structure in the filaments forming at its periphery, the speed of the shock driven by the PWN into surrounding ejecta (by inferring the cooling rates behind the shock), and the morphology and ionizational structure of the Rayleigh-Taylor (R-T) fingers. We quantify a number of asymmetries between the northwest (NW)more » and southeast (SE) quadrants of the Crab Nebula. The lack of observed filaments in the NW, and our observations of the spatial extent of [O III] emission lead us to conclude that cooling rates are slower, and therefore the shock speeds are greater, in the NW quadrant of the nebula, compared with the SE. We conclude that R-T fingers are longer, more ionizationally stratified, and apparently more massive in the NW than in the SE, and the R-T instability appears more fully developed in the NW.« less

  20. INTERNAL PROPER MOTIONS IN THE ESKIMO NEBULA

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

    García-Díaz, Ma. T.; Gutiérrez, L.; Steffen, W.

    We present measurements of internal proper motions at more than 500 positions of NGC 2392, the Eskimo Nebula, based on images acquired with WFPC2 on board the Hubble Space Telescope at two epochs separated by 7.695 yr. Comparisons of the two observations clearly show the expansion of the nebula. We measured the amplitude and direction of the motion of local structures in the nebula by determining their relative shift during that interval. In order to assess the potential uncertainties in the determination of proper motions in this object, in general, the measurements were performed using two different methods, used previously in themore » literature. We compare the results from the two methods, and to perform the scientific analysis of the results we choose one, the cross-correlation method, because it is more reliable. We go on to perform a ''criss-cross'' mapping analysis on the proper motion vectors, which helps in the interpretation of the velocity pattern. By combining our results of the proper motions with radial velocity measurements obtained from high resolution spectroscopic observations, and employing an existing 3D model, we estimate the distance to the nebula to be 1.3 kpc.« less

  1. Facilitating NASA Earth Science Data Processing Using Nebula Cloud Computing

    NASA Astrophysics Data System (ADS)

    Chen, A.; Pham, L.; Kempler, S.; Theobald, M.; Esfandiari, A.; Campino, J.; Vollmer, B.; Lynnes, C.

    2011-12-01

    Cloud Computing technology has been used to offer high-performance and low-cost computing and storage resources for both scientific problems and business services. Several cloud computing services have been implemented in the commercial arena, e.g. Amazon's EC2 & S3, Microsoft's Azure, and Google App Engine. There are also some research and application programs being launched in academia and governments to utilize Cloud Computing. NASA launched the Nebula Cloud Computing platform in 2008, which is an Infrastructure as a Service (IaaS) to deliver on-demand distributed virtual computers. Nebula users can receive required computing resources as a fully outsourced service. NASA Goddard Earth Science Data and Information Service Center (GES DISC) migrated several GES DISC's applications to the Nebula as a proof of concept, including: a) The Simple, Scalable, Script-based Science Processor for Measurements (S4PM) for processing scientific data; b) the Atmospheric Infrared Sounder (AIRS) data process workflow for processing AIRS raw data; and c) the GES-DISC Interactive Online Visualization ANd aNalysis Infrastructure (GIOVANNI) for online access to, analysis, and visualization of Earth science data. This work aims to evaluate the practicability and adaptability of the Nebula. The initial work focused on the AIRS data process workflow to evaluate the Nebula. The AIRS data process workflow consists of a series of algorithms being used to process raw AIRS level 0 data and output AIRS level 2 geophysical retrievals. Migrating the entire workflow to the Nebula platform is challenging, but practicable. After installing several supporting libraries and the processing code itself, the workflow is able to process AIRS data in a similar fashion to its current (non-cloud) configuration. We compared the performance of processing 2 days of AIRS level 0 data through level 2 using a Nebula virtual computer and a local Linux computer. The result shows that Nebula has significantly

  2. Distinguishing between HII regions and planetary nebulae with Hi-GAL, WISE, MIPSGAL, and GLIMPSE

    NASA Astrophysics Data System (ADS)

    Anderson, L. D.; Zavagno, A.; Barlow, M. J.; García-Lario, P.; Noriega-Crespo, A.

    2012-01-01

    Context. H II regions and planetary nebulae (PNe) both emit at radio and infrared (IR) wavelengths, and angularly small H II regions can be mistaken for PNe. This problem of classification is most severe for H II regions in an early evolutionary stage, those that are extremely distant, or those that are both young and distant. Previous work has shown that H II regions and PNe can be separated based on their infrared colors. Aims: Using data from the Herschel Hi-GAL survey, as well as WISE and the Spitzer MIPSGAL and GLIMPSE surveys, we wish to establish characteristic IR colors that can be used to distinguish between H II regions and PNe. Methods: We perform aperture photometry measurements for a sample of 126 H II regions and 43 PNe at wavelengths from 8.0 μm to 500 μm. Results: We find that H II regions and PNe have distinct IR colors. The most robust discriminating color criteria are [F12/F8] < 0.3, [F160/F12] > 1.3, and [F160/F24] > 0.8 (or alternately [F160/F22] > 0.8), where the brackets indicate the log of the flux ratio. All three of these criteria are individually satisfied by over 98% of our sample of H II regions and by ~10% of our sample of PNe. Combinations of these colors are more robust in separating the two populations; for example all H II regions and no PNe satisfy [F12/F8] < 0.4 and [F160/F22] > 0.8. When applied to objects of unknown classification, these criteria prove useful in separating the two populations. The dispersion in color is relatively small for H II regions; this suggests that any evolution in these colors with time for H II regions must be relatively modest. The spectral energy distributions (SEDs) of H II regions can be separated into "warm" and "cold" components. The "cold" component is well-fit by a grey-body of temperature 25 K. The SEDs of nearly two-thirds of our sample of H II regions peak at 160 μm and one third peak at 70 μm. For PNe, 67% of the SEDs peak at 70 μm, 23% peak at either 22 μm or 24 μm, and 9% (two

  3. Hubble Finds an Hourglass Nebula around a Dying Star

    NASA Image and Video Library

    1996-01-16

    This Hubble telescope snapshot of MyCn18, a young planetary nebula, reveals that the object has an hourglass shape with an intricate pattern of etchings in its walls. A planetary nebula is the glowing relic of a dying, Sun-like star.

  4. Monitoring of the Crab Nebula with Chandra and Other Observatories Including HST

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.

    2014-01-01

    Subsequent to the detections AGILE and Fermi/LAT of the gamma-ray flares from the Crab Nebula in the fall of 2010, this team has been monitoring the X-Ray emission from the Crab on a regular basis. X-Ray observations have taken place typically once per month when viewing constraints allow and more recently four times per year. There have been notable exceptions, e.g. in April of 2011 and March 2013 when we initiated a set of Chandra Target of opportunity observations in conjunction with bright gamma-ray flares. For much of the time regular HST observations were made in conjunction with the Chandra observations. The aim of this program to further characterize, in depth, the X-Ray and optical variations that take place in the nebula, and by so doing determine the regions which contribute to the harder X-ray variations and, if possible, determine the precise location within the Nebula of the origin of the gamma-ray flares. As part of this project members of the team have developed Singular Value Decomposition techniques to sequences of images in order to more accurately characterize features. The current status of the project will be presented highlighting studies of the inner knot and possible correlations with the flares.

  5. The Photoevaporation of a Neutral Structure by an EUV+FUV Radiation Field

    NASA Astrophysics Data System (ADS)

    Lora, Veronica; Vasconcelos, M. J.; Raga, A. C.; Cerqueira, A. H.; Esquivel, A.

    The expansion of an HII region into a surrounding inhomogeneous molecular cloud, leads to the formation of elongated "elephant trunk" structures. The EUV photo-ionising radiation and FUV dissociating radiation from newly born stars photo-evaporate their parental neutral cloud, leading to the formation of dense clumps in the tips of elephant trunks, that could in principle eventually form stars. We study th effects of including a photo-dissociating FUV flux in models of fragmentation of a photo-evaporating, self-gravitating molecular cloud.

  6. Are major dissociative disorders characterized by a qualitatively different kind of dissociation?

    PubMed

    Rodewald, Frauke; Dell, Paul F; Wilhelm-Gossling, Claudia; Gast, Ursula

    2011-01-01

    A total of 66 patients with a major dissociative disorder, 54 patients with nondissociative disorders, and 30 nonclinical controls were administered the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised, the Dissociative Experiences Scale, the Multidimensional Inventory of Dissociation, and the Symptom Checklist 90-Revised. Dissociative patients reported significantly more dissociative and nondissociative symptoms than did nondissociative patients and nonclinical controls. When general psychopathology was controlled, the dissociation scores of dissociative patients were still significantly higher than those of both other groups, whereas the dissociation scores of nondissociative patients and nonclinical controls no longer differed. These findings appear to be congruent with a typological model of dissociation that distinguishes between 2 qualitatively different kinds of dissociation. Specifically, the results of this study suggest that the dissociation that occurs in major dissociative disorders (i.e., dissociative identity disorder [DID] and dissociative disorder not otherwise specified, Type 1 [DDNOS-1]) is qualitatively different from the dissociation that occurs in persons who do not have a dissociative disorder. In contrast to previous research, the dissociation of persons who do not have a dissociative disorder is not limited to absorption; it covers a much wider range of phenomena. The authors hypothesize that different mechanisms produce the dissociation of persons with DID and DDNOS-1 as opposed to the dissociation of persons who do not have a dissociative disorder.

  7. Transformation of Graphitic and Amorphous Carbon Dust to Complex Organic Molecules in a Massive Carbon Cycle in Protostellar Nebulae

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Johnson, Natasha M.

    2012-01-01

    More than 95% of silicate minerals and other oxides found in meteorites were melted, or vaporized and recondensed in the Solar Nebula prior to their incorporation into meteorite parent bodies. Gravitational accretion energy and heating via radioactive decay further transformed oxide minerals accreted into planetesimals. In such an oxygen-rich environment the carbonaceous dust that fell into the nebula as an intimate mixture with oxide grains should have been almost completely converted to CO. While some pre-collapse, molecular-cloud carbonaceous dust does survive, much in the same manner as do pre-solar oxide grains, such materials constitute only a few percent of meteoritic carbon and are clearly distinguished by elevated D/H, N-15/N-16, C-13/C-12 ratios or noble gas patterns. Carbonaceous Dust in Meteorites: We argue that nearly all of the carbon in meteorites was synthesized in the Solar Nebula from CO and that this CO was generated by the reaction of carbonaceous dust with solid oxides, water or OH. It is probable that some fraction of carbonaceous dust that is newly synthesized in the Solar Nebula is also converted back into CO by additional thermal processing. CO processing might occur on grains in the outer nebula through irradiation of CO-containing ice coatings or in the inner nebula via Fischer-Tropsch type (FTT) reactions on grain surfaces. Large-scale transport of both gaseous reaction products and dust from the inner nebula out to regions where comets formed would spread newly formed carbonaceous materials throughout the solar nebula. Formation of Organic Carbon: Carbon dust in the ISM might easily be described as inorganic graphite or amorphous carbon, with relatively low structural abundances of H, N, O and S . Products of FTT reactions or organics produced via irradiation of icy grains contain abundant aromatic and aliphatic hydrocarbons. aldehydes, keytones, acids, amines and amides.. The net result of the massive nebular carbon cycle is to convert

  8. Dissociable roles of default-mode regions during episodic encoding.

    PubMed

    Maillet, David; Rajah, M Natasha

    2014-04-01

    We investigated the role of distinct regions of the default-mode network (DMN) during memory encoding with fMRI. Subjects encoded words using either a strategy that emphasized self-referential (pleasantness) processing, or one that emphasized semantic (man-made/natural) processing. During encoding subjects were intermittently presented with thought probes to evaluate if they were concentrated and on-task or exhibiting task-unrelated thoughts (TUT). After the scanning session subjects performed a source retrieval task to determine which of two judgments they performed for each word at encoding. Source retrieval accuracy was higher for words encoded with the pleasantness vs. the man-made/natural task and there was a trend for higher performance for words preceding on-task vs. TUT reports. fMRI results show that left anterior medial PFC and left angular gyrus activity was greater during successful vs. unsuccessful encoding during both encoding tasks. Greater activity in left anterior cingulate and bilateral lateral temporal cortex was related successful vs. unsuccessful encoding only in the pleasantness task. In contrast, posterior cingulate, right anterior cingulate and right temporoparietal junction were activated to a greater extent in unsuccessful vs. successful encoding across tasks. Finally, activation in posterior cingulate and bilateral dorsolateral prefrontal cortex was related to TUT across tasks; moreover, we observed a conjunction in posterior cingulate between encoding failure and TUT. We conclude that DMN regions play dissociable roles during memory formation, and that their association with subsequent memory may depend on the manner in which information is encoded and retrieved. Crown Copyright © 2013. Published by Elsevier Inc. All rights reserved.

  9. The Generation of Lighting in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey; Desch, S. J.; DeVincenzi, Donald (Technical Monitor)

    1998-01-01

    The process that melted and formed the chondrules, mm-sized glassy beads within meteorites, has not been conclusively identified. Origin by lightning in the solar nebula is consistent with many features of chondrules, but no viable model of lightning has yet been advanced. We present a model demonstrating how lightning could be generated in the solar nebula which differs from previous models in three important aspects. First, we identify a new', powerful charging mechanism that is based on the differences in contact potentials between particles of different composition, a form of triboelectric charging. In the presence of fine silicate grains and fine iron metal grains, large silicate particles (the chondrules) can acquire charges of +10(exp 5) e. Second, we assume that the chondrule precursor particles are selectively concentrated in clumps 1 - 100 km in size by the turbulent concentration mechanism described by Cuzzi et al. (1996). The concentration of these highly charged particles into clumps, in a background of negatively charged metal grains, is what generates the strong electric fields. Third, we make refinements in the estimates of the breakdown electric field and the ionization rate. We calculate that electric fields large enough to trigger breakdown easily could have existed over regions large enough (approx. 100km) to generate very large discharges of electrical energy (approx. 10(exp 16)erg). The discharges would have been sufficiently energetic and frequent to have formed the chondrules. We place constraints on the generation of lightning and conclude that it could not be generated if the abundance of Al-26 in chondrules was as high as the level in the CAls. This conclusion is consistent with isotopic analyses of chondrules. This possibly implies that Al-26 was non-uniformly distributed in the solar nebula or that the chondrules formed several Myr after the CAIs.

  10. Inside the Flame Nebula

    NASA Image and Video Library

    2014-05-07

    This composite image shows one of the clusters, NGC 2024, which is found in the center of the so-called Flame Nebula about 1,400 light years from Earth. Astronomers have studied two star clusters using NASA Chandra and infrared telescopes.

  11. Photometry and imaging of the peculiar planetary nebula IRAS 21282 + 5050

    NASA Technical Reports Server (NTRS)

    Kwok, Sun; Hrivnak, Bruce J.; Langill, Philip P.

    1993-01-01

    We report visible, near-infrared, and mid-infrared photometry of the IRAS planetary nebula 21282+ 5050. Narrow-band photometry at 10 microns confirms the presence of the 11.3-micron PAH feature. IRAS 21282+5050 belongs to a small group of planetary nebulae with WC11 nuclei and PAH emission. The spectral energy distribution shows that majority of the flux is emitted in the infrared, and the object has one of the highest infrared excesses among all planetary nebulae. Optical imaging (after subtraction of the central star) reveals a nebula of size of about 7 x 5 arcsec which is elongated along the N-S direction.

  12. Radio observations of globulettes in the Carina nebula

    NASA Astrophysics Data System (ADS)

    Haikala, L. K.; Gahm, G. F.; Grenman, T.; Mäkelä, M. M.; Persson, C. M.

    2017-06-01

    Context. The Carina nebula hosts a large number of globulettes. An optical study of these tiny molecular clouds shows that the majority are of planetary mass, but there are also those with masses of several tens up to a few hundred Jupiter masses. Aims: We seek to search for, and hopefully detect, molecular line emission from some of the more massive objects; in case of successful detection we aim to map their motion in the Carina nebula complex and derive certain physical properties. Methods: We carried out radio observations of molecular line emission in 12CO and 13CO (2-1) and (3-2) of 12 globulettes in addition to positions in adjacent shell structures using APEX. Results: All selected objects were detected with radial velocities shifted relative to the emission from related shell structures and background molecular clouds. Globulettes along the western part of an extended dust shell show a small spread in velocity with small velocity shifts relative to the shell. This system of globulettes and shell structures in the foreground of the bright nebulosity surrounding the cluster Trumpler 14 is expanding with a few km s-1 relative to the cluster. A couple of isolated globulettes in the area move at similar speed. Compared to similar studies of the molecular line emission from globulettes in the Rosette nebula, we find that the integrated line intensity ratios and line widths are very different. The results show that the Carina objects have a different density/temperature structure than those in the Rosette nebula. In comparison the apparent size of the Carina globulettes is smaller, owing to the larger distance, and the corresponding beam filling factors are small. For this reason we were unable to carry out a more detailed modelling of the structure of the Carina objects in the way as performed for the Rosette objects. Conclusions: The Carina globulettes observed are compact and denser than objects of similar mass in the Rosette nebula. The distribution and

  13. Photodissociation Regions in the Interstellar Medium of Galaxies

    NASA Technical Reports Server (NTRS)

    Hollenbach, David J.; Tielens, A. G. G. M.; DeVincenzi, Donald L. (Technical Monitor)

    1999-01-01

    The interstellar medium of galaxies is the reservoir out of which stars are born and into which stars inject newly created elements as they age. The physical properties of the interstellar medium are governed in part by the radiation emitted by these stars. Far-ultraviolet (6 eV less than h(nu) less than 13.6 eV) photons from massive stars dominate the heating and influence the chemistry of the neutral atomic gas and much of the molecular gas in galaxies. Predominantly neutral regions of the interstellar medium in which the heating and chemistry are regulated by far ultraviolet photons are termed Photo-Dissociation Regions (PDRs). These regions are the origin of most of the non-stellar infrared (IR) and the millimeter and submillimeter CO emission from galaxies. The importance of PDRs has become increasingly apparent with advances in IR and submillimeter astronomy. The IR emission from PDRs includes fine structure lines of C, C+, and O; rovibrational lines of H2, rotational lines of CO; broad middle features of polycyclic aromatic hydrocarbons; and a luminous underlying IR continuum from interstellar dust. The transition of H to H2 and C+ to CO occurs within PDRs. Comparison of observations with theoretical models of PDRs enables one to determine the density and temperature structure, the elemental abundances, the level of ionization, and the radiation field. PDR models have been applied to interstellar clouds near massive stars, planetary nebulae, red giant outflows, photoevaporating planetary disks around newly formed stars, diffuse clouds, the neutral intercloud medium, and molecular clouds in the interstellar radiation field-in summary, much of the interstellar medium in galaxies. Theoretical PDR models explain the observed correlations of the [CII] 158 microns with the COJ = 1-0 emission, the COJ = 1-0 luminosity with the interstellar molecular mass, and the [CII] 158 microns plus [OI] 63 microns luminosity with the IR continuum luminosity. On a more global

  14. The Impact of FU Orionis Outbursts and the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Bell, Robbins; Young, Richard E. (Technical Monitor)

    1998-01-01

    including the following effects: (1) heating of the planet forming region by direct radiation from the hot inner nebula; (2) heating by the diffuse radiation field of a coccooning envelope; and (3) time-dependent penetration of the increased luminosity from the above sources into the optically thick nebula. Some of this work is currently in progress. The potential effects on condensation and migration in the nebula and the thermal processing of solids will be evaluated.

  15. Tracing the energetics and evolution of dust with Spitzer: a chapter in the history of the Eagle Nebula

    NASA Astrophysics Data System (ADS)

    Flagey, N.; Boulanger, F.; Noriega-Crespo, A.; Paladini, R.; Montmerle, T.; Carey, S. J.; Gagné, M.; Shenoy, S.

    2011-07-01

    Context. The Spitzer GLIMPSE and MIPSGAL surveys have revealed a wealth of details about the Galactic plane in the infrared (IR) with orders of magnitude higher sensitivity, higher resolution, and wider coverage than previous IR observations. The structure of the interstellar medium (ISM) is tightly connected to the countless star-forming regions. We use these surveys to study the energetics and dust properties of the Eagle Nebula (M 16), one of the best known star-forming regions. Aims: We present MIPSGAL observations of M 16 at 24 and 70 μm and combine them with previous IR data. The mid-IR image shows a shell inside the well-known molecular borders of the nebula, as in the ISO and MSX observations from 15 to 21 μm. The morphologies at 24 and 70 μm are quite different, and its color ratio is unusually warm. The far-IR image resembles the one at 8 μm that enhances the structure of the molecular cloud and the "pillars of creation". We use this set of IR data to analyze the dust energetics and properties within this template for Galactic star-forming regions. Methods: We measure IR spectral energy distributions (SEDs) across the entire nebula, both within the inner shell and the photodissociation regions (PDRs). We use the DUSTEM model to fit these SEDs and constrain the dust temperature, the dust-size distribution, and the radiation field intensity relative to that provided by the star cluster NGC 6611 (χ/χ0). Results: Within the PDRs, the inferred dust temperature (~35 K), the dust-size distribution, and the radiation field intensity (χ/χ0 < 1) are consistent with expectations. Within the inner shell, the dust is hotter (~70 K). Moreover, the radiation field required to fit the SED is larger than that provided by NGC 6611 (χ/χ0 > 1). We quantify two solutions to this problem: (1) The size distribution of the dust in the shell is not that of interstellar dust. There is a significant enhancement of the carbon dust-mass in stochastically heated very small

  16. Dissociative amnesia.

    PubMed

    Staniloiu, Angelica; Markowitsch, Hans J

    2014-08-01

    Dissociative amnesia is one of the most enigmatic and controversial psychiatric disorders. In the past two decades, interest in the understanding of its pathophysiology has surged. In this report, we review new data about the epidemiology, neurobiology, and neuroimaging of dissociative amnesia and show how advances in memory research and neurobiology of dissociation inform proposed pathogenetic models of the disorder. Dissociative amnesia is characterised by functional impairment. Additionally, preliminary data suggest that affected people have an increased and possibly underestimated suicide risk. The prevalence of dissociative amnesia differs substantially across countries and populations. Symptoms and disease course also vary, indicating a possibly heterogeneous disorder. The accompanying clinical features differ across cultural groups. Most dissociative amnesias are retrograde, with memory impairments mainly involving the episodic-autobiographical memory domain. Anterograde dissociative amnesia occurring without significant retrograde memory impairments is rare. Functional neuroimaging studies of dissociative amnesia with prevailing retrograde memory impairments show changes in the network that subserves autobiographical memory. At present, no evidence-based treatments are available for dissociative amnesia and no broad framework exists for its rehabilitation. Further research is needed into its neurobiology, course, treatment options, and strategies to improve differential diagnoses. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Turbulent Magnetic Relaxation in Pulsar Wind Nebulae

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

    Zrake, Jonathan; Arons, Jonathan

    We present a model for magnetic energy dissipation in a pulsar wind nebula. A better understanding of this process is required to assess the likelihood that certain astrophysical transients may be powered by the spin-down of a “millisecond magnetar.” Examples include superluminous supernovae, gamma-ray bursts, and anticipated electromagnetic counterparts to gravitational wave detections of binary neutron star coalescence. Our model leverages recent progress in the theory of turbulent magnetic relaxation to specify a dissipative closure of the stationary magnetohydrodynamic (MHD) wind equations, yielding predictions of the magnetic energy dissipation rate throughout the nebula. Synchrotron losses are self-consistently treated. To demonstratemore » the model’s efficacy, we show that it can reproduce many features of the Crab Nebula, including its expansion speed, radiative efficiency, peak photon energy, and mean magnetic field strength. Unlike ideal MHD models of the Crab (which lead to the so-called σ -problem), our model accounts for the transition from ultra to weakly magnetized plasma flow and for the associated heating of relativistic electrons. We discuss how the predicted heating rates may be utilized to improve upon models of particle transport and acceleration in pulsar wind nebulae. We also discuss implications for the Crab Nebula’s γ -ray flares, and point out potential modifications to models of astrophysical transients invoking the spin-down of a millisecond magnetar.« less

  18. Turbulent Magnetic Relaxation in Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Zrake, Jonathan; Arons, Jonathan

    2017-09-01

    We present a model for magnetic energy dissipation in a pulsar wind nebula. A better understanding of this process is required to assess the likelihood that certain astrophysical transients may be powered by the spin-down of a “millisecond magnetar.” Examples include superluminous supernovae, gamma-ray bursts, and anticipated electromagnetic counterparts to gravitational wave detections of binary neutron star coalescence. Our model leverages recent progress in the theory of turbulent magnetic relaxation to specify a dissipative closure of the stationary magnetohydrodynamic (MHD) wind equations, yielding predictions of the magnetic energy dissipation rate throughout the nebula. Synchrotron losses are self-consistently treated. To demonstrate the model’s efficacy, we show that it can reproduce many features of the Crab Nebula, including its expansion speed, radiative efficiency, peak photon energy, and mean magnetic field strength. Unlike ideal MHD models of the Crab (which lead to the so-called σ-problem), our model accounts for the transition from ultra to weakly magnetized plasma flow and for the associated heating of relativistic electrons. We discuss how the predicted heating rates may be utilized to improve upon models of particle transport and acceleration in pulsar wind nebulae. We also discuss implications for the Crab Nebula’s γ-ray flares, and point out potential modifications to models of astrophysical transients invoking the spin-down of a millisecond magnetar.

  19. Hubble Hatches Image of Rotten Egg Nebula Shocks

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Some 5,000 light years (2,900 trillion miles) from Earth, in the constellation Puppis, is the 1.4 light years (more than 8 trillion miles) long Calabash Nebula, referred to as the Rotten Egg Nebula because of its sulfur content which would produce an awful odor if one could smell in space. This image of the nebula captured by NASA's Hubble Space Telescope (HST) depicts violent gas collisions that produced supersonic shock fronts in a dying star. Stars, like our sun, will eventually die and expel most of their material outward into shells of gas and dust These shells eventually form some of the most beautiful objects in the universe, called planetary nebulae. The yellow in the image depicts the material ejected from the central star zooming away at speeds up to one and a half million kilometers per hour (one million miles per hour). Due to the high speeds of the gas, shock-fronts are formed on impact and heat the surrounding gas. Although computer calculations have predicted the existence and structure of such shocks for some time, previous observations have not been able to prove the theory.

  20. Hard X-ray Variations in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Chaplin, V.; Connaughton, V.; hide

    2013-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, approximately 7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/PCA was particularly variable, changing by up to approximately 3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. I will present updated light curves in multiple energy bands for the Crab nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL and MAXI, and a 16-year long light curve from RXTE/PCA.

  1. Hard X-ray Variations in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgarter, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Chaplin, V.; Connaughton, V.; hide

    2012-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, a approx.7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/PCA was particularly variable, changing by up to approx.3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. I will present updated light curves in multiple energy bands for the Crab nebula, including recent data from Fermi GBM, Swift/BAT, and MAXI, and a 16-year long light curve from RXTE/PCA.

  2. Hard X-ray Variations in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.; Cherry, M. L.; Case, G. L.; Baumgartner, W. H.; Beklen, E.; Bhat, P. N.; Briggs, M. S.; Camero-Arranz, A.; Connaughton, V.; Finger, M. H.; hide

    2013-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, approximately 7% (70 mcrab) decline was discovered in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline was independently confirmed with four other instruments: the RXTE/PCA, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA from 1999-2010 was consistent with the pulsar spin-down, indicating that the observed changes were nebular. From 2001 to 2010, the Crab nebula flux measured with RXTE/ PCA was particularly variable, changing by up to approximately 3.5% per year in the 15-50 keV band. These variations were confirmed with INTEGRAL/SPI starting in 2003, Swift/BAT starting in 2005, and Fermi GBM starting in 2008. Before 2001 and since 2010, the Crab nebula flux has appeared more stable, varying by less than 2% per year. I will present updated light curves in multiple energy bands for the Crab Nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL and MAXI, and a 16-year long light curve from RXTE/PCA.

  3. Lots of Small Stars Born in Starburst Region

    NASA Astrophysics Data System (ADS)

    1999-10-01

    -known Trapezium cluster in the Orion Nebula . In fact, the star cluster in NGC 3603 is in many respects very similar to the core of the large, ionizing cluster in the approx. eight times more distant Tarantula Nebula in the LMC. The new VLT observations ESO PR Photo 38a/99 ESO PR Photo 38a/99 [Preview - JPEG: 400 x 447 pix - 296k] [Normal - JPEG: 800 x 894 pix - 956k] [Full-Res - JPEG: 1366 x 1526 pix - 1.7M] ESO PR Photo 38b/99 ESO PR Photo 38b/99 [Preview - JPEG: 400 x 448 pix - 200k] [Full-Res - JPEG: 516 x 578 pix - 238k] Caption : ESO PR Photo 38a/99 is a composite "false-colour" infrared image of the starburst region NGC 3603 that is composed from three exposures obtained with the multi-mode ISAAC instrument at the Nasmyth focus of the first 8.2-m VLT Unit Telescope (ANTU) in April 1999. Three near-infrared filters were used, J s (wavelength 1.24 µm; here reproduced in blue), H (1.65 µm; green) and K s (2.17 µm; red). The intensities are scaled in logarithmic units and the field measures 3.4 x 3.4 arcmin 2 , or about 20 x 20 light-years 2 at the distance of the nebula. North is up; East to the left. The central cluster is the densest concentration of massive stars known in the Milky Way (this area is enlarged in ESO PR Photo 38b/99 ; the field shown is about 2.5 x 2.5 light-years 2 ). It hosts more than 50 hot O-type stars. The brightest star in the field is the red supergiant IRS4 ; it is located about 80 arcsec NE of the center. About 18 arcsec N of the center are the ring nebula and the bipolar outflows around the blue supergiant Sher25 . The photo also shows three proplyd-like objects [2] that have been recently discovered; they are similar to those seen in Orion Nebula, but 20-30 times more extended. About 1 arcmin SSE of the central cluster are seen the brightest members of the deeply embedded proto cluster IRS9 . The nebulosities to the South and West of the center appear to be red because of strong emission in the Bracket-gamma spectral line from hydrogen atoms

  4. Products of Dissociative Recombination in the Ionosphere

    NASA Technical Reports Server (NTRS)

    Cosby, Philip

    1996-01-01

    SRI International undertook a novel experimental measurement of the product states formed by dissociative ro-combination (DR) of C2(+), NO(+), and N2(+) as a function of both electron energy and reactant ion vibrational level. For these measurements we used a recently developed experimental technique for measuring dissociation product distributions that allows both the branching ratios to be accurately determined and the electronic and ro-vibrational state composition of the reactant ions to be specified. DR is the dominant electron loss mechanism in all regions of the ionosphere. In this process, electron attachment to the molecular ion produces an unstable neutral molecule that rapidly dissociates.

  5. A Hyperspectral View of the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Charlebois, M.; Drissen, L.; Bernier, A.-P.; Grandmont, F.; Binette, L.

    2010-05-01

    We have obtained spatially resolved spectra of the Crab nebula in the spectral ranges 450-520 nm and 650-680 nm, encompassing the Hβ, [O III] λ4959, λ5007, Hα, [N II] λ6548, λ6584, and [S II] λ6717, λ6731 emission lines, with the imaging Fourier transform spectrometer SpIOMM at the Observatoire du Mont-Mégantic's 1.6 m telescope. We first compare our data with published observations obtained either from a Fabry-Perot interferometer or from a long-slit spectrograph. Using a spectral deconvolution technique similar to the one developed by Čadež et al., we identify and resolve multiple emission lines separated by large Doppler shifts and contained within the rapidly expanding filamentary structure of the Crab. This allows us to measure important line ratios, such as [N II]/Hα, [S II]/Hα, and [S II] λ6717 /[S II] λ6731 of individual filaments, providing a new insight on the SE-NW asymmetry in the Crab. From our analysis of the spatial distribution of the electronic density and of the respective shocked versus photoionized gas components, we deduce that the skin-less NW region must have evolved faster than the rest of the nebula. Assuming a very simple expansion model for the ejecta material, our data provide us with a complete tridimensional view of the Crab.

  6. Magnetic fields in central stars of planetary nebulae?

    NASA Astrophysics Data System (ADS)

    Jordan, S.; Bagnulo, S.; Werner, K.; O'Toole, S. J.

    2012-06-01

    Context. Most planetary nebulae have bipolar or other non-spherically symmetric shapes. Magnetic fields in the central star may be responsible for this lack of symmetry, but observational studies published to date have reported contradictory results. Aims: We search for correlations between a magnetic field and departures from the spherical geometry of the envelopes of planetary nebulae. Methods: We determine the magnetic fields from spectropolarimetric observations of ten central stars of planetary nebulae. The results of the analysis of the observations of four stars were previously presented and discussed in the literature, while the observations of six stars, plus additional measurements of a star previously observed, are presented here for the first time. Results: All our determinations of magnetic field in the central planetary nebulae are consistent with null results. Our field measurements have a typical error bar of 150-300 G. Previous spurious field detections using data acquired with FORS1 (FOcal Reducer and low dispersion Spectrograph) of the Unit Telescope 1 (UT1) of the Very Large Telescope (VLT) were probably due to the use of different wavelength calibration solutions for frames obtained at different position angles of the retarder waveplate. Conclusions: There is currently no observational evidence of magnetic fields with a strength of the order of hundreds Gauss or higher in the central stars of planetary nebulae. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile, under programme ID 072.D-0089 (PI = Jordan) and 075.D-0289 (PI = Jordan).

  7. Observatories Combine to Crack Open the Crab Nebula

    NASA Image and Video Library

    2017-12-08

    Astronomers have produced a highly detailed image of the Crab Nebula, by combining data from telescopes spanning nearly the entire breadth of the electromagnetic spectrum, from radio waves seen by the Karl G. Jansky Very Large Array (VLA) to the powerful X-ray glow as seen by the orbiting Chandra X-ray Observatory. And, in between that range of wavelengths, the Hubble Space Telescope's crisp visible-light view, and the infrared perspective of the Spitzer Space Telescope. This video starts with a composite image of the Crab Nebula, a supernova remnant that was assembled by combining data from five telescopes spanning nearly the entire breadth of the electromagnetic spectrum: the Very Large Array, the Spitzer Space Telescope, the Hubble Space Telescope, the XMM-Newton Observatory, and the Chandra X-ray Observatory. The video dissolves to the red-colored radio-light view that shows how a neutron star’s fierce “wind” of charged particles from the central neutron star energized the nebula, causing it to emit the radio waves. The yellow-colored infrared image includes the glow of dust particles absorbing ultraviolet and visible light. The green-colored Hubble visible-light image offers a very sharp view of hot filamentary structures that permeate this nebula. The blue-colored ultraviolet image and the purple-colored X-ray image shows the effect of an energetic cloud of electrons driven by a rapidly rotating neutron star at the center of the nebula. Read more: go.nasa.gov/2r0s8VC Credits: NASA, ESA, J. DePasquale (STScI)

  8. A radial velocity survey of the Carina Nebula's O-type stars

    NASA Astrophysics Data System (ADS)

    Kiminki, Megan M.; Smith, Nathan

    2018-06-01

    We have obtained multi-epoch observations of 31 O-type stars in the Carina Nebula using the CHIRON spectrograph on the CTIO/SMARTS 1.5-m telescope. We measure their radial velocities to 1-2 km s-1 precision and present new or updated orbital solutions for the binary systems HD 92607, HD 93576, HDE 303312, and HDE 305536. We also compile radial velocities from the literature for 32 additional O-type and evolved massive stars in the region. The combined data set shows a mean heliocentric radial velocity of 0.6 km s-1. We calculate a velocity dispersion of ≤9.1 km s-1, consistent with an unbound, substructured OB association. The Tr 14 cluster shows a marginally significant 5 km s-1 radial velocity offset from its neighbour Tr 16, but there are otherwise no correlations between stellar position and velocity. The O-type stars in Cr 228 and the South Pillars region have a lower velocity dispersion than the region as a whole, supporting a model of distributed massive star formation rather than migration from the central clusters. We compare our stellar velocities to the Carina Nebula's molecular gas and find that Tr 14 shows a close kinematic association with the Northern Cloud. In contrast, Tr 16 has accelerated the Southern Cloud by 10-15 km s-1, possibly triggering further massive star formation. The expansion of the surrounding H II region is not symmetric about the O-type stars in radial velocity space, indicating that the ionized gas is constrained by denser material on the far side.

  9. A search for ejecta nebulae around Wolf-Rayet stars using the SHS Hα survey

    NASA Astrophysics Data System (ADS)

    Stock, D. J.; Barlow, M. J.

    2010-12-01

    Recent large-scale Galactic plane Hα surveys allow a re-examination of the environs of Wolf-Rayet (WR) stars for the presence of a circumstellar nebula. Using the morphologies of WR nebulae known to be composed of stellar ejecta as a guide, we constructed ejecta nebula criteria similar to those of Chu and searched for likely WR ejecta nebulae in the Southern Hα Survey (SHS). A new WR ejecta nebula around WR 8 is found and its morphology is discussed. The fraction of WR stars with ejecta-type nebulae is roughly consistent between the Milky Way (MW) and Large Magellanic Cloud (LMC) at around 5-6 per cent, with the MW sample dominated by nitrogen-rich WR central stars (WN type) and the LMC stars having a higher proportion of carbon-rich WR central stars (WC type). We compare our results with those of previous surveys, including those of Marston and Miller & Chu, and find broad consistency. We investigate several trends in the sample: most of the clear examples of ejecta nebulae have WNh central stars, and very few ejecta nebulae have binary central stars. Finally, the possibly unique evolutionary status of the nebula around the binary star WR 71 is explored.

  10. Neutral carbon in the Egg Nebula (AFGL 2688)

    NASA Technical Reports Server (NTRS)

    Huggins, P. J.; Masson, C.; Frerking, M. A.; Beichman, C. A.; Keene, J.; Phillips, T. G.; Wootten, H. A.

    1983-01-01

    A search for sub-mm C I emission from seven stars that are surrounded by dense molecular gas shells has led to the detection, in the case of the 'Egg Nebula' (AFGL 2688), of an 0.9 K line implying a C I/CO value greater than 5. The material surrounding this star must be extremely carbon-rich, and it is suggested that the apparently greater extent of the C I emission region may be due to the effects of the the galactic UV field on the shell's chemistry, as suggested by Huggins and Glassgold (1982).

  11. Dissociative experiences and dissociative minds: Exploring a nomological network of dissociative functioning.

    PubMed

    Schimmenti, Adriano

    2016-01-01

    In this study, the psychometric properties of the Dissociative Experiences Scale-II (DES-II) were tested in a sample of Italian adults, and a nomological network of dissociative functioning based on current psychodynamic research was examined. A total of 794 participants (55% females) ranging in age from 18 to 64 completed the DES-II and other measures of theory of mind, alexithymia, attachment style, and empathy. The Italian translation of the DES-II showed high internal consistency, adequate item-to-scale homogeneity, and good split-half reliability. A single-factor solution including the 8 items of pathological dissociation (DES-T) adequately fit the data. Participants who reported higher levels of dissociative experiences showed significantly lower scores on theory of mind and empathy than other participants. They also showed significantly higher scores on alexithymia, preoccupied attachment, and fearful attachment. Results of the study support the view that people who suffer from severe dissociative experiences may also have difficulties mentalizing and regulating affects and that they may feel uncomfortable in close relationships because they have a negative view of the self. This can inform clinical work with dissociative individuals, who could benefit from therapies that consider their potential problems with mentalization, empathy, affect regulation, and attachment.

  12. Mixing and Transport in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Boss, Alan P.

    2003-01-01

    models of marginally gravitationally unstable disks to study the preservation of isotopic heterogeneity in evolving protoplanetary disks. Such heterogeneity might arise from the infall onto the disk s surface of solids processed in the X-wind region of the disk, or derived from stellar nucleosynthesis and injected by R-T fingers. The technique used consists of solving a color equation, identical to the gas continuity equation, which follows the time evolution in three space dimensions of an arbitrarily placed initial color field, i.e., a dye inserted the disk. The models show that significant concentrations of color could persist for time periods of about a thousand years or more, even in the most dynamically active region of such a disk. Such a time period might be long enough for solids to coagulate and grow to significant sizes while retaining the isotopic signature of their birth region in the nebula.

  13. A ROTATIONALLY POWERED MAGNETAR NEBULA AROUND SWIFT J1834.9–0846

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

    Torres, Diego F.

    A wind nebula generating extended X-ray emission was recently detected surrounding Swift J1834.9–0846. This is the first magnetar for which such a wind nebula was found. Here, we investigate whether there is a plausible scenario where the pulsar wind nebula (PWN) can be sustained without the need of advocating for additional sources of energy other than rotational. We do this by using a detailed radiative and dynamical code that studies the evolution of the nebula and its particle population in time. We find that such a scenario indeed exists: Swift J1834.9–0846's nebula can be explained as being rotationally powered, asmore » all other known PWNe are, if it is currently being compressed by the environment. The latter introduces several effects, the most important of which is the appearance of adiabatic heating, being increasingly dominant over the escape of particles as reverberation goes by. The need of reverberation naturally explains why this is the only magnetar nebula detected and provides estimates for Swift 1834.9–0846's age.« less

  14. Light and Velocity Variability in Seven Bright Proto-Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    McGuire, Ryan

    2009-01-01

    Light and Velocity Variability in Seven Bright Proto-Planetary Nebulae R.B. McGuire, C.M. Steele, B.J. Hrivnak, W. Lu, D. Bohlender, C.D. Scarfe We present new contemporaneous light and velocity observations of seven proto-planetary nebulae obtained over the past two years. Proto-planetary nebulae are objects evolving between the AGB and planetary nebula phases. In these seven objects, the central star is bright (V= 7-10), surrounded by a faint nebula. We knew from past monitoring that the light from each of these varied by a few tenths of a magnitude over intervals of 30-150 days and that the velocity varied by 10 km/s. These appear to be due to pulsation. With these new contemporaneous observations, we are able to measure the correlation between the brightness, color, and velocity, which will constrain the pulsation models. This is an ongoing project with the light monitoring being carried out with the Valparaiso University 0.4 m telescope and CCD camera and the radial velocity observations being carried out with the Dominion Astrophysical Observatory 1.8 m telescope and spectrograph. This research is partially supported by NSF grant 0407087 and the Indiana Space Grant Consortium.

  15. Spatially-resolved Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

    NASA Astrophysics Data System (ADS)

    Swartz, Douglas A.; Weisskopf, M. C.; Zavlin, V.; Bucciantini, N.; Clarke, T. E.; Karovska, M.; Pavlov, G. G.; van der Horst, A.; Yukita, M.

    2013-04-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXO J061705.3+222127, in the supernova remnant IC443 confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar interpretation, (2) the non-thermal surrounding nebula is likely powered by a pulsar wind, and (3) the thermal-dominated spectrum at greater distances is consistent with emission from the supernova remnant. The observations further reveal, for the first time, a ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar location. The cometary shape of the nebula, suggesting motion towards the southwest, appears to be subsonic; there is no evidence for a strong bow shock and the ring, presumably formed at a wind termination shock, is not distorted by motion through the ambient medium.

  16. Spatially-resolved Spectroscopy of the IC443 Pulsar Wind Nebula and Environs

    NASA Technical Reports Server (NTRS)

    Swartz, D. A.; Weisskopf, M. C.; Zavlin, V. E.; Bucciantini, N.; Clarke, T. E.; Karovska, M.; Pavlov, G. G.; O'Dell, S. L.; vanderHorst, A J.; Yukita, M.

    2013-01-01

    Deep Chandra ACIS observations of the region around the putative pulsar, CXOU J061705.3+222117, in the supernova remnant IC443 reveal, for the first time, a ring-like morphology surrounding the pulsar and a jet-like structure oriented roughly north-south across the ring and through the pulsar location. The observations further confirm that (1) the spectrum and flux of the central object are consistent with a rotation-powered pulsar interpretation, (2) the non-thermal surrounding nebula is likely powered by the pulsar wind, and (3) the thermal-dominated spectrum at greater distances is consistent with emission from the supernova remnant. The cometary shape of the nebula, suggesting motion towards the southwest (or, equivalently, flow of ambient medium to the northeast), appears to be subsonic; there is no evidence for a strong bow shock, and the circular ring is not distorted by motion through the ambient medium.

  17. New Radio and Optical Expansion Rate Measurements of the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Bietenholz, M. F.; Nugent, R. L.

    2016-06-01

    We present new JVLA radio observations of the Crab nebula, which we use, along with older observations taken over a ~30 yr period, to determined the expansion rate of the synchrotron nebula. We find a convergence date for the radio synchrotron nebula of AD 1255 +/- 27. We also re-evaluated the expansion rate of the optical line emitting filaments, and we show that the traditional estimates of their convergence date are slightly biased. We find an un-biased convergence date of AD 1091 +/- 34, ~40 yr earlier than previous estimates. Our results show that both the synchrotron nebula and the optical line-emitting filaments have been accelerated since the explosion in AD 1054, but former more strongly than the latter. This finding supports the picture that the filaments are the result of the Rayleigh-Taylor instability at the interface between the pulsar-wind nebula and the surrounding freely-expanding supernova ejecta, and rules out models where the pulsar wind bubble is interacting directly with the pre-supernova wind of the Crab's progenitor. Our new observations were taken ~2 months after the gamma-ray flare of 2012 July, and also allow us to put a sensitive limit on any radio emission associated with the flare of <0.0002 times the radio luminosity that of the nebula.

  18. On the X-ray temperature of hot gas in diffuse nebulae

    NASA Astrophysics Data System (ADS)

    Toalá, J. A.; Arthur, S. J.

    2018-05-01

    X-ray emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3]× 106 K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae (PNe), Wolf-Rayet nebulae (WR) and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

  19. On the X-ray temperature of hot gas in diffuse nebulae

    NASA Astrophysics Data System (ADS)

    Toalá, J. A.; Arthur, S. J.

    2018-07-01

    X-ray-emitting diffuse nebulae around hot stars are observed to have soft-band temperatures in the narrow range [1-3] × 106K, independent of the stellar wind parameters and the evolutionary stage of the central star. We discuss the origin of this X-ray temperature for planetary nebulae, Wolf-Rayet (WR) nebulae, and interstellar wind bubbles around hot young stars in our Galaxy and the Magellanic Clouds. We calculate the differential emission measure (DEM) distributions as a function of temperature from previously published simulations and combine these with the X-ray emission coefficient for the 0.3-2.0 keV band to estimate the X-ray temperatures. We find that all simulated nebulae have DEM distributions with steep negative slopes, which is due to turbulent mixing at the interface between the hot shocked stellar wind and the warm photoionized gas. Sharply peaked emission coefficients act as temperature filters and emphasize the contribution of gas with temperatures close to the peak position, which coincides with the observed X-ray temperatures for the chemical abundance sets we consider. Higher metallicity nebulae have lower temperature and higher luminosity X-ray emission. We show that the second temperature component found from spectral fitting to X-ray observations of WR nebulae is due to a significant contribution from the hot shocked stellar wind, while the lower temperature principal component is dominated by nebular gas. We suggest that turbulent mixing layers are the origin of the soft X-ray emission in the majority of diffuse nebulae.

  20. Zero-Point Energy Constraint for Unimolecular Dissociation Reactions. Giving Trajectories Multiple Chances To Dissociate Correctly.

    PubMed

    Paul, Amit K; Hase, William L

    2016-01-28

    A zero-point energy (ZPE) constraint model is proposed for classical trajectory simulations of unimolecular decomposition and applied to CH4* → H + CH3 decomposition. With this model trajectories are not allowed to dissociate unless they have ZPE in the CH3 product. If not, they are returned to the CH4* region of phase space and, if necessary, given additional opportunities to dissociate with ZPE. The lifetime for dissociation of an individual trajectory is the time it takes to dissociate with ZPE in CH3, including multiple possible returns to CH4*. With this ZPE constraint the dissociation of CH4* is exponential in time as expected for intrinsic RRKM dynamics and the resulting rate constant is in good agreement with the harmonic quantum value of RRKM theory. In contrast, a model that discards trajectories without ZPE in the reaction products gives a CH4* → H + CH3 rate constant that agrees with the classical and not quantum RRKM value. The rate constant for the purely classical simulation indicates that anharmonicity may be important and the rate constant from the ZPE constrained classical trajectory simulation may not represent the complete anharmonicity of the RRKM quantum dynamics. The ZPE constraint model proposed here is compared with previous models for restricting ZPE flow in intramolecular dynamics, and connecting product and reactant/product quantum energy levels in chemical dynamics simulations.

  1. The Rings Around the Egg Nebula

    NASA Technical Reports Server (NTRS)

    Harpaz, Amos; Rappaport, Saul; Soker, Noam

    1997-01-01

    We present an eccentric binary model for the formation of the proto-planetary nebula CRL 2688 (the Egg Nebula) that exhibits multiple concentric shells. Given the apparent regularity of the structure in the Egg Nebula, we postulate that the shells are caused by the periodic passages of a companion star. Such an orbital period would have to lie in the range of 100-500 yr, the apparent time that corresponds to the spacing between the rings. We assume, in this model, that an asymptotic giant branch (AGB) star, which is the origin of the matter within the planetary nebula, loses mass in a spherically symmetric wind. We further suppose that the AGB star has an extended atmosphere (out to approximately 10 stellar radii) in which the outflow speed is less than the escape speed; still farther out, grains form and radiation pressure accelerates the grains along with the trapped gas to the escape speed. Once escape speed has been attained, the presence of a companion star will not significantly affect the trajectories of the matter leaving in the wind and the mass loss will be approximately spherically symmetric. On the other hand, if the companion star is sufficiently close that the Roche lobe of the AGB star moves inside the extended atmosphere, then the slowly moving material will be forced to flow approximately along the critical potential surface (i.e., the Roche lobe) until it flows into the potential lobe of the companion star. Therefore, in our model, the shells are caused by periodic cessations of the isotropic wind rather than by any periodic enhancement in the mass-loss process. We carry out detailed binary evolution calculations within the context of this scenario, taking into account the nuclear evolution and stellar wind losses of the giant as well as the effects of mass loss and mass transfer on the evolution of the eccentric binary orbit. From the initial binary parameters that we find are required to produce a multiple concentric shell nebula and the known

  2. A New Population of Galactic Bulge Planetary Nebulas

    NASA Astrophysics Data System (ADS)

    Stenborg, T. N.

    A new population of Galactic bulge planetary nebulas is presented. Nebula candidates were discovered by systematically reviewing archival [OIII] on/off band survey imaging of the central -5° ≤ l ≤ 5°, -5° ≤ b ≤ 5° region around the Galactic centre. An image segmentation and interleaving scheme was developed to facilitate this review. The resultant candidates (> 200) were then double checked against complementary archival Hα sky survey data to screen for obvious planetary nebula (PN) mimics or spurious image artefacts. Confirmatory spectroscopy of the PN candidates was pursued with thin slit, fibre multiobject and wide field spectrographs. Custom software was built to streamline interfacing with third-party spectroscopic management tools and a parallel greedy set cover algorithm implemented for efficient field selection in constrained multi-object observations. The combined imaging and spectroscopic evidence yielded true (4), probable (31) and possible (83) PNs toward the bulge. Secondary discoveries such as new PN mimics and late type stars were by-products of the confirmatory spectroscopy. Instances of literature PN duplication encountered during the investigation were noticed and documented. Spectral analysis of new PNs, including those obtained with a new optimised sky subtraction technique devised and demonstrated here, provided diagnostic data allowing radial velocity and Balmer decrement determination. Using a combined diameter and radial velocity criterion, bona fide bulge PNs were distinguished from new foreground PNs. Where Balmer decrements were available for new bulge PNs, differential aperture photometry was used to provide a modest data increment to Galactic bulge planetary nebula luminosity function (PNLF). The PNLF was revised with data from some new bulge PNs, but more significantly, by a series of corrections to the data derived from previously known bulge PNs (~225), such as improved filter transmission effects, statistically

  3. The nature of the ionised nebula surrounding the red supergiant W26

    NASA Astrophysics Data System (ADS)

    Wesson, Roger

    2015-08-01

    The red supergiant W26 in the massive star cluster Westerlund 1 is surrounded by a compact ionised nebula. This is unique among RSGs, and the excitation mechanism of the nebula is not yet known - it may be ionised by an unseen compact companion, or by a nearby blue supergiant. We present new observations of the nebula: high resolution spatially resolved spectra taken with FLAMES at the VLT show that the nebula is a ring, with velocities consistent with that expected for red supergiant ejecta, and ruling out the possibility of a Luminous Blue Variable-type eruption preceding the RSG phase as the origin of the nebula. A triangular patch of nebulosity outside the ring appears to be associated with W26, and may be material stripped from the expanding ring by the cumulative cluster wind and radiation field.

  4. 3He Abundances in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Guzman-Ramirez, Lizette

    2017-10-01

    Determination of the 3He isotope is important to many fields of astrophysics, including stellar evolution, chemical evolution, and cosmology. The isotope is produced in stars which evolve through the planetary nebula phase. Planetary nebulae are the final evolutionary phase of low- and intermediate-mass stars, where the extensive mass lost by the star on the asymptotic giant branch is ionised by the emerging white dwarf. This ejecta quickly disperses and merges with the surrounding ISM. 3He abundances in planetary nebulae have been derived from the hyperfine transition of the ionised 3He, 3He+, at the radio rest frequency 8.665 GHz. 3He abundances in PNe can help test models of the chemical evolution of the Galaxy. Many hours have been put into trying to detect this line, using telescopes like the Effelsberg 100m dish of the Max Planck Institute for Radio Astronomy, the National Radio Astronomy Observatory (NRAO) 140-foot telescope, the NRAO Very Large Array, the Arecibo antenna, the Green Bank Telescope, and only just recently, the Deep Space Station 63 antenna from the Madrid Deep Space Communications Complex.

  5. Constraints on the Detection of the Solar Nebula's Oxidation State Through Asteroid Observations

    NASA Technical Reports Server (NTRS)

    Abell, P. A.; Gaffey, M. J.; Hardersen, P. S.

    2005-01-01

    Introduction: Asteroids represent the only in situ surviving population of planetesimals from the formation of the inner solar system and therefore include materials from the very earliest stages of solar system formation. Hence, these bodies can provide constraints on the processes and conditions that were present during this epoch and can be used to test current models and theories describing the late solar nebula, the early solar system and subsequent planetary accretion. From detailed knowledge of asteroid mineralogic compositions the probable starting materials, thermal histories, and oxidation states of asteroid parent bodies can be inferred. If such data can be obtained from specific mainbelt source regions, then this information can be used to map out the formation conditions of the late solar nebula within the inner solar system and possibly distinguish any trends in oxidation state that may be present.

  6. Planck intermediate results: XXXIV. The magnetic field structure in the Rosette Nebula

    DOE PAGES

    Aghanim, N.; Alves, M. I. R.; Arnaud, M.; ...

    2016-02-09

    Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). In this paper, we combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and themore » formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about 3 μG (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 cm -3. The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered asa whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette’s parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45° on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4%. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 6.5–9 μG. Finally, the present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the

  7. Planck intermediate results: XXXIV. The magnetic field structure in the Rosette Nebula

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

    Aghanim, N.; Alves, M. I. R.; Arnaud, M.

    Planck has mapped the polarized dust emission over the whole sky, making it possible to trace the Galactic magnetic field structure that pervades the interstellar medium (ISM). In this paper, we combine polarization data from Planck with rotation measure (RM) observations towards a massive star-forming region, the Rosette Nebula in the Monoceros molecular cloud, to study its magnetic field structure and the impact of an expanding H ii region on the morphology of the field. We derive an analytical solution for the magnetic field, assumed to evolve from an initially uniform configuration following the expansion of ionized gas and themore » formation of a shell of swept-up ISM. From the RM data we estimate a mean value of the line-of-sight component of the magnetic field of about 3 μG (towards the observer) in the Rosette Nebula, for a uniform electron density of about 12 cm -3. The dust shell that surrounds the Rosette H ii region is clearly observed in the Planck intensity map at 353 GHz, with a polarization signal significantly different from that of the local background when considered asa whole. The Planck observations constrain the plane-of-the-sky orientation of the magnetic field in the Rosette’s parent molecular cloud to be mostly aligned with the large-scale field along the Galactic plane. The Planck data are compared with the analytical model, which predicts the mean polarization properties of a spherical and uniform dust shell for a given orientation of the field. This comparison leads to an upper limit of about 45° on the angle between the line of sight and the magnetic field in the Rosette complex, for an assumed intrinsic dust polarization fraction of 4%. This field direction can reproduce the RM values detected in the ionized region if the magnetic field strength in the Monoceros molecular cloud is in the range 6.5–9 μG. Finally, the present analytical model is able to reproduce the RM distribution across the ionized nebula, as well as the

  8. The Tarantula Nebula as a template for extragalactic star forming regions from VLT/MUSE and HST/STIS

    NASA Astrophysics Data System (ADS)

    Crowther, Paul A.; Caballero-Nieves, Saida M.; Castro, Norberto; Evans, Christopher J.

    2017-11-01

    We present VLT/MUSE observations of NGC 2070, the dominant ionizing nebula of 30 Doradus in the LMC, plus HST/STIS spectroscopy of its central star cluster R136. Integral Field Spectroscopy (MUSE) and pseudo IFS (STIS) together provides a complete census of all massive stars within the central 30×30 parsec2 of the Tarantula. We discuss the integrated far-UV spectrum of R136, of particular interest for UV studies of young extragalactic star clusters. Strong He iiλ1640 emission at very early ages (1-2 Myr) from very massive stars cannot be reproduced by current population synthesis models, even those incorporating binary evolution and very massive stars. A nebular analysis of the integrated MUSE dataset implies an age of ~4.5 Myr for NGC 2070. Wolf-Rayet features provide alternative age diagnostics, with the primary contribution to the integrated Wolf-Rayet bumps arising from R140 rather than the more numerous H-rich WN stars in R136. Caution should be used when interpreting spatially extended observations of extragalactic star-forming regions.

  9. Face photo-sketch synthesis and recognition.

    PubMed

    Wang, Xiaogang; Tang, Xiaoou

    2009-11-01

    In this paper, we propose a novel face photo-sketch synthesis and recognition method using a multiscale Markov Random Fields (MRF) model. Our system has three components: 1) given a face photo, synthesizing a sketch drawing; 2) given a face sketch drawing, synthesizing a photo; and 3) searching for face photos in the database based on a query sketch drawn by an artist. It has useful applications for both digital entertainment and law enforcement. We assume that faces to be studied are in a frontal pose, with normal lighting and neutral expression, and have no occlusions. To synthesize sketch/photo images, the face region is divided into overlapping patches for learning. The size of the patches decides the scale of local face structures to be learned. From a training set which contains photo-sketch pairs, the joint photo-sketch model is learned at multiple scales using a multiscale MRF model. By transforming a face photo to a sketch (or transforming a sketch to a photo), the difference between photos and sketches is significantly reduced, thus allowing effective matching between the two in face sketch recognition. After the photo-sketch transformation, in principle, most of the proposed face photo recognition approaches can be applied to face sketch recognition in a straightforward way. Extensive experiments are conducted on a face sketch database including 606 faces, which can be downloaded from our Web site (http://mmlab.ie.cuhk.edu.hk/facesketch.html).

  10. Modelling jets, tori and flares in pulsar wind nebulae

    DOE PAGES

    Porth, Oliver; Buehler, Rolf; Olmi, Barbara; ...

    2017-03-22

    In this contribution we review the recent progress in the modelling of Pulsar Wind Nebulae (PWN). We start with a brief overview of the relevant physical processes in the magnetosphere, the wind-zone and the inflated nebula bubble. Radiative signatures and particle transport processes obtained from 3D simulations of PWN are discussed in the context of optical and X-ray observations. We then proceed to consider particle acceleration in PWN and elaborate on what can be learned about the particle acceleration from the dynamical structures called GwispsG observed in the Crab nebula. We also discuss recent observational and theoretical results of gamma-raymore » flares and the inner knot of the Crab nebula, which had been proposed as the emission site of the flares. Here, we extend the discussion to GeV flares from binary systems in which the pulsar wind interacts with the stellar wind from a companion star. The chapter concludes with a discussion of solved and unsolved problems posed by PWN.« less

  11. The surprising Crab pulsar and its nebula: a review.

    PubMed

    Bühler, R; Blandford, R

    2014-06-01

    The Crab nebula and its pulsar (referred to together as 'the Crab') have historically played a central role in astrophysics. True to this legacy, several unique discoveries have been made recently. The Crab was found to emit gamma-ray pulsations up to energies of 400 GeV, beyond what was previously expected from pulsars. Strong gamma-ray flares, of durations of a few days, were discovered from within the nebula, while the source was previously expected to be stable in flux on these time scales. Here we review these intriguing and suggestive developments. In this context we give an overview of the observational properties of the Crab and our current understanding of pulsars and their nebulae.

  12. Menkhib and the California Nebula

    NASA Image and Video Library

    2010-05-07

    This infrared image from NASA Wide-field Infrared Survey Explorer features one of the bright stars in the constellation Perseus, named Menkhib, along with a large star forming cloud commonly called the California Nebula.

  13. Photo-Induced Assembly of a Luminescent Tetraruthenium Square.

    PubMed

    Laramée-Milette, Baptiste; Nastasi, Francesco; Puntoriero, Fausto; Campagna, Sebastiano; Hanan, Garry S

    2017-11-21

    Self-assembly is a powerful synthetic tool that has led to the development of one-, two- and three-dimensional architectures. From MOFs to molecular flasks, self-assembled materials have proven to be of great interest to the scientific community. Here we describe a strategy for the construction and de-construction of a supramolecular structure through unprecedented photo-induced assembly and dis-assembly. The combination of two approaches, a [n×1]-directional bonding strategy and a ligand photo-dissociation strategy, allows the photo-induced assembly of a polypyridyl Ru II precursor into a discrete molecular square. Diffusion-ordered NMR spectroscopy confirmed the synthesis of a higher volume species, while the identity of the species was established by high-resolution mass spectrometry and single-crystal X-ray diffraction studies. The self-assembled square is not obtained by classical thermal techniques in similar conditions, but is obtained only by light-irradiation. The tetraruthenium square has an excited-state lifetime (135 ns), 40 times that of its mononuclear precursor and its luminescence quantum yield (1.0 %) is three orders of magnitude higher. These remarkable luminescence properties are closely related to the relatively rigid square structure of the tetraruthenium assembly, as suggested by slow radiationless decay and transient absorption spectroscopy. The results described herein are a rare example of photo-induced assembly and dis-assembly processes, and can open the way to a new avenue in supramolecular chemistry, leading to the preparation of structurally organized supermolecules by photochemical techniques. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. A Protosolar Nebula Origin for the Ices Agglomerated by Comet 67P/Churyumov-Gerasimenko

    NASA Astrophysics Data System (ADS)

    Mousis, O.; Lunine, J. I.; Luspay-Kuti, A.; Guillot, T.; Marty, B.; Ali-Dib, M.; Wurz, P.; Altwegg, K.; Bieler, A.; Hässig, M.; Rubin, M.; Vernazza, P.; Waite, J. H.

    2016-03-01

    The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula (PSN) is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from crystalline ices condensed in the PSN. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud or from the very distant regions of the PSN. On the basis of existing laboratory and modeling data, we find that the N2/CO and Ar/CO ratios measured in the coma of the Jupiter-family comet 67P/Churyumov-Gerasimenko by the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis instrument on board the European Space Agency’s Rosetta spacecraft match those predicted for gases trapped in clathrates. If these measurements are representative of the bulk N2/CO and Ar/CO ratios in 67P/Churyumov-Gerasimenko, it implies that the ices accreted by the comet formed in the nebula and do not originate from the interstellar medium, supporting the idea that the building blocks of outer solar system bodies have been formed from clathrates and possibly from pure crystalline ices. Moreover, because 67P/Churyumov-Gerasimenko is impoverished in Ar and N2, the volatile enrichments observed in Jupiter’s atmosphere cannot be explained solely via the accretion of building blocks with similar compositions and require an additional delivery source. A potential source may be the accretion of gas from the nebula that has been progressively enriched in heavy elements due to photoevaporation.

  15. New expansion rate measurements of the Crab nebula in radio and optical

    NASA Astrophysics Data System (ADS)

    Bietenholz, M. F.; Nugent, R. L.

    2015-12-01

    We present new radio measurements of the expansion rate of the Crab nebula's synchrotron nebula over a ˜30-yr period. We find a convergence date for the radio synchrotron nebula of CE 1255 ± 27. We also re-evaluated the expansion rate of the optical-line-emitting filaments, and we show that the traditional estimates of their convergence date are slightly biased. Using an unbiased Bayesian analysis, we find a convergence date for the filaments of CE 1091 ± 34 (˜40 yr earlier than previous estimates). Our results show that both the synchrotron nebula and the optical-line-emitting filaments have been accelerated since the explosion in CE 1054, but that the synchrotron nebula has been relatively strongly accelerated, while the optical filaments have been only slightly accelerated. The finding that the synchrotron emission expands more rapidly than the filaments supports the picture that the latter are the result of the Rayleigh-Taylor instability at the interface between the pulsar-wind nebula and the surrounding freely expanding supernova ejecta, and rules out models where the pulsar-wind bubble is interacting directly with the pre-supernova wind of the Crab's progenitor.

  16. A Spectroscopic and Photometric Study of the Planetary Nebulae Kn 61 and Pa 5

    NASA Astrophysics Data System (ADS)

    García-Díaz, Ma. T.; González-Buitrago, D.; López, J. A.; Zharikov, S.; Tovmassian, G.; Borisov, N.; Valyavin, G.

    2014-09-01

    We present the first morpho-kinematical analysis of the planetary nebulae Kn 61 and Pa 5 and explore the nature of their central stars. Our analysis is based on high-resolution and medium-resolution spectroscopic observations, deep narrow-band imaging, and integral photometry. This material allows us to identify the morphological components and study their kinematics. The direct images and spectra indicate an absence of the characteristic [N II] and [S II] emission lines in both nebulae. The nebular spectrum of Kn 61 suggests a hydrogen deficient planetary nebula and the stellar spectrum of the central star reveals a hydrogen-deficient PG 1159-type star. The [O III] position velocity diagram reveals that Kn 61 is a closed, empty, spherical shell with a thin border and a filamentary surface expanding at 67.6 km s-1 and the shell is currently not expanding isotropically. We derived a kinematic age of ~1.6 × 104 yr for an assumed distance of 4 kpc. A photometric period of ~5.7(±0.4) days has been detected for Kn 61, indicating the presence of a possible binary system at its core. A possible link between filamentary spherical shells and PG 1159-type stars is noted. The morphology of Pa 5 is dominated by an equatorial toroid and faint polar extensions. The equatorial region of this planetary nebula is expanding at 45.2 km s-1. The stellar spectrum corresponds to a very hot star and is dominated by a steep blue rising continuum and He II, Balmer, and Ca II photospheric lines.

  17. Chandra Confirmation of a Pulsar Wind Nebula in DA 495

    NASA Technical Reports Server (NTRS)

    Arzoumanian, Z.; Safi-Harb, S.; Landecker, T.L.; Kothes, R.; Camilo, F.

    2008-01-01

    As part of a multiwavelength study of the unusual radio supernova remnant DA 495, we present observations made with the Chandra X-ray Observatory. Imaging and spectroscopic analysis confirms the previously detected X-ray source at the heart of the annular radio nebula, establishing the radiative properties of two key emission components: a soft unresolved source with a blackbody temperature of 1 MK consistent with a neutron star, surrounded by a nontherma1 nebula 40" in diameter exhibiting a power-law spectrum with photon index Gamma = 1.63, typical of a pulsar wind nebula. Morphologically, the nebula appears to be slightly extended along a direction, in projection on the sky, previously demonstrated to be of significance in radio and ASCA observations; we argue that this represents the orientation of the pulsar spin axis. At smaller scales, a narrow X-ray feature is seen extending out 5" from the point source, but energetic arguments suggest that it is not the resolved termination shock of the pulsar wind against the ambient medium. Finally, we argue based on synchrotron lifetimes in the nebular magnetic field that DA 495 represents the first example of a pulsar wind nebula in which electromagnetic flux makes up a significant part, together with particle flux, of the neutron star's wind.

  18. Subliminal processes, dissociation and the 'I'.

    PubMed

    Bob, Petr

    2003-06-01

    The study of unconscious processes leads to the hypothesis of the limit of consciousness, which involves two main kinds of psychic activity. The first represents psychic contents which are subliminal for their low energy, the second subliminal contents which are inaccessible to consciousness because they are dissociated in the subliminal region. Dissociation is a concept introduced by Pierre Janet for splitting consciousness due to traumatic events or during hypnosis. It takes a more general form in Hilgard's neo-dissociation theory of hypnotic phenomena and also in Jung's theory of the collective unconscious. Further generalization links it to the modern findings of explicit and implicit perception, leading to a shift in dissociation from hypothesis to clinical, experimental and theoretical reality. Studies in hypnosis also point to the existence of an integrative psychic entity, that comprises the conscious 'I'. Hilgard called this the hidden observer, and his findings represent empirical confirmation of Jung's term for the Self as mirror 'I', which leads to many important consequences for self-discovery and the meaning of life.

  19. Electron-impact dissociative excitation and ionization of N{sub 2}D{sup +}

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

    Fogle, M.; Bahati, E. M.; Bannister, M. E.

    Absolute cross sections for electron-impact dissociation of N{sub 2}D{sup +} producing N{sub 2}{sup +}, ND{sup +}, and N{sup +} ion fragments were measured in the 5- to 100-eV range using a crossed electron-ion beams technique. In the 5- to 20-eV region, in which dissociative excitation (DE) is the principal contributing mechanism, N{sub 2}{sup +} production dominates. The N{sub 2}{sup +} + D dissociation channel shows a large resonant-like structure in the DE cross section, as observed previously in electron impact dissociation of triatomic dihydride species [M. Fogle, E. M. Bahati, M. E. Bannister, S. H. M. Deng, C. R. Vane,more » R. D. Thomas, and V. Zhaunerchyk, Phys. Rev. A 82, 042720 (2010)]. In the dissociative ionization (DI) region, 20- to 100-eV, N{sub 2}{sup +}, ND{sup +}, and N{sup +} ion fragment production are comparable. The observance of the ND{sup +} and N{sup +} ion fragments indicate breaking of the N - N bond along certain dissociation channels.« less

  20. Stellar Parameters and Radial Velocities of Hot Stars in the Carina Nebula

    NASA Astrophysics Data System (ADS)

    Hanes, Richard J.; McSwain, M. Virginia; Povich, Matthew S.

    2018-05-01

    The Carina Nebula is an active star-forming region in the southern sky that is of particular interest due to the presence of a large number of massive stars in a wide array of evolutionary stages. Here, we present the results of the spectroscopic analysis of 82 B-type stars and 33 O-type stars that were observed in 2013 and 2014. For 82 B-type stars without line blending, we fit model spectra from the Tlusty BSTAR2006 grid to the observed profiles of Hγ and He λλ4026, 4388, and 4471 to measure the effective temperatures, surface gravities, and projected rotational velocities. We also measure the masses, ages, radii, bolometric luminosities, and distances of these stars. From the radial velocities measured in our sample, we find 31 single lined spectroscopic binary candidates. We find a high dispersion of radial velocities among our sample stars, and we argue that the Carina Nebula stellar population has not yet relaxed and become virialized.

  1. A new survey of nebulae around Galactic Wolf-Rayet stars in the northern sky

    NASA Technical Reports Server (NTRS)

    Miller, Grant J.; Chu, You-Hua

    1993-01-01

    Interference filter CCD images have been obtained in H-alpha and forbidden O III 5007 A for 62 Wolf-Rayet (W-R) stars, representing a complete survey of nebulae around Galactic W-R stars in the northern sky. We find probable new ring nebulae around W-R stars number 113, 116 and 132, and possible new ring nebulae around W-R stars number 133 and 153. All survey images showing nebulosities around W-R stars are presented in this paper. New physical information is derived from the improved images of known ring nebulae. The absence of ring nebulae around most W-R stars is discussed.

  2. Discovery of powerful gamma-ray flares from the Crab Nebula.

    PubMed

    Tavani, M; Bulgarelli, A; Vittorini, V; Pellizzoni, A; Striani, E; Caraveo, P; Weisskopf, M C; Tennant, A; Pucella, G; Trois, A; Costa, E; Evangelista, Y; Pittori, C; Verrecchia, F; Del Monte, E; Campana, R; Pilia, M; De Luca, A; Donnarumma, I; Horns, D; Ferrigno, C; Heinke, C O; Trifoglio, M; Gianotti, F; Vercellone, S; Argan, A; Barbiellini, G; Cattaneo, P W; Chen, A W; Contessi, T; D'Ammando, F; DePris, G; Di Cocco, G; Di Persio, G; Feroci, M; Ferrari, A; Galli, M; Giuliani, A; Giusti, M; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Fuschino, F; Marisaldi, M; Mereghetti, S; Morelli, E; Moretti, E; Morselli, A; Pacciani, L; Perotti, F; Piano, G; Picozza, P; Prest, M; Rapisarda, M; Rappoldi, A; Rubini, A; Sabatini, S; Soffitta, P; Vallazza, E; Zambra, A; Zanello, D; Lucarelli, F; Santolamazza, P; Giommi, P; Salotti, L; Bignami, G F

    2011-02-11

    The well-known Crab Nebula is at the center of the SN1054 supernova remnant. It consists of a rotationally powered pulsar interacting with a surrounding nebula through a relativistic particle wind. The emissions originating from the pulsar and nebula have been considered to be essentially stable. Here, we report the detection of strong gamma-ray (100 mega-electron volts to 10 giga-electron volts) flares observed by the AGILE satellite in September 2010 and October 2007. In both cases, the total gamma-ray flux increased by a factor of three compared with the non-flaring flux. The flare luminosity and short time scale favor an origin near the pulsar, and we discuss Chandra Observatory x-ray and Hubble Space Telescope optical follow-up observations of the nebula. Our observations challenge standard models of nebular emission and require power-law acceleration by shock-driven plasma wave turbulence within an approximately 1-day time scale.

  3. IUE observations of the 'Butterfly' Nebula M2-9

    NASA Technical Reports Server (NTRS)

    Feibelman, W. A.

    1984-01-01

    IUE observations of the peculiar 'Butterfy' nebula M2-9 indicate that it is not a normal planetary nebula. The ultraviolet spectrum is characterized by few emission lines and a weak continuum. Mg II 2800 A is the strongest emission line present and may be indicative of a binary nucleus. Lines of N v, Q I, N III, N IV, Si III, and C III are seen, but C IV and O III are conspicuous by their absence. T(e) = 10,250 + or - 400 K was determined for the core. Nitrogen in the core is found to be overabundant by about a factor of 5 over the solar value. M2-9 may be an object in the early stages of becoming a planetary nebula.

  4. The Dissociative Subtype of Post-traumatic Stress Disorder: Research Update on Clinical and Neurobiological Features.

    PubMed

    van Huijstee, Jytte; Vermetten, Eric

    2017-10-21

    Recently, a dissociative subtype of post-traumatic stress disorder (PTSD) has been included in the DSM-5. This review focuses on the clinical and neurobiological features that distinguish the dissociative subtype of PTSD from non-dissociative PTSD. Clinically, the dissociative subtype of PTSD is associated with high PTSD severity, predominance of derealization and depersonalization symptoms, a more significant history of early life trauma, and higher levels of comorbid psychiatric disorders. Furthermore, PTSD patients with dissociative symptoms exhibit different psychophysiological and neural responses to the recall of traumatic memories. While individuals with non-dissociative PTSD exhibit an increased heart rate, decreased activation of prefrontal regions, and increased activation of the amygdala in response to traumatic reminders, individuals with the dissociative subtype of PTSD show an opposite pattern. It has been proposed that dissociation is a regulatory strategy to restrain extreme arousal in PTSD through hyperinhibition of limbic regions. In this research update, promises and pitfalls in current research studies on the dissociative subtype of PTSD are listed. Inclusion of the dissociative subtype of PTSD in the DSM-5 stimulates research on the prevalence, symptomatology, and neurobiology of the dissociative subtype of PTSD and poses a challenge to improve treatment outcome in PTSD patients with dissociative symptoms.

  5. Dying Star Shrouded by a Blanket of Hailstones Forms the Bug Nebula

    NASA Image and Video Library

    2017-12-08

    Release Date: May 3, 2004 A Dying Star Shrouded by a Blanket of Hailstones Forms the Bug Nebula (NGC 6302) The Bug Nebula, NGC 6302, is one of the brightest and most extreme planetary nebulae known. The fiery, dying star at its center is shrouded by a blanket of icy hailstones. This NASA Hubble Wide Field Plantery Camera 2 image shows impressive walls of compressed gas, laced with trailing strands and bubbling outflows. Object Names: NGC 6302, Bug Nebula Image Type: Astronomical Credit: NASA, ESA and A.Zijlstra (UMIST, Manchester, UK) To learn more about this image go to: hubblesite.org/gallery/album/nebula/pr2004046a/ 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

  6. Onboard photo:Astro-1 in Cargo Bay

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Onboard the Space Shuttle Orbiter Columbia (STS-35), the various components of the Astro-1 payload are seen backdropped against dark space. Parts of the Hopkins Ultraviolet Telescope (HUT), Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE) are visible on the Spacelab pallet. The Broad-Band X-Ray Telescope (BBXRT) is behind the pallet and is not visible in this scene. The smaller cylinder in the foreground is the igloo. The igloo was a pressurized container housing the Command Data Management System, that interfaced with the in-cabin controllers to control the Instrument Pointing System (IPS) and the telescopes. The Astro Observatory was designed to explore the universe by observing and measuring the ultraviolet radiation from celestial objects. Astronomical targets of observation selected for Astro missions included planets, stars, star clusters, galaxies, clusters of galaxies, quasars, remnants of exploded stars (supernovae), clouds of gas and dust (nebulae), and the interstellar medium. Managed by the Marshall Space Flight Center, the Astro-1 was launched aboard the Space Shuttle Orbiter Columbia (STS-35) on December 2, 1990.

  7. Central Stars of Mid-Infrared Nebulae Discovered with Spitzer and WISE

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.

    2017-02-01

    Searches for compact mid-IR nebulae with the Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE), accompanied by spectroscopic observations of central stars of these nebulae led to the discovery of many dozens of massive stars at different evolutionary stages, of which the most numerous are candidate luminous blue variables (LBVs). In this paper, we give a census of candidate and confirmed Galactic LBVs revealed with Spitzer and WISE, and present some new results of spectroscopic observations of central stars of mid-IR nebulae.

  8. Fusion of multichannel local and global structural cues for photo aesthetics evaluation.

    PubMed

    Luming Zhang; Yue Gao; Zimmermann, Roger; Qi Tian; Xuelong Li

    2014-03-01

    Photo aesthetic quality evaluation is a fundamental yet under addressed task in computer vision and image processing fields. Conventional approaches are frustrated by the following two drawbacks. First, both the local and global spatial arrangements of image regions play an important role in photo aesthetics. However, existing rules, e.g., visual balance, heuristically define which spatial distribution among the salient regions of a photo is aesthetically pleasing. Second, it is difficult to adjust visual cues from multiple channels automatically in photo aesthetics assessment. To solve these problems, we propose a new photo aesthetics evaluation framework, focusing on learning the image descriptors that characterize local and global structural aesthetics from multiple visual channels. In particular, to describe the spatial structure of the image local regions, we construct graphlets small-sized connected graphs by connecting spatially adjacent atomic regions. Since spatially adjacent graphlets distribute closely in their feature space, we project them onto a manifold and subsequently propose an embedding algorithm. The embedding algorithm encodes the photo global spatial layout into graphlets. Simultaneously, the importance of graphlets from multiple visual channels are dynamically adjusted. Finally, these post-embedding graphlets are integrated for photo aesthetics evaluation using a probabilistic model. Experimental results show that: 1) the visualized graphlets explicitly capture the aesthetically arranged atomic regions; 2) the proposed approach generalizes and improves four prominent aesthetic rules; and 3) our approach significantly outperforms state-of-the-art algorithms in photo aesthetics prediction.

  9. Spatially Resolved Far-Infrared Spectroscopic Analysis of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Rattray, Rebecca; Ueta, Toshiya

    2015-01-01

    Planetary Nebulae (PNs) are late-life intermediate-mass (1-8 solar mass) stars that have shed their outer layers. A wide variety of morphologies and physical conditions is seen in PNs, but a complete understanding of what causes these various conditions is still needed. Spatially resolved far-infrared spectroscopic analysis has been performed on 11 targets using both PACS and SPIRE instruments on the Herschel Space Observatory as part of the Herschel Planetary Nebula Survey (HerPlaNS). Far-IR lines probe the ionized parts of the nebulae and suffer less extinction than optical lines, so observations in the far-IR are critical to our complete understanding of PNs. Because PNs are extended objects, the spectral mapping capabilities of both PACS and SPIRE allow us to better understand the spatial variations of the objects by tracking line strengths as a function of location within the nebula. The far-IR lines detected in this study can be used as tracers of electron density and electron temperature which are critical parameters in radiative transfer modeling of PNs. Information on atomic, ionic, and molecular lines identified in these 11 targets will be presented.

  10. Creation and Distribution of CAIs in the Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Cuzzi, J. N.; Davis, S. S.; Dobrovolskis, A. R.

    2003-01-01

    CaAl rich refractory mineral inclusions (CAIs) found at 1 - 10% mass fraction in primitive chondrites appear to be several million years older than the dominant (chondrule) components in the same parent bodies. A prevalent concern is that it is difficult to retain CAIs for this long against gas-drag-induced radial drift into the sun. We assess a hot inner (turbulent) nebula context for CAI formation, using analytical models of nebula evolution and particle diffusion. We show that outward radial diffusion in a weakly turbulent nebula can prevent significant numbers of CAI-size particles from being lost into the sun for times of 1 - 3 x 10(exp 6) years. To match the CAI abundances quantitatively, we advocate an enhancement of the inner hot nebula in silicate-forming material, due to rapid inward migration of very primitive, silicate and carbon rich, meter-sized objects. 'Combustion' of the carbon into CO would make the CAI formation environment more reduced than solar, as certain observations imply. Abundant CO might also play a role in mass-independent chemical fractionation of oxygen isotopes as seen in CAIs and associated primitive, high-temperature condensates.

  11. Polarization due to dust scattering in the planetary nebula Cn1-1

    NASA Technical Reports Server (NTRS)

    Bhatt, Harish C.

    1989-01-01

    The peculiar emission-line object Cn1-1 (=HDE330036=PK330+4 degrees 1), classified both as a symbiotic star and as a planetary nebula, was detected by the Infrared Astronomical Satellite (IRAS) as a strong source of far-infrared dust in the system. Bhatt and Mallik (1986) discussed the nature of the dust in Cn1-1 and argued that the object is a Type I protoplanetary nebula in a binary system. The argument presented here is that the polarization is intrinsic to Cn1-1 and is due to scattering by large (compared to interstellar) dust grains in the protoplanetary nebula that are asymmetrically distributed around the central star. The large degree of polarization (approximately 3 percent for the Cn1-1 distance of approximately 450 pc) with a large lambda(sub max) is naturally explained if it is caused by scattering by large dust grains in the Cn1-1 nebula. Since the H(sub alpha) line is also polarized at the same level and position angle as the continuum, the dust must be asymmetrically distributed around the central star. The morphology of the protoplanetary nebula in Cn1-1 may be bipolar. Thus, the polarization observations support the suggestion that Cn1-1 is a bipolar Type I planetary nebula.

  12. Dissociative photoionization of isoprene: experiments and calculations.

    PubMed

    Liu, Xianyun; Zhang, Weijun; Wang, Zhenya; Huang, Mingqiang; Yang, Xibin; Tao, Ling; Sun, Yue; Xu, Yuntao; Shan, Xiaobin; Liu, Fuyi; Sheng, Liusi

    2009-03-01

    Vacuum ultraviolet (VUV) dissociative photoionization of isoprene in the energy region 8.5-18 eV was investigated with photoionization mass spectroscopy (PIMS) using synchrotron radiation (SR). The ionization energy (IE) of isoprene as well as the appearance energies (AEs) of its fragment ions C(5)H(7) (+), C(5)H(5) (+), C(4)H(5) (+), C(3)H(6) (+), C(3)H(5) (+), C(3)H(4) (+), C(3)H(3) (+) and C(2)H(3) (+) were determined with photoionization efficiency (PIE) curves. The dissociation energies of some possible dissociation channels to produce those fragment ions were also determined experimentally. The total energies of C(5)H(8) and its main fragments were calculated using the Gaussian 03 program and the Gaussian-2 method. The IE of C(5)H(8), the AEs for its fragment ions, and the dissociation energies to produce them were predicted using the high-accuracy energy model. According to our results, the experimental dissociation energies were in reasonable agreement with the calculated values of the proposed photodissociation channels of C(5)H(8). Copyright (c) 2009 John Wiley & Sons, Ltd.

  13. Pathological Dissociation as Measured by the Child Dissociative Checklist

    ERIC Educational Resources Information Center

    Wherry, Jeffrey N.; Neil, Debra A.; Taylor, Tamara N.

    2009-01-01

    The component structure of the Child Dissociative Checklist was examined among abused children. A factor described as pathological dissociation emerged that was predicted by participants being male. There also were differences in pathological dissociation between groups of sexually abused and physically abused children. Replication of this factor…

  14. Dissociative absorption: An empirically unique, clinically relevant, dissociative factor.

    PubMed

    Soffer-Dudek, Nirit; Lassri, Dana; Soffer-Dudek, Nir; Shahar, Golan

    2015-11-01

    Research of dissociative absorption has raised two questions: (a) Is absorption a unique dissociative factor within a three-factor structure, or a part of one general dissociative factor? Even when three factors are found, the specificity of the absorption factor is questionable. (b) Is absorption implicated in psychopathology? Although commonly viewed as "non-clinical" dissociation, absorption was recently hypothesized to be specifically associated with obsessive-compulsive symptoms. To address these questions, we conducted exploratory and confirmatory factor analyses on 679 undergraduates. Analyses supported the three-factor model, and a "purified" absorption scale was extracted from the original inclusive absorption factor. The purified scale predicted several psychopathology scales. As hypothesized, absorption was a stronger predictor of obsessive-compulsive symptoms than of general psychopathology. In addition, absorption was the only dissociative scale that longitudinally predicted obsessive-compulsive symptoms. We conclude that absorption is a unique and clinically relevant dissociative tendency that is particularly meaningful to obsessive-compulsive symptoms. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. The Magnetic Field Toward the Young Planetary Nebula K 3-35

    NASA Astrophysics Data System (ADS)

    Gómez, Y.; Tafoya, D.; Anglada, G.; Miranda, L. F.; Torrelles, J. M.; Patel, N. A.; Hernández, R. Franco

    2009-04-01

    K 3-35 is a planetary nebula (PN) where H2O maser emission has been detected, suggesting that it departed from the proto-PNe phase only some decades ago. Interferometric VLA observations of the OH 18 cm transitions in K 3-35 are presented. OH maser emission is detected in all four ground state lines (1612, 1665, 1667, and 1720 MHz). All the masers appear blueshifted with respect to the systemic velocity of the nebula and have different spatial and kinematic distributions. The OH 1665 and 1720 MHz masers appear spatially coincident with the core of the nebula, while the OH 1612 and 1667 MHz ones exhibit a more extended distribution. We suggest that the 1665 and 1720 masers arise from a region close to the central star, possibly in a torus, while the 1612 and 1667 lines originate mainly from the extended northern lobe of the outflow. It is worth noting that the location and velocity of the OH 1720 MHz maser emission are very similar to those of the H2O masers (coinciding within 0farcs1 and ~ 2 km s-1, respectively). We suggest that the pumping mechanism in the H2O masers could be produced by the same shock that is exciting the OH 1720 MHz transition. A high degree of circular polarization (> 50%) was found to be present in some features of the 1612, 1665, and 1720 MHz emission. For the 1665 MHz transition at ~ +18 km s-1 the emission with left and right circular polarizations (LCP and RCP) coincide spatially within a region of ~ 0farcs03 in diameter. Assuming that these RCP and LCP 1665 features come from a Zeeman pair, we estimate a magnetic field of ~ 0.9 mG within 150 AU from the 1.3 cm continuum peak. This value is in agreement with a solar-type magnetic field associated with evolved stars.

  16. Dissociative symptoms and dissociative disorder comorbidity in patients with obsessive-compulsive disorder.

    PubMed

    Belli, Hasan; Ural, Cenk; Vardar, Melek Kanarya; Yesılyurt, Sema; Oncu, Fatıh

    2012-10-01

    The present study attempted to assess the dissociative symptoms and overall dissociative disorder comorbidity in patients with obsessive-compulsive disorder (OCD). In addition, we examined the relationship between the severity of obsessive-compulsive symptoms and dissociative symptoms. All patients admitted for the first time to the psychiatric outpatient unit were included in the study. Seventy-eight patients had been diagnosed as having OCD during the 2-year study period. Patients had to meet the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for OCD. Most (76.9%; n = 60) of the patients were female, and 23.1% (n = 18) of the patients were male. Dissociation Questionnaire was used to measure dissociative symptoms. The Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition Dissociative Disorders interviews and Yale-Brown Obsessive Compulsive Checklist and Severity Scale were used. Eleven (14%) of the patients with OCD had comorbid dissociative disorder. The most prevalent disorder in our study was dissociative depersonalization disorder. Dissociative amnesia and dissociative identity disorder were common as well. The mean Yale-Brown score was 23.37 ± 7.27 points. Dissociation Questionnaire scores were between 0.40 and 3.87 points, and the mean was 2.23 ± 0.76 points. There was a statistically significant positive correlation between Yale-Brown points and Dissociation Questionnaire points. We conclude that dissociative symptoms among patients with OCD should alert clinicians for the presence of a chronic and complex dissociative disorder. Clinicians may overlook an underlying dissociative process in patients who have severe symptoms of OCD. However, a lack of adequate response to cognitive-behavioral and drug therapy may be a consequence of dissociative process. Copyright © 2012 Elsevier Inc. All rights reserved.

  17. Fermi-LAT Search for Pulsar Wind Nebulae around gamma-ray Pulsars

    DOE PAGES

    Ackermann, M.; Ajello, M.; Baldini, L.; ...

    2010-12-13

    The high sensitivity of the Fermi-LAT (Large Area Telescope) offers the first opportunity to study faint and extended GeV sources such as pulsar wind nebulae (PWNe). After one year of observation the LAT detected and identified three PWNe: the Crab Nebula, Vela-X, and the PWN inside MSH 15-52. In the meantime, the list of LAT detected pulsars increased steadily. These pulsars are characterized by high energy loss rates (more » $$\\dot{E}$$) from ~3 × 10 33 erg s –1 to 5 × 10 38 erg s –1 and are therefore likely to power a PWN. This paper summarizes the search for PWNe in the off-pulse windows of 54 LAT-detected pulsars using 16 months of survey observations. Ten sources show significant emission, seven of these likely being of magnetospheric origin. The detection of significant emission in the off-pulse interval offers new constraints on the γ-ray emitting regions in pulsar magnetospheres. The three other sources with significant emission are the Crab Nebula, Vela-X, and a new PWN candidate associated with the LAT pulsar PSR J1023–5746, coincident with the TeV source HESS J1023–575. Here, we further explore the association between the HESS and the Fermi source by modeling its spectral energy distribution. Lastly, flux upper limits derived for the 44 remaining sources are used to provide new constraints on famous PWNe that have been detected at keV and/or TeV energies.« less

  18. Dissociation and serenity induction.

    PubMed

    Zoellner, Lori A; Sacks, Matthew B; Foa, Edna B

    2007-09-01

    Dissociation is a common experience during or immediately after a traumatic event; yet, most of the current knowledge regarding dissociation is retrospective in nature. The aim of the present study investigated a non-pharmacological method of dissociative induction with a clinical sample. Participants with PTSD and non-trauma exposed participants were randomly assigned to receive either a dissociative induction, or a serenity induction, based on modified Velten mood induction procedures. Participants receiving the dissociative induction reported higher state-dissociation than those receiving the serenity induction. The PTSD group reported greater state dissociation than the non-trauma exposed group, regardless of induction. State dissociation was related to trait dissociation, PTSD severity, and depression. The present results provide an initial demonstration of the viability for inducing state dissociation in the laboratory with a PTSD sample.

  19. Electrical discharge heating of chondrules in the solar nebula

    NASA Technical Reports Server (NTRS)

    Love, Stanley G.; Keil, Klaus; Scott, Edward R. D.

    1995-01-01

    We present a rudimentary theoretical assessment of electrical discharge heating as a candidate mechanism for the formation of chondrules in the solar nebula. The discharge model combines estimates of the properties of the nebula, a mechanism for terrestrial thunderstorm electrification, and some fundamental electrical properties of gases. Large uncertainties in the model inputs limit these calculations to order-or-magnitude accuracy. Despite the uncertainty, it is possible to estimate an upper limit to the efficiency of nebular discharges at melting millimeter-sized stony objects. We find that electrical arcs analogous to terrestrial lightning could have occurred in the nebula, but that under most conditions these discharges probably could not have melted chondrules. Despite our difficulties, we believe the topic worthy of further investigation and suggest some experiments which could improve our understanding of nebular discharges.

  20. A spectroscopic and photometric study of the planetary nebulae Kn 61 and Pa 5

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

    García-Díaz, Ma. T.; González-Buitrago, D.; López, J. A.

    2014-09-01

    We present the first morpho-kinematical analysis of the planetary nebulae Kn 61 and Pa 5 and explore the nature of their central stars. Our analysis is based on high-resolution and medium-resolution spectroscopic observations, deep narrow-band imaging, and integral photometry. This material allows us to identify the morphological components and study their kinematics. The direct images and spectra indicate an absence of the characteristic [N II] and [S II] emission lines in both nebulae. The nebular spectrum of Kn 61 suggests a hydrogen deficient planetary nebula and the stellar spectrum of the central star reveals a hydrogen-deficient PG 1159-type star. Themore » [O III] position velocity diagram reveals that Kn 61 is a closed, empty, spherical shell with a thin border and a filamentary surface expanding at 67.6 km s{sup –1} and the shell is currently not expanding isotropically. We derived a kinematic age of ∼1.6 × 10{sup 4} yr for an assumed distance of 4 kpc. A photometric period of ∼5.7(±0.4) days has been detected for Kn 61, indicating the presence of a possible binary system at its core. A possible link between filamentary spherical shells and PG 1159-type stars is noted. The morphology of Pa 5 is dominated by an equatorial toroid and faint polar extensions. The equatorial region of this planetary nebula is expanding at 45.2 km s{sup –1}. The stellar spectrum corresponds to a very hot star and is dominated by a steep blue rising continuum and He II, Balmer, and Ca II photospheric lines.« less

  1. YSOVAR: Six Pre-main-sequence Eclipsing Binaries in the Orion Nebula Cluster

    DTIC Science & Technology

    2012-06-25

    reserved. Printed in the U.S.A. YSOVAR: SIX PRE-MAIN-SEQUENCE ECLIPSING BINARIES IN THE ORION NEBULA CLUSTER M. Morales-Calderón1,2, J. R. Stauffer1, K. G...multi-color light curves for∼2400 candidate Orion Nebula Cluster (ONC) members from our Warm Spitzer Exploration Science Program YSOVAR, we have...readable tables 1. INTRODUCTION The Orion Nebula Cluster (ONC) contains several thousand members, and since it is nearby, it provides an excellent em

  2. Uncaging a catalytic hydrogen peroxide generator through the photo-induced release of nitric oxide from a {MnNO}(6) complex.

    PubMed

    Iwamoto, Yuji; Kodera, Masahito; Hitomi, Yutaka

    2015-06-11

    The photo-initiated cytotoxicity of a newly developed manganese nitrosyl {MnNO}(6) complex (UG1NO) to HeLa cells is described. The complex was found to be strongly cytotoxic after being exposed to light with a wavelength of 650 nm. Cell death was caused by a manganese(II) complex, UG1, generated from UG1NO through the photo-dissociation of NO, rather than by NO directly. Mechanistic studies revealed that UG1 consumes O2 only in the presence of a reducing agent to catalytically produce H2O2.

  3. Carbon Chemistry in Planetary Nebulae: Observations of the CCH Radical

    NASA Astrophysics Data System (ADS)

    Schmidt, Deborah Rose; Ziurys, Lucy

    2015-08-01

    The presence of infrared (IR) emission features observed in interstellar environments is consistent with models that suggest they are produced by complex organic species containing both aliphatic and aromatic components (Kwok & Zhang 2011). These IR signals change drastically over the course of the AGB, proto-planetary, and planetary nebulae phases, and this dramatic variation is yet to be understood. The radical CCH is a potential tracer of carbon chemistry and its evolution in dying stars. CCH is very common in carbon-rich circumstellar envelopes of AGB stars, and is present in the proto-planetary nebulae. It has also been observed at one position in the very young planetary nebula, NGC 7027 (Hasegawa & Kwok 2001), as well as at one position in the Helix Nebula (Tenenbaum et al. 2009) - a dense clump east of the central white dwarf. In order to further probe the chemistry of carbon, we have initiated a search for CCH in eight PNe previously detected in HCN and HCO+ from a survey conducted by Schmidt and Ziurys, using the telescopes of the Arizona Radio Observatory (ARO). Observations of the N=1→0 transition of CCH at 87 GHz have been conducted using the new ARO 12-m ALMA prototype antenna, while measurements of the N=3→2 transition at 262 GHz are being made with the ARO Sub-Millimeter Telescope (SMT). We also have extended our study in the Helix Nebula. Thus far, CCH has been detected at 8 new positions across the Helix Nebula, and appears to be widespread in this source. The radical has also been identified in K4-47, M3-28, K3-17, and K3-58. These sources represent a range of nebular ages. Additional observations are currently being conducted for CCH in other PNe, as well as abundance analyses. These results will be presented.

  4. The blue supergiant MN18 and its bipolar circumstellar nebula

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.; Bestenlehner, J. M.; Bodensteiner, J.; Langer, N.; Greiner, J.; Grebel, E. K.; Berdnikov, L. N.; Beletsky, Y.

    2015-11-01

    We report the results of spectrophotometric observations of the massive star MN18 revealed via discovery of a bipolar nebula around it with the Spitzer Space Telescope. Using the optical spectrum obtained with the Southern African Large Telescope, we classify this star as B1 Ia. The evolved status of MN18 is supported by the detection of nitrogen overabundance in the nebula, which implies that it is composed of processed material ejected by the star. We analysed the spectrum of MN18 by using the code CMFGEN, obtaining a stellar effective temperature of ≈21 kK. The star is highly reddened, E(B - V) ≈ 2 mag. Adopting an absolute visual magnitude of MV = -6.8 ± 0.5 (typical of B1 supergiants), MN18 has a luminosity of log L/L⊙ ≈ 5.42 ± 0.30, a mass-loss rate of ≈(2.8-4.5) × 10- 7 M⊙ yr- 1, and resides at a distance of ≈5.6^{+1.5} _{-1.2} kpc. We discuss the origin of the nebula around MN18 and compare it with similar nebulae produced by other blue supergiants in the Galaxy (Sher 25, HD 168625, [SBW2007] 1) and the Large Magellanic Cloud (Sk-69°202). The nitrogen abundances in these nebulae imply that blue supergiants can produce them from the main-sequence stage up to the pre-supernova stage. We also present a K-band spectrum of the candidate luminous blue variable MN56 (encircled by a ring-like nebula) and report the discovery of an OB star at ≈17 arcsec from MN18. The possible membership of MN18 and the OB star of the star cluster Lynga 3 is discussed.

  5. A PROTOSOLAR NEBULA ORIGIN FOR THE ICES AGGLOMERATED BY COMET 67P/CHURYUMOV–GERASIMENKO

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

    Mousis, O.; Vernazza, P.; Lunine, J. I.

    The nature of the icy material accreted by comets during their formation in the outer regions of the protosolar nebula (PSN) is a major open question in planetary science. Some scenarios of comet formation predict that these bodies agglomerated from crystalline ices condensed in the PSN. Concurrently, alternative scenarios suggest that comets accreted amorphous ice originating from the interstellar cloud or from the very distant regions of the PSN. On the basis of existing laboratory and modeling data, we find that the N{sub 2}/CO and Ar/CO ratios measured in the coma of the Jupiter-family comet 67P/Churyumov–Gerasimenko by the Rosetta Orbitermore » Spectrometer for Ion and Neutral Analysis instrument on board the European Space Agency’s Rosetta spacecraft match those predicted for gases trapped in clathrates. If these measurements are representative of the bulk N{sub 2}/CO and Ar/CO ratios in 67P/Churyumov–Gerasimenko, it implies that the ices accreted by the comet formed in the nebula and do not originate from the interstellar medium, supporting the idea that the building blocks of outer solar system bodies have been formed from clathrates and possibly from pure crystalline ices. Moreover, because 67P/Churyumov–Gerasimenko is impoverished in Ar and N{sub 2}, the volatile enrichments observed in Jupiter’s atmosphere cannot be explained solely via the accretion of building blocks with similar compositions and require an additional delivery source. A potential source may be the accretion of gas from the nebula that has been progressively enriched in heavy elements due to photoevaporation.« less

  6. Shell nebulae around luminous evolved stars

    NASA Technical Reports Server (NTRS)

    Dufour, Reginald J.

    1989-01-01

    Shell nebulae around luminous Population I Wolf-Rayet, Of, and P-Cygni stars are astrophysically interesting since they are indicators of pre-supernova mass loss and how such massive stars prepare their surrounding interstellar medium prior to explosion. Some twenty-odd such nebulae are known, for which detailed study of their morphological and spectroscopic characteristics have only begun in this decade. In this paper, some of these characteristics are reviewed in general, and new observations are reported. Emphasis has been placed on several 'prototype 'objects (NGC 7635, NGC 2359, NGC 6888, and the Eta Carinae condensations) to illustrate the varied massive-star mass-loss, the physics of their winds and shell ejecta, and related nucleosynthesis effects in the compositions of the winds and shells.

  7. The mysterious age invariance of the planetary nebula luminosity function bright cut-off

    NASA Astrophysics Data System (ADS)

    Gesicki, K.; Zijlstra, A. A.; Miller Bertolami, M. M.

    2018-05-01

    Planetary nebulae mark the end of the active life of 90% of all stars. They trace the transition from a red giant to a degenerate white dwarf. Stellar models1,2 predicted that only stars above approximately twice the solar mass could form a bright nebula. But the ubiquitous presence of bright planetary nebulae in old stellar populations, such as elliptical galaxies, contradicts this: such high-mass stars are not present in old systems. The planetary nebula luminosity function, and especially its bright cut-off, is almost invariant between young spiral galaxies, with high-mass stars, and old elliptical galaxies, with only low-mass stars. Here, we show that new evolutionary tracks of low-mass stars are capable of explaining in a simple manner this decades-old mystery. The agreement between the observed luminosity function and computed stellar evolution validates the latest theoretical modelling. With these models, the planetary nebula luminosity function provides a powerful diagnostic to derive star formation histories of intermediate-age stars. The new models predict that the Sun at the end of its life will also form a planetary nebula, but it will be faint.

  8. Why convective heat transport in the solar nebula was inefficient

    NASA Technical Reports Server (NTRS)

    Cassen, P.

    1993-01-01

    The radial distributions of the effective temperatures of circumstellar disks associated with pre-main sequence (T Tauri) stars are relatively well-constrained by ground-based and spacecraft infrared photometry and radio continuum observations. If the mechanisms by which energy is transported vertically in the disks are understood, these data can be used to constrain models of the thermal structure and evolution of solar nebula. Several studies of the evolution of the solar nebula have included the calculation of the vertical transport of heat by convection. Such calculations rely on a mixing length theory of transport and some assumption regarding the vertical distribution of internal dissipation. In all cases, the results of these calculations indicate that transport by radiation dominates that by convection, even when the nebula is convectively unstable. A simple argument that demonstrates the generality (and limits) of this result, regardless of the details of mixing length theory or the precise distribution of internal heating is presented. It is based on the idea that the radiative gradient in an optically thick nebula generally does not greatly exceed the adiabatic gradient.

  9. Catalogues of planetary nebulae.

    NASA Astrophysics Data System (ADS)

    Acker, A.

    Firstly, the general requirements concerning catalogues are studied for planetary nebulae, in particular concerning the objects to be included in a catalogue of PN, their denominations, followed by reflexions about the afterlife and comuterized versions of a catalogue. Then, the basic elements constituting a catalogue of PN are analyzed, and the available data are looked at each time.

  10. THE CHANDRA X-RAY SURVEY OF PLANETARY NEBULAE (CHANPLANS): PROBING BINARITY, MAGNETIC FIELDS, AND WIND COLLISIONS

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

    Kastner, J. H.; Montez, R. Jr.; Rapson, V.

    2012-08-15

    We present an overview of the initial results from the Chandra Planetary Nebula Survey (CHANPLANS), the first systematic (volume-limited) Chandra X-Ray Observatory survey of planetary nebulae (PNe) in the solar neighborhood. The first phase of CHANPLANS targeted 21 mostly high-excitation PNe within {approx}1.5 kpc of Earth, yielding four detections of diffuse X-ray emission and nine detections of X-ray-luminous point sources at the central stars (CSPNe) of these objects. Combining these results with those obtained from Chandra archival data for all (14) other PNe within {approx}1.5 kpc that have been observed to date, we find an overall X-ray detection rate ofmore » {approx}70% for the 35 sample objects. Roughly 50% of the PNe observed by Chandra harbor X-ray-luminous CSPNe, while soft, diffuse X-ray emission tracing shocks-in most cases, 'hot bubbles'-formed by energetic wind collisions is detected in {approx}30%; five objects display both diffuse and point-like emission components. The presence (or absence) of X-ray sources appears correlated with PN density structure, in that molecule-poor, elliptical nebulae are more likely to display X-ray emission (either point-like or diffuse) than molecule-rich, bipolar, or Ring-like nebulae. All but one of the point-like CSPNe X-ray sources display X-ray spectra that are harder than expected from hot ({approx}100 kK) central stars emitting as simple blackbodies; the lone apparent exception is the central star of the Dumbbell nebula, NGC 6853. These hard X-ray excesses may suggest a high frequency of binary companions to CSPNe. Other potential explanations include self-shocking winds or PN mass fallback. Most PNe detected as diffuse X-ray sources are elliptical nebulae that display a nested shell/halo structure and bright ansae; the diffuse X-ray emission regions are confined within inner, sharp-rimmed shells. All sample PNe that display diffuse X-ray emission have inner shell dynamical ages {approx}< 5 Multiplication

  11. A high-resolution image of the inner shell of the P Cygni nebula in the infrared [Fe II] line

    NASA Astrophysics Data System (ADS)

    Arcidiacono, C.; Ragazzoni, R.; Morossi, C.; Franchini, M.; di Marcantonio, P.; Kulesa, C.; McCarthy, D.; Briguglio, R.; Xompero, M.; Busoni, L.; Quirós-Pacheco, F.; Pinna, E.; Boutsia, K.; Paris, D.

    2014-09-01

    Using the adaptive optics system of the Large Binocular Telescope, we have obtained near-infrared camera PISCES images of the inner shell of the nebula around the luminous blue variable star P Cygni in the [Fe II] emission line at 1.6435 μm. We have combined the images in order to cover a field of view of about 20 arcsec around P Cygni, thus providing the high-resolution (0.08 arcsec) two-dimensional spatial distribution of the inner shell of the P Cygni nebula in [Fe II]. We have identified several nebular emission regions that are characterized by a signal-to-noise ratio > 3. A comparison of our results with those available in the literature shows full consistency with the findings of Smith & Hartigan, which are based on radial velocity measurements, and relatively good agreement with the extension of emission nebula in [N II] λ6584 found by Barlow et al. We have clearly also detected extended emission inside the radial distance R = 7.8 arcsec and outside R = 9.7 arcsec, which are the nebular boundaries proposed by Smith & Hartigan. New complementary spectroscopic observations are planned in order to measure radial velocities and to derive the three-dimensional distribution of the P Cygni nebula.

  12. Dissociative Identity Disorders in Korea: Two Recent Cases.

    PubMed

    Kim, Ilbin; Kim, Daeho; Jung, Hyun-Jin

    2016-03-01

    Although dissociative identity disorder (DID), the most severe of the dissociative disorders, has retained its own diagnostic entity since its introduction in the DSM-III, cases of DID are rarely seen in South and East Asia, likely due to the higher prevalence of possession disorder. We report two patients with DID who were recently admitted to our inpatient psychiatric unit and demonstrated distinct transitions to several identities. Their diagnoses were confirmed through a structured interview for dissociative disorders and possible differential diagnoses were ruled out by psychological, neuroimaging, and laboratory tests. The rapid transition to a Westernized, individualized society along with an increase in child abuse, might contribute to an increase in DID, previously under-diagnosed in this region.

  13. Analysis of Co-spatial UV-Optical STIS Spectra of Six Planetary Nebulae From HST Cycle 19 GO 12600

    NASA Astrophysics Data System (ADS)

    Reid Miller, Timothy; Henry, Richard B. C.; Dufour, Reginald J.; Kwitter, Karen; Shaw, Richard A.; Balick, Bruce; Corradi, Romano

    2015-08-01

    We present an analysis of six spatially resolved planetary nebulae (PNe), NGC 3242, NGC 5315, NGC5882, NGC 7662, IC 2165, and IC 3568, from observations in the Cycle 19 program GO 12600 using HSTSTIS. These six observations cover the wavelength range 1150-10,270 Å with 0.2 and 0.5 arcsec wideslits, and are co-spatial to 0.1 arcsec along a 25 arcsec length across each nebula. The wavelength andspatial coverage enabled this detailed study of physical conditions and abundances from UV and opticalline emissions (compared to only optical lines) for these six PNe. The first UV lines of interest are thoseof carbon. The resolved lines of C III] 1906.68 and 1908.73 yielded a direct measurement of the densitywithin the volume occupied by doubly-ionized carbon and other similar co-spatial ions as well ascontributed to an accurate measurement of the carbon abundance. Each PN spectrum was divided intosmaller spatial regions in order to assess inferred density variations among the regions along the entireslit. There is a clear difference in the inferred density for several regions of each PNe. Variations inelectron temperature and chemical abundances were also probed and shown to be nearly completelyhomogeneous within the errors. Lastly, these nebulae were modeled in detail with the photoionizationcode CLOUDY. This modeling tested different density profiles in order to reproduce the observed densityvariations and temperature fluctuations, and constrain central star parameters. We gratefullyacknowledge generous support from NASA through grants related to the Cycle 19 program GO 12600, aswell as from the University of Oklahoma.

  14. Resonance Trapping due to Nebula Disk Torques

    NASA Astrophysics Data System (ADS)

    Hahn, J. M.; Ward, W. R.

    1996-03-01

    A protoplanet embedded in the solar nebula launches spiral density waves from its Lindblad resonances in the gas disk, and its gravitational attraction for these disturbances results in a mutual torque exerted between the protoplanet and the disk. Consequently the orbit of a sufficiently massive protoplanet may decay on a timescale shorter than the nebula lifetime, and this mechanism is most significant during the formation of the cores of the giant planets. Due to their increased mobility, migrating protoplanets may have been able to accrete large swaths of the disk and/or encounter other protoplanets. Thus disk torques may have played an important role in determining the formation history and orbit spacings of the giant planets. An interesting phenomenon also associated with orbit decay is resonance trapping, whereby a large body is able to halt further orbit decay of smaller bodies at commensurability resonances. Examples of this effect include the trapping of planetesimals experiencing aerodynamic gas drag and dust suffering Poynting-Robertson drag. Below we address the cosmogonic implications of resonance trapping of planetary embryos experiencing orbit decay due to nebula disk torques. The following employs an approach similar to Malhotra's (1993) discussion of the gas drag trapping problem.

  15. Water-maser emission from a planetary nebula with a magnetized torus.

    PubMed

    Miranda, L F; Gómez, Y; Anglada, G; Torrelles, J M

    2001-11-15

    A star like the Sun becomes a planetary nebula towards the end of its life, when the envelope ejected during the earlier giant phase becomes photoionized as the surface of the remnant star reaches a temperature of approximately 30,000 K. The spherical symmetry of the giant phase is lost in the transition to a planetary nebula, when non-spherical shells and powerful jets develop. Molecules that were present in the giant envelope are progressively destroyed by the radiation. The water-vapour masers that are typical of the giant envelopes therefore are not expected to persist in planetary nebulae. Here we report the detection of water-maser emission from the planetary nebula K3-35. The masers are in a magnetized torus with a radius of about 85 astronomical units and are also found at the surprisingly large distance of about 5,000 astronomical units from the star, in the tips of bipolar lobes of gas. The precessing jets from K3-35 are probably involved in the excitation of the distant masers, although their existence is nevertheless puzzling. We infer that K3-35 is being observed at the very moment of its transformation from a giant star to a planetary nebula.

  16. Optical Spectrum of the Compact Planetary Nebula IC 5117

    NASA Technical Reports Server (NTRS)

    Hyung, Siek; Aller, Lawrence H.; Feibelman, Walter A.; Lee, Seong-Jae; Fisher, Richard R. (Technical Monitor)

    2001-01-01

    High resolution spectroscopic data of the very compact planetary nebula IC 5117 are obtained in the optical wavelengths, 3700A - 10050A, with the Hamilton Echelle Spectrograph at Lick Observatory, and which have been analyzed along with the International Ultraviolet Explorer (IUE) UV archive data. Although a diagnostic diagram shows significant density and temperature fluctuations, our analysis indicates that the nebular gas may be represented by a homogeneous shell of extremely high density gas, N(sub epsilon) approx. 90 000 /cu cm. The average electron temperatures, e.g. indicated by the [OIII] diagnostics, are around 12 000 K. We construct a photoionization model to represent most of the observed line intensities, and the physical condition of this compact nebulosity. Based on the semi-empirical ionization correction approach, and model indications, we derived the elemental abundances: He, C, N, O, Ne, and Ar appear to be normal or marginally depleted compared to the average planetary nebula, while the remaining elements, S, Cl, and K appear to be enhanced. IC 5117 is perhaps a very young compact planetary nebula, slightly more evolved than the other well-known compact planetary nebula IC 4997. The central stellar temperature is likely to be around 120 000 K, evolved from a C-rich AGB progenitor.

  17. Dissociation in patients with dissociative seizures: relationships with trauma and seizure symptoms.

    PubMed

    Pick, S; Mellers, J D C; Goldstein, L H

    2017-05-01

    This study aimed to extend the current understanding of dissociative symptoms experienced by patients with dissociative (psychogenic, non-epileptic) seizures (DS), including psychological and somatoform types of symptomatology. An additional aim was to assess possible relationships between dissociation, traumatic experiences, post-traumatic symptoms and seizure manifestations in this group. A total of 40 patients with DS were compared with a healthy control group (n = 43), matched on relevant demographic characteristics. Participants completed several self-report questionnaires, including the Multiscale Dissociation Inventory (MDI), Somatoform Dissociation Questionnaire-20, Traumatic Experiences Checklist and the Post-Traumatic Diagnostic Scale. Measures of seizure symptoms and current emotional distress (Hospital Anxiety and Depression Scale) were also administered. The clinical group reported significantly more psychological and somatoform dissociative symptoms, trauma, perceived impact of trauma, and post-traumatic symptoms than controls. Some dissociative symptoms (i.e. MDI disengagement, MDI depersonalization, MDI derealization, MDI memory disturbance, and somatoform dissociation scores) were elevated even after controlling for emotional distress; MDI depersonalization scores correlated positively with trauma scores while seizure symptoms correlated with MDI depersonalization, derealization and identity dissociation scores. Exploratory analyses indicated that somatoform dissociation specifically mediated the relationship between reported sexual abuse and DS diagnosis, along with depressive symptoms. A range of psychological and somatoform dissociative symptoms, traumatic experiences and post-traumatic symptoms are elevated in patients with DS relative to healthy controls, and seem related to seizure manifestations. Further studies are needed to explore peri-ictal dissociative experiences in more detail.

  18. The planetary nebulae population in the nuclear regions of M31: the SAURON view

    NASA Astrophysics Data System (ADS)

    Pastorello, Nicola; Sarzi, Marc; Cappellari, Michele; Emsellem, Eric; Mamon, Gary A.; Bacon, Roland; Davies, Roger L.; de Zeeuw, P. Tim

    2013-04-01

    The study of extragalactic planetary nebulae (PNe) in the optical regions of galaxies, where the properties of their stellar population can be best characterized, is a promising ground to better understand the late evolution of stars across different galactic environments. Following a first study of the central regions of M32 that illustrated the power of integral field spectroscopy (IFS) in detecting and measuring the [O III] λ5007 emission of PNe against a strong stellar background, we turn to the very nuclear PN population of M31, within ˜80 pc of its centre. We show that PNe can also be found in the presence of emission from diffuse gas, as commonly observed in early-type galaxies and in the bulge of spirals, and further illustrate the excellent sensitivity of IFS in detecting extragalactic PNe through a comparison with narrow-band images obtained with the Hubble Space Telescope. Contrary to the case of the central regions of M32, the nuclear PNe population of M31 is only marginally consistent with the generally adopted form of the PNe luminosity function (PNLF). In particular, this is due to a lack of PNe with absolute magnitude M5007 brighter than -3, which would only result from a rather unfortunate draw from such a model PNLF. The nuclear stellar population of M31 is quite different from that of the central regions of M32, which is characterized in particular by a larger metallicity and a remarkable ultraviolet (UV) upturn. We suggest that the observed lack of bright PNe in the nuclear regions of M31 is due to a horizontal-branch population that is more tilted towards less massive and hotter He-burning stars, so that its progeny consists mostly of UV-bright stars that fail to climb back up the asymptotic giant branch (AGB) and only a few, if any, bright PNe powered by central post-AGB stars. These results are also consistent with recent reports on a dearth of bright post-AGB stars towards the nucleus of M31, and lend further support to the idea that the

  19. DISCOVERY OF TWIN WOLF-RAYET STARS POWERING DOUBLE RING NEBULAE

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

    Mauerhan, Jon C.; Wachter, Stefanie; Van Dyk, Schuyler D.

    We have spectroscopically discovered a pair of twin, nitrogen-type, hydrogen-rich, Wolf-Rayet stars (WN8-9h) that are both surrounded by circular, mid-infrared-bright nebulae detected with the Spitzer Space Telescope and MIPS instrument. The emission is probably dominated by a thermal continuum from cool dust, but also may contain contributions from atomic line emission. There is no counterpart at shorter Spitzer/IRAC wavelengths, indicating a lack of emission from warm dust. The two nebulae are probably wind-swept stellar ejecta released by the central stars during a prior evolutionary phase. The nebulae partially overlap on the sky and we speculate on the possibility that theymore » are in the early stage of a collision. Two other evolved massive stars have also been identified within the area subtended by the nebulae, including a carbon-type Wolf-Rayet star (WC8) and an O7-8 III-I star, the latter of which appears to be embedded in one of the larger WN8-9h nebulae. The derived distances to these stars imply that they are coeval members of an association lying 4.9 {+-} 1.2 kpc from Earth, near the intersection of the Galaxy's Long Bar and the Scutum-Centaurus spiral arm. This new association represents an unprecedented display of complex interactions between multiple stellar winds, outflows, and the radiation fields of evolved massive stars.« less

  20. SYNCHROTRON HEATING BY A FAST RADIO BURST IN A SELF-ABSORBED SYNCHROTRON NEBULA AND ITS OBSERVATIONAL SIGNATURE

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

    Yang, Yuan-Pei; Dai, Zi-Gao; Zhang, Bing, E-mail: zhang@physics.unlv.edu

    Fast radio bursts (FRBs) are mysterious transient sources. If extragalactic, as suggested by their relative large dispersion measures, their brightness temperatures must be extremely high. Some FRB models (e.g., young pulsar model, magnetar giant flare model, or supra-massive neutron star collapse model) suggest that they may be associated with a synchrotron nebula. Here we study a synchrotron-heating process by an FRB in a self-absorbed synchrotron nebula. If the FRB frequency is below the synchrotron self-absorption frequency of the nebula, electrons in the nebula would absorb FRB photons, leading to a harder electron spectrum and enhanced self-absorbed synchrotron emission. In themore » meantime, the FRB flux is absorbed by the nebula electrons. We calculate the spectra of FRB-heated synchrotron nebulae, and show that the nebula spectra would show a significant hump in several decades near the self-absorption frequency. Identifying such a spectral feature would reveal an embedded FRB in a synchrotron nebula.« less

  1. TEARING THE VEIL: INTERACTION OF THE ORION NEBULA WITH ITS NEUTRAL ENVIRONMENT

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

    Van der Werf, Paul P.; Goss, W. M.; O'Dell, C. R.

    2013-01-10

    We present H I 21 cm observations of the Orion Nebula, obtained with the Karl G. Jansky Very Large Array, at an angular resolution of 7.''2 Multiplication-Sign 5.''7 and a velocity resolution of 0.77 km s{sup -1}. Our data reveal H I absorption in the Veil toward the radio continuum of the H II region, and H I emission arising from the Orion Bar photon-dominated region (PDR) and from the Orion-KL outflow. In the Orion Bar PDR, the H I signal peaks in the same layer as the H{sub 2} near-infrared vibrational line emission, in agreement with models of themore » photodissociation of H{sub 2}. The gas temperature in this region is approximately 540 K, and the H I abundance in the interclump gas in the PDR is 5%-10% of the available hydrogen nuclei. Most of the gas in this region therefore remains molecular. Mechanical feedback on the Veil manifests itself through the interaction of ionized flow systems in the Orion Nebula, in particular the Herbig-Haro object HH 202, with the Veil. These interactions give rise to prominent blueward velocity shifts of the gas in the Veil. The unambiguous evidence for interaction of this flow system with the Veil shows that the distance between the Veil and the Trapezium stars needs to be revised downward to about 0.4 pc. The depth of the ionized cavity is about 0.7 pc, which is much smaller than the depth and the lateral extent of the Veil. Our results reaffirm the blister model for the M42 H II region, while also revealing its relation to the neutral environment on a larger scale.« less

  2. Modeling Line Emission from Structures Seen at High Resolution in the Nebulae m1 and M16

    NASA Astrophysics Data System (ADS)

    Sankrit, Ravi

    1998-12-01

    Narrow band images of the Crab Nebula supernova remnant and of the Eagle Nebula H II region taken with the Hubble Space Telescope (HST) show the ionization structure of the emitting gas in unprecedented detail because of the high spatial resolution. The physics of the emission processes-shock excited emission and photoionized emission-is well understood. Sophisticated numerical codes are used to model the ionization structure and emission observed in these images. It is found that the thin skin of material around the Crab synchrotron nebula visible in (O III) λ5007 emission is best explained as the cooling region behind a shock driven by the synchrotron nebula into a surrounding remnant of freely expanding ejecta. Shock models, with parameters derived from independently known properties of the Crab, explain the observed spectrum of the skin while photoionization models fail to explain the observed strength of high ionization lines such as C IV λ1549. This result is clear evidence that the synchrotron nebula is interacting with an extended remnant of ejecta, which in turn has significant implications for the structure and evolution of the Crab. At HST resolution, it is seen that low ionization emission, from lines such as (O I) λ6300, is concentrated in sharp structures while high ionization emission (from (O III) λ5007) is much more diffuse. Individual filaments are found to lie along a sequence of ionization structure ranging from features in which all lines are concentrated in the same compact volume through features with low ionization cores surrounded by high ionization envelopes. Photoionization models of cylindrically symmetrical filaments with varying 'core-halo' density profiles can match the observed variation in the filament structure in the Crab. A photoionization model of a uniform low density medium matches the extended diffuse component which dominates the high ionization emission. It is found that detailed knowledge of the filament structures

  3. Discovery of a parsec-scale bipolar nebula around MWC 349A

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Menten, K. M.

    2012-05-01

    We report the discovery of a bipolar nebula around the peculiar emission-line star MWC 349A using archival Spitzer Space Telescope 24 μm data. The nebula extends over several arcminutes (up to 5 pc) and has the same orientation and geometry as the well-known subarcsecond-scale (~400 times smaller) bipolar radio nebula associated with this star. We discuss the physical relationship between MWC 349A and the nearby B0 III star MWC 349B and propose that both stars were members of a hierarchical triple system, which was ejected from the core of the Cyg OB2 association several Myr ago and recently was dissolved into a binary system (now MWC 349A) and a single unbound star (MWC 349B). Our proposal implies that MWC 349A is an evolved massive star (likely a luminous blue variable) in a binary system with a low-mass star. A possible origin of the bipolar nebula around MWC 349A is discussed.

  4. The interaction between giant gaseous protoplanets and the primitive solar nebula

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.

    1979-01-01

    The manner in which a giant gaseous protoplanet becomes embedded in the primitive solar nebula determines surface boundary conditions which must be used in studying the evolution of such objects. On the one hand, if the system resembles a contact binary system, then the envelope of the protoplanet should approach the entropy of the surrounding nebula. On the other hand angular momentum transfer by resonance and tidal effects between the nebula and the protoplanet may cause the nebula to exhibit a zone of avoidance near the protoplanet, thus inhibiting exchange of material. This problem has been studied with a computer program developed by D. N. C. Lin which simulates disk hydrodynamics by particle motions with dissipation. These studies suggest that for expected values of the protoplanet/protosun mass ratios, significant inhibition of mass exchange is likely, so that it is a reasonable next step to undertake protoplanet evolution studies with the imposition of minimum protoplanet surface temperatures.

  5. A New Radio Spectral Line Survey of Planetary Nebulae: Exploring Radiatively Driven Heating and Chemistry of Molecular Gas

    NASA Astrophysics Data System (ADS)

    Bublitz, Jesse

    Planetary nebulae contain shells of cold gas and dust whose heating and chemistry is likely driven by UV and X-ray emission from their central stars and from wind-collision-generated shocks. We present the results of a survey of molecular line emissions in the 88 - 235 GHz range from nine nearby (<1.5 kpc) planetary nebulae using the 30 m telescope at the Institut de Radioastronomie Millimetrique. Rotational transitions of nine molecules, including the well-studied CO isotopologues and chemically important trace species, were observed and the results compared with and augmented by previous studies of molecular gas in PNe. Lines of the molecules HCO+, HNC, HCN, and CN, which were detected in most objects, represent new detections for five planetary nebulae in our study. Flux ratios were analyzed to identify correlations between the central star and/or nebular ultraviolet/X-ray luminosities and the molecular chemistries of the nebulae. Analysis reveals the apparent dependence of the HNC/HCN line ratio on PN central star UV luminosity. There exists no such clear correlation between PN X-rays and various diagnostics of PN molecular chemistry. The correlation between HNC/HCN ratio and central star UV luminosity hints at the potential of molecular emission line studies of PNe for improving our understanding of the role that high-energy radiation plays in the heating and chemistry of photodissociation regions.

  6. Text, photo, and line extraction in scanned documents

    NASA Astrophysics Data System (ADS)

    Erkilinc, M. Sezer; Jaber, Mustafa; Saber, Eli; Bauer, Peter; Depalov, Dejan

    2012-07-01

    We propose a page layout analysis algorithm to classify a scanned document into different regions such as text, photo, or strong lines. The proposed scheme consists of five modules. The first module performs several image preprocessing techniques such as image scaling, filtering, color space conversion, and gamma correction to enhance the scanned image quality and reduce the computation time in later stages. Text detection is applied in the second module wherein wavelet transform and run-length encoding are employed to generate and validate text regions, respectively. The third module uses a Markov random field based block-wise segmentation that employs a basis vector projection technique with maximum a posteriori probability optimization to detect photo regions. In the fourth module, methods for edge detection, edge linking, line-segment fitting, and Hough transform are utilized to detect strong edges and lines. In the last module, the resultant text, photo, and edge maps are combined to generate a page layout map using K-Means clustering. The proposed algorithm has been tested on several hundred documents that contain simple and complex page layout structures and contents such as articles, magazines, business cards, dictionaries, and newsletters, and compared against state-of-the-art page-segmentation techniques with benchmark performance. The results indicate that our methodology achieves an average of ˜89% classification accuracy in text, photo, and background regions.

  7. Gas Dynamics in Planetary Nebulae: From Macro-structures to FLIERs

    NASA Astrophysics Data System (ADS)

    Perinotto, Mario

    2000-10-01

    Purpose of this paper is to clarify how Planetary Nebulae (PNe) are very interesting laboratories to study cosmic gas dynamics. I first recall the history of PNe which are generated from low and intermediate mass stars through successive mass loss processes starting in the Reg Giant phase of evolution and continuing also after the termination of the pulsed AGB phase, where most of the nebular mass is believed to be ejected. The correponding stellar winds are the ingredients of the nebula. Their initial properties and subsequent mutual interactions, under the action of the evolving stellar radiation field, are responsible for the properties of the nebula. The observed structures of PNe are considered in detail. Larger scale macroscopic structures (MACS) are examined separately from quite smaller scale microscopic structures (MICS). The formation of MACS, at least in cases of round to moderately elliptical PNe, is shown to be reasonably well understood in terms of existing hydrodynamical models. Considering the kinematical behaviour, MICS can be separated into FLIERs (Fast Low Ionization Emitting Regions) and SLOWERs (slowly moving). Attention is focussed on FLIERs and on the proposed mechanisms to interpret them. Recent observations with the Hubble Space Telescope have provided us with a wealth of detailed (subarcsec) information on the nebular structures. The inner structure of FLIERs is here illustrated to consist of substructures of various shapes with an high degree of individually from object to object, also within the same PN. These new data call for deeper thoretical efforts to solve the problems of cosmic gas dynamics, posed by their observed properties. An ample account is given of the most relevant original works, in an effort to allow the non specialist reader to quickly become acquainted with the status of art in the various aspects of the subject.

  8. Spatial distribution of carbon dust in the early solar nebula and the carbon content of planetesimals

    NASA Astrophysics Data System (ADS)

    Gail, Hans-Peter; Trieloff, Mario

    2017-09-01

    Context. A high fraction of carbon bound in solid carbonaceous material is observed to exist in bodies formed in the cold outskirts of the solar nebula, while bodies in the region of terrestrial planets contain only very small mass fractions of carbon. Most of the solid carbon component is lost and converted into CO during the spiral-in of matter as the Sun accretes matter from the solar nebula. Aims: We study the fate of the carbonaceous material that entered the proto-solar disc by comparing the initial carbon abundance in primitive solar system material and the abundance of residual carbon in planetesimals and planets in the asteroid belt and the terrestrial planet region. Methods: We constructed a model for the composition of the pristine carbonaceous material from observational data on the composition of the dust component in comets and of interplanetary dust particles and from published data on pyrolysis experiments. This material entered the inner parts of the solar nebula during the course of the build-up of the proto-sun by accreting matter from the proto-stellar disc. Based on a one-zone evolution model of the solar nebula, we studied the pyrolysis of the refractory and volatile organic component and the concomitant release of hydrocarbons of high molecular weight under quiescent conditions of disc evolution, while matter migrates into the central parts of the solar nebula. We also studied the decomposition and oxidation of the carbonaceous material during violent flash heating events, which are thought to be responsible for the formation of chondrules. To do this, we calculated pyrolysis and oxidation of the carbonaceous material in temperature spikes that were modeled according to cosmochemical models for the temperature history of chondrules. Results: We find that the complex hydrocarbon components of the carbonaceous material are removed from the disc matter in the temperature range between 250 and 400 K, but the amorphous carbon component survives to

  9. Theoretical, observational, and isotopic estimates of the lifetime of the solar nebula

    NASA Technical Reports Server (NTRS)

    Podosek, Frank A.; Cassen, Patrick

    1994-01-01

    There are a variety of isotopic data for meteorites which suggest that the protostellar nebula existed and was involved in making planetary materials for some 10(exp 7) yr or more. Many cosmochemists, however, advocate alternative interpretations of such data in order to comply with a perceived constraint, from theoretical considerations, that the nebula existed only for a much shorter time, usually stated as less than or equal to 10(exp 6) yr. In this paper, we review evidence relevant to solar nebula duration which is available through three different disciplines: theoretical modeling of star formation, isotopic data from meteorites, and astronomical observations of T Tauri stars. Theoretical models based on observations of present star-forming regions indicate that stars like the Sun form by dynamical gravitational collapse of dense cores of cold molcular clouds in the interstellar clouds in the interstellar medium. The collapse to a star and disk occurs rapidly, on a time scale of the order 10(exp 5) yr. Disks evolve by dissipating energy while redistributing angular momentum, but it is difficult to predict the rate of evolution, particularly for low mass (compared to the star) disks which nonetheless still contain enough material to account for the observed planetary system. There is no compelling evidence, from available theories of disk structure and evolution, that the solar nebula must have evolved rapidly and could not have persisted for more than 1 Ma. In considering chronoloically relevant isotopic data for meteorites, we focus on three methodologies: absolute ages by U-Pb/Pb-Pb, and relative ages by short-lived radionuclides (especially Al-26) and by evolution of Sr-87/Sr-86. Two kinds of meteoritic materials-refractory inclusions such as CAIs and differential meteorites (eucrites and augrites) -- appear to have experienced potentially dateable nebular events. In both cases, the most straightforward interpretations of the available data indicate

  10. Theoretical, observational, and isotopic estimates of the lifetime of the solar nebula

    NASA Technical Reports Server (NTRS)

    Podosek, Frank A.; Cassen, Patrick

    1994-01-01

    There are a variety of isotopic data for meteorites which suggest that the protostellar nebula existed and was involved in making planetary materials for some 10(exp 7) yr or more. Many cosmochemists, however, advocate alternative interpretations of such data in order to comply with a perceived constraint, from theoretical considerations, that the nebula existed only for a much shorter time, usually stated as less than or = 10(exp 6) yr. In this paper, we review evidence relevant to solar nebula duration which is available through three different disciplines: theoretical modelling of star formation, isotopic data from meteorites, and astronomical observations of T Tauri stars. Theoretical models based on observations of present star-forming regions indicate that stars like the Sun form by dynamical gravitational collapse of dense cores of cold molecular clouds in the interstellar medium. The collapse to a star and disk occurs rapidly on a time scale of the order 10(exp 5) yr. Disks evolve by dissipating energy while redistributing angular momentum, but it is difficult to predict the rate of evolution, particularly for low mass (compared to the star) disks which nonetheless still contain enough material to account for the observed planetary system. There is no compelling evidence, from available theories of disk structure and evolution, that the solar nebula must have evolved rapidly and could not have persisted for more than 1 Ma. In considering chronologically relevant isotopic data for meteorites, we focus on three methodologies: absolute ages by U-Pb/Pb-Pb, and relative ages by short-lived radionuclides (especially Al-26) and by evolution of Sr-87/Sr-86. Two kinds of meteoritic materials-refractory inclusions such as CAIs and differentiated meteorites (eucrites and angrites) - appear to have experience potentially dateable nebular events. In both case, the most straightforward interpretations of the available data indicate nebular events spanning several Ma. We

  11. Fermi LAT detection of enhanced gamma-ray emission from the Crab Nebula region

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh; Buehler, Rolf; Hays, Elizabeth; Dutka, Michael

    2012-07-01

    The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed a significant increase in the gamma-ray activity from a source positionally consistent with the Crab Nebula on July 3, 2012. Preliminary LAT analysis indicates that the daily-averaged gamma-ray emission (E >100 MeV) from the direction of the Crab doubled from (2.4 +/- 0.5) x 10^-6 ph/cm2/sec (statistical errors only) on July 2nd to (5.5 +/- 0.7) x 10^-6 ph/cm2/sec on July 3rd, a factor of 2 greater than the average flux of (2.75 +/- 0.10) x 10^-6 ph/cm2/sec reported in the second Fermi LAT catalog (2FGL, Nolan et al.

  12. The solar nebula redox state as recorded by the most reduced chondrules of five primitive chondrites

    NASA Technical Reports Server (NTRS)

    Johnson, M. C.

    1986-01-01

    Mafic minerals in the most reduced chondrules of five primitive meteorites were analyzed with an electron microprobe to determine the lower limit on their FeO contents. The accuracy obtained was + or - 0.01 weight percent FeO. The thermodynamic relationship between mole fraction FeSiO3 and pO2 of the ambient nebular gas at the time of mineral equilibration was established, and was used to infer the local O/H ratio of the nebular gas during chondrule formation. The lowest ferrosilite compositions reflected equilibration at 1500 K with a gas 2-18 times more oxidizing than a gas of solar composition. Olivines in low-FeO unequilibrated ordinary chondrites (UOC) chondrules are uniformly more FeO-rich than coexisting pyroxenes. This discrepancy suggests that a significant change in the O/H ratio of the nebular gas occurred between the time of olivine and pyroxene crystallization in the region of the nebula where UOCs formed. Mineral compositions in the chondrules of two C2 chondrites studied suggest they formed in a more homogeneous region of the nebula than the UOCs.

  13. The VELA-X-Pulsar Wind Nebula Revisited with Four Years of Fermi Large Area Telescope Observations

    NASA Technical Reports Server (NTRS)

    Grondin, M. -H.; Romani, R. W.; Lemoine-Goumard, M.; Guillemot, L.; Harding, Alice K.; Reposeur, T.

    2013-01-01

    The Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833-45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2deg × 3deg south of the pulsar and observed in the radio, X-ray, and very high energy ?-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysis of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.

  14. The Vela-X pulsar wind nebula revisited with four years of Fermi Large Area Telescope observations

    DOE PAGES

    Grondin, M. -H.; Romani, R. W.; Lemoine-Goumard, M.; ...

    2013-08-21

    Here, the Vela supernova remnant (SNR) is the closest SNR to Earth containing an active pulsar, the Vela pulsar (PSR B0833–45). This pulsar is an archetype of the middle-aged pulsar class and powers a bright pulsar wind nebula (PWN), Vela-X, spanning a region of 2° × 3° south of the pulsar and observed in the radio, X-ray, and very high energy γ-ray domains. The detection of the Vela-X PWN by the Fermi Large Area Telescope (LAT) was reported in the first year of the mission. Subsequently, we have reinvestigated this complex region and performed a detailed morphological and spectral analysismore » of this source using 4 yr of Fermi-LAT observations. This study lowers the threshold for morphological analysis of the nebula from 0.8 GeV to 0.3 GeV, allowing for the inspection of distinct energy bands by the LAT for the first time. We describe the recent results obtained on this PWN and discuss the origin of the newly detected spatial features.« less

  15. POST ASYMPTOTIC GIANT BRANCH BIPOLAR REFLECTION NEBULAE: RESULT OF DYNAMICAL EJECTION OR SELECTIVE ILLUMINATION?

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

    Koning, N.; Kwok, Sun; Steffen, W., E-mail: nico.koning@ucalgary.ca, E-mail: sunkwok@hku.hk, E-mail: wsteffen@astrosen.unam.mx

    2013-03-10

    A model for post asymptotic giant branch bipolar reflection nebulae has been constructed based on a pair of evacuated cavities in a spherical dust envelope. Many of the observed features of bipolar nebulae, including filled bipolar lobes, an equatorial torus, searchlight beams, and a bright central light source, can be reproduced. The effects on orientation and dust densities are studied and comparisons with some observed examples are offered. We suggest that many observed properties of bipolar nebulae are the result of optical effects and any physical modeling of these nebulae has to take these factors into consideration.

  16. Effective negative ion profile of low-latitude D-region during solar flares evaluated from VLF signal analysis

    NASA Astrophysics Data System (ADS)

    Basak, Tamal; Chakrabarti, Sandip Kumar

    Our objective is to study the effects of solar energetic phenomena on the lower ionosphere using subionospherically propagating Very Low Frequency signals. In this work, we dealt with the negative ion contents of the lower D-region during flares. We did a generalized study of the variation of the lambda-parameter both with height and time. In this purpose, we numerically solved the D-region electron continuity equation, where, we supplied the N_e-profile calculated from LWPC results. The results generally agree with those present in the literature, namely, the effect on the negative ion density during flares due to photo-electron detachment and photo-dissociation processes. However, for our VLF propagation path of interest, we found that the negative ions exist till somewhat higher altitudes (˜ 73-74 km) than the high-latitude D-region heights. Other workers did model study on Cl(-) ions and its complex compounds at nighttime in high latitude ionosphere. They reported that, though negative ions are less abundant in daytime, in lower latitudes its availability increases, which supports our results.

  17. Unveiling the True Metallicity and Stellar Populations of Planetary Nebula Progenitor Stars

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet L.; Geballe, T. R.; Sterling, N. C.

    2011-01-01

    We have measured the recently identified 3.625 micron [Zn IV] fine-structure line (Dinerstein & Geballe 2001, ApJ, 562, 515) in a dozen Galactic planetary nebulae (Dinerstein et al. 2007, BAAS, 211, 100.14). Because Zn is the least refractory of the Fe peak elements, the gas phase [Zn/H] abundance can be used as a proxy for the elemental [Fe/H] in the progenitor star, in contrast to Fe itself, which is heavily depleted into dust. We find that the observed Milky Way nebulae fall into two categories: objects which have roughly solar values of [Zn/H] and [O/Zn]; and nebulae with low Zn (clustering around [Zn/H] = -0.6) and elevated [O/H]. Most of the latter group have high radial velocities, |vrad| > 60 km/s. Our interpretation is that the objects with solar abundances and low velocities originate from thin disk stars, while the nebulae with low Zn are descendants of thick disk stars. A further implication is that the common assumption that O and other alpha species are reliable indicators of metallicity in planetary nebulae is not necessarily valid, and can lead to erroneous conclusions about the parent stellar population. This effect is particularly acute for O since [O/Fe] can be large, especially in metal-poor populations. In a planetary nebula formed by a star with this abundance pattern, a high value of [(O, alpha)/Fe] can offset a low [Fe/H], producing near-solar abundances for O and other alpha species. This can make it appear that the star belongs to a more metal-rich (in [Fe/H]) population than is actually the case. Obtaining Zn abundances for larger samples of planetary nebulae will be crucial to disentangling these abundance ratios and breaking the potential degeneracy of the O and alpha abundances. (This research was supported by NSF grant 0708245.)

  18. Existence of an 16O-rich gaseous reservoir in the solar nebula.

    PubMed

    Krot, Alexander N; McKeegan, Kevin D; Leshin, Laurie A; MacPherson, Glenn J; Scott, Edward R D

    2002-02-08

    Carbonaceous chondrite condensate olivine grains from two distinct petrographic settings, calcium-aluminum-rich inclusion (CAI) accretionary rims and amoeboid olivine aggregates (AOAs), are oxygen-16 (16O) enriched at the level previously observed inside CAIs. This requires that the gas in the nebular region where these grains condensed was 16O-rich. This contrasts with an 16O-poor gas present during the formation of chondrules, suggesting that CAIs and AOAs formed in a spatially restricted region of the solar nebula containing 16O-rich gas. The 16O-rich gas composition may have resulted either from mass-independent isotopic chemistry or from evaporation of regions with enhanced dust/gas ratios, possibly in an X-wind environment near the young Sun.

  19. C/O ratios in planetary nebulae with dual-dust chemistry from faint optical recombination lines

    NASA Astrophysics Data System (ADS)

    García-Rojas, J.; Delgado-Inglada, G.; García-Hernández, D. A.; Dell'Agli, F.; Lugaro, M.; Karakas, A. I.; Rodríguez, M.

    2018-02-01

    We present deep high-resolution (R ˜ 15 000) and high-quality UVES optical spectrophotometry of nine planetary nebulae with dual-dust chemistry. We compute physical conditions from several diagnostics. Ionic abundances for a large number of ions of N, O, Ne, S, Cl, Ar, K, Fe and Kr are derived from collisionally excited lines. Elemental abundances are computed using state-of-the-art ionization correction factors. We derive accurate C/O ratios from optical recombination lines. We have re-analysed additional high-quality spectra of 14 PNe from the literature following the same methodology. Comparison with asymptotic giant branch models reveals that about half of the total sample objects are consistent with being descendants of low-mass progenitor stars (M < 1.5 M⊙). Given the observed N/O, C/O and He/H ratios, we cannot discard that some of the objects come from more massive progenitor stars (M > 3-4 M⊙) that have suffered a mild hot bottom burning. None of the objects seem to be descendant of very massive progenitors. We propose that in most of the planetary nebulae studied here, the polycyclic aromatic hydrocarbons have been formed through the dissociation of the CO molecule. The hypothesis of a last thermal pulse that turns O-rich PNe into C-rich PNe is discarded, except in three objects, that show C/O > 1. We also discuss the possibility of an He pre-enrichment to explain the most He-enriched objects. We cannot discard another scenarios like extra mixing, stellar rotation or binary interactions to explain the chemical abundances behaviour observed in our sample.

  20. Physics of the primitive solar nebula and of giant gaseous protoplanets

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.

    1978-01-01

    It has been proposed that the supernova responsible for injecting Al-26 into the early solar system was in fact responsible for triggering the collapse of an interstellar cloud in order to produce a system of stars, one of which would be the solar system. Details concerning the mechanism involved in such a process are discussed. Attention is given to the evolution of the primitive solar nebula, the instabilities in the primitive solar nebula, and the giant gaseous protoplanets. The principal conclusion to be drawn from the material presented is that the primitive solar nebula was a rather chaotic place, highly turbulent, with the multiple formation of giant gaseous protoplanets.

  1. Lifetime of the solar nebula constrained by meteorite paleomagnetism

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

    Wang, Huapei; Weiss, Benjamin P.; Bai, Xue-Ning

    We present that a key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (<0.6 microtesla) at 4563.5 ± 0.1 million years ago, ~3.8 million years after solar system formation. This indicates that the solar nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation ofmore » chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. In conclusion, the core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.« less

  2. Lifetime of the solar nebula constrained by meteorite paleomagnetism.

    PubMed

    Wang, Huapei; Weiss, Benjamin P; Bai, Xue-Ning; Downey, Brynna G; Wang, Jun; Wang, Jiajun; Suavet, Clément; Fu, Roger R; Zucolotto, Maria E

    2017-02-10

    A key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (<0.6 microtesla) at 4563.5 ± 0.1 million years ago, ~3.8 million years after solar system formation. This indicates that the solar nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation of chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. The core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation. Copyright © 2017, American Association for the Advancement of Science.

  3. Lifetime of the solar nebula constrained by meteorite paleomagnetism

    DOE PAGES

    Wang, Huapei; Weiss, Benjamin P.; Bai, Xue-Ning; ...

    2017-02-10

    We present that a key stage in planet formation is the evolution of a gaseous and magnetized solar nebula. However, the lifetime of the nebular magnetic field and nebula are poorly constrained. We present paleomagnetic analyses of volcanic angrites demonstrating that they formed in a near-zero magnetic field (<0.6 microtesla) at 4563.5 ± 0.1 million years ago, ~3.8 million years after solar system formation. This indicates that the solar nebula field, and likely the nebular gas, had dispersed by this time. This sets the time scale for formation of the gas giants and planet migration. Furthermore, it supports formation ofmore » chondrules after 4563.5 million years ago by non-nebular processes like planetesimal collisions. In conclusion, the core dynamo on the angrite parent body did not initiate until about 4 to 11 million years after solar system formation.« less

  4. An atlas of synthetic line profiles of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Morisset, C.; Stasinska, G.

    2008-04-01

    We have constructed a grid of photoionization models of spherical, elliptical and bipolar planetary nebulae. Assuming different velocity fields, we have computed line profiles corresponding to different orientations, slit sizes and positions. The atlas is meant both for didactic purposes and for the interpretation of data on real nebulae. As an application, we have shown that line profiles are often degenerate, and that recovering the geometry and velocity field from observations requires lines from ions with different masses and different ionization potentials. We have also shown that the empirical way to measure mass-weighted expansion velocities from observed line widths is reasonably accurate if considering the HWHM. For distant nebulae, entirely covered by the slit, the unknown geometry and orientation do not alter the measured velocities statistically. The atlas is freely accessible from internet. The Cloudy_3D suite and the associated VISNEB tool are available on request.

  5. Ultraviolet Imaging Telescope images of the reflection nebula NGC 7023 - Derivation of ultraviolet scattering properties of dust grains

    NASA Technical Reports Server (NTRS)

    Witt, Adolf N.; Petersohn, Jens K.; Bohlin, Ralph C.; O'Connell, Robert W.; Roberts, Morton S.; Smith, Andrew M.; Stecher, Theodore P.

    1992-01-01

    The Ultraviolet Imaging Telescope as part of the Astro-1 mission, was used to obtain high-resolution surface brightness distribution data in six ultraviolet wavelength bands for the bright reflection nebula NGC 7023. From the quantitative comparison of the measured surface brightness gradients ratios of nebular to stellar flux, and detail radial surface brightness profiles with corresponding data from the visible, two major conclusions results: (1) the scattering in the near- and far-ultraviolet in this nebula is more strongly forward-directed than in the visible; (2) the dust albedo in the ultraviolet for wavelengths not less than 140 nm is identical to that in the visible, with the exception of the 220 nm bump in the extinction curve. In the wavelengths region of the bump, the albedo is reduced by 25 to 30 percent in comparison with wavelengths regions both shorter and longer. This lower albedo is expected, if the bump is a pure absorption feature.

  6. BUBBLES AND KNOTS IN THE KINEMATICAL STRUCTURE OF THE BIPOLAR PLANETARY NEBULA NGC 2818

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

    Vazquez, Roberto, E-mail: vazquez@astro.unam.mx

    2012-06-01

    High-resolution Hubble Space Telescope archive imaging and high-dispersion spectroscopy are used to study the complex morphological and kinematical structure of the planetary nebula, NGC 2818. We analyze narrowband H{alpha}, [O III], [N II], [S II], and He II images, addressing important morphological features. Ground-based long-slit echelle spectra were obtained crossing NGC 2818 at five different positions to precisely determine kinematical features in the structure of the nebula. A distance of 2.5 kpc was used to determine physical scales. Constructing models to fit the data with modern computational tools, we find NGC 2818 is composed of (1) a non-uniform bipolar structuremore » with a semimajor axis of 0.92 pc (75''), possibly deformed by the stellar wind, (2) a 0.17 pc (14'') diameter central region, which is potentially the remnant of an equatorial enhancement, and (3) a great number of cometary knots. These knots are preferentially located inside a radius of 0.24 pc (20'') around the central star. The major axis of the main structure is oriented at i {approx_equal} 60 Degree-Sign with respect to the line of sight and at P.A. = +89 Degree-Sign on the plane of the sky. Expansion velocities of this nebula are V{sub pol} = 105 km s{sup -1} and V{sub eq} = 20 km s{sup -1}, which lead to our estimate of the kinematical age of {tau}{sub k} {approx_equal} 8400 {+-} 3400 yr (assuming homologous expansion). Our observations do not support the idea that high-velocity collimated ejections are responsible for the formation of microstructures inside the nebula. We determine the systemic velocity of NGC 2818 to be V{sub HEL} = +26 {+-} 2 km s{sup -1}.« less

  7. New CNO Elemental Abundances in Planetary Nebulae from Spatially Resolved UV/Optical Emission Lines

    NASA Astrophysics Data System (ADS)

    Shaw, Richard A.; Kwitter, Karen B.; Henry, Richard B. C.; Dufour, Reginald J.; Balick, Bruce; Corradi, Romano

    2015-01-01

    We obtained HST/STIS long-slit spectra spanning 0.11 to 1.1 μm of co-spatial regions in 10 Galactic planetary nebulae (Dufour, et al., this conference), of which six present substantial changes in ionization with position. Under the assumption that elemental abundances are constant within these nebulae (but exterior to the wind of the central star), these spectra present a unique opportunity to examine the applicability of common ionization correction factors (ICFs) for deriving abundances. ICFs are the most common direct method in abundance analysis for accounting for unobserved or undetected ionization stages in nebulae, yet most ICF recipes have not been rigorously examined through modeling nor empirically tested through observation. In this preliminary study, we focussed on the astrophysically important abundances of C and N where strong ionic transitions are scarce in optical band, but plentiful in the satellite UV. We derived physical diagnostics (extinction, Te, Ne) and ionic abundances for the species of interest at various positions along the slit for each PN. We compared the elemental abundances derived from direct summation of the ionic abundances in the UV and optical to those derived using only optical emission, but corrected using standard ICFs. We found that the abundances were usually in good agreement, but there were significant exceptions. We also found that setting upper limits on emission from undetected ions was sometimes helpful in constraining the correction factors. Work is underway to construct photoionization models of these nebulae (see Miller, et al., this conference) to address the question of why ICFs are sometimes inaccurate, and to explore other ICF recipes for those cases.Support for Program number GO-12600 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.

  8. Gigahertz-peaked spectra pulsars in Pulsar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Basu, R.; RoŻko, K.; Kijak, J.; Lewandowski, W.

    2018-04-01

    We have carried out a detailed study of the spectral nature of six pulsars surrounded by pulsar wind nebulae (PWNe). The pulsar flux density was estimated using the interferometric imaging technique of the Giant Metrewave Radio Telescope at three frequencies 325, 610, and 1280 MHz. The spectra showed a turnover around gigahertz frequency in four out of six pulsars. It has been suggested that the gigahertz-peaked spectrum (GPS) in pulsars arises due to thermal absorption of the pulsar emission in surrounding medium like PWNe, H II regions, supernova remnants, etc. The relatively high incidence of GPS behaviour in pulsars surrounded by PWNe imparts further credence to this view. The pulsar J1747-2958 associated with the well-known Mouse nebula was also observed in our sample and exhibited GPS behaviour. The pulsar was detected as a point source in the high-resolution images. However, the pulsed emission was not seen in the phased-array mode. It is possible that the pulsed emission was affected by extreme scattering causing considerable smearing of the emission at low radio frequencies. The GPS spectra were modelled using the thermal free-free absorption and the estimated absorber properties were largely consistent with PWNe. The spatial resolution of the images made it unlikely that the point source associated with J1747-2958 was the compact head of the PWNe, but the synchrotron self-absorption seen in such sources was a better fit to the estimated spectral shape.

  9. Actively learning human gaze shifting paths for semantics-aware photo cropping.

    PubMed

    Zhang, Luming; Gao, Yue; Ji, Rongrong; Xia, Yingjie; Dai, Qionghai; Li, Xuelong

    2014-05-01

    Photo cropping is a widely used tool in printing industry, photography, and cinematography. Conventional cropping models suffer from the following three challenges. First, the deemphasized role of semantic contents that are many times more important than low-level features in photo aesthetics. Second, the absence of a sequential ordering in the existing models. In contrast, humans look at semantically important regions sequentially when viewing a photo. Third, the difficulty of leveraging inputs from multiple users. Experience from multiple users is particularly critical in cropping as photo assessment is quite a subjective task. To address these challenges, this paper proposes semantics-aware photo cropping, which crops a photo by simulating the process of humans sequentially perceiving semantically important regions of a photo. We first project the local features (graphlets in this paper) onto the semantic space, which is constructed based on the category information of the training photos. An efficient learning algorithm is then derived to sequentially select semantically representative graphlets of a photo, and the selecting process can be interpreted by a path, which simulates humans actively perceiving semantics in a photo. Furthermore, we learn a prior distribution of such active graphlet paths from training photos that are marked as aesthetically pleasing by multiple users. The learned priors enforce the corresponding active graphlet path of a test photo to be maximally similar to those from the training photos. Experimental results show that: 1) the active graphlet path accurately predicts human gaze shifting, and thus is more indicative for photo aesthetics than conventional saliency maps and 2) the cropped photos produced by our approach outperform its competitors in both qualitative and quantitative comparisons.

  10. Ring Nebulae: Tracers of the CNO Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Mesa-Delgado, A.; Esteban, C.; García-Rojas, J.

    Preliminary results are presented from spectroscopic data in the optical range of the Galactic ring nebulae NGC 6888, G2:4+1:4, RCW 58 and Sh2-308. Deep observations with long exposure times were carried out at the 6.5m Clay Telescope and at the 10.4m Gran Telescopio Canarias. In NGC 6888, recombination lines of C ii, O ii and N ii are detected with signal-to-noise ratios higher than 8. The chemical content of NGC 6888 is discussed within the chemical enrichment predicted by evolution models of massive stars. For all nebulae, a forthcoming work will content in-depth details about observations, analysis and final results (Esteban et al. 2015, in prep.).

  11. The albedo of particles in reflection nebulae

    NASA Technical Reports Server (NTRS)

    Rush, W. F.

    1974-01-01

    The relation between the apparent angular extent of a reflection nebula and the apparent magnitude of its illuminating star was reconsidered under a less restrictive set of assumptions. A computational technique was developed which permits the use of fits to the observed m-log a values to determine the albedo of particles composing reflection nebulae, providing only that a phase function and average optical thickness are assumed. Multiple scattering, anisotropic phase functions, and illumination by the general star field are considered, and the albedo of reflection nebular particles appears to be the same as that for interstellar particles in general. The possibility of continuous fluorescence contributions to the surface brightness is also considered.

  12. Radiative Feedback from Massive Stars as Traced by Multiband Imaging and Spectroscopic Mosaics

    NASA Astrophysics Data System (ADS)

    Berne, Olivier; Habart, Emilie; Peeters, Els; Abergel, A.; Bergin, E.; Bernard-Salas, J.; Bron, E.; Cami, J.; Cazaux, S.; Dartois, E.; Fuente, A.; Goicoechea, J.; Gordon, K.; Onaka, T.; Robberto, M.; Roellig, M.; Tielens, A.; Vincente, S.; Wolfire, M.; Okada, Y.

    2017-11-01

    Massive stars disrupt their natal molecular cloud material by dissociating molecules, ionizing atoms and molecules, and heating the gas and dust. These processes drive the evolution of interstellar matter in our Galaxy and throughout the Universe from the era of vigorous star formation at redshifts of 1-3, to the present day. Much of this interaction occurs in Photo-Dissociation Regions (PDRs) where far-ultraviolet photons of these stars create a largely neutral, but warm region of gas and dust. PDR emission dominates the IR spectra of star-forming galaxies and also provides a unique tool to study in detail the physical and chemical processes that are relevant for most of the mass in inter- and circumstellar media including diffuse clouds, protoplanetary disk- and molecular cloud surfaces, globules, planetary nebulae, and starburst galaxies. We propose to provide template datasets designed to identify key PDR characteristics in JWST spectra in order to guide the preparation of Cycle 2 proposals on star-forming regions in our Galaxy and beyond. We plan to obtain the first spatially resolved, high spectral resolution IR observations of a PDR using NIRCam, NIRSpec, and MIRI. These data will test widely used theoretical models and extend them into the JWST era. We have engaged the broader community as exemplified by the supporting large international team of 138 scientists. We will assist the community interested in JWST observations of PDRs through science-enabling products that will guide observational planning and allow fast data analysis. We will train the community through telecons and dedicated workshops.

  13. Runaway stars in the Gum Nebula

    NASA Technical Reports Server (NTRS)

    Got, J. R., III; Ostriker, J. P.

    1971-01-01

    It is proposed that the two pulsars PSR 0833-45 (the Vela pulsar) and MP 0835 are runaways from a common binary system originally located in the B association around gamma Velorum. Arguments are presented for a simple model of the Gum nebula in which two distinct ionized regions are present. The first consists of the Stromgren spheres of gamma Velorum and zeta Puppis, while the second is a larger, more filamentary region ionized by the supernova explosion associated with PSR 0833-45. Using this model and the available dispersion measures, the distances to the two pulsars were estimated and found to be compatible with a runaway origin. The position angle of the rotation axis of PSR 0833-45 is also compatible with this origin. The masses of the parent stars of the two pulsars can be deduced from the runaway star dynamics and an assumed age for MP 0835. It is concluded that the masses were in excess of 10 solar masses. The dynamically-determined parent star masses are in agreement with the values expected for evolved members of the B association around gamma Velorum.

  14. HUBBLE CAPTURES UNVEILING OF PLANETARY NEBULA

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This Wide Field and Planetary Camera 2 image captures the infancy of the Stingray nebula (Hen-1357), the youngest known planetary nebula. In this image, the bright central star is in the middle of the green ring of gas. Its companion star is diagonally above it at 10 o'clock. A spur of gas (green) is forming a faint bridge to the companion star due to gravitational attraction. The image also shows a ring of gas (green) surrounding the central star, with bubbles of gas to the lower left and upper right of the ring. The wind of material propelled by radiation from the hot central star has created enough pressure to blow open holes in the ends of the bubbles, allowing gas to escape. The red curved lines represent bright gas that is heated by a 'shock' caused when the central star's wind hits the walls of the bubbles. The nebula is as large as 130 solar systems, but, at its distance of 18,000 light-years, it appears only as big as a dime viewed a mile away. The Stingray is located in the direction of the southern constellation Ara (the Altar). The colors shown are actual colors emitted by nitrogen (red), oxygen (green), and hydrogen (blue). The filters used were F658N ([N II]), F502N ([O III]), and F487N (H-beta). The observations were made in March 1996. Credit: Matt Bobrowsky, Orbital Sciences Corporation and NASA

  15. Ring nebulae around Wolf-Rayet stars in M33

    NASA Technical Reports Server (NTRS)

    Drissen, Laurent; Shara, Michael M.; Moffat, Anthony F. J.

    1991-01-01

    Results of a systematic search for H II ring nebulae surrounding Wolf-Rayet (WR) stars in M33 are presented. Eleven objects are found to be good candidates, while eight others are classified as possible WR ring nebulae. The WR rings in M33 are larger on average than their Galactic counterparts, but the H-alpha luminosity of most of them is comparable to the bright Galactic wind-blown bubbles. The rings are associated with WC as well as with WN stars.

  16. Diffuse X-ray emission from the Dumbbell Nebula?

    NASA Technical Reports Server (NTRS)

    Chu, You-Hua; Kwitter, Karen B.; Kaler, James B.

    1993-01-01

    We have analyzed ROSAT Position Sensitive Proportional Counter pointed observations of the Dumbbell Nebula and find that the previously reported 'extended' X-ray emission is an instrumental electronic ghost image at the softest energy band. At slightly higher energy bands, the image of the Dumbbell is not very different from that of the white dwarf HZ43. We conclude that the X-ray emission of the Dumbbell Nebula comes from its central star. A blackbody model is fitted to the spectrum and the best-fit temperature of not greater than 136,000 +/- 10,000 K is in excellent agreement with the Zanstra temperatures.

  17. Particle Acceleration in Pulsar Wind Nebulae: PIC Modelling

    NASA Astrophysics Data System (ADS)

    Sironi, Lorenzo; Cerutti, Benoît

    We discuss the role of PIC simulations in unveiling the origin of the emitting particles in PWNe. After describing the basics of the PIC technique, we summarize its implications for the quiescent and the flaring emission of the Crab Nebula, as a prototype of PWNe. A consensus seems to be emerging that, in addition to the standard scenario of particle acceleration via the Fermi process at the termination shock of the pulsar wind, magnetic reconnection in the wind, at the termination shock and in the Nebula plays a major role in powering the multi-wavelength signatures of PWNe.

  18. The global evolution of the primordial solar nebula

    NASA Technical Reports Server (NTRS)

    Ruden, S. P.; Lin, D. N. C.

    1986-01-01

    Complete radial, time-dependent calculations of the structure and evolution of the primordial solar nebula during the viscous diffusion stage are presented. The viscous stress is derived from analytic one-zone models of the vertical nebular structure based on detailed grain opacities. Comparisons with full numerical integrations indicate that the effective viscous alpha parameter is about 0.01. The evolution time of a minimum mass nebula is one-million yr or less. The flow pattern of fluid elements in the disk is examined and the implications the results have on the theory of the formation of the solar system are discussed.

  19. A COMPREHENSIVE SEARCH FOR STELLAR BOWSHOCK NEBULAE IN THE MILKY WAY: A CATALOG OF 709 MID-INFRARED SELECTED CANDIDATES

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

    Kobulnicky, Henry A.; Chick, William T.; Schurhammer, Danielle P.

    2016-12-01

    We identify 709 arc-shaped mid-infrared nebula in 24 μ m Spitzer Space Telescope or 22 μ m Wide Field Infrared Explorer surveys of the Galactic Plane as probable dusty interstellar bowshocks powered by early-type stars. About 20% are visible at 8 μ m or at shorter mid-infrared wavelengths. The vast majority (660) have no previous identification in the literature. These extended infrared sources are strongly concentrated near the Galactic mid-plane, with an angular scale height of ∼0.°6. All host a symmetrically placed star implicated as the source of a stellar wind sweeping up interstellar material. These are candidate “runaway” starsmore » potentially having high velocities in the reference frame of the local medium. Among the 286 objects with measured proper motions, we find an unambiguous excess with velocity vectors aligned with the infrared morphology—kinematic evidence that many of these are “runaway” stars with large peculiar motions responsible for the bowshock signature. We discuss a population of “in situ” bowshocks (∼103 objects) that face giant H ii regions where the relative motions between the star and ISM may be caused by bulk outflows from an overpressured bubble. We also identify ∼58 objects that face 8 μ m bright-rimmed clouds and apparently constitute a sub-class of in situ bowshocks where the stellar wind interacts with a photoevaporative flow (PEF) from an eroding molecular cloud interface (i.e., “PEF bowshocks”). Orientations of the arcuate nebulae exhibit a correlation over small angular scales, indicating that external influences such as H ii regions are responsible for producing some bowshock nebulae. However, the vast majority of the nebulae in this sample appear to be isolated (499 objects) from obvious external influences.« less

  20. Molecular gas excitation in Kleinmann-Low nebula

    NASA Astrophysics Data System (ADS)

    Callejo, Gonzague; Lemaire, Jean-Louis; Le Petit, F.; Pineau Des Forets, Guillaume; Field, David

    2004-12-01

    The Orion molecular cloud OMC-1 is the perfect object for the study of the dense interstellar medium accounting for active star formation; the intrinsic complexity of this region serves as a stallion, both for observing techniques and for interstellar medium modelling. A detailed dynamic and spectroscopic study has been performed using VLT and CFHT observations of the infrared Kleinmann-Low nebula; yielding a complete small-scale structure in velocity and most importantly powerful diagnosis tools in order to put a new light into the gas behaviour. These results allow to build up a consistent model of the gas excitation, and a clear dynamical view of the region. The crucial action of the shock waves is confirmed, and the discrepancies between the observations and the standard models are discussed. The consequences of this modelling will be discussed in terms of extinction, magnetic field, and other quantities related to induced star formation. The goodness of the models used for the interpretations will be also discussed and some future directions of investigation enhanced.

  1. THE ROTTEN EGG NEBULA A PLANETARY NEBULA IN THE MAKING

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The object shown in these NASA/ESA Hubble Space Telescope images is a remarkable example of a star going through death throes just as it dramatically transforms itself from a normal red giant star into a planetary nebula. This process happens so quickly that such objects are quite rare, even though astronomers believe that most stars like the Sun will eventually go through such a phase. This star, with the prosaic name of OH231.8+4.2, is seen in these infrared pictures blowing out gas and dust in two opposite directions. So much dust has been cast off and now surrounds the star that it cannot be seen directly, only its starlight that is reflected off the dust. The flow of gas is very fast, with a velocity up to 450,000 mph (700,000 km/h). With extreme clarity, these Hubble Near Infrared Camera and Multi-Object Spectrometer (NICMOS) images reveal that the fast-moving gas and dust are being collimated into several thin streamers (on the right) and a jet-like structure (on the left), which can be seen extending away from the centers of both pictures. On the right, wisps of material in jet-like streamers appear to strike some dense blobs of gas. This interaction must produce strong shock waves in the gas. The pictures represent two views of the object. The color image is a composite of four images taken with different NICMOS infrared filters on March 28, 1998. It shows that the physical properties of the material, both composition and temperature, vary significantly throughout the outflowing material. The black-and-white image was taken with one NICMOS infrared filter. That image is able to show more clearly the faint detail and structure in the nebula than can be achieved with the color composites. Observations by radio astronomers have found many unusual molecules in the gas around this star, including many containing sulfur, such as hydrogen sulfide and sulfur dioxide. These sulfur compounds are believed to be produced in the shock waves passing through the gas

  2. Unraveling the Helix Nebula: Its Structure and Knots

    NASA Astrophysics Data System (ADS)

    O'Dell, C. R.; McCullough, Peter R.; Meixner, Margaret

    2004-11-01

    Through Hubble Space Telescope (HST) imaging of the inner part of the main ring of the Helix Nebula, together with CTIO 4 m images of the fainter outer parts, we have a view of unprecedented quality of the nearest bright planetary nebula. These images have allowed us to determine that the main ring of the nebula is composed of an inner disk of about 499" diameter (0.52 pc) surrounded by an outer ring (in reality a torus) of 742" diameter (0.77 pc) whose plane is highly inclined to the plane of the disk. This outer ring is surrounded by an outermost ring of 1500" (1.76 pc) diameter, which is flattened on the side colliding with the ambient interstellar medium. The inner disk has an extended distribution of low-density gas along its rotational axis of symmetry, and the disk is optically thick to ionizing radiation, as is the outer ring. Published radial velocities of the knots provide support for the two-component structure of the main ring of the nebula and for the idea that the knots found there are expanding along with the nebular material from which they recently originated. These velocities indicate a spatial expansion velocity of the inner disk of 40 and 32 km s-1 for the outer ring, which yields expansion ages of 6560 and 12,100 yr, respectively. The outermost ring may be partially ionized through scattered recombination continuum from the inner parts of the nebula, but shocks certainly are occurring in it. This outermost ring probably represents a third period of mass loss by the central star. There is one compact, outer object that is unexplained, showing shock structures indicating a different orientation of the gas flow from that of the nebula. There is a change in the morphology of the knots as a function of the distance from the local ionization front. This supports a scenario in which the knots are formed in or near the ionization front and are then sculpted by the stellar radiation from the central star as the ionization front advances beyond them

  3. Analysis of Co-spatial UV-Optical STIS Spectra of Seven Planetary Nebulae From HST Cycle 19 GO 12600

    NASA Astrophysics Data System (ADS)

    Miller, Timothy R.; Henry, Richard B. C.; Dufour, Reginald J.; Kwitter, Karen B.; Shaw, Richard A.; Balick, Bruce; Corradi, Romano

    2016-01-01

    We present an analysis of seven spatially resolved planetary nebulae (PNe), NGC 2440, NGC 3242, NGC 5315, NGC 5882, NGC 7662, IC 2165, and IC 3568, from observations in the Cycle 19 program GO 12600 using HST STIS. These seven observations cover the wavelength range 1150-10,270 Å with 0.2 and 0.5 arcsec wide slits, and are co-spatial to within 0.1 arcsec along a 25 arcsec length across each nebula. The wavelength and spatial coverage enabled a detailed study of physical conditions and abundances from UV and optical line emissions (compared to only optical lines) for these seven PNe. The first UV lines of interest are those of carbon. The resolved lines of C III] 1906.68 and 1908.73 yielded a direct measurement of the density within the volume occupied by doubly-ionized carbon and other similar co-spatial ions as well as contributed to an accurate measurement of the carbon abundance. Each PN spectrum was divided into smaller spatial regions or segments in order to assess inferred density variations among the regions along the entire slit. There is a clear difference in the inferred density for several regions of each PNe. Variations in electron temperature and chemical abundances were also probed and shown to be completely homogeneous within the errors. Lastly, these nebulae were modeled in detail with the photoionization code CLOUDY. This modeling constrained the central star parameters of temperature and luminosity and tested the effects different density profiles have on these parameters. We gratefully acknowledge generous support from NASA through grants related to the Cycle 19 program GO 12600, as well as from the University of Oklahoma.

  4. NOAA Photo Library - Other NOAA Photo Sites

    Science.gov Websites

    National Marine Mammal Laboratory Resource Assessment and Conservation Engineering Fish Photos by Family Florida - Melbourne: Post Storm Damage Surveys and Summaries Florida - Tallahassee: Virtual Office Tour Kentucky - Jackson: Virtual Tour Kentucky - Louisville: Photo Album Kentucky - Paducah: Photo Gallery

  5. Kinematics and spectra of planetary nebulae with O VI-sequence nuclei

    NASA Technical Reports Server (NTRS)

    Johnson, H. M.

    1976-01-01

    Spectral features of NGC 5189 and NGC 6905 are tabulated. Fabry-Perot profiles around H alpha and O III lambda 5007 of NGC 5189, NGC 6905, NGC 246, and NGC 1535, are illustrated. The latter planetary nebula is a non-O VI-sequence, comparison object of high excitation. The kinematics of the four planetary nebulae are simply analyzed. Discussion of these data is motivated by the possibility of collisional excitation by high-speed ejecta from broad-lined O VI-sequence nuclei, and by the opportunity to make a comparison with conditions in the supernova remnant or ring nebula, G2.4 + 1.4, which contains an O VI-sequence nucleus of Population I.

  6. Spitzer Observations of MF 16 Nebula and the Associated Ultraluminous X-Ray Source

    DTIC Science & Technology

    2012-06-01

    reserved. Printed in the U.S.A. SPITZER OBSERVATIONS OF MF 16 NEBULA AND THE ASSOCIATED ULTRALUMINOUS X-RAY SOURCE C. T. Berghea and R. P. Dudik United...associated nebula MF 16. This ULX has very similar properties to the famous Holmberg II ULX, the first ULX to show a prominent infrared [O iv] emission...the most interesting developments in ULX history is the discovery in recent years of large ionized bubble nebulae around some of the most famous ULXs

  7. Chandra Discovers X-Ray Ring Around Cosmic Powerhouse in Crab Nebula

    NASA Astrophysics Data System (ADS)

    1999-09-01

    After barely two months in space, NASA's Chandra X-ray Observatory has taken a stunning image of the Crab Nebula, the spectacular remains of a stellar explosion, and has revealed something never seen before: a brilliant ring around the nebula's heart. Combined with observations from the Hubble Space Telescope, the image provides important clues to the puzzle of how the cosmic "generator," a pulsing neutron star, energizes the nebula, which still glows brightly almost 1,000 years after the explosion. "The inner ring is unique," said Professor Jeff Hester of Arizona State University, Tempe, AZ. "It has never been seen before, and it should tell us a lot about how the energy from the pulsar gets into the nebula. It's like finding the transmission lines between the power plant and the light bulb." Professor Mal Ruderman of Columbia University, New York, NY, agreed. "The X-rays Chandra sees are the best tracer of where the energy is. With images such as these, we can directly diagnose what is going on." What is going on, according to Dr. Martin Weisskopf, Chandra Project Scientist from NASA's Marshall Space Flight Center, Huntsville, AL, is awesome. "The Crab pulsar is accelerating particles up to the speed of light and flinging them out into interstellar space at an incredible rate." The image shows tilted rings or waves of high-energy particles that appear to have been flung outward over the distance of a light year from the central star, and high-energy jets of particles blasting away from the neutron star in a direction perpendicular to the spiral. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous X-ray images have shown the outer parts of the jet and hinted at the ring structure. With Chandra's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with Chandra's Advanced CCD Imaging Spectrometer and High Energy Transmission

  8. Turbulent Concentration of mm-Size Particles in the Protoplanetary Nebula: Scale-Dependent Cascades

    NASA Technical Reports Server (NTRS)

    Cuzzi, J. N.; Hartlep, T.

    2015-01-01

    The initial accretion of primitive bodies (here, asteroids in particular) from freely-floating nebula particles remains problematic. Traditional growth-by-sticking models encounter a formidable "meter-size barrier" (or even a mm-to-cm-size barrier) in turbulent nebulae, making the preconditions for so-called "streaming instabilities" difficult to achieve even for so-called "lucky" particles. Even if growth by sticking could somehow breach the meter size barrier, turbulent nebulae present further obstacles through the 1-10km size range. On the other hand, nonturbulent nebulae form large asteroids too quickly to explain long spreads in formation times, or the dearth of melted asteroids. Theoretical understanding of nebula turbulence is itself in flux; recent models of MRI (magnetically-driven) turbulence favor low-or- no-turbulence environments, but purely hydrodynamic turbulence is making a comeback, with two recently discovered mechanisms generating robust turbulence which do not rely on magnetic fields at all. An important clue regarding planetesimal formation is an apparent 100km diameter peak in the pre-depletion, pre-erosion mass distribution of asteroids; scenarios leading directly from independent nebula particulates to large objects of this size, which avoid the problematic m-km size range, could be called "leapfrog" scenarios. The leapfrog scenario we have studied in detail involves formation of dense clumps of aerodynamically selected, typically mm-size particles in turbulence, which can under certain conditions shrink inexorably on 100-1000 orbit timescales and form 10-100km diameter sandpile planetesimals. There is evidence that at least the ordinary chondrite parent bodies were initially composed entirely of a homogeneous mix of such particles. Thus, while they are arcane, turbulent concentration models acting directly on chondrule size particles are worthy of deeper study. The typical sizes of planetesimals and the rate of their formation can be

  9. A SUCCESSFUL BROADBAND SURVEY FOR GIANT Ly{alpha} NEBULAE. II. SPECTROSCOPIC CONFIRMATION

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

    Prescott, Moire K. M.; Dey, Arjun; Jannuzi, Buell T., E-mail: mkpresco@physics.ucsb.edu

    2013-01-01

    Using a systematic broadband search technique, we have carried out a survey for large Ly{alpha} nebulae (or Ly{alpha} {sup b}lobs{sup )} at 2 {approx}< z {approx}< 3 within 8.5 deg{sup 2} of the NOAO Deep Wide-Field Survey Booetes field, corresponding to a total survey comoving volume of Almost-Equal-To 10{sup 8} h {sup -3} {sub 70} Mpc{sup 3}. Here, we present our spectroscopic observations of candidate giant Ly{alpha} nebulae. Of 26 candidates targeted, 5 were confirmed to have Ly{alpha} emission at 1.7 {approx}< z {approx}< 2.7, 4 of which were new discoveries. The confirmed Ly{alpha} nebulae span a range of Ly{alpha}more » equivalent widths, colors, sizes, and line ratios, and most show spatially extended continuum emission. The remaining candidates did not reveal any strong emission lines, but instead exhibit featureless, diffuse, blue continuum spectra. Their nature remains mysterious, but we speculate that some of these might be Ly{alpha} nebulae lying within the redshift desert (i.e., 1.2 {approx}< z {approx}< 1.6). Our spectroscopic follow-up confirms the power of using deep broadband imaging to search for the bright end of the Ly{alpha} nebula population across enormous comoving volumes.« less

  10. Hubble Captures Spectacular "Landscape" in the Carina Nebula

    NASA Image and Video Library

    2017-12-08

    NASA image release April 22, 2010 NASA's Hubble Space Telescope captured this billowing cloud of cold interstellar gas and dust rising from a tempestuous stellar nursery located in the Carina Nebula, 7,500 light-years away in the southern constellation Carina. This pillar of dust and gas serves as an incubator for new stars and is teeming with new star-forming activity. Hot, young stars erode and sculpt the clouds into this fantasy landscape by sending out thick stellar winds and scorching ultraviolet radiation. The low-density regions of the nebula are shredded while the denser parts resist erosion and remain as thick pillars. In the dark, cold interiors of these columns new stars continue to form. In the process of star formation, a disk around the proto-star slowly accretes onto the star's surface. Part of the material is ejected along jets perpendicular to the accretion disk. The jets have speeds of several hundreds of miles per second. As these jets plow into the surround nebula, they create small, glowing patches of nebulosity, called Herbig-Haro (HH) objects. Long streamers of gas can be seen shooting in opposite directions off the pedestal on the upper right-hand side of the image. Another pair of jets is visible in a peak near the top-center of the image. These jets (known as HH 901 and HH 902, respectively) are common signatures of the births of new stars. This image celebrates the 20th anniversary of Hubble's launch and deployment into an orbit around Earth. Hubble's Wide Field Camera 3 observed the pillar on Feb. 1-2, 2010. The colors in this composite image correspond to the glow of oxygen (blue), hydrogen and nitrogen (green), and sulfur (red). Object Names: HH 901, HH 902 Image Type: Astronomical Credit: NASA, ESA, and M. Livio and the Hubble 20th Anniversary Team (STScI) To read learn more about this image go to: www.nasa.gov/mission_pages/hubble/science/hubble20th-img.... NASA Goddard Space Flight Center is home to the nation's largest organization

  11. Numerical two-dimensional calculations of the formation of the solar nebula

    NASA Technical Reports Server (NTRS)

    Bodenheimer, Peter H.

    1991-01-01

    Numerical two dimensional calculations of the formation of the solar nebula are presented. The following subject areas are covered: (1) observational constraints of the properties of the initial solar nebula; (2) the physical problem; (3) review if two dimensional calculations of the formation phase; (4) recent models with hydrodynamics and radiative transport; and (5) further evolution of the system.

  12. Electron-impact dissociation of molecular hydrogen into neutral fragments

    NASA Astrophysics Data System (ADS)

    Scarlett, Liam H.; Tapley, Jonathan K.; Fursa, Dmitry V.; Zammit, Mark C.; Savage, Jeremy S.; Bray, Igor

    2018-02-01

    We present convergent close-coupling calculations of electron-impact dissociation of the ground state of molecular hydrogen into neutral fragments over the range of impact energies from 6 to 300 eV. The calculations account for dissociative excitation, excitation radiative decay dissociation, and predissociation through all bound electronic triplet states, and singlet states up to the D' 1 Π u state. An estimate is given for the contribution from the remaining bound electronic singlet states. Our results are in agreement with the recommended data of Yoon et al. [J. Phys. Chem. Ref. Data 37, 913 (2008)] in the low (6-12 eV) and high (60-70 eV) energy regions, but somewhat lower at the intermediate energies.

  13. SMA Spectral Line Survey of the Proto-Planetary Nebula CRL 618

    NASA Astrophysics Data System (ADS)

    Patel, Nimesh A.; Gottlieb, Carl; Young, Ken; Kaminski, Tomasz Tomek; McCarthy, Michael; Menten, Karl; Primiani, Rurik; Lee, Chin-Fei; Gupta, Harshal

    2018-01-01

    Carbon-rich Asymptotic Giant Branch (AGB) stars are major sources of gas and dust in the interstellar medium. AGB stars remain in their evolutionary stage for 1 to 10 Myrs, during which they have very high mass loss rates that increase at the end. During the brief (~1000 yr) period in the evolution from the AGB to the Planetary Nebula (PN) stage there are dramatic changes in the morphology from nearly spherical symmetry, to bipolar, quadrupolar and more complex structures, with the development of both slow and fast (100 km/s) outflows. The molecular composition of these objects' cirumstellar envelopes also evolves from being similar to that of parent AGB star (mainly diatomic and small polyatomic species), to more complex molecules (including ions).We have started an observational study of a sample of Proto-Planetary nebulae (PPN) with the Submillimeter Array to carry out spectral-line surveys of ~60 GHz frequency coverage in the 345 GHz band (similar to our published IRC+10216 line survey of 2011). Here we present preliminary results from the line survey of the carbon-rich PPN CRL 618, covering a frequency range of 281.9 to 359.4 GHz. Observations were carried out in January 2016 and September 2017, with the SMA in compact (3" angular resolution) and very extended (0.5") configurations, respectively.More than 1100 lines were detected in CRL 618. The majority of them can be attributed to HC3N and c-C3H2, and their isotopologues. About 350 lines are as yet unassigned. The continuum emission is unresolved even at 0.5" resolution. Several hydrogen recombination lines are detected from the central HII region. Lines of CO, HCO+, CS show the fast outflow wings, while the majority of molecular emission arises from a compact region of about 1" diameter. We present LTEmodeling and rotation temperature diagram analysis of HC3N, c-C3H2, CH3CN, and their isotopologues. We plan to observe another PPN, CRL 2688 with the SMA in 2018. Together, these imaging line surveys will

  14. North America Nebula in Different Lights

    NASA Image and Video Library

    2011-02-10

    This view of the North America nebula combines both visible and infrared light observations, taken by the Digitized Sky Survey and NASA Spitzer Space Telescope. Clusters of young stars about one million years old can be found throughout the image.

  15. Contemporary concepts of dissociation.

    PubMed

    Avdibegović, Esmina

    2012-10-01

    The concept of dissociation was developed in the late 19th century by Pierre Janet for conditions of "double consciousness" in hypnosis, hysteria, spirit possession and mediumship. He defined dissociation as a deficit in the capacity of integration of two or more different "systems of ideas and functions that constitute personality", and suggested that it can be related to a genetic component, to severe illness and fatigue, and particularly to experiencing adverse, potentially traumatizing events. By the late 20th century, various and often contradictory concepts of dissociation were suggested, which were either insufficient or exceedingly including when compared to the original idea. Currently, dissociation is used to describe a wide range of normal and abnormal phenomena as a process in which behaviour, thoughts and emotions can become separated one from another. A complete presentation of mechanisms involved in dissociation is still unknown. Scientific research on basic processes of dissociation is derived mainly from studies of hypnosis and post-traumatic stress disorder. Given the controversies in modern concepts of dissociation, some researchers and theorists suggest return to the original understanding of dissociation as a basic premise for the further development of the concept of dissociation.

  16. Properties and Spatial Distribution of Dust Emission in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Sonneborn, G.; Temim, T.; Dwek, E.; Arendt, R.; Gehrz, R.; Slane, P.

    2011-01-01

    The nature and quantity of dust produced in supernovae (SNe) is still poorly understood. Recent IR observations of freshly-formed dust in supernova remnants (SNRs) have yielded significantly lower dust masses than predicted by theoretical models and observations high-redshift galaxies. The Crab Nebula's pulsar wind is thought to be sweeping up freshly-formed SN dust along with the SN ejecta. The evidence for this dust was found in the form of an IR bump in the integrated spectrum of the Crab and in extinction against the synchrotron nebula that revealed the presence of dust in the filament cores. We present the first spatially-resolved emission spectra of dust in the Crab Nebula acquired with the Spitzer Space Telescope. The IR spectra are dominated by synchrotron emission and show forbidden line emission from both sides of the expanding nebula, including emission from [S III], [Si II], [Ne II], [Ne III], [Ne V], [Ar III], [Ar V], [Fe II], and [Ni II]. We extrapolated a synchrotron spectral data cube from the Spitzer 3.6 and 4.5 micron images, and subtracted this contribution from our 15-40 micron spectral data to produce a map of the residual continuum emission from dust. The emission appears to be concentrated along the ejecta filaments and is well described by astronomical silicates at an average temperature of 65 K. The estimated mass of dust in the Crab Nebula is 0.008 solar masses.

  17. The 'semitorrid' gas observed in the direction of Gamma-2 Velorum and the Gum nebula

    NASA Technical Reports Server (NTRS)

    Bruhweiler, F. C.; Kondo, J.; Mccluskey, G. E., Jr.

    1979-01-01

    On the basis of recent IUE observations in the far-ultraviolet, the authors report the detection of a 'semitorrid' region of the interstellar medium in the direction of Gamma-2 Velorum and the Gum nebula. The characteristic temperature of this gas is in the 40,000 K range, between the warm (around 1000 K) and hot (roughly 100,000-1,000,000 K) regions reported by various investigators. This temperature is compatible with the theoretical temperature ascribed to the 'fossil Stromgren sphere' by Brandt et al. and Alexander et al.

  18. Rapid gamma-ray flux variability during the 2013 March Crab Nebula flare

    DOE PAGES

    Mayer, Michael; Buehler, Rolf; Hays, Elizabeth; ...

    2013-09-11

    Here, we report on a bright flare in the Crab Nebula detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The period of significantly increased luminosity occurred in 2013 March and lasted for approximately two weeks. During this period, we observed flux variability on timescales of approximately 5 hr. The combined photon flux above 100 MeV from the pulsar and its nebula reached a peak value of (12.5 ± 0.8) • 10 –6 cm –2 s –1 on 2013 March 6. This value exceeds the average flux by almost a factor of six and impliesmore » a ~20 times higher flux for the synchrotron component of the nebula alone. This is the second brightest flare observed from this source. Spectral and temporal analysis of the LAT data collected during the outburst reveal a rapidly varying synchrotron component of the Crab Nebula while the pulsar emission remains constant in time.« less

  19. NASA Explores the Carina Nebula by Touch

    NASA Image and Video Library

    2017-12-08

    Release Date March 30, 2010 The raised arcs, lines, dots, and other markings in this 17-by-11-inch Hubble Space Telescope image of the Carina Nebula highlight important features in the giant gas cloud, allowing visually impaired people to feel what they cannot see and form a picture of the nebula in their minds. To read more abou this image go to: www.nasa.gov/mission_pages/hubble/science/carina-touch.html Credit: NASA, ESA, and M. Mutchler (STScI/AURA) and N. Grice (You Can Do Astronomy LLC) NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

  20. Analysis of Co-spatial UV-Optical STIS Spectra of Planetary Nebulae From HST Cycle 19 GO 12600

    NASA Astrophysics Data System (ADS)

    Miller, Timothy R.; Henry, Richard B. C.; Dufour, Reginald J.; Kwitter, Karen B.; Shaw, Richard A.; Balick, Bruce; Corradi, Romano

    2015-01-01

    We present an analysis of five spatially resolved planetary nebulae (PNe), NGC 5315, NGC 5882, NGC 7662, IC 2165, and IC 3568, from observations in the Cycle 19 program GO 12600 using HST STIS. Details of the observations and data are presented in the poster by Dufour et al. in this session. These five observations cover the wavelength range 1150-10,270 Å with 0.2 and 0.5 arcsec wide slits, and are co-spatial to 0.1 arcsec along a 25 arcsec length across each nebula. This unprecedented resolution in both wavelength and spatial coverage enabled detailed studies of physical conditions and abundances from UV line ion emissions (compared to optical lines). We first analyzed the low- and moderate-resolution UV emission lines of carbon using the resolved lines of C III] 1906.68 and 1908.73, which yielded a direct measurement of the density within the volume occupied by doubly-ionized carbon and other similar co-spatial ions. Next, each PN spectrum was divided into spatial sub-regions in order to assess inferred density variations among the sub-regions along the entire slit. Variations in electron temperature and chemical abundances were also probed. Lastly, these nebulae were modeled in detail with the photoionization code CLOUDY. This modeling tested different density profiles in order to reproduce the observed density variations and temperature fluctuations, and constrain central star parameters. We gratefully acknowledge generous support from NASA through grants related to the Cycle 19 program GO 12600, as well as from the University of Oklahoma.

  1. Hubble Space Telescope Image: Planetary Nebula IC 4406

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This Hubble Space Telescope image reveals a rainbow of colors in this dying star, called IC 446. Like many other so-called planetary nebulae, IC 4406 exhibits a high degree of symmetry. The nebula's left and right halves are nearly mirror images of the other. If we could fly around IC 446 in a spaceship, we would see that the gas and dust form a vast donut of material streaming outward from the dying star. We do not see the donut shape in this photograph because we are viewing IC 4406 from the Earth-orbiting HST. From this vantage point, we are seeing the side of the donut. This side view allows us to see the intricate tendrils of material that have been compared to the eye's retina. In fact, IC 4406 is dubbed the 'Retina Nebula.' The donut of material confines the intense radiation coming from the remnant of the dying star. Gas on the inside of the donut is ionized by light from the central star and glows. Light from oxygen atoms is rendered blue in this image; hydrogen is shown as green, and nitrogen as red. The range of color in the final image shows the differences in concentration of these three gases in the nebula. This image is a composite of data taken by HST's Wide Field Planetary Camera 2 in June 2001 and in January 2002 by Bob O'Dell (Vanderbilt University) and collaborators, and in January by the Hubble Heritage Team (STScI). Filters used to create this color image show oxygen, hydrogen, and nitrogen gas glowing in this object.

  2. Personal Photo Enhancement Using Internet Photo Collections.

    PubMed

    Zhang, Chenxi; Gao, Jizhou; Wang, Oliver; Georgel, Pierre; Yang, Ruigang; Davis, James; Frahm, Jan-Michael; Pollefeys, Marc

    2013-04-26

    Given the growth of Internet photo collections we now have a visual index of all major cities and tourist sites in the world. However, it is still a difficult task to capture that perfect shot with your own camera when visiting these places, especially when your camera itself has limitations, such as a limited field of view. In this paper, we propose a framework to overcome the imperfections of personal photos of tourist sites using the rich information provided by large scale Internet photo collections. Our method deploys state-of-the-art techniques for constructing initial 3D models from photo collections. The same techniques are then used to register personal photos to these models, allowing us to augment personal 2D images with 3D information. This strong available scene prior allows us to address a number of traditionally challenging image enhancement techniques, and achieve high quality results using simple and robust algorithms. Specifically, we demonstrate automatic foreground segmentation, mono-to-stereo conversion, the field of view expansion, photometric enhancement, and additionally automatic annotation with geo-location and tags. Our method clearly demonstrates some possible benefits of employing the rich information contained in on-line photo databases to efficiently enhance and augment one’s own personal photos.

  3. The co-occurrence of PTSD and dissociation: differentiating severe PTSD from dissociative-PTSD.

    PubMed

    Armour, Cherie; Karstoft, Karen-Inge; Richardson, J Don

    2014-08-01

    A dissociative-posttraumatic stress disorder (PTSD) subtype has been included in the DSM-5. However, it is not yet clear whether certain socio-demographic characteristics or psychological/clinical constructs such as comorbid psychopathology differentiate between severe PTSD and dissociative-PTSD. The current study investigated the existence of a dissociative-PTSD subtype and explored whether a number of trauma and clinical covariates could differentiate between severe PTSD alone and dissociative-PTSD. The current study utilized a sample of 432 treatment seeking Canadian military veterans. Participants were assessed with the Clinician Administered PTSD Scale (CAPS) and self-report measures of traumatic life events, depression, and anxiety. CAPS severity scores were created reflecting the sum of the frequency and intensity items from each of the 17 PTSD and 3 dissociation items. The CAPS severity scores were used as indicators in a latent profile analysis (LPA) to investigate the existence of a dissociative-PTSD subtype. Subsequently, several covariates were added to the model to explore differences between severe PTSD alone and dissociative-PTSD. The LPA identified five classes: one of which constituted a severe PTSD group (30.5 %), and one of which constituted a dissociative-PTSD group (13.7 %). None of the included, demographic, trauma, or clinical covariates were significantly predictive of membership in the dissociative-PTSD group compared to the severe PTSD group. In conclusion, a significant proportion of individuals report high levels of dissociation alongside their PTSD, which constitutes a dissociative-PTSD subtype. Further investigation is needed to identify which factors may increase or decrease the likelihood of membership in a dissociative-PTSD subtype group compared to a severe PTSD only group.

  4. Chandra X-Ray Observatory Image of Crab Nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    After barely 2 months in space, the Chandra X-Ray Observatory (CXO) took this sturning image of the Crab Nebula, the spectacular remains of a stellar explosion, revealing something never seen before, a brilliant ring around the nebula's heart. The image shows the central pulsar surrounded by tilted rings of high-energy particles that appear to have been flung outward over a distance of more than a light-year from the pulsar. Perpendicular to the rings, jet-like structures produced by high-energy particles blast away from the pulsar. Hubble Space Telescope images have shown moving knots and wisps around the neutron star, and previous x-ray images have shown the outer parts of the jet and hinted at the ring structure. With CXO's exceptional resolution, the jet can be traced all the way in to the neutron star, and the ring pattern clearly appears. The image was made with CXO's Advanced Charge-Coupled Device (CCD) Imaging Spectrometer (ACIS) and High Energy Transmission Grating. The Crab Nebula, easily the most intensively studied object beyond our solar system, has been observed using virtually every astronomical instrument that could see that part of the sky

  5. High Temperature Planetary Nebulae in the Magellanic Clouds

    NASA Astrophysics Data System (ADS)

    Maran, Stephen P.

    Following up on our recent discovery that a very hot planetary in the Small Magellanic Cloud has an extraordinary underabundance of carbon, we propose to observe two similar hot planetaries in the Clouds with IUE as part of an optical/UV investigation. The objectives are (1) to test the suggestion that high nebular electron temperatures can result from a strong deficiency of carbon that deprives the nebula of an important cooling channel; and (2) to determine accurate chemical abundances to constrain limits on the efficiency of "hot bottom burning" in massive progenitors of planetary nebulae. The targets are SMC 25 (Te = 34,000 K) and LMC 88 (= 25,500 K). These UV observations of targets not previously observed with IUE will be combined, for analysis, with visible wavelength spectra of both targets from the Anglo-Australian Telescope and the 2-3-m Siding Spring reflector. The objects will also be compared in the analysis stage with previous IUE observations (and consequent modeling) of type I planetaries in the Clouds. Model nebulae will be calculated, and physical parameters of the central stars will be inferred.

  6. A new Wolf-Rayet star and its circumstellar nebula in Aquila

    NASA Astrophysics Data System (ADS)

    Gvaramadze, V. V.; Kniazev, A. Y.; Hamann, W.-R.; Berdnikov, L. N.; Fabrika, S.; Valeev, A. F.

    2010-04-01

    We report the discovery of a new Wolf-Rayet star in Aquila via detection of its circumstellar nebula (reminiscent of ring nebulae associated with late WN stars) using the Spitzer Space Telescope archival data. Our spectroscopic follow-up of the central point source associated with the nebula showed that it is a WN7h star (we named it WR121b). We analysed the spectrum of WR121b by using the Potsdam Wolf-Rayet model atmospheres, obtaining a stellar temperature of ~=50kK. The stellar wind composition is dominated by helium with ~20 per cent of hydrogen. The stellar spectrum is highly reddened [E(B - V) = 2.85mag]. Adopting an absolute magnitude of Mv = -5.7, the star has a luminosity of logL/Lsolar = 5.75 and a mass-loss rate of 10-4.7Msolaryr-1, and resides at a distance of 6.3kpc. We searched for a possible parent cluster of WR121b and found that this star is located at ~=1° from the young star cluster embedded in the giant HII region W43 (containing a WN7+a/OB? star - WR121a). We also discovered a bow shock around the O9.5III star ALS9956, located at from the cluster. We discuss the possibility that WR121b and ALS9956 are runaway stars ejected from the cluster in W43. Based on observations collected at the German-Spanish Astronomical Center, Calar Alto, jointly operated by the Max-Planck-Institut für Astronomie Heidelberg and the Instituto de Astrofísica de Andalucía (CSIC). E-mail: vgvaram@mx.iki.rssi.ru (VVG); akniazev@saao.ac.za (AYK); wrh@astro.physik.uni-potsdam.de (WRH); berdnik@sai.msu.ru (LNB); fabrika@sao.ru (SF); azamat@sao.ru (AFV)

  7. 2-45 Micron Infrared Spectroscopy of Carbon-Rich Proto-Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Hrivnak, Bruce J.; Volk, Kevin; Kwok, Sun

    2000-01-01

    Infrared Space Observatory (ISO) 2-45 micron observations of seven proto-planetary nebulae (PPNs) and two other carbon-rich objects are presented. The unidentified emission features at 21 and 30 microns are detected in six sources, including four new detections of the 30 micron feature. This previously unresolved 30 micron feature is now resolved and found to consist of a broad feature peaking at 27.2 microns (the '30 micron' feature) and a narrower feature at 25.5 microns (the '26 micron' feature). This new 26 micron feature is detected in eight sources and is particularly strong in IRAS Z02229 + 6208 and 16594-4656. The unidentified infrared (UIR) emission features at 3.3, 6.2, 7.7, and 11.3 microns which are commonly observed in planetary nebulae and H II regions, are also seen in these PPNs. However, their strengths relative to the continuum plateaus at 8 and 12 microns are weaker than in planetary nebulae. The 6.9 micron feature, seen almost exclusively in PPNs, is strong. New millimeter CO and HCN observations were made; they support the carbon-rich nature of the objects and yield the expansion velocities of the gaseous envelopes. The spectral energy distributions of these PPNs were fitted with a radiative-transfer model, taking into account the emission features at 21, 26, and 30 microns. A significant fraction of the total energy output is emitted in these features: as high as 20% in the 30 micron feature and 8% in the 21 micron feature. The fact that so much energy is carried in these features suggests that the material responsible for these features must be made of abundant elements and most likely involves carbon. SiS, appears to be ruled out as the emitter of the 21 micron feature due to the absence of a predicted companion feature.

  8. Planetary nebulae populations as tracers of the stellar kinematics and light in the outer halos of galaxies and the intracluster regions in the nearby clusters

    NASA Astrophysics Data System (ADS)

    Arnaboldi, Magda

    2015-08-01

    Planetary nebulae have been used sucessfully to trace the kinematics of stars and the spatial distribution of the parent stellar populations in regions where the continuum of the integrated light is only 1% of the night sky. The observed wavelength of the PN strong emission in the [OIII] line at 5007 A measures the line-of-sight velocity of that single star and can be used to derive the two-dimensional velocity fields in these extreme outer regions of galaxies and their angular momentum content out to 10 effective radii. The specific frequency or the PN luminosity number and the morphology of the PN luminosity function are probes of the properties of the parent stellar population, like the star formation history and metallicity. I will present the latest results from the survey of PN population in external galaxies and in the Virgo cluster, and the implications on the coexistence of galaxy halos and intracluster light, and the constraints of their stellar motions and physical parameters.

  9. Observations Of Planetary Nebula NGC 3242 Using STIS From HST19 GO 12600

    NASA Astrophysics Data System (ADS)

    Miller, Timothy R.; Dufour, Reginald J.; Henry, Richard B. C.; Kwitter, Karen B.; Shaw, Richard A.; Balick, Bruce; Corradi, Romano

    2014-06-01

    During HST Cycle 19, we obtained long-slit spectra using STIS of the planetary nebula NGC 3242 with higher spatial resolution than previously published. The full wavelength range is around 1100-10200Å, covering many nebular lines for determining numerous ionic abundances and electron densities and temperatures. In this work, we first analyze the low- and moderate-resolution UV emission lines of carbon, nitrogen and oxygen. In particular, the resolved lines of C_III] 1907 and C_III] 1909 have yielded a direct measurement of one of the dominant ionic species for carbon and a determination of the density occupied by doubly-ionized carbon and other similar ions. Next, the spatial emission profile of these lines reveals variations in the inferred density along the line of sight from about 2800-11500 cm-3, compared with a value ~3800 cm-3, when averaged over the entire slit. Similarly, the electron temperature is around 12000K for the entire slit and ranges from about 11400-14000K when the slit is divided into smaller sub-regions. Lastly, these sub-regions of the nebula have been modeled in detail with the photoionization code CLOUDY. This modeling will assess the density profile that produces the observed density variation, reproduce the temperature fluctuations, and constrain the central star temperature. We acknowledge the gracious support from HST and the University of Oklahoma.

  10. A symmetric bipolar nebula around MWC 922.

    PubMed

    Tuthill, P G; Lloyd, J P

    2007-04-13

    We report regular and symmetric structure around dust-enshrouded Be star MWC 922 obtained with infrared imaging. Biconical lobes that appear nearly square in aspect, forming this "Red Square" nebula, are crossed by a series of rungs that terminate in bright knots or "vortices," and an equatorial dark band crossing the core delimits twin hyperbolic arcs. The intricate yet cleanly constructed forms that comprise the skeleton of the object argue for minimal perturbation from global turbulent or chaotic effects. We also report the presence of a linear comb structure, which may arise from optically projected shadows of a periodic feature in the inner regions, such as corrugations in the rim of a circumstellar disk. The sequence of nested polar rings draws comparison with the triple-ring system seen around the only naked-eye supernova in recent history: SN1987A.

  11. The surface brightness of reflection nebulae. Ph.D. Thesis, Dec. 1972

    NASA Technical Reports Server (NTRS)

    Rush, W. F.

    1974-01-01

    Hubble's equation relating the maximum apparent angular extent of a reflection nebula to the apparent magnitude of the illuminating star has been reconsidered under a set of less restrictive assumptions. A computational technique is developed which permits the use of fits to observed m, log a values to determine the albedo of the particles composing reflection nebulae, providing only that one assumes a particular phase function. Despite the fact that all orders of scattering, anisotropic phase functions, and illumination by the general stellar field are considered, the albedo which is determined for reflection nebulae by this method appears larger than that for interstellar particles in general. The possibility that the higher surface brightness might be due to a continuous fluorescence mechanism is considered both theoretically and observationally.

  12. K*-charmonium dissociation cross sections and charmonium dissociation rates in hadronic matter

    NASA Astrophysics Data System (ADS)

    Liu, Feng-Rong; Ji, Shi-Tao; Xu, Xiao-Ming

    2016-08-01

    K*-charmonium dissociation reactions in hadronic matter are studied in the Born approximation, in the quark-interchange mechanism, and with a temperature-dependent quark potential. We obtain the temperature dependence of the unpolarized cross sections for the reactions K^* J/ψ to bar DD_s^ + ,bar D^* D_s^ + ,bar DD_s^{* + } , and bar D^* D_s^{* + } ; K^* χ _c to bar DD_s^ + ,bar D^* D_s^ + ,bar DD_s^{* + } , and bar D^* D_s^{* + } . We use the cross sections for charmonium dissociation in collisions with pions, ρ mesons, kaons, vector kaons, and η mesons to calculate the dissociation rates of charmonium with five types of mesons. Because of the temperature dependence of the meson masses, dissociation cross sections, and meson distribution functions, the charmonium dissociation rates generally increase with increasing temperature and decrease with increasing charmonium momentum from 2.2 GeV/c. We find that the first derivative of the dissociation rate with respect to the charmonium momentum is zero when the charmonium is at rest. While the η + ψ' and the η + χ c dissociation reactions can be neglected, the J/ ψ, ψ', and χ c dissociations are caused by collisions with pions, ρ mesons, kaons, vector kaons, and η mesons.

  13. Onboard Photo:Astro-1 Ultraviolet Telescope in Cargo Bay

    NASA Technical Reports Server (NTRS)

    1990-01-01

    Onboard the Space Shuttle Orbiter Columbia (STS-35), the various components of the Astro-1 payload are seen backdropped against a blue and white Earth. Parts of the Hopkins Ultraviolet Telescope (HUT), the Ultraviolet Imaging Telescope (UIT), and the Wisconsin Ultraviolet Photo-Polarimetry Experiment (WUPPE) are visible on the Spacelab pallet. The Broad-Band X-Ray Telescope (BBXRT) is behind the pallet and is not visible in this scene. The smaller cylinder in the foreground is the igloo. The igloo was a pressurized container housing the Command Data Management System, that interfaced with the in-cabin controllers to control the Instrument Pointing System (IPS) and the telescopes. The Astro Observatory was designed to explore the universe by observing and measuring the ultraviolet radiation from celestial objects. Astronomical targets of observation selected for Astro missions included planets, stars, star clusters, galaxies, clusters of galaxies, quasars, remnants of exploded stars (supernovae), clouds of gas and dust (nebulae), and the interstellar medium. Managed by the Marshall Space Flight Center, the Astro-1 was launched aboard the Space Shuttle Orbiter Columbia (STS-35) on December 2, 1990.

  14. Photoevaporation of Clumps in Photodissociation Regions

    NASA Technical Reports Server (NTRS)

    Gorti, Uma; Hollenbach, David; DeVincenzi, D. (Technical Monitor)

    2002-01-01

    We present the results of an investigation of the effects of Far Ultraviolet (FUV) radiation (6.0eV < hv < 13.6eV) from hot early type OB stars on clumps in star-forming molecular clouds. Clumps in FUV-illuminated regions (or photodissociation regions or PDRs) undergo external heating and photodissociation as they are exposed to the FUV field, resulting in a loss of cold, molecular lump mass as it is converted to warm atomic gas. The heating, if rapid, creates strong photoevaporative mass flows off the clump surfaces, and drives shocks into the clumps, compressing them to high densities. The clumps lose mass on relatively short timescales. The evolution of an individual clump is found to be sensitive to three dimensionless parameters: Nc0, the ratio of the initial column density of the clump to the column N(0) approx. 10(exp 21) cm(exp -2) of a warm FUV-heated surface region; upsilon, the ratio of the sound speed in the heated surface to that in the cold clump material: and t(FUV)t(c), the ratio of the "turn-on time" t(FUV) of the heating flux on a clump to its initial sound crossing-time t(c). The evolution also depends on whether a confining interclump medium exists, or whether the interclump region has negligible pressure, as is the case for turbulence-generated clumps. In this paper, we use spherical 1-D numerical hydrodynamic models as well as approximate analytical models to study the dependence of clump photoevaporation on the physical parameters of the clump, and to derive the dynamical evolution, mass loss rates and photoevaporative timescales of a clump for a variety of astrophysical situations. Turbulent clumps evolve so that their column densities are equal to a critical value determined by the local FUV field, and typically have short photo evaporation timescales, approx. 10(exp 4-5) years for a 1 M(solar mass) clump in a typical star-forming region (Nc0 = 10, upsilon = 10). Clumps with insufficient magnetic pressure support, and in strong FUV fields

  15. Dissociation in Psychiatric Disorders: A Meta-Analysis of Studies Using the Dissociative Experiences Scale.

    PubMed

    Lyssenko, Lisa; Schmahl, Christian; Bockhacker, Laura; Vonderlin, Ruben; Bohus, Martin; Kleindienst, Nikolaus

    2018-01-01

    Dissociation is a complex, ubiquitous construct in psychopathology. Symptoms of dissociation are present in a variety of mental disorders and have been connected to higher burden of illness and poorer treatment response, and not only in disorders with high levels of dissociation. This meta-analysis offers a systematic and evidence-based study of the prevalence and distribution of dissociation, as assessed by the Dissociative Experiences Scale, within different categories of mental disorders, and it updates an earlier meta-analysis. More than 1,900 original publications were screened, and 216 were included in the meta-analysis, comprising 15,219 individuals in 19 diagnostic categories. The largest mean dissociation scores were found in dissociative disorders (mean scores >35), followed by posttraumatic stress disorder, borderline personality disorder, and conversion disorder (mean scores >25). Somatic symptom disorder, substance-related and addictive disorders, feeding and eating disorders, schizophrenia, anxiety disorder, OCD, and most affective disorders also showed mean dissociation scores >15. Bipolar disorders yielded the lowest dissociation scores (mean score, 14.8). The findings underline the importance of careful psychopathological assessment of dissociative symptoms in the entire range of mental disorders.

  16. An Application-Based Performance Evaluation of NASAs Nebula Cloud Computing Platform

    NASA Technical Reports Server (NTRS)

    Saini, Subhash; Heistand, Steve; Jin, Haoqiang; Chang, Johnny; Hood, Robert T.; Mehrotra, Piyush; Biswas, Rupak

    2012-01-01

    The high performance computing (HPC) community has shown tremendous interest in exploring cloud computing as it promises high potential. In this paper, we examine the feasibility, performance, and scalability of production quality scientific and engineering applications of interest to NASA on NASA's cloud computing platform, called Nebula, hosted at Ames Research Center. This work represents the comprehensive evaluation of Nebula using NUTTCP, HPCC, NPB, I/O, and MPI function benchmarks as well as four applications representative of the NASA HPC workload. Specifically, we compare Nebula performance on some of these benchmarks and applications to that of NASA s Pleiades supercomputer, a traditional HPC system. We also investigate the impact of virtIO and jumbo frames on interconnect performance. Overall results indicate that on Nebula (i) virtIO and jumbo frames improve network bandwidth by a factor of 5x, (ii) there is a significant virtualization layer overhead of about 10% to 25%, (iii) write performance is lower by a factor of 25x, (iv) latency for short MPI messages is very high, and (v) overall performance is 15% to 48% lower than that on Pleiades for NASA HPC applications. We also comment on the usability of the cloud platform.

  17. Imaging the Crab nebula when it is flaring in gamma-rays

    NASA Astrophysics Data System (ADS)

    De Luca, Andrea

    2012-10-01

    One of the most intriguing results of the gamma-ray instruments currently in orbit has been the detection of powerful flares from the Crab Nebula in September 2010. In April 2011 a similar flare, lasting several days, made the nebula the brightest source in the gamma-ray sky. A critical reassessment of long term behavior of the Crab flux clearly showed that both Agile and Fermi had already detected similar events in October 2007 and February 2009, pointing to a recurrence time of once per year. A HST observing strategy must be set up to react promptly to any possible new brightening of the Crab in gamma rays. In September 2010 we requested a DD observation which was promptly accepted and carried out. However, the lack of a suitable reference image hampered our efforts to pinpoint the sites of possible variability inside the nebula. Thus, while now we ask for a triggered TOO observation of the Crab Nebula with ACS/WFC in case a gamma-ray flare is announced by the Agile and/or Fermi missions, we are also organizing a regular {monthly} monitoring of the source both in X-ray and optical through a joint Chandra-HST proposal.

  18. Dust to planetesimals - Settling and coagulation in the solar nebula

    NASA Technical Reports Server (NTRS)

    Weidenschilling, S. J.

    1980-01-01

    The behavior of solid particles in a low-mass solar nebula during settling to the central plane and the formation of planetesimals is discussed. The gravitational instability in a dust layer and collisional accretion are examined as possible mechanisms of planetesimal formation. The shear between the gas and a dust layer is considered along with the differences in the planetesimal formation mechanisms between the inner and outer nebula. A numerical model for computing simultaneous coagulation and settling is described.

  19. MCNeil's Nebula in Orion: The Outburst History

    NASA Astrophysics Data System (ADS)

    Briceño, C.; Vivas, A. K.; Hernández, J.; Calvet, N.; Hartmann, L.; Megeath, T.; Berlind, P.; Calkins, M.; Hoyer, S.

    2004-05-01

    We present a sequence of I-band images obtained at the Venezuela 1 m Schmidt telescope during the outburst of the nebula recently discovered by J. W. McNeil in the Orion L1630 molecular cloud. We derive photometry spanning the preoutburst state and the brightening itself, which is a unique record including 14 epochs and spanning a timescale of ~5 years. We constrain the beginning of the outburst at some time between 2003 October 28 and November 15. The light curve of the object at the vertex of the nebula, the likely exciting source of the outburst, reveals that it has brightened ~5 mag in about 4 months. The timescale for the nebula to develop is consistent with the light-travel time, indicating that we are observing light from the central source scattered by the ambient cloud into the line of sight. We also show recent FLWO optical spectroscopy of the exciting source and of the nearby HH 22. The spectrum of the source is highly reddened; in contrast, the spectrum of HH 22 shows a shock spectrum superposed on a continuum, most likely the result of reflected light from the exciting source reaching the HH object through a much less reddened path. The blue portion of this spectrum is consistent with an early B spectral type, similar to the early outburst spectrum of the FU Orionis variable star V1057 Cygni; we estimate a luminosity of L~219 Lsolar. The eruptive behavior of McNeil's Nebula, its spectroscopic characteristics and luminosity, suggest that we may be witnessing an FU Ori event on its way to maximum. By further monitoring this object, we will be able decide whether or not it qualifies as a member of this rare class of objects. Based on observations obtained at the Llano del Hato National Astronomical Observatory of Venezuela, operated by CIDA for the Ministerio de Ciencia y Tecnología, and at the Fred Lawrence Whipple Observatory (FLWO) of the Smithsonian Institution.

  20. Discovery of X-ray emission associated with the Gum Nebula

    NASA Technical Reports Server (NTRS)

    Leahy, D. A.; Nousek, J.; Garmire, G.

    1992-01-01

    The Gum Nebula was observed by the A-2 LED proportional counters on the HEAO-1 satellite as part of the all-sky survey. The first detection of X-ray emission associated with the Gum Nebula is reported. Soft X-ray spectra were constructed from the A-2 LED PHA data. Single temperature Raymond-Smith models were fitted to the observed spectra to yield temperature, column density and emission measure. The temperature is 6 x 10 exp 5 K, the column density 4 x 10 exp 20/sq cm, and the emission measure 5 cm exp-6 pc. The X-ray and optical properties of the Gum Nebula are consistent with a supernova remnant in the shell stage of evolution, which was the product of an energetic (3 x 10 exp 51 ergs) supernova explosion which occurred about 2 x 10 exp 6 yr ago.

  1. The fine nebula dust component: A key to chondrule formation by lightning

    NASA Technical Reports Server (NTRS)

    Wasson, J. T.; Rasmussen, K. L.

    1994-01-01

    Our assessment indicates that chondrule formation by lightning is indeed possible in the solar nebula. Previously the overriding objection to the lightning process of chondrule formation has been that low nebula pressures prevented the buildup of large potential differences. The breakdown potential is controlled by the mean free live distance of an electron. We calculate the mean free live distance in pure H2 gas at 2 AU to be approximately 500 m. A fine dust load constituting 4 wt% of the dust in the dusty midplane region leads to a reduced mean free live distance of only 7 m. Very conservatively we estimate the breakdown potential to be at least 10, 1.8, and 0.7 V/cm at 1, 2, and 3 AU respectively. We set the radius of the lightning bolt equal to the kinetic mean free path of the gas. Our calculations based on electron drift velocities in a fully ionized H2 gas show that first strike durations are 0.96, 3.4, and 7.0 ms at 1, 2, and 3 AU respectively, in much better accordance with the meteoritic evidence than previous estimates of 10-100 s.

  2. Studies of bipolar nebulae. VI - Optical spectrophotometric mapping of GL 2688 /the Cygnus EGG Nebula/

    NASA Technical Reports Server (NTRS)

    Cohen, M.; Kuhi, L. V.

    1980-01-01

    Optical scanner spectra are presented for ten positions in the lobes of GL 2688. Color gradients exist across the nebulae, probably due to systematic variations in the sizes of typical scattering grains. Molecular emissions C2, C3, and SiC2 are found, similar to the spectra of comets. Resonance fluorescence seems to be indicated.

  3. Cosmic Spider is Good Mother

    NASA Astrophysics Data System (ADS)

    2006-04-01

    Hanging above the Large Magellanic Cloud (LMC) - one of our closest galaxies - in what some describe as a frightening sight, the Tarantula nebula is worth looking at in detail. Also designated 30 Doradus or NGC 2070, the nebula owes its name to the arrangement of its brightest patches of nebulosity that somewhat resemble the legs of a spider. This name, of the biggest spiders on Earth, is also very fitting in view of the gigantic proportions of the celestial nebula - it measures nearly 1,000 light years across! ESO PR Photo 11/06 ESO PR Photo 13b/06 Tarantula's Central Cluster, R136 The Tarantula nebula is the largest emission nebula in the sky and also one of the largest known star-forming regions in all the Milky Way's neighbouring galaxies. Located about 170,000 light-years away, in the southern constellation Dorado (The Swordfish), it can be seen with the unaided eye. As shown in this image obtained with the FORS1 multi-mode instrument on ESO's Very Large Telescope, its structure is fascinatingly complex, with a large number of bright arcs and apparently dark areas in between. Inside the giant emission nebula lies a cluster of young, massive and hot stars, denoted R 136, whose intense radiation and strong winds make the nebula glow, shaping it into the form of a giant arachnid. The cluster is about 2 to 3 million years old, that is, almost from 'yesterday' in the 13.7 billion year history of the Universe. Several of the brighter members in the immediate surroundings of the dense cluster are among the most massive stars known, with masses well above 50 times the mass of our Sun. The cluster itself contains more than 200 massive stars. ESO PR Photo 11/06 ESO PR Photo 13c/06 The Stellar Cluster Hodge 301 In the upper right of the image, another cluster of bright, massive stars is seen. Known to astronomers as Hodge 301, it is about 20 million years old, or about 10 times older than R136. The more massive stars of Hodge 301 have therefore already exploded as

  4. Spectral Characteristics of Young Stars Associated with the Sh2-296 Nebula

    NASA Astrophysics Data System (ADS)

    Fernandes, Beatriz; Gregorio-Hetem, Jane

    Aiming to contribute to the understanding of star formation and evolution in the Canis Major (CMa R1) Molecular Clouds Complex, we analyze the spectral characteristics of a population of young stars associated with the arc-shaped nebula Sh2-296. Our XMM/Newton observations detected 109 X-ray sources in the region and optical spectroscopy was performed with Gemini telescope for 85 optical counterparts. We identified and characterized 51 objects that present features typically found in young objects, such as Hα emission and strong absorption on the Li I line.

  5. Dissociative disorders in medical settings.

    PubMed

    MacPhee, Edward

    2013-10-01

    Despite the challenges of conducting research on dissociation and the dissociative disorders, our understanding has grown greatly over the past three decades, including our knowledge of the often overlooked sensorimotor manifestations of dissociation, more commonly referred to as somatoform dissociation. This article will first review the definitions and presentations of dissociation in general along with recent research on the concept of somatoform dissociation. Then, each of the dissociative disorders and conversion disorder will be discussed in further detail as well as how they might present in a medical setting. Current recommendations for diagnosis and treatment will also be provided.

  6. Hierarchies of Models: Toward Understanding Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Knuth, Kevin H.; Hajian, Arsen R.; Clancy, Daniel (Technical Monitor)

    2003-01-01

    Stars like our sun (initial masses between 0.8 to 8 solar masses) end their lives as swollen red giants surrounded by cool extended atmospheres. The nuclear reactions in their cores create carbon, nitrogen and oxygen, which are transported by convection to the outer envelope of the stellar atmosphere. As the star finally collapses to become a white dwarf, this envelope is expelled from the star to form a planetary nebula (PN) rich in organic molecules. The physics, dynamics, and chemistry of these nebulae are poorly understood and have implications not only for our understanding of the stellar life cycle but also for organic astrochemistry and the creation of prebiotic molecules in interstellar space. We are working toward generating three-dimensional models of planetary nebulae (PNe), which include the size, orientation, shape, expansion rate and mass distribution of the nebula. Such a reconstruction of a PN is a challenging problem for several reasons. First, the data consist of images obtained over time from the Hubble Space Telescope (HST) and spectra obtained from Kitt Peak National Observatory (KPNO) and Cerro Tololo Inter-American Observatory (CTIO). These images are of course taken from a single viewpoint in space, which amounts to a very challenging tomographic reconstruction. Second, the fact that we have two disparate and orthogonal data types requires that we utilize a method that allows these data to be used together to obtain a solution. To address these first two challenges we employ Bayesian model estimation using a parameterized physical model that incorporates much prior information about the known physics of the PN. In our previous works we have found that the forward problem of the comprehensive model is extremely time consuming. To address this challenge, we explore the use of a set of hierarchical models, which allow us to estimate increasingly more detailed sets of model parameters. These hierarchical models of increasing complexity are akin

  7. Hierarchies of Models: Toward Understanding Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Knuth, Kevin H.; Hajian, Arsen R.; Clancy, Daniel (Technical Monitor)

    2002-01-01

    Stars like our sun (initial masses between 0.8 to 8 solar masses) end their lives as swollen red giants surrounded by cool extended atmospheres. The nuclear reactions in their cores create carbon, nitrogen and oxygen, which are transported by convection to the outer envelope of the stellar atmosphere. As the star finally collapses to become a white dwarf, this envelope is expelled from the star to form a planetary nebula (PN) rich in organic molecules. The physics, dynamics, and chemistry of these nebulae are poorly understood and have implications not only for our understanding of the stellar life cycle but also for organic astrochemistry and the creation of prebiotic molecules in interstellar space. We are working toward generating three-dimensional models of planetary nebulae (PNe), which include the size, orientation, shape, expansion rate and mass distribution of the nebula. Such a reconstruction of a PN is a challenging problem for several reasons. First, the data consist of images obtained over time from the Hubble Space Telescope (HST) and spectra obtained from Kitt Peak National Observatory (KPNO) and Cerro Tololo Inter-American Observatory (CTIO). These images are of course taken from a single viewpoint in space, which amounts to a very challenging tomographic reconstruction. Second, the fact that we have two disparate and orthogonal data types requires that we utilize a method that allows these data to be used together to obtain a solution. To address these first two challenges we employ Bayesian model estimation using a parameterized physical model that incorporates much prior information about the known physics of the PN. In our previous works we have found that the forward problem of the comprehensive model is extremely time consuming. To address this challenge, we explore the use of a set of hierarchical models, which allow us to estimate increasingly more detailed sets of model parameters. These hierarchical models of increasing complexity are akin

  8. Temperature anisotropy of the Jovian sulfur nebula

    NASA Technical Reports Server (NTRS)

    Eviatar, A.; Siscoe, G. L.; Mekler, Y.

    1979-01-01

    The apparent paradox between the reported observation of a 3-eV gyration energy of Jupiter's ionized sulfur nebula and its observed thickness is discussed. An observation of the thickness of the cloud taken nearly edge-on is presented and shown to imply a large bounce-averaged anisotropy of the sulfur in temperature. These observations are used to construct a self-consistent model of the sulfur nebula in which the sulfur ions are injected by Io as ions and remain sufficiently collisionless in the magnetosphere to maintain the anisotropy for a time longer than a characteristic diffusion time. It is also shown that the proton-electron plasma is collisionally thermalized and provides an adequate means of tapping the rotational energy of the planet to provide the power radiated in the sulfur lines.

  9. Nebula/DSCR1 upregulation delays neurodegeneration and protects against APP-induced axonal transport defects by restoring calcineurin and GSK-3β signaling.

    PubMed

    Shaw, Jillian L; Chang, Karen T

    2013-01-01

    Post-mortem brains from Down syndrome (DS) and Alzheimer's disease (AD) patients show an upregulation of the Down syndrome critical region 1 protein (DSCR1), but its contribution to AD is not known. To gain insights into the role of DSCR1 in AD, we explored the functional interaction between DSCR1 and the amyloid precursor protein (APP), which is known to cause AD when duplicated or upregulated in DS. We find that the Drosophila homolog of DSCR1, Nebula, delays neurodegeneration and ameliorates axonal transport defects caused by APP overexpression. Live-imaging reveals that Nebula facilitates the transport of synaptic proteins and mitochondria affected by APP upregulation. Furthermore, we show that Nebula upregulation protects against axonal transport defects by restoring calcineurin and GSK-3β signaling altered by APP overexpression, thereby preserving cargo-motor interactions. As impaired transport of essential organelles caused by APP perturbation is thought to be an underlying cause of synaptic failure and neurodegeneration in AD, our findings imply that correcting calcineurin and GSK-3β signaling can prevent APP-induced pathologies. Our data further suggest that upregulation of Nebula/DSCR1 is neuroprotective in the presence of APP upregulation and provides evidence for calcineurin inhibition as a novel target for therapeutic intervention in preventing axonal transport impairments associated with AD.

  10. The Orion Nebula: Still Full of Surprises

    NASA Astrophysics Data System (ADS)

    2011-01-01

    This ethereal-looking image of the Orion Nebula was captured using the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the La Silla Observatory, Chile. This nebula is much more than just a pretty face, offering astronomers a close-up view of a massive star-forming region to help advance our understanding of stellar birth and evolution. The data used for this image were selected by Igor Chekalin (Russia), who participated in ESO's Hidden Treasures 2010 astrophotography competition. Igor's composition of the Orion Nebula was the seventh highest ranked entry in the competition, although another of Igor's images was the eventual overall winner. The Orion Nebula, also known as Messier 42, is one of the most easily recognisable and best-studied celestial objects. It is a huge complex of gas and dust where massive stars are forming and is the closest such region to the Earth. The glowing gas is so bright that it can be seen with the unaided eye and is a fascinating sight through a telescope. Despite its familiarity and closeness there is still much to learn about this stellar nursery. It was only in 2007, for instance, that the nebula was shown to be closer to us than previously thought: 1350 light-years, rather than about 1500 light-years. Astronomers have used the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile to observe the stars within Messier 42. They found that the faint red dwarfs in the star cluster associated with the glowing gas radiate much more light than had previously been thought, giving us further insights into this famous object and the stars that it hosts. The data collected for this science project, with no original intention to make a colour image, have now been reused to create the richly detailed picture of Messier 42 shown here. The image is a composite of several exposures taken through a total of five different filters. Light that passed through a red filter as well as light from a filter that

  11. FORMING CHONDRITES IN A SOLAR NEBULA WITH MAGNETICALLY INDUCED TURBULENCE

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

    Hasegawa, Yasuhiro; Turner, Neal J.; Masiero, Joseph

    Chondritic meteorites provide valuable opportunities to investigate the origins of the solar system. We explore impact jetting as a mechanism of chondrule formation and subsequent pebble accretion as a mechanism of accreting chondrules onto parent bodies of chondrites, and investigate how these two processes can account for the currently available meteoritic data. We find that when the solar nebula is ≤5 times more massive than the minimum-mass solar nebula at a ≃ 2–3 au and parent bodies of chondrites are ≤10{sup 24} g (≤500 km in radius) in the solar nebula, impact jetting and subsequent pebble accretion can reproduce a number ofmore » properties of the meteoritic data. The properties include the present asteroid belt mass, the formation timescale of chondrules, and the magnetic field strength of the nebula derived from chondrules in Semarkona. Since this scenario requires a first generation of planetesimals that trigger impact jetting and serve as parent bodies to accrete chondrules, the upper limit of parent bodies’ masses leads to the following implications: primordial asteroids that were originally ≥10{sup 24} g in mass were unlikely to contain chondrules, while less massive primordial asteroids likely had a chondrule-rich surface layer. The scenario developed from impact jetting and pebble accretion can therefore provide new insights into the origins of the solar system.« less

  12. Storm of Stars in the Trifid Nebula

    NASA Image and Video Library

    2014-01-29

    Radiation and winds from massive stars have blown a cavity into the surrounding dust and gas, creating the Trifid nebula, as seen here in infrared light by NASA Wide-field Infrared Survey Explorer, or WISE.

  13. A BROADBAND EMISSION MODEL OF MAGNETAR WIND NEBULAE

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

    Tanaka, Shuta J.

    2016-08-20

    Angular momentum loss by the plasma wind is considered as a universal feature of isolated neutron stars including magnetars. The wind nebulae that are powered by magnetars allow us to compare the wind properties and the spin evolution of magnetars with those of rotation-powered pulsars (RPPs). In this paper, we construct a broadband emission model of magnetar wind nebulae (MWNe). This model is similar to past studies of young pulsar wind nebulae (PWNe) around RPPs, but is modified for the application to MWNe that have far less observational information than the young PWNe. We apply the model to the MWNmore » around the youngest (∼1 kyr) magnetar, 1E 1547.0-5408, which has the largest spin-down power L {sub spin} among all the magnetars. However, the MWN is faint because of the low L {sub spin} of 1E 1547.0-5408 when compared to the young RPPs. Since most parameters are not well constrained by only an X-ray flux upper limit of the MWN, we adopt the model’s parameters from the young PWN Kes 75 around PSR J1846-0258, which is a peculiar RPP showing magnetar-like behaviors. The model predicts that γ -ray flux will be detected in a future TeV γ -ray observation by CTA (Cherenkov Telescope Array). The MWN spectrum does not allow us to test the hypothesis that 1E 1547.0-5408 had a period of milliseconds at its birth because the particles injected during the early phase of evolution suffered from severe adiabatic and synchrotron losses. Furthermore, both observational and theoretical studies of the wind nebulae around magnetars are required to constrain the wind and the spin-down properties of magnetars.« less

  14. A Broadband Emission Model of Magnetar Wind Nebulae

    NASA Astrophysics Data System (ADS)

    Tanaka, Shuta J.

    2016-08-01

    Angular momentum loss by the plasma wind is considered as a universal feature of isolated neutron stars including magnetars. The wind nebulae that are powered by magnetars allow us to compare the wind properties and the spin evolution of magnetars with those of rotation-powered pulsars (RPPs). In this paper, we construct a broadband emission model of magnetar wind nebulae (MWNe). This model is similar to past studies of young pulsar wind nebulae (PWNe) around RPPs, but is modified for the application to MWNe that have far less observational information than the young PWNe. We apply the model to the MWN around the youngest (˜1 kyr) magnetar, 1E 1547.0-5408, which has the largest spin-down power L spin among all the magnetars. However, the MWN is faint because of the low L spin of 1E 1547.0-5408 when compared to the young RPPs. Since most parameters are not well constrained by only an X-ray flux upper limit of the MWN, we adopt the model’s parameters from the young PWN Kes 75 around PSR J1846-0258, which is a peculiar RPP showing magnetar-like behaviors. The model predicts that γ-ray flux will be detected in a future TeV γ-ray observation by CTA (Cherenkov Telescope Array). The MWN spectrum does not allow us to test the hypothesis that 1E 1547.0-5408 had a period of milliseconds at its birth because the particles injected during the early phase of evolution suffered from severe adiabatic and synchrotron losses. Furthermore, both observational and theoretical studies of the wind nebulae around magnetars are required to constrain the wind and the spin-down properties of magnetars.

  15. Hubble sniffs out a brilliant star death in a “rotten egg” nebula

    NASA Image and Video Library

    2017-12-08

    The Calabash Nebula, pictured here — which has the technical name OH 231.8+04.2 — is a spectacular example of the death of a low-mass star like the sun. This image taken by the NASA/ESA Hubble Space Telescope shows the star going through a rapid transformation from a red giant to a planetary nebula, during which it blows its outer layers of gas and dust out into the surrounding space. The recently ejected material is spat out in opposite directions with immense speed — the gas shown in yellow is moving close to one million kilometers per hour (621,371 miles per hour). Astronomers rarely capture a star in this phase of its evolution because it occurs within the blink of an eye — in astronomical terms. Over the next thousand years the nebula is expected to evolve into a fully-fledged planetary nebula. The nebula is also known as the Rotten Egg Nebula because it contains a lot of sulphur, an element that, when combined with other elements, smells like a rotten egg — but luckily, it resides over 5,000 light-years away in the constellation of Puppis. Credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt 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

  16. A simple way to model nebulae with distributed ionizing stars

    NASA Astrophysics Data System (ADS)

    Jamet, L.; Morisset, C.

    2008-04-01

    Aims: This work is a follow-up of a recent article by Ercolano et al. that shows that, in some cases, the spatial dispersion of the ionizing stars in a given nebula may significantly affect its emission spectrum. The authors found that the dispersion of the ionizing stars is accompanied by a decrease in the ionization parameter, which at least partly explains the variations in the nebular spectrum. However, they did not research how other effects associated to the dispersion of the stars may contribute to those variations. Furthermore, they made use of a unique and simplified set of stellar populations. The scope of the present article is to assess whether the variation in the ionization parameter is the dominant effect in the dependence of the nebular spectrum on the distribution of its ionizing stars. We examined this possibility for various regimes of metallicity and age. We also investigated a way to model the distribution of the ionizing sources so as to bypass expensive calculations. Methods: We wrote a code able to generate random stellar populations and to compute the emission spectra of their associated nebulae through the widespread photoionization code cloudy. This code can process two kinds of spatial distributions of the stars: one where all the stars are concentrated at one point, and one where their separation is such that their Strömgren spheres do not overlap. Results: We found that, in most regimes of stellar population ages and gas metallicities, the dependence of the ionization parameter on the distribution of the stars is the dominant factor in the variation of the main nebular diagnostics with this distribution. We derived a method to mimic those effects with a single calculation that makes use of the common assumptions of a central source and a spherical nebula, in the case of constant density objects. This represents a computation time saving by a factor of at least several dozen in the case of H ii regions ionized by massive clusters.

  17. The Owl and other strigiform nebulae: multipolar cavities within a filled shell

    NASA Astrophysics Data System (ADS)

    García-Díaz, Ma T.; Steffen, W.; Henney, W. J.; López, J. A.; García-López, F.; González-Buitrago, D.; Áviles, A.

    2018-06-01

    We present the results of long-slit echelle spectroscopy and deep narrow-band imaging of the Owl Nebula (NGC 3587), obtained at the Observatorio Astronómico Nacional, San Pedro Mártir. These data allow us to construct an iso-velocity data cube and develop a 3-D morpho-kinematic model. We find that, instead of the previously assumed bipolar dumbbell shape, the inner cavity consists of multi-polar fingers within an overall tripolar structure. We identify three additional planetary nebulae that show very similar morphologies and kinematics to the Owl, and propose that these constitute a new class of strigiform (owl-like) nebulae. Common characteristics of the strigiform nebulae include a double-shell (thin outside thick) structure, low-luminosity and high-gravity central stars, the absence of a present-day stellar wind, and asymmetric inner cavities, visible in both optical and mid-infrared emission lines, that show no evidence for surrounding bright rims. The origin of the cavities is unclear, but they may constitute relics of an earlier stage of evolution when the stellar wind was active.

  18. RAPID GAMMA-RAY FLUX VARIABILITY DURING THE 2013 MARCH CRAB NEBULA FLARE

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

    Mayer, M.; Buehler, R.; Hays, E.

    2013-10-01

    We report on a bright flare in the Crab Nebula detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The period of significantly increased luminosity occurred in 2013 March and lasted for approximately two weeks. During this period, we observed flux variability on timescales of approximately 5 hr. The combined photon flux above 100 MeV from the pulsar and its nebula reached a peak value of (12.5 ± 0.8) · 10{sup –6} cm{sup –2} s{sup –1} on 2013 March 6. This value exceeds the average flux by almost a factor of six and implies amore » ∼20 times higher flux for the synchrotron component of the nebula alone. This is the second brightest flare observed from this source. Spectral and temporal analysis of the LAT data collected during the outburst reveal a rapidly varying synchrotron component of the Crab Nebula while the pulsar emission remains constant in time.« less

  19. Constraining the Turbulence Scale and Mixing of a Crushed Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Ng, Chi Yung; Ma, Y. K.; Bucciantini, Niccolo; Slane, Patrick O.; Gaensler, Bryan M.; Temim, Tea

    2016-04-01

    Pulsar wind nebulae (PWNe) are synchrotron-emitting nebulae resulting from the interaction between pulsars' relativistic particle outflows and the ambient medium. The Snail PWN in supernova remnant G327.1-1.1 is a rare system that has recently been crushed by supernova reverse shock. We carried out radio polarization observations with the Australia Telescope Compact Array and found highly ordered magnetic field structure in the nebula. This result is surprising, given the turbulent environment expected from hydrodynamical simulations. We developed a toymodel and compared simple simulations with observations to constrain the characteristic turbulence scale in the PWN and the mixing with supernova ejecta. We estimate that the turbulence scale is about one-eighth to one-sixth of the nebula radius and a pulsar wind filling factor of 50-75%. The latter implies substantial mixing of the pulsar wind with the surrounding supernova ejecta.This work is supported by an ECS grant of the Hong Kong Government under HKU 709713P. The Australia Telescope is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.

  20. Spatially-Dependent Modelling of Pulsar Wind Nebula G0.9+0.1

    NASA Astrophysics Data System (ADS)

    van Rensburg, C.; Krüger, P. P.; Venter, C.

    2018-03-01

    We present results from a leptonic emission code that models the spectral energy distribution of a pulsar wind nebula by solving a Fokker-Planck-type transport equation and calculating inverse Compton and synchrotron emissivities. We have created this time-dependent, multi-zone model to investigate changes in the particle spectrum as they traverse the pulsar wind nebula, by considering a time and spatially-dependent B-field, spatially-dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. Our code predicts the radiation spectrum at different positions in the nebula, yielding the surface brightness versus radius and the nebular size as function of energy. We compare our new model against more basic models using the observed spectrum of pulsar wind nebula G0.9+0.1, incorporating data from H.E.S.S. as well as radio and X-ray experiments. We show that simultaneously fitting the spectral energy distribution and the energy-dependent source size leads to more stringent constraints on several model parameters.

  1. Spatially dependent modelling of pulsar wind nebula G0.9+0.1

    NASA Astrophysics Data System (ADS)

    van Rensburg, C.; Krüger, P. P.; Venter, C.

    2018-07-01

    We present results from a leptonic emission code that models the spectral energy distribution of a pulsar wind nebula by solving a Fokker-Planck-type transport equation and calculating inverse Compton and synchrotron emissivities. We have created this time-dependent, multizone model to investigate changes in the particle spectrum as they traverse the pulsar wind nebula, by considering a time and spatially dependent B-field, spatially dependent bulk particle speed implying convection and adiabatic losses, diffusion, as well as radiative losses. Our code predicts the radiation spectrum at different positions in the nebula, yielding the surface brightness versus radius and the nebular size as function of energy. We compare our new model against more basic models using the observed spectrum of pulsar wind nebula G0.9+0.1, incorporating data from H.E.S.S. as well as radio and X-ray experiments. We show that simultaneously fitting the spectral energy distribution and the energy-dependent source size leads to more stringent constraints on several model parameters.

  2. N44C nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Resembling the hair in Botticelli's famous portrait of the birth of Venus, an image from NASA's Hubble Space Telescope has captured softly glowing filaments streaming from hot young stars in a nearby nebula.

    The image, presented by the Hubble Heritage Project, was taken in 1996 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The image is available online at

    http://heritage.stsci.edu , http://oposite.stsci.edu/pubinfo/pr/2002/12 orhttp://www.jpl.nasa.gov/images/wfpc .

    On the top right of the image is a source of its artistic likeness, a network of nebulous filaments surrounding the Wolf-Rayet star. This type of rare star is characterized by an exceptionally vigorous 'wind' of charged particles. The shock of the wind colliding with the surrounding gas causes the gas to glow.

    The Wolf-Rayet star is part of N44C, a nebula of glowing hydrogen gas surrounding young stars in the Large Magellanic Cloud. Visible from the Southern Hemisphere, the Large Magellanic Cloud is a small companion galaxy to the Milky Way.

    What makes N44C peculiar is the temperature of the star that illuminates it. The most massive stars -- those that are 10 to 50 times more massive than the Sun -- have maximum temperatures of 30,000 to 50,000 degrees Celsius (54,000 to 90,000 degrees Fahrenheit). The temperature of this star is about 75,000 degrees Celsius (135,000 degrees Fahrenheit). This unusually high temperature may be due to a neutron star or black hole that occasionally produces X-rays but is now inactive.

    N44C is part of a larger complex that includes young, hot, massive stars, nebulae, and a 'superbubble' blown out by multiple supernova explosions. Part of the superbubble is seen in red at the very bottom left of the Hubble image.

    The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard

  3. Spatially resolved spectroscopy of WR ring nebulae. I - NGC 2359 and RCW 78

    NASA Astrophysics Data System (ADS)

    Esteban, C.; Vilchez, J. M.; Manchado, A.; Edmunds, M. G.

    1990-01-01

    We report detailed spatially resolved spectroscopy of the WR nebulae NGC 2359 and RCW 78 surrounding the WN 5 HD 56925 and WN 8 HD 117688 stars. The aim of this work has been to study possible abundance inhomogeneities and the ionization structure of the nebulae, as well as to derive reliable values for the degree of self-enrichment. In NGC 2359 the derived ratio O2+/O+ shows localized variations resulting from the compression of the gas in the filaments with respect to the shell gas. Effective temperatures for the central stars of both nebulae have been estimated on the basis of the ionization structure; the values found appear appropriate for their spectral types. Abundances of O/H, NIH, Ne/H, and He/H have been determined in twelve different positions in NGC 2359, covering its different morphological zones. No significant differences in the N/H and O/H abundances across the nebula have been found, although He/H shows marginal evidence for localized enhancements. In the case of RCW 78 the derived value of O/H is roughly solar, but He/H and NIH may be slightly overabundant. The results suggest that the amount of chemical self-enrichment of these WR nebulae is, at most, small.

  4. Dissociative disorders in DSM-5.

    PubMed

    Spiegel, David; Loewenstein, Richard J; Lewis-Fernández, Roberto; Sar, Vedat; Simeon, Daphne; Vermetten, Eric; Cardeña, Etzel; Brown, Richard J; Dell, Paul F

    2011-12-21

    We present recommendations for revision of the diagnostic criteria for the Dissociative Disorders (DDs) for DSM-5. The periodic revision of the DSM provides an opportunity to revisit the assumptions underlying specific diagnoses and the empirical support, or lack of it, for the defining diagnostic criteria. This paper reviews clinical, phenomenological, epidemiological, cultural, and neurobiological data related to the DDs in order to generate an up-to-date, evidence-based set of DD diagnoses and diagnostic criteria for DSM-5. First, we review the definitions of dissociation and the differences between the definitions of dissociation and conceptualization of DDs in the DSM-IV-TR and the ICD-10, respectively. Also, we review more general conceptual issues in defining dissociation and dissociative disorders. Based on this review, we propose a revised definition of dissociation for DSM-5 and discuss the implications of this definition for understanding dissociative symptoms and disorders. We make the following recommendations for DSM-5: 1. Depersonalization Disorder (DPD) should include derealization symptoms as well. 2. Dissociative Fugue should become a subtype of Dissociative Amnesia (DA). 3. The diagnostic criteria for DID should be changed to emphasize the disruptive nature of the dissociation and amnesia for everyday as well as traumatic events. The experience of possession should be included in the definition of identity disruption. 4. Dissociative Trance Disorder should be included in the Unspecified Dissociative Disorder (UDD) category. There is a growing body of evidence linking the dissociative disorders to a trauma history, and to specific neural mechanisms. © 2011 Wiley Periodicals, Inc.

  5. Dissociative disorders in DSM-5.

    PubMed

    Spiegel, David; Loewenstein, Richard J; Lewis-Fernández, Roberto; Sar, Vedat; Simeon, Daphne; Vermetten, Eric; Cardeña, Etzel; Dell, Paul F

    2011-09-01

    We present recommendations for revision of the diagnostic criteria for the Dissociative Disorders (DDs) for DSM-5. The periodic revision of the DSM provides an opportunity to revisit the assumptions underlying specific diagnoses and the empirical support, or lack of it, for the defining diagnostic criteria. This paper reviews clinical, phenomenological, epidemiological, cultural, and neurobiological data related to the DDs in order to generate an up-to-date, evidence-based set of DD diagnoses and diagnostic criteria for DSM-5. First, we review the definitions of dissociation and the differences between the definitions of dissociation and conceptualization of DDs in the DSM-IV-TR and the ICD-10, respectively. Also, we review more general conceptual issues in defining dissociation and dissociative disorders. Based on this review, we propose a revised definition of dissociation for DSM-5 and discuss the implications of this definition for understanding dissociative symptoms and disorders. We make the following recommendations for DSM-5: 1. Depersonalization Disorder (DPD) should derealization symptoms as well. 2. Dissociative Fugue should become a subtype of Dissociative Amnesia (DA). 3. The diagnostic criteria for DID should be changed to emphasize the disruptive nature of the dissociation and amnesia for everyday as well as traumatic events. The experience of possession should be included in the definition of identity disruption. 4. Should Dissociative Trance Disorder should be included in the Unspecified Dissociative Disorder (UDD) category. There is a growing body of evidence linking the dissociative disorders to a trauma history, and to specific neural mechanisms. © 2011 Wiley-Liss, Inc.

  6. Predictors of trait dissociation and peritraumatic dissociation induced via cold pressor.

    PubMed

    Gómez-Pérez, Lydia; López-Martínez, Alicia Eva; Asmundson, Gordon John Glenn

    2013-11-30

    Understanding which factors predict individual dissociative response during stressful situations is important to clarify the nature of dissociation and the mechanisms associated to its use as a coping strategy. The present study examined (1) whether experiential avoidance (EA), anxiety sensitivity (AS), depressive symptoms, and state anxiety concurrently predicted trait dissociation (TD)-absorption, amnesia, depersonalization, and total TD scores-and laboratory induced dissociation (LID); and (2) whether TD and catastrophizing predicted LID. We also examined whether catastrophizing mediated the relationships between both AS and depressive symptoms and LID. A total of 101 female undergraduate students participated in a cold pressor task, which significantly induced dissociation. Results of hierarchical regression analyses showed that AS at Time 1 (9 months before the experimental session), as well as depressive symptoms and catastrophizing at the time of the experiment (Time 2), predicted LID at Time 2. Depressive symptoms at Time 2 predicted total TD, absorption, and amnesia scores. AS at Time 1 and depressive symptoms at Time 2 predicted depersonalization. AS, depressive symptoms, and catastrophizing seem to facilitate the use of dissociative strategies by healthy individuals, even in response to non-traumatic but discomforting stress. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  7. Sequencing Larger Intact Proteins (30-70 kDa) with Activated Ion Electron Transfer Dissociation

    NASA Astrophysics Data System (ADS)

    Riley, Nicholas M.; Westphall, Michael S.; Coon, Joshua J.

    2018-01-01

    The analysis of intact proteins via mass spectrometry can offer several benefits to proteome characterization, although the majority of top-down experiments focus on proteoforms in a relatively low mass range (<30 kDa). Recent studies have focused on improving the analysis of larger intact proteins (up to 75 kDa), but they have also highlighted several challenges to be addressed. One major hurdle is the efficient dissociation of larger protein ions, which often to do not yield extensive fragmentation via conventional tandem MS methods. Here we describe the first application of activated ion electron transfer dissociation (AI-ETD) to proteins in the 30-70 kDa range. AI-ETD leverages infrared photo-activation concurrent to ETD reactions to improve sequence-informative product ion generation. This method generates more product ions and greater sequence coverage than conventional ETD, higher-energy collisional dissociation (HCD), and ETD combined with supplemental HCD activation (EThcD). Importantly, AI-ETD provides the most thorough protein characterization for every precursor ion charge state investigated in this study, making it suitable as a universal fragmentation method in top-down experiments. Additionally, we highlight several acquisition strategies that can benefit characterization of larger proteins with AI-ETD, including combination of spectra from multiple ETD reaction times for a given precursor ion, multiple spectral acquisitions of the same precursor ion, and combination of spectra from two different dissociation methods (e.g., AI-ETD and HCD). In all, AI-ETD shows great promise as a method for dissociating larger intact protein ions as top-down proteomics continues to advance into larger mass ranges. [Figure not available: see fulltext.

  8. The Elephant Trunk Nebula and the Trumpler 37 cluster: contribution of triggered star formation to the total population of an H II region

    NASA Astrophysics Data System (ADS)

    Getman, Konstantin V.; Feigelson, Eric D.; Sicilia-Aguilar, Aurora; Broos, Patrick S.; Kuhn, Michael A.; Garmire, Gordon P.

    2012-11-01

    Rich young stellar clusters produce H ii regions whose expansion into the nearby molecular cloud is thought to trigger the formation of new stars. However, the importance of this mode of star formation is uncertain. This investigation seeks to quantify triggered star formation (TSF) in IC 1396A (aka the Elephant Trunk Nebula), a bright-rimmed cloud (BRC) on the periphery of the nearby giant H ii region IC 1396 produced by the Trumpler 37 cluster. X-ray selection of young stars from Chandra X-ray Observatory data is combined with existing optical and infrared surveys to give a more complete census of the TSF population. Over 250 young stars in and around IC 1396A are identified; this doubles the previously known population. A spatio-temporal gradient of stars from the IC 1396A cloud towards the primary ionizing star HD 206267 is found. We argue that the TSF mechanism in IC 1396A is a radiation-driven implosion process persisting over several million years. Analysis of the X-ray luminosity and initial mass functions indicates that >140 stars down to 0.1 M⊙ were formed by TSF. Considering other BRCs in the IC 1396 H ii region, we estimate the TSF contribution for the entire H ii region exceeds 14-25 per cent today, and may be higher over the lifetime of the H ii region. Such triggering on the periphery of H ii regions may be a significant mode of star formation in the Galaxy.

  9. Experimental simulations of sulfide formation in the solar nebula.

    PubMed

    Lauretta, D S; Lodders, K; Fegley, B

    1997-07-18

    Sulfurization of meteoritic metal in H2S-H2 gas produced three different sulfides: monosulfide solid solution [(Fe,Ni)1-xS], pentlandite [(Fe,Ni)9-xS8], and a phosphorus-rich sulfide. The composition of the remnant metal was unchanged. These results are contrary to theoretical predictions that sulfide formation in the solar nebula produced troilite (FeS) and enriched the remaining metal in nickel. The experimental sulfides are chemically and morphologically similar to sulfide grains in the matrix of the Alais (class CI) carbonaceous chondrite, suggesting that these meteoritic sulfides may be condensates from the solar nebula.

  10. OPTICAL SPECTROSCOPY OF X-RAY-SELECTED YOUNG STARS IN THE CARINA NEBULA

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

    Vaidya, Kaushar; Chen, Wen-Ping; Lee, Hsu-Tai

    We present low-resolution optical spectra for 29 X-ray sources identified as either massive star candidates or low-mass pre-main-sequence (PMS) star candidates in the clusters Trumpler 16 and Trumpler 14 of the Carina Nebula. Spectra of two more objects (one with an X-ray counterpart, and one with no X-ray counterpart), not originally our targets, but found close (∼3″) to two of our targets, are presented as well. Twenty early-type stars, including an O8 star, seven B1–B2 stars, two B3 stars, a B5 star, and nine emission-line stars, are identified. Eleven T Tauri stars, including eight classical T Tauri stars (CTTSs) and threemore » weak-lined T Tauri stars, are identified. The early-type stars in our sample are more reddened compared to the previously known OB stars of the region. The Chandra hardness ratios of our T Tauri stars are found to be consistent with the Chandra hardness ratios of T Tauri stars of the Orion Nebula Cluster. Most early-type stars are found to be nonvariable in X-ray emission, except the B2 star J104518.81–594217.9, the B3 star J104507.84–594134.0, and the Ae star J104424.76–594555.0, which are possible X-ray variables. J104452.20–594155.1, a CTTS, is among the brightest and the hardest X-ray sources in our sample, appears to be a variable, and shows a strong X-ray flare. The mean optical and near-infrared photometric variability in the V and K{sub s} bands, of all sources, is found to be ∼0.04 and 0.05 mag, respectively. The T Tauri stars show significantly larger mean variation, ∼0.1 mag, in the K{sub s} band. The addition of one O star and seven B1–B2 stars reported here contributes to an 11% increase of the known OB population in the observed field. The 11 T Tauri stars are the first ever confirmed low-mass PMS stars in the Carina Nebula region.« less

  11. EVOLUTION OF THE CRAB NEBULA IN A LOW ENERGY SUPERNOVA

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

    Yang, Haifeng; Chevalier, Roger A., E-mail: hy4px@virginia.edu, E-mail: rac5x@virginia.edu

    The nature of the supernova leading to the Crab Nebula has long been controversial because of the low energy that is present in the observed nebula. One possibility is that there is significant energy in extended fast material around the Crab but searches for such material have not led to detections. An electron capture supernova model can plausibly account for the low energy and the observed abundances in the Crab. Here, we examine the evolution of the Crab pulsar wind nebula inside a freely expanding supernova and find that the observed properties are most consistent with a low energy event.more » Both the velocity and radius of the shell material, and the amount of gas swept up by the pulsar wind point to a low explosion energy (∼10{sup 50} erg). We do not favor a model in which circumstellar interaction powers the supernova luminosity near maximum light because the required mass would limit the freely expanding ejecta.« less

  12. Hubble Spins a Web Into a Giant Red Spider Nebula

    NASA Image and Video Library

    2017-12-08

    Huge waves are sculpted in this two-lobed nebula called the Red Spider Nebula, located some 3,000 light-years away in the constellation of Sagittarius. This warm planetary nebula harbors one of the hottest stars known and its powerful stellar winds generate waves 100 billion kilometers (62.4 billion miles) high. The waves are caused by supersonic shocks, formed when the local gas is compressed and heated in front of the rapidly expanding lobes. The atoms caught in the shock emit the spectacular radiation seen in this image. Image credit: ESA/Garrelt Mellema (Leiden University, the Netherlands) 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

  13. Three dimensions of dissociative amnesia.

    PubMed

    Dell, Paul F

    2013-01-01

    Principal axis factor analysis with promax rotation extracted 3 factors from the 42 memory and amnesia items of the Multidimensional Inventory of Dissociation (MID) database (N = 2,569): Discovering Dissociated Actions, Lapses of Recent Memory and Skills, and Gaps in Remote Memory. The 3 factors' shared variance ranged from 36% to 64%. Construed as scales, the 3 factor scales had Cronbach's alpha coefficients of .96, .94, and .93, respectively. The scales correlated strongly with mean Dissociative Experiences Scale scores, mean MID scores, and total scores on the Structured Clinical Interview for DSM-IV Dissociative Disorders-Revised (SCID-D-R). What is interesting is that the 3 amnesia factors exhibited a range of correlations with SCID-D-R Amnesia scores (.52, .63, and .70, respectively), suggesting that the SCID-D-R Amnesia score emphasizes gaps in remote memory over amnesias related to dissociative identity disorder. The 3 amnesia factor scales exhibited a clinically meaningful pattern of significant differences among dissociative identity disorder, dissociative disorder not otherwise specified-1, dissociative amnesia, depersonalization disorder, and nonclinical participants. The 3 amnesia factors may have greater clinical utility for frontline clinicians than (a) amnesia as discussed in the context of the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, nosology of the dissociative disorders or (b) P. Janet's (1893/1977 ) 4-fold classification of dissociative amnesia. The author recommends systematic study of the phenomenological differences within specific dissociative symptoms and their differential relationship to specific dissociative disorders.

  14. Most Detailed Image of the Crab Nebula

    NASA Image and Video Library

    2005-12-01

    The Crab Nebula is one of the most intricately structured and highly dynamical objects ever observed. The new Hubble image of the Crab was assembled from 24 individual exposures taken with the NASA/ESA Hubble Space Telescope

  15. Planet engulfment and the planetary nebula morphology mystery

    NASA Astrophysics Data System (ADS)

    Boyle, Laura A.

    2018-04-01

    This thesis presents an investigation into the galactic population of planetary nebulae (PNe) whose progenitors have evolved through the engulfment of massive planets during the asymptotic giant branch (AGB) phase of their evolution. The objective of this research was to investigate the hypothesis that planet engulfment can aid in explaining the observed non-spherical planetary nebula (PN) population, as a complementary shaping mechanism to the binary hypothesis. This was performed by the design and development of a new research tool, simsplash (SIMulationS for the PLAnet Shaping Hypothesis), which was developed for the specific purpose of conducting, for the first time, a population synthesis of planet engulfment in planetary nebula progenitors. The first step in this investigation involved modelling the tidal evolution of planets orbiting PN progenitor stars to determine the importance of the adopted initial conditions and input physics in the stellar models and their effects on the orbital evolution of star-planet systems. The next step was to determine the probabilities of stars having and engulfing massive planets as a function of stellar mass and metallicity. This was achieved by combining the tidal evolution treatment with both the known exoplanet populations, as well as theoretical planet populations, and the occurrence rates of massive planets. Finally, taking into consideration the results from the analyses described above, a PN population synthesis was performed using the star formation history and metallicity evolution of the galaxy as well as varying forms of the initial mass function and planetary nebula formation constraints. The population of visible PNe in the present-day galaxy was calculated to consist of a total of 16,500±2,200 PNe, of which 240±20 PNe (≃ 1.5%) have evolved from the engulfment of a massive planet on the AGB and 3,300±200 PNe are the result of binary interactions (≃ 20%), translating to an expected non-spherical population

  16. Medium-resolution échelle spectroscopy of the Red Square Nebula, MWC 922

    NASA Astrophysics Data System (ADS)

    Wehres, N.; Ochsendorf, B. B.; Tielens, A. G. G. M.; Cox, N. L. J.; Kaper, L.; Bally, J.; Snow, T. P.

    2017-05-01

    Context. Medium-resolution échelle spectra of the Red Square Nebula surrounding the star MWC 922 are presented. The spectra have been obtained in 2010 and 2012 using the X-shooter spectrograph mounted on the Very Large Telescope (VLT) in Paranal, Chile. The spectrum covers a wavelength range between 300 nm-2.5 μm and shows that the nebula is rich in emission lines. Aims: We aim to identify the emission lines and use them as a tool to determine the physical and chemical characteristics of the nebula. The emission lines are also used to put constraints on the structure of the nebula and on the nature of the central stars. Methods: We analyzed and identified emission lines that indicated that the Red Square Nebula consists of a low density bipolar outflow, eminent in the broad emission component seen in [Fe II], as well as in P Cygni line profiles indicative of fast outflowing material. The narrow component in the [Fe II] lines is most likely formed in the photosphere of a surrounding disk. Some of the emission lines show a pronounced double peaked profile, such as Ca II, indicating an accretion disk in Keplerian rotation around the central star. [O I] emission lines are formed in the neutral atomic zone separating the ionized disk photosphere from the molecular gas in the interior of the disk, which is prominent in molecular CO emission in the near-IR. [N II] and [S II] emission clearly originates in a low density but fairly hot (7 000-10 000 K) nebular environment. H I recombination lines trace the extended nebula as well as the photosphere of the disk. Results: These findings put constraints on the evolution of the central objects in MWC 922. The Red Square shows strong similarities to the Red Rectangle Nebula, both in morphology and in its mid-IR spectroscopic characteristics. As for the Red Rectangle, the observed morphology of the nebula reflects mass-loss in a binary system. Specifically, we attribute the biconical morphology and the associated rung

  17. Equations for calculating the properties of dissociated steam

    NASA Astrophysics Data System (ADS)

    Aminov, R. Z.; Gudym, A. A.

    2017-08-01

    The equations of state for dissociated steam have been developed in the temperature and pressure ranges of 1250-2300 K and 0.01-10.00 MPa for calculating thermodynamic processes in thermal power units operating on high-temperature steam. These equations are based on the property tables for dissociated steam derived at a reference temperature of 0 K. It is assumed that the initial substance is steam, the dissociation of which—in accordance with the most likely chemical reactions—results in formation of molecules of hydrogen, oxygen, steam, hydroxyl, and atoms of oxygen and hydrogen. Differential thermodynamic correlations, considering a change in the chemical potential and the composition of the mixture, during the steam dissociation are used. A reference temperature of 0.01°C used in the calculation of parameters of nondissociated steam has been adopted to predict processes in thermal power units without matching the reference temperatures and to account for transformation of dissociated steam into its usual form for which there is the international system of equations with the water triple point of 0.01°C taken as the reference. In the investigated region, the deviation of dissociated steam properties from those of nondissociated steam, which increases with decreasing the pressure or increasing the temperature, was determined. For a pressure of 0.02 MPa and a temperature of 2200 K, these deviations are 512 kJ/kg for the enthalpy, 0.2574 kJ/(kg K) for the entropy, and 3.431 kJ/(kg K) for the heat capacity at constant pressure. The maximum deviation of the dissociated steam properties calculated by the developed equations from the handbook values that these equations are based on does not exceed 0.03-0.05%.

  18. Charge Transfer Dissociation of Complex Oligosaccharides: Comparison with Collision-Induced Dissociation and Extreme Ultraviolet Dissociative Photoionization

    NASA Astrophysics Data System (ADS)

    Ropartz, David; Li, Pengfei; Fanuel, Mathieu; Giuliani, Alexandre; Rogniaux, Hélène; Jackson, Glen P.

    2016-10-01

    The structural characterization of oligosaccharides still challenges the field of analytical chemistry. Tandem mass spectrometry offers many advantages toward this aim, although the generic fragmentation method (low-energy collision-induced dissociation) shows clear limitations and is often insufficient to retrieve some essential structural information on these molecules. In this work, we present the first application of helium charge transfer dissociation (He-CTD) to characterize the structure of complex oligosaccharides. We compare this method with low-energy collision-induced dissociation and extreme-ultraviolet dissociative photoionization (XUV-DPI), which was shown previously to ensure the successful characterization of complex glycans. Similarly to what could be obtained by XUV-DPI, He-CTD provides a complete description of the investigated structures by producing many informative cross-ring fragments and no ambiguous fragmentation. Unlike XUV-DPI, which is performed at a synchrotron source, He-CTD has the undeniable advantage of being implementable in a conventional benchtop ion trap in a conventional laboratory setting.

  19. Molecular studies of Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Zhang, Yong

    2017-10-01

    Circumstellar envelopes (CEs) around evolved stars are an active site for the production of molecules. After evolving through the Asymptotic Giant Branch (AGB), proto-planetary nebula (PPN), to planetary nebula (PN) phases, CEs ultimately merge with the interstellar medium (ISM). The study of molecules in PNe, therefore, is essential to understanding the transition from stellar to interstellar materials. So far, over 20 molecular species have been discovered in PNe. The molecular composition of PNe is rather different from those of AGB and PPNe, suggesting that the molecules synthesized in PN progenitors have been heavily processed by strong ultraviolet radiation from the central star. Intriguingly, fullerenes and complex organic compounds having aromatic and aliphatic structures can be rapidly formed and largely survive during the PPN/PN evolution. The similar molecular compositions in PNe and diffuse clouds as well as the detection of C60 + in the ISM reinforce the view that the mass-loss from PNe can significantly enrich the ISM with molecular species, some of which may be responsible for the diffuse interstellar bands. In this contribution, I briefly summarize some recent observations of molecules in PNe, with emphasis on their implications on circumstellar chemistry.

  20. Water Fountains in the Sky: Streaming Water Jets from Aging Star Provide Clues to Planetary-Nebula Formation

    NASA Astrophysics Data System (ADS)

    2002-06-01

    reach the end of their "normal" lives, in which they are powered by nuclear fusion of hydrogen atoms in their cores, they begin to blow off their outer atmospheres, then eventually collapse to a white dwarf, about the size of the Earth. Intense ultraviolet radiation from the white dwarf causes the gas thrown off earlier to glow, producing a planetary nebula. Planetary nebulae, many visible to amateurs with backyard telescopes, have been studied by astronomers for years. About 1600 planetary nebulae have been found, and astronomers believe many more exist in our Milky Way Galaxy. Some are spherical, but most are not, displaying a variety of often intricate, beautiful shapes. The fact that many of these objects are not spherical was long known, but a series of spectacular images made with the Hubble Space Telescope in 1997 reinforced that fact dramatically. "The problem for scientists is, how do you get from a star that we know is a sphere to a planetary nebula that is far from being a sphere and yet came from that star," said Imai. Some theorists suggested that old stars must be somehow producing jets of material that help form the odd-shaped planetary nebulae, but such jets had, until now, never been seen. W43A was known to have regions near it in which water molecules are amplifying, or strengthening, radio emission at a frequency of 22 GigaHertz. Such regions are called masers, because they amplify microwave radiation the same way a laser amplifies light radiation. Imai's team used the VLBA, the sharpest radio "eye" in the world, to find out where these masers are. To their surprise, they found that the maser regions are strung out in two curved lines, moving in opposite directions from the star at about 325,000 miles per hour. "The path of the jets is curved like a corkscrew, as if whatever is squirting them out is slowly rotating, or precessing, like a child's top wobbles just before it falls down," said Diamond. What is producing the jets? "We're not sure," Diamond