Sample records for nebulae iv synthesis

  1. 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

  2. Organic Analysis of Catalytic Fischer-Tropsch Synthesis Products and Ordinary Chondrite Meteorites by Stepwise Pyrolysis-GCMS: Organics in the Early Solar Nebula

    NASA Technical Reports Server (NTRS)

    Locke, Darren R.; Yazzie, Cyriah A.; Burton, Aaron S.; Niles, Paul B.; Johnson, Natasha M.

    2014-01-01

    Abiotic generation of complex organic compounds, in the early solar nebula that formed our solar system, is hypothesized by some to occur via Fischer-Tropsch (FT) synthesis. In its simplest form, FT synthesis involves the low temperature (<300degC) catalytic reaction of hydrogen and carbon monoxide gases to form more complex hydrocarbon compounds, primarily n-alkanes, via reactive nano-particulate iron, nickel, or cobalt, for example. Industrially, this type of synthesis has been utilized in the gas-to-liquid process to convert syngas, produced from coal, natural gas, or biomass, into paraffin waxes that can be cracked to produce liquid diesel fuels. In general, the effect of increasing reaction temperature (>300degC) produces FT products that include lesser amounts of n-alkanes and greater alkene, alcohol, and polycyclic aromatic hydrocarbon (PAH) compounds. We have begun to experimentally investigate FT synthesis in the context of abiotic generation of organic compounds in the early solar nebula. It is generally thought that the early solar nebula included abundant hydrogen and carbon monoxide gases and nano-particulate matter such as iron and metal silicates that could have catalyzed the FT reaction. The effect of FT reaction temperature, catalyst type, and experiment duration on the resulting products is being investigated. These solid organic products are analyzed by thermal-stepwise pyrolysis-GCMS and yield the types and distribution of hydrocarbon compounds released as a function of temperature. We show how the FT products vary by reaction temperature, catalyst type, and experimental duration and compare these products to organic compounds found to be indigenous to ordinary chondrite meteorites. We hypothesize that the origin of organics in some chondritic meteorites, that represent an aggregation of materials from the early solar system, may at least in part be from FT synthesis that occurred in the early solar nebula.

  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. Actinide Corroles: Synthesis and Characterization of Thorium(IV) and Uranium(IV) bis(-chloride) Dimers

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

    Ward, Ashleigh L.; Buckley, Heather L.; Gryko, Daniel T.

    2013-12-01

    The first synthesis and structural characterization of actinide corroles is presented. Thorium(IV) and uranium(IV) macrocycles of Mes2(p-OMePh)corrole were synthesised and characterized by single-crystal X-ray diffraction, UV-Visible spectroscopy, variable-temperature 1H NMR, ESI mass spectrometry and cyclic voltammetry.

  5. 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

  6. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula.

    PubMed

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-06-09

    In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)-CO-N2-noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system.

  7. 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.

  8. Synthesis of refractory organic matter in the ionized gas phase of the solar nebula

    PubMed Central

    Kuga, Maïa; Marty, Bernard; Marrocchi, Yves; Tissandier, Laurent

    2015-01-01

    In the nascent solar system, primitive organic matter was a major contributor of volatile elements to planetary bodies, and could have played a key role in the development of the biosphere. However, the origin of primitive organics is poorly understood. Most scenarios advocate cold synthesis in the interstellar medium or in the outer solar system. Here, we report the synthesis of solid organics under ionizing conditions in a plasma setup from gas mixtures (H2(O)−CO−N2−noble gases) reminiscent of the protosolar nebula composition. Ionization of the gas phase was achieved at temperatures up to 1,000 K. Synthesized solid compounds share chemical and structural features with chondritic organics, and noble gases trapped during the experiments reproduce the elemental and isotopic fractionations observed in primitive organics. These results strongly suggest that both the formation of chondritic refractory organics and the trapping of noble gases took place simultaneously in the ionized areas of the protoplanetary disk, via photon- and/or electron-driven reactions and processing. Thus, synthesis of primitive organics might not have required a cold environment and could have occurred anywhere the disk is ionized, including in its warm regions. This scenario also supports N2 photodissociation as the cause of the large nitrogen isotopic range in the solar system. PMID:26039983

  9. 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

  10. 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...

  11. Highly ionized gas in the Gum nebula and elsewhere - A comparison of IUE and Copernicus satellite results

    NASA Technical Reports Server (NTRS)

    Edgar, Richard J.; Savage, Blair D.

    1992-01-01

    The data from six high-dispersion IUE echelle spectra are averaged in order to obtain an interstellar absorption line spectrum with an S/N of about 30 and a resolution of about 25 km/s. The interstellar lines of C IV and Si IV are very strong and broad and N V is detected. The profiles for these species and Al III are compared to the Copernicus satellite profiles for O VI. The high ionization lines toward HD 64760 are much stronger and broader than those recorded toward Zeta Pup and Gamma super 2 Vel, the two exciting stars of the Gum nebula. The profiles for Al III and Si IV are similar and considerably narrower than the O VI profile. An origin in photoionized Gum nebula gas is suggested as the most likely explanation for Al III and Si IV. The C IV profile has a high positive velocity wing extending to approximately +80 km/s, which is similar in appearance to the positive velocity portion of the O VI profile. It is inferred that a substantial part of the observed C IV has an origin in the collisionally ionized gas most likely rsponsible for the O VI.

  12. 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.

  13. 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.

  14. Titanium(IV) isopropoxide mediated synthesis of pyrimidin-4-ones.

    PubMed

    Ramanjulu, Joshi M; Demartino, Michael P; Lan, Yunfeng; Marquis, Robert

    2010-05-21

    A novel, one-step method for the synthesis of tri- and tetrasubstituted pyrimidin-4-ones is reported. This method involves a titanium(IV)-mediated cyclization involving two sequential condensations of primary and beta-ketoamides. The reaction is operationally facile, readily scalable, and offers rapid entry into differentially substituted pyrimidin-4-one scaffolds. The high functional group compatibility allows for substantial diversification in the products generated from this transformation.

  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. Synthesis and Characterization of Tin(IV) Oxide Obtained by Chemical Vapor Deposition Method

    NASA Astrophysics Data System (ADS)

    Nagirnyak, Svitlana V.; Lutz, Victoriya A.; Dontsova, Tatiana A.; Astrelin, Igor M.

    2016-07-01

    The effect of precursors on the characteristics of tin oxide obtained by chemical vapor deposition (CVD) method was investigated. The synthesis of nanosized tin(IV) oxide was carried out with the use of two different precursors: tin(II) oxalate obtained using tin chloride(II) and oxalic acid; tin(II) oxalate obtained using tin chloride(II); and ammonium oxalate. The synthesized tin(IV) oxide samples were studied by electron microscopy, X-ray diffraction and optical spectra. The lattice parameters of tin(IV) oxide samples were defined, the bandgap of samples were calculated.

  17. 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.

  18. 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

  19. 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.)

  20. Spectrophotometry of Bowen resonance fluorescence lines in three planetary nebulae

    NASA Technical Reports Server (NTRS)

    O'Dell, C. R.; Miller, Christopher O.

    1992-01-01

    The results are presented of a uniquely complete, carefully reduced set of observations of the O III Bowen fluorescence lines in the planetary nebulae NGC 6210, NGC 7027, and NGC 7662. A detailed comparison with the predictions of radiative excitation verify that some secondary lines are enhanced by selective population by the charge exchange mechanism involving O IV. Charge exchange is most important in NGC 6210, which is of significantly lower ionization than the other nebulae. In addition to the principal Bowen lines arising from Ly-alpha pumping of the O III O1 line, lines arising from pumping of the O3 line are also observed. Comparison of lines produced by O1 and O3 with the theoretical predictions of Neufeld indicate poor agreement; comparison with the theoretical predictions of Harrington show agreement with NGC 7027 and NGC 7662.

  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. Titanium(IV)-Catalyzed Stereoselective Synthesis of Spirooxindole-1-pyrrolines

    PubMed Central

    2015-01-01

    A stereoselective cyclization between alkylidene oxindoles and 5-methoxyoxazoles has been developed using catalytic titanium(IV) chloride (as low as 5 mol %) to afford spiro[3,3′-oxindole-1-pyrrolines] in excellent yield (up to 99%) and diastereoselectivity (up to 99:1). Using a chiral scandium(III)–indapybox/BArF complex affords enantioenriched spirooxindole-1-pyrrolines where a ligand-induced reversal of diastereoselectivity is observed. This methodology is further demonstrated for the synthesis of pyrrolines from malonate alkylidene and coumarin derivatives. PMID:25474118

  3. Ultraviolet absorption by highly ionized atoms in the Orion Nebula

    NASA Technical Reports Server (NTRS)

    Franco, J.; Savage, B. D.

    1982-01-01

    The International Ultraviolet Explorer was used to obtain high-resolution, far-UV spectra of theta 1 A, theta 1 C, theta 1 D, and theta 2 A Orionis. The interstellar absorption lines in these spectra are discussed with an emphasis on the high-ionization lines of C IV and Si IV. Theta 2 A Ori has interstellar C IV and Si IV absorption of moderate strength at the velocity found for normal H II region ions. Theta 1 C Ori has very strong interstellar C IV and Si IV absorption at velocities blueshifted by about 25 km/s from that found for the normal H II region ions. The possible origin of the high-ionization lines by three processes is considered: X-ray ionization, collisional ionization, and UV photoionization. It is concluded that the C IV and Si IV ions toward theta 2 A and theta 1 C Ori are likely produced by UV photoionization of surrounding nebular gas. In the case of theta 1 C Ori, the velocity shift of the high-ionization lines may be produced through the acceleration of high-density globules in the core of the nebula by the stellar wind of theta 1 C Ori.

  4. 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

  5. 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.

  6. 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.

  7. Design, synthesis and biological evaluation of novel pyrazolo-pyrimidinones as DPP-IV inhibitors in diabetes.

    PubMed

    Sagar, Sneha R; Agarwal, Jessica K; Pandya, Dhaivat H; Dash, Ranjeet Prasad; Nivsarkar, Manish; Vasu, Kamala K

    2015-10-15

    We report the design, synthesis, biological activity and docking studies of series of novel pyrazolo[3,4-d]pyrimidinones as DPP-IV inhibitors in diabetes. Molecules were synthesized and evaluated for their DPP-IV inhibition activity. Compounds 5e, 5k, 5o and 6a were found to be potent inhibitors of DPP-IV enzyme. Amongst all the synthesized compounds, 6-methyl-5-(4-methylpyridin-2-yl)-1-phenyl-1H-pyrazolo[3,4-d]pyrimidin-4(5H)-one (5k) was found to be the most active based on in vitro DPP-IV studies and also exhibited promising in vivo blood glucose lowering activity in male Wistar rats. Copyright © 2015. Published by Elsevier Ltd.

  8. Organic synthesis via irradiation and warming of ice grains in the solar nebula.

    PubMed

    Ciesla, Fred J; Sandford, Scott A

    2012-04-27

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments to which they were exposed. We found that icy grains originating in the outer disk, where temperatures were less than 30 kelvin, experienced ultraviolet irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural by-products of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

  9. Organic Synthesis via Irradiation and Warming of Ice Grains in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Ciesla, Fred J.; Sanford, Scott A.

    2012-01-01

    Complex organic compounds, including many important to life on Earth, are commonly found in meteoritic and cometary samples, though their origins remain a mystery. We examined whether such molecules could be produced within the solar nebula by tracking the dynamical evolution of ice grains in the nebula and recording the environments they were exposed to. We found that icy grains originating in the outer disk, where temperatures were less than 30 K, experienced UV irradiation exposures and thermal warming similar to that which has been shown to produce complex organics in laboratory experiments. These results imply that organic compounds are natural byproducts of protoplanetary disk evolution and should be important ingredients in the formation of all planetary systems, including our own.

  10. 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.

  11. 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.

  12. Design and synthesis of aminocoumarin derivatives as DPP-IV inhibitors and anticancer agents.

    PubMed

    Soni, Rina; Soman, Shubhangi S

    2018-09-01

    DPP-IV "a moonlighting protein" has immerged as promising pathway to control Type 2 diabetes as well as found to play key role in earlier stages of cancer. Here we have reported design, synthesis and applications of aminocoumarin derivatives as DPP-IV inhibitors. Compounds have been synthesized and studied for their DPP-IV inhibition activity. Three compounds have shown moderate inhibition at 100 µM concentration. All compounds were also screened for their anticancer activity against A549 (Lung cancer cell line), MCF-7 (Breast cancer cell line) using MTT assay. One of the compounds has shown very good anticancer activity with IC 50 value 24 ± 0.1 nM against A549 cell line. Copyright © 2018 Elsevier Inc. All rights reserved.

  13. Aperture-synthesis observations of carbon monoxide in the Egg Nebula

    NASA Technical Reports Server (NTRS)

    Heiligman, G. M.; Berge, G. L.; Claussen, M. J.; Leighton, R. B.; Lo, K. Y.; Masson, C. R.; Moffet, A. T.; Phillips, T. G.; Sargent, A. I.; Wannier, P. G.

    1986-01-01

    Observations of the 2.6-mm CO emission of the bipolar nebular CRL 2688, obtained with resolution 7 arcsec using the mm-wave interferometer at Owens Valley during December 1982-June 1983, are reported. The emission of a 10 x 15-arcsec core, centered on the optical reflection nebula and probably surrounded by a large cloud of cooler gas, is found to have a main-axis velocity gradient of 3 km/s arcsec and an excitation temperature of about 70 K.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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

  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. 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)

  1. High-temperature Ionization-induced Synthesis of Biologically Relevant Molecules in the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Bekaert, David V.; Derenne, Sylvie; Tissandier, Laurent; Marrocchi, Yves; Charnoz, Sebastien; Anquetil, Christelle; Marty, Bernard

    2018-06-01

    Biologically relevant molecules (hereafter biomolecules) have been commonly observed in extraterrestrial samples, but the mechanisms accounting for their synthesis in space are not well understood. While electron-driven production of organic solids from gas mixtures reminiscent of the photosphere of the protosolar nebula (PSN; i.e., dominated by CO–N2–H2) successfully reproduced key specific features of the chondritic insoluble organic matter (e.g., elementary and isotopic signatures of chondritic noble gases), the molecular diversity of organic materials has never been investigated. Here, we report that a large range of biomolecules detected in meteorites and comets can be synthesized under conditions typical of the irradiated gas phase of the PSN at temperatures = 800 K. Our results suggest that organic materials—including biomolecules—produced within the photosphere would have been widely dispersed in the protoplanetary disk through turbulent diffusion, providing a mechanism for the distribution of organic meteoritic precursors prior to any thermal/photoprocessing and subsequent modification by secondary parent body processes. Using a numerical model of dust transport in a turbulent disk, we propose that organic materials produced in the photosphere of the disk would likely be associated with small dust particles, which are coupled to the motion of gas within the disk and therefore preferentially lofted into the upper layers of the disk where organosynthesis occurs.

  2. 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.

  3. 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.

  4. 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

  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. Where Do Messy Planetary Nebulae Come From?

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2017-03-01

    If you examined images of planetary nebulae, you would find that many of them have an appearance that is too messy to be accounted for in the standard model of how planetary nebulae form. So what causes these structures?Examples of planetary nebulae that have a low probability of having beenshaped by a triple stellar system. They are mostly symmetric, with only slight departures (labeled) that can be explained by instabilities, interactions with the interstellar medium, etc. [Bear and Soker 2017]A Range of LooksAt the end of a stars lifetime, in the red-giant phase, strong stellar winds can expel the outer layers of the star. The hot, luminous core then radiates in ultraviolet, ionizing the gas of the ejected stellar layers and causing them to shine as a brightly colored planetary nebula for a few tens of thousands of years.Planetary nebulae come in a wide variety of morphologies. Some are approximately spherical, but others can be elliptical, bipolar, quadrupolar, or even more complex.Its been suggested that non-spherical planetary nebulae might be shaped by the presence of a second star in a binary system with the source of the nebula but even this scenario should still produce a structure with axial or mirror symmetry.A pair of scientists from Technion Israel Institute of Technology, Ealeal Bear and Noam Soker, argue that planetary nebulae with especially messy morphologies those without clear axial or point symmetries may have been shaped by an interacting triple stellar system instead.Examples of planetary nebulae that might have been shaped by a triple stellar system. They have some deviations from symmetry but also show signs of interacting with the interstellar medium. [Bear and Soker 2017]Departures from SymmetryTo examine this possibility more closely, Bear and Soker look at a sample of thousands planetary nebulae and qualitatively classify each of them into one of four categories, based on the degree to which they show signs of having been shaped by a

  7. The Remarkable Synchrotron Nebula Associated with PSR J1015-5719

    NASA Astrophysics Data System (ADS)

    Ng, Chi Yung; Bandiera, Rino; Hunstead, Richard; Johnston, Simon

    2017-08-01

    We report the discovery of a synchrotron nebula G283.1-0.59 associated with the young and energetic pulsar J1015-5719. Radio observations using the Molonglo Observatory Synthesis Telescope (MOST) and the Australia Telescope Compact Array (ATCA) at 36, 16, 6, and 3 cm reveal a complex morphology for the source. The pulsar is embedded in the "head" of the nebula with fan-shaped diffuse emission. This is connected to a circular bubble structure of 20" radius and followed by a collimated tail extending over 1'. Polarization measurements show a highly ordered magnetic field in the nebula. The intrinsic B-field wraps around the edge of the head and shows an azimuthal configuration near the pulsar, then switches direction quasi-periodically near the bubble and in the tail. Together with the flat radio spectrum observed, we suggest that this system is most plausibly a pulsar wind nebula (PWN), with the head as a bow shock that has a low Mach number and the bubble as a shell expanding in a dense environment, possibly due to flow instabilities. In addition, the bubble could act as a magnetic bottle trapping the relativistic particles. A comparison with other bow-shock PWNe with higher Mach numbers shows similar structure and B-field geometry, implying that pulsar velocity may not be the most critical factor in determining the properties of these systems.ATCA is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. MOST is operated by The University of Sydney with support from the Australian Research Council and the Science Foundation for Physics within the University of Sydney. This work is supported by an ECS grant under HKU 709713P.

  8. 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

  9. DISCOVERY OF RUBIDIUM, CADMIUM, AND GERMANIUM EMISSION LINES IN THE NEAR-INFRARED SPECTRA OF PLANETARY NEBULAE

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

    Sterling, N. C.; Dinerstein, Harriet L.; Kaplan, Kyle F.

    We identify [Rb iv] 1.5973 and [Cd iv] 1.7204 μm emission lines in high-resolution (R = 40,000) near-infrared spectra of the planetary nebulae (PNe) NGC 7027 and IC 5117, obtained with the Immersion GRating INfrared Spectrometer (IGRINS) on the 2.7 m telescope at McDonald Observatory. We also identify [Ge vi] 2.1930 μm in NGC 7027. Alternate identifications for these features are ruled out based on the absence of other multiplet members and/or transitions with the same upper levels. Ge, Rb, and Cd can be enriched in PNe by s-process nucleosynthesis during the asymptotic giant branch stage of evolution. To determine ionic abundances, we calculate [Rb iv] collision strengthsmore » and use approximations for those of [Cd iv] and [Ge vi]. Our identification of [Rb iv] 1.5973 μm is supported by the agreement between Rb{sup 3+}/H{sup +} abundances found from this line and the 5759.55 Å feature in NGC 7027. Elemental Rb, Cd, and Ge abundances are derived with ionization corrections based on similarities in ionization potential ranges between the detected ions and O and Ne ionization states. Our analysis indicates abundances 2–4 times solar for Rb and Cd in both nebulae. Ge is subsolar in NGC 7027, but its abundance is uncertain due to the large and uncertain ionization correction. The general consistency of the measured relative s-process enrichments with predictions from models appropriate for these PNe (2.0–2.5 M{sub ⊙}, [Fe/H] = −0.37) demonstrates the potential of using PN compositions to test s-process nucleosynthesis models.« less

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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

  15. Revisiting the Orion Nebula

    NASA Astrophysics Data System (ADS)

    2004-06-01

    Orion the Hunter is perhaps the best-known constellation in the sky, well placed in the winter for observers in both the northern and southern hemispheres, and instantly recognisable. Just below Orion's belt (three distinctive stars in a row), the hilt of his sword holds a great jewel in the sky, the beautiful Orion Nebula. Bright enough to be seen with the naked eye, the nebula, also known as Messier 42, is a wide complex of gas and dust, illuminated by several massive and hot stars at its core, the famous Trapezium stars. For astronomers, Orion is surely one of the most important constellations, as it contains one of the nearest and most active stellar nurseries in the Milky Way, the galaxy in which we live. Here tens of thousands of new stars have formed within the past ten million years or so - a very short span of time in astronomical terms. For comparison: our own Sun is now 4,600 million years old and has not yet reached half-age. Reduced to a human time-scale, star formation in Orion would have been going on for just one month as compared to the Sun's 40 years. In fact, located at a distance of 1500 light years, the Orion Nebula plays such an important role in astrophysics that it can be argued that our understanding of star formation is for a large part based on the Orion Nebula. It is thus no surprise that the Orion Nebula is one of the most studied objects in the night sky (see for example the various related ESO Press Photos and Releases: ESO Press Photo 03a/98, ESO Press Photos 03a-d/01, ESO Press Photos 12a-e/01, ESO Press Release 14/01,...). The richness of the stellar cluster inside the Orion Nebula makes it an ideal, and unique, target for high resolution and wide-field imaging. Following some pioneering work made a few years ago, an international team of astronomers [1], led by Massimo Robberto (European Space Agency and Space Telescope Science Institute), used the Wide Field Imager (WFI), a 67-million pixel digital camera that is installed at the

  16. SALT HRS discovery of a long-period double-degenerate binary in the planetary nebula NGC 1360

    NASA Astrophysics Data System (ADS)

    Miszalski, B.; Manick, R.; Mikołajewska, J.; Iłkiewicz, K.; Kamath, D.; Van Winckel, H.

    2018-01-01

    Whether planetary nebulae (PNe) are predominantly the product of binary stellar evolution as some population synthesis models (PSM) suggest remains an open question. Around 50 short-period binary central stars (P ∼ 1 d) are known, but with only four with measured orbital periods over 10 d, our knowledge is severely incomplete. Here we report on the first discovery from a systematic Southern African Large Telescope (SALT) High Resolution Spectrograph (HRS) survey for long-period binary central stars. We find a 142 d orbital period from radial velocities of the central star of NGC 1360, HIP 16566. NGC 1360 appears to be the product of common-envelope (CE) evolution, with nebula features similar to post-CE PNe, albeit with an orbital period considerably longer than expected to be typical of post-CE PSM. The most striking feature is a newly identified ring of candidate low-ionization structures. Previous spatiokinematic modelling of the nebula gives a nebula inclination of 30° ± 10°, and assuming the binary nucleus is coplanar with the nebula, multiwavelength observations best fit a more massive, evolved white dwarf (WD) companion. A WD companion in a 142 d orbit is not the focus of many PSM, making NGC 1360 a valuable system with which to improve future PSM work. HIP 16566 is amongst many central stars in which large radial velocity variability was found by low-resolution surveys. The discovery of its binary nature may indicate long-period binaries may be more common than PSM models predict.

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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

  14. Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via Ti(II)/Ti(IV) redox catalysis.

    PubMed

    Gilbert, Zachary W; Hue, Ryan J; Tonks, Ian A

    2016-01-01

    Pyrroles are structurally important heterocycles. However, the synthesis of polysubstituted pyrroles is often challenging. Here, we report a multicomponent, Ti-catalysed formal [2+2+1] reaction of alkynes and diazenes for the oxidative synthesis of penta- and trisubstituted pyrroles: a nitrenoid analogue to classical Pauson-Khand-type syntheses of cyclopentenones. Given the scarcity of early transition-metal redox catalysis, preliminary mechanistic studies are presented. Initial stoichiometric and kinetic studies indicate that the mechanism of this reaction proceeds through a formally Ti(II)/Ti(IV) redox catalytic cycle, in which an azatitanacyclobutene intermediate, resulting from [2+2] alkyne + Ti imido coupling, undergoes a second alkyne insertion followed by reductive elimination to yield pyrrole and a Ti(II) species. The key component for catalytic turnover is the reoxidation of the Ti(II) species to a Ti(IV) imido via the disproportionation of an η(2)-diazene-Ti(II) complex.

  15. Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via TiII/TiIV redox catalysis

    NASA Astrophysics Data System (ADS)

    Gilbert, Zachary W.; Hue, Ryan J.; Tonks, Ian A.

    2016-01-01

    Pyrroles are structurally important heterocycles. However, the synthesis of polysubstituted pyrroles is often challenging. Here, we report a multicomponent, Ti-catalysed formal [2+2+1] reaction of alkynes and diazenes for the oxidative synthesis of penta- and trisubstituted pyrroles: a nitrenoid analogue to classical Pauson-Khand-type syntheses of cyclopentenones. Given the scarcity of early transition-metal redox catalysis, preliminary mechanistic studies are presented. Initial stoichiometric and kinetic studies indicate that the mechanism of this reaction proceeds through a formally TiII/TiIV redox catalytic cycle, in which an azatitanacyclobutene intermediate, resulting from [2+2] alkyne + Ti imido coupling, undergoes a second alkyne insertion followed by reductive elimination to yield pyrrole and a TiII species. The key component for catalytic turnover is the reoxidation of the TiII species to a TiIV imido via the disproportionation of an η2-diazene-TiII complex.

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. A Search for Mid-Infrared Emission Lines of F and Na in Planetary Nebulae with EXES on SOFIA: Testing AGB Nucleosynthesis

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet L.; Sterling, N. C.; Richter, Matthew J.; DeWitt, Curtis; Montiel, Edward J.; Karakas, Amanda I.

    2018-01-01

    We report results from a search for mid-infrared emission lines of F (Z = 9) and Na (Z =11) in planetary nebulae using the Echelon-Cross-Echelle Spectrometer, EXES (DeWitt, C., et al. 2012, SPIE, 8446, id. 84461A) on the Stratospheric Facility for Infrared Astronomy (SOFIA Young et al. 2012, ApJL, 749, L17). As the envelopes of former AGB stars, planetary nebulae carry the imprint of all nuclear reactions that occurred over the star’s lifetime. Complex sequences of reactions during the late evolutionary stages may produce – or in some cases destroy – F and Na. Due to sensitivity to uncertainties in the interior physical conditions and key processes (e.g. convection, mass loss), their predicted final abundances vary widely for different sets of theoretical models (Karakas & Lugaro 2016, ApJ, 825, 26). During a flight series with EXES in May 2017, we looked for [Na III] 7.39 μm and the as-yet undetected fine structure transitions [F IV] 25.8 μm and [F V] 13.4 μm. The F lines were observed at resolving power R = 50,000, while Na was observed with R ≈ 2000. We observed a spectral region containing the [F IV] line and [O IV] 25.9 μm in 3 planetary nebulae descended from stars of ≈ 2.5 – 4 M⊙ (NGC 6886, NGC 7027, and Hb 5), and [F V] in NGC 7027 only. We observed NGC 6886 and IC 5117 in the [Na III] setting, which included the H I 6-5 Pfund α line at 7.46 μm. Simultaneous measurement of O+3 and H+ enables us to derive reliable ionic abundance ratios from the [F IV] and [Na III] lines. We obtained high S/N on the [Na III] line in IC 5117 but were unsuccessful in detecting either F line in any of our targets. We present our upper limits, compare them to values in the literature from optical spectra, and discuss our findings in the context of evolutionary models.This research is supported by NASA/USRA subcontract SOF 05-0121. Support for EXES is provided via collaborative agreement NNXAI85A between NASA Ames Research Center and the University of

  1. 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

  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 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.

  4. 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.

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. New portrait of Omega Nebula's glistening watercolours

    NASA Astrophysics Data System (ADS)

    2009-07-01

    The Omega Nebula, sometimes called the Swan Nebula, is a dazzling stellar nursery located about 5500 light-years away towards the constellation of Sagittarius (the Archer). An active star-forming region of gas and dust about 15 light-years across, the nebula has recently spawned a cluster of massive, hot stars. The intense light and strong winds from these hulking infants have carved remarkable filigree structures in the gas and dust. When seen through a small telescope the nebula has a shape that reminds some observers of the final letter of the Greek alphabet, omega, while others see a swan with its distinctive long, curved neck. Yet other nicknames for this evocative cosmic landmark include the Horseshoe and the Lobster Nebula. Swiss astronomer Jean-Philippe Loys de Chéseaux discovered the nebula around 1745. The French comet hunter Charles Messier independently rediscovered it about twenty years later and included it as number 17 in his famous catalogue. In a small telescope, the Omega Nebula appears as an enigmatic ghostly bar of light set against the star fields of the Milky Way. Early observers were unsure whether this curiosity was really a cloud of gas or a remote cluster of stars too faint to be resolved. In 1866, William Huggins settled the debate when he confirmed the Omega Nebula to be a cloud of glowing gas, through the use of a new instrument, the astronomical spectrograph. In recent years, astronomers have discovered that the Omega Nebula is one of the youngest and most massive star-forming regions in the Milky Way. Active star-birth started a few million years ago and continues through today. The brightly shining gas shown in this picture is just a blister erupting from the side of a much larger dark cloud of molecular gas. The dust that is so prominent in this picture comes from the remains of massive hot stars that have ended their brief lives and ejected material back into space, as well as the cosmic detritus from which future suns form. The

  11. 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

  12. 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

  13. Stark broadening of Ca IV spectral lines of astrophysical interest

    NASA Astrophysics Data System (ADS)

    Alonso-Medina, A.; Colón, C.

    2014-12-01

    Ca IV emission lines are under the preview of Solar Ultraviolet Measurements of Emitted Radiation device aboard the Solar and Heliospheric Observatory. Also, lines of the Ca IV in planetary nebulae NGC 7027 were detected with the Short Wavelength Spectrometer on board the Infrared Space Observatory. These facts justify an attempt to provide new spectroscopic parameters of Ca IV. There are no theoretical or experimental Stark broadening data for Ca IV. Using the Griem semi-empirical approach and the COWAN code, we report in this paper calculated values of the Stark broadening parameters for 467 lines of Ca IV. They were calculated using a set of wavefunctions obtained by using Hartree-Fock relativistic calculations. These lines arising from 3s23p4ns (n = 4, 5), 3s23p44p, 3s23p4nd (n = 3, 4) configurations. Stark widths and shifts are presented for an electron density of 1017 cm-3 and temperatures T = 10 000, 20 000 and 50 200 K. As these data cannot be compared to others in the literature, we present an analysis of the different regularities of the values presented in this work.

  14. 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.

  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. BINARY CENTRAL STARS OF PLANETARY NEBULAE DISCOVERED THROUGH PHOTOMETRIC VARIABILITY. IV. THE CENTRAL STARS OF HaTr 4 AND Hf 2-2

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

    Hillwig, Todd C.; Schaub, S. C.; Bond, Howard E.

    We explore the photometrically variable central stars of the planetary nebulae HaTr 4 and Hf 2-2. Both have been classified as close binary star systems previously based on their light curves alone. Here, we present additional arguments and data confirming the identification of both as close binaries with an irradiated cool companion to the hot central star. We include updated light curves, orbital periods, and preliminary binary modeling for both systems. We also identify for the first time the central star of HaTr 4 as an eclipsing binary. Neither system has been well studied in the past, but we utilizemore » the small amount of existing data to limit possible binary parameters, including system inclination. These parameters are then compared to nebular parameters to further our knowledge of the relationship between binary central stars of planetary nebulae and nebular shaping and ejection.« less

  17. 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).

  18. 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

  19. 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

  20. Determination of hyperfine-induced transition rates from observations of a planetary nebula.

    PubMed

    Brage, Tomas; Judge, Philip G; Proffitt, Charles R

    2002-12-31

    Observations of the planetary nebula NGC3918 made with the STIS instrument on the Hubble Space Telescope reveal the first unambiguous detection of a hyperfine-induced transition 2s2p 3P(o)(0)-->2s2 1S0 in the berylliumlike emission line spectrum of N IV at 1487.89 A. A nebular model allows us to confirm a transition rate of 4x10(-4) sec(-1)+/-33% for this line. The measurement represents the first independent confirmation of the transition rate of hyperfine-induced lines in low ionization stages, and it provides support for the techniques used to compute these transitions for the determination of very low densities and isotope ratios.

  1. 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.

  2. 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.

  3. Synthesis of Molecular Oxygen via Irradiation of Ice Grains in the Protosolar Nebula

    NASA Astrophysics Data System (ADS)

    Mousis, O.; Ronnet, T.; Lunine, J. I.; Maggiolo, R.; Wurz, P.; Danger, G.; Bouquet, A.

    2018-05-01

    Molecular oxygen has been detected in the coma of comet 67P/Churyumov–Gerasimenko with a mean abundance of 3.80 ± 0.85% by the ROSINA mass spectrometer on board the Rosetta spacecraft. To account for the presence of this species in comet 67P/Churyumov–Gerasimenko, it has been shown that the radiolysis of ice grain precursors of comets is a viable mechanism in low-density environments, such as molecular clouds. Here, we investigate the alternative possibility that the icy grains present in the midplane of the protosolar nebula were irradiated during their vertical transport between the midplane and the upper layers over a large number of cycles, as a result of turbulent mixing. Consequently, these grains spent a non-negligible fraction of their lifetime in the disk’s upper regions, where the irradiation by cosmic rays was strong. To do so, we used a coupled disk-transport-irradiation model to calculate the time evolution of the molecular oxygen abundance radiolytically produced in ice grains. Our computations show that, even if a significant fraction of the icy particles has followed a back and forth cycle toward the upper layers of the disk over tens of millions of years, a timespan far exceeding the formation timescale of comet 67P/Churyumov–Gerasimenko, the amount of produced molecular oxygen is at least two orders of magnitude lower than the Rosetta observations. We conclude that the most likely scenario remains the formation of molecular oxygen in low-density environments, such as the presolar cloud, prior to the genesis of the protosolar nebula.

  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. 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

  6. 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.

  7. Synthesis and characterization of ester and amide derivatives of titanium(IV) carboxymethylphosphonate

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

    Melánová, Klára, E-mail: klara.melanova@upce.cz; Beneš, Ludvík; Trchová, Miroslava

    2013-06-15

    A set of layered ester and amide derivatives of titanium(IV) carboxymethylphosphonate was prepared by solvothermal treatment of amorphous titanium(IV) carboxymethylphosphonate with corresponding 1-alkanols, 1,ω-alkanediols, 1-aminoalkanes, 1,ω-diaminoalkanes and 1,ω-amino alcohols and characterized by powder X-ray diffraction, IR spectroscopy and thermogravimetric analysis. Whereas alkyl chains with one functional group form bilayers tilted to the layers, 1,ω-diaminoalkanes and most of 1,ω-alkanediols form bridges connecting the adjacent layers. In the case of amino alcohols, the alkyl chains form bilayer and either hydroxyl or amino group is used for bonding. This simple method for the synthesis of ester and amide derivatives does not require preparationmore » of acid chloride derivative as a precursor or pre-intercalation with alkylamines and can be used also for the preparation of ester and amide derivatives of titanium carboxyethylphosphonate and zirconium carboxymethylphosphonate. - Graphical abstract: Ester and amide derivatives of layered titanium carboxymethylphosphonate were prepared by solvothermal treatment of amorphous solid with alkanol or alkylamine. - Highlights: • Ester and amide derivatives of titanium carboxymethylphosphonate. • Solvothermal treatment of amorphous solid with alkanol or alkylamine. • Ester and amide formation confirmed by IR spectroscopy.« less

  8. 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.

  9. 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.

  10. Synthesis and Characterization of Cerium(IV) Metallocenes

    DOE PAGES

    Sutton, Andrew; Clark, David Lewis; Scott, Brian Lindley; ...

    2015-12-11

    In this study, by applying a salt metathesis approach between Ce(OtBu 3) 2(NO 3) 2(THF) 2 and the potassium salts of mono- and ditrimethylsilyl substituted cyclopentadienes, we were able to isolate two new Ce(IV) metallocenes, including to the best of our knowledge, the first structurally characterized bis-cyclopentadiene Ce(IV) compound.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  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. 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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. Herschel Planetary Nebula Survey (HerPlaNS). hydrogen recombination laser lines in Mz 3

    NASA Astrophysics Data System (ADS)

    Aleman, Isabel; Exter, Katrina; Ueta, Toshiya; Walton, Samuel; Tielens, A. G. G. M.; Zijlstra, Albert; Montez, Rodolfo; Abraham, Zulema; Otsuka, Masaaki; Beaklini, Pedro P. B.; van Hoof, Peter A. M.; Villaver, Eva; Leal-Ferreira, Marcelo L.; Mendoza, Edgar; Lépine, Jacques D. R.

    2018-07-01

    The bipolar nebula Menzel 3 (Mz 3) was observed as part of the Herschel Planetary Nebula Survey (HerPlaNS), which used the PACS and SPIRE instruments aboard the Herschel Space Observatory to study a sample of planetary nebulae (PNe). In this paper, one of the series describing HerPlaNS results, we report the detection of H I recombination lines (HRLs) in the spectrum of Mz 3. Inspection of the spectrum reveals the presence of 12 HRLs in the 55-680 µm range covered by the PACS and SPIRE instruments (H11α to H21α and H14β). The presence of HRLs in this range is unusual for PNe and has not been reported in Mz 3 before. Our analysis indicates that the HRLs we observed are enhanced by laser effect occurring in the core of Mz 3. Our arguments for this are (i) the available Mz 3 optical to submillimetre HRL α line intensity ratios are not well reproduced by the spontaneous emission of optically thin ionized gas, as would be typical for nebular gas in PNe; (ii) the compact core of Mz 3 is responsible for a large fraction of the Herschel HRLs emission; (iii) the line intensity ratios for Mz 3 are very similar to those in the core emission of the well known star MWC 349A, where laser effect is responsible for the enhancement of HRLs in the Herschel wavelength range; (iv) the physical characteristics relevant to cause laser effect in the core of MWC 349A are very similar to those in the core of Mz 3.

  10. 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

  11. 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

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. Beta-ketoacyl-acyl carrier protein synthase IV: a key enzyme for regulation of medium-chain fatty acid synthesis in Cuphea lanceolata seeds.

    PubMed

    Schütt, Burkhardt Siegfried; Abbadi, Amine; Loddenkötter, Brigitte; Brummel, Monika; Spener, Friedrich

    2002-09-01

    With the aim of elucidating the mechanisms involved in the biosynthesis of medium-chain fatty acids in Cuphea lanceolata Ait., a crop accumulating up to 90% decanoic acid in seed triacylglycerols, cDNA clones of a beta-ketoacyl-acyl carrier protein (ACP) synthase IV (clKAS IV, EC 2.3.1.41) were isolated from C. lanceolata seed embryos. The amino acid sequence deduced from clKAS IV cDNA showed 80% identity to other plant KAS II-type enzymes, 55% identity towards plant KAS I and over 90% towards other Cuphea KAS IV-type sequences. Recombinant clKAS IV was functionally overexpressed in Escherichia coli, and substrate specificity of purified enzyme showed strong preference for elongation of short-chain and medium-chain acyl-ACPs (C4- to C10-ACP) with nearly equal activity. Further elongation steps were catalysed with distinctly less activity. Moreover, short- and medium-chain acyl-ACPs exerted a chain-length-specific and concentration-dependent substrate inhibition of clKAS IV. Based on these findings a regulatory mechanism for medium-chain fatty acid synthesis in C. lanceolata is presented.

  18. '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

  19. 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.

  20. 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.

  1. 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

  2. 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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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.

  8. Asymmetric synthesis of a potent, aminopiperidine-fused imidazopyridine dipeptidyl peptidase IV inhibitor.

    PubMed

    Xu, Feng; Corley, Edward; Zacuto, Michael; Conlon, David A; Pipik, Brenda; Humphrey, Guy; Murry, Jerry; Tschaen, David

    2010-03-05

    A practical asymmetric synthesis of a novel aminopiperidine-fused imidazopyridine dipeptidyl peptidase IV (DPP-4) inhibitor 1 has been developed. Application of a unique three-component cascade coupling with chiral nitro diester 7, which is easily accessed via a highly enantioselective Michael addition of dimethyl malonate to a nitrostyrene, allows for the assembly of the functionalized piperidinone skeleton in one pot. Through a base-catalyzed, dynamic crystallization-driven process, the cis-piperidionone 16a is epimerized to the desired trans isomer 16b, which is directly crystallized from the crude reaction stream in high yield and purity. Isomerization of the allylamide 16b in the presence of RhCl(3) is achieved without any epimerization of the acid/base labile stereogenic center adjacent to the nitro group on the piperidinone ring, while the undesired enamine intermediate is consumed to <0.5% by utilizing a trace amount of HCl generated from RhCl(3). The amino lactam 4, obtained through hydrogenation and hydrolysis, is isolated as its crystalline pTSA salt from the reaction solution directly, as such intramolecular transamidation has been dramatically suppressed via kinetic control. Finally, a Cu(I) catalyzed coupling-cyclization allows for the formation of the tricyclic structure of the potent DPP-4 inhibitor 1. The synthesis, which is suitable for large scale preparation, is accomplished in 23% overall yield.

  9. 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).

  10. 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)

  11. 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.

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. THE TRIFID NEBULA: STELLAR SIBLING RIVALRY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This NASA Hubble Space Telescope image of the Trifid Nebula reveals a stellar nursery being torn apart by radiation from a nearby, massive star. The picture also provides a peek at embryonic stars forming within an ill-fated cloud of dust and gas, which is destined to be eaten away by the glare from the massive neighbor. This stellar activity is a beautiful example of how the life cycles of stars like our Sun is intimately connected with their more powerful siblings. The Hubble image shows a small part of a dense cloud of dust and gas, a stellar nursery full of embryonic stars. This cloud is about 8 light-years away from the nebula's central star, which is beyond the top of this picture. Located about 9,000 light-years from Earth, the Trifid resides in the constellation Sagittarius. A stellar jet [the thin, wispy object pointing to the upper left] protrudes from the head of a dense cloud and extends three-quarters of a light-year into the nebula. The jet's source is a very young stellar object that lies buried within the cloud. Jets such as this are the exhaust gases of star formation. Radiation from the massive star at the center of the nebula is making the gas in the jet glow, just as it causes the rest of the nebula to glow. The jet in the Trifid is a 'ticker tape,' telling the history of one particular young stellar object that is continuing to grow as its gravity draws in gas from its surroundings. But this particular ticker tape will not run for much longer. Within the next 10,000 years the glare from the central, massive star will continue to erode the nebula, overrunning the forming star, and bringing its growth to an abrupt and possibly premature end. Another nearby star may have already faced this fate. The Hubble picture shows a 'stalk' [the finger-like object] pointing from the head of the dense cloud directly toward the star that powers the Trifid. This stalk is a prominent example of the evaporating gaseous globules, or 'EGGs,' that were seen

  17. 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.

  18. 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.

  19. 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

  20. 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

  1. 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.

  2. 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.

  3. 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.

  4. 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

  5. An upper limit on interstellar C IV in the spectrum of gamma-2 Velorum

    NASA Technical Reports Server (NTRS)

    Lengyel-Frey, D.; Stecher, T. P.; West, D. K.

    1975-01-01

    An upper limit on the column density of C IV along the line of sight to gamma-2 Vel is derived from upper limits placed on the equivalent widths of the interstellar C IV doublet with rest wavelengths at 1548.20 A and 1550.77 A. A lower limit of 250,000 K is calculated for the electron temperature of O VI emitting regions by combining the C IV results with a measurement of the column density of interstellar O VI for the same star and using calculations for the relative ionization of some abundant elements as a function of electron temperature in a low-density plasma. Since gamma-2 Vel is in the central part of the Gum Nebula, the high temperature suggested by these results is shown to support the idea that a high-temperature phase of the interstellar medium, possibly maintained by supernova explosions, may exist.-

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.

  5. Deep He II and C IV Spectroscopy of a Giant Lyα Nebula: Dense Compact Gas Clumps in the Circumgalactic Medium of a z ~ 2 Quasar

    NASA Astrophysics Data System (ADS)

    Arrigoni Battaia, Fabrizio; Hennawi, Joseph F.; Prochaska, J. Xavier; Cantalupo, Sebastiano

    2015-08-01

    The recent discovery by Cantalupo et al. of the largest (˜500 kpc) luminous (L ≃ 1.43 × 1045 erg s-1) Lyα nebula associated with the quasar UM287 (z = 2.279) poses a great challenge to our current understanding of the astrophysics of the halos hosting massive z ˜ 2 galaxies. Either an enormous reservoir of cool gas is required M ≃ 1012 M⊙, exceeding the expected baryonic mass available, or one must invoke extreme gas clumping factors not present in high-resolution cosmological simulations. However, observations of Lyα emission alone cannot distinguish between these two scenarios. We have obtained the deepest ever spectroscopic integrations in the He ii λ1640 and C iv λ1549 emission lines with the goal of detecting extended line emission, but detect neither line to a 3σ limiting SB ≃ 10-18 erg s-1 cm-2 arcsec-2. We construct simple models of the expected emission spectrum in the highly probable scenario that the nebula is powered by photoionization from the central hyper-luminous quasar. The non-detection of He ii implies that the nebular emission arises from a mass Mc ≲ 6.4 × 1010 M⊙ of cool gas on ˜200 kpc scales, distributed in a population of remarkably dense (nH ≳ 3 cm-3) and compact (R ≲ 20 pc) clouds, which would clearly be unresolved by current cosmological simulations. Given the large gas motions suggested by the Lyα line (v ≃ 500 km s-1), it is unclear how these clouds survive without being disrupted by hydrodynamic instabilities. Our work serves as a benchmark for future deep integrations with current and planned wide-field IFU spectrographs such as MUSE, KCWI, and KMOS. Our observations and models suggest that a ≃10 hr exposure would likely detect ˜10 rest-frame UV/optical emission lines, opening up the possibility of conducting detailed photoionization modeling to infer the physical state of gas in the circumgalactic medium. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Direct reductive amination of aldehyde bisulfite adducts induced by 2-picoline borane: application to the synthesis of a DPP-IV inhibitor.

    PubMed

    Faul, Margaret; Larsen, Rob; Levinson, Adam; Tedrow, Jason; Vounatsos, Filisaty

    2013-02-15

    Aldehyde-bisulfite adducts dervied from unstable parent aldehydes were reductively alkylated in a direct fashion with a variety of amines. This approach features the use of 2-picoline borane as the reducing agent and a protic solvent for the reaction media and has been successfully applied to the synthesis of a DPP-IV inhibitor and a variety of other amines.

  11. 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.

  12. Hafnium(IV) chloride complexes with chelating β-ketiminate ligands: Synthesis, spectroscopic characterization and volatility study

    NASA Astrophysics Data System (ADS)

    Patil, Siddappa A.; Medina, Phillip A.; Antic, Aleks; Ziller, Joseph W.; Vohs, Jason K.; Fahlman, Bradley D.

    2015-09-01

    The synthesis and characterization of four new β-ketiminate hafnium(IV) chloride complexes dichloro-bis[4-(phenylamido)pent-3-en-2-one]-hafnium (4a), dichloro-bis[4-(4-methylphenylamido)pent-3-en-2-one]-hafnium (4b), dichloro-bis[4-(4-methoxyphenylamido)pent-3-en-2-one]-hafnium (4c), and dichloro-bis[4-(4-chlorophenylamido)pent-3-en-2-one]-hafnium (4d) are reported. All the complexes (4a-d) were characterized by spectroscopic methods (1H NMR, 13C NMR, IR), and elemental analysis while the compound 4c was further examined by single-crystal X-ray diffraction, revealing that the complex is monomer with the hafnium center in octahedral coordination environment and oxygens of the chelating N-O ligands are trans to each other and the chloride ligands are in a cis arrangement. Volatile trends are established for four new β-ketiminate hafnium(IV) chloride complexes (4a-d). Sublimation enthalpies (ΔHsub) were calculated from thermogravimetric analysis (TGA) data, which show that, the dependence of ΔHsub on the molecular weight (4a-c) and inductive effects from chlorine (4d).

  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. 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.

  15. Do all Planetary Nebulae result from Common Envelopes?

    NASA Astrophysics Data System (ADS)

    De Marco, O.; Moe, M.; Herwig, F.; Politano, M.

    2005-12-01

    The common envelope interaction is responsible for evolved close binaries. Some of these binaries reside in the middle of planetary nebulae (PN). Conventional wisdom has it that only about 10% of all PN contain close binary central stars. Recent observational results, however, strongly suggest that most or even all PN are in close binary systems. Interestingly, our population synthesis calculations predict that the number of post-common envelope PN is in agreement with the total number of PN in the Galaxy. On the other hand, if all stars (single and in binaries) with mass between ˜1-8 M⊙ eject a PN, there would be 10-20 times many more PN in the galaxy than observed. This theoretical result is in agreement with the observations in suggesting that binary interactions play a functional rather than marginal role in the creation of PN. FH acknowledges funds from the U.S. Dept. of Energy, under contract W-7405-ENG-36 to Los Alamos National Laboratory. MP gratefully acknowledges NSF grant AST-0328484 to Marquette University.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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

  10. 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.

  11. 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.

  12. 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.

  13. A Genetic Selection for dinB Mutants Reveals an Interaction between DNA Polymerase IV and the Replicative Polymerase That Is Required for Translesion Synthesis.

    PubMed

    Scotland, Michelle K; Heltzel, Justin M H; Kath, James E; Choi, Jung-Suk; Berdis, Anthony J; Loparo, Joseph J; Sutton, Mark D

    2015-09-01

    Translesion DNA synthesis (TLS) by specialized DNA polymerases (Pols) is a conserved mechanism for tolerating replication blocking DNA lesions. The actions of TLS Pols are managed in part by ring-shaped sliding clamp proteins. In addition to catalyzing TLS, altered expression of TLS Pols impedes cellular growth. The goal of this study was to define the relationship between the physiological function of Escherichia coli Pol IV in TLS and its ability to impede growth when overproduced. To this end, 13 novel Pol IV mutants were identified that failed to impede growth. Subsequent analysis of these mutants suggest that overproduced levels of Pol IV inhibit E. coli growth by gaining inappropriate access to the replication fork via a Pol III-Pol IV switch that is mechanistically similar to that used under physiological conditions to coordinate Pol IV-catalyzed TLS with Pol III-catalyzed replication. Detailed analysis of one mutant, Pol IV-T120P, and two previously described Pol IV mutants impaired for interaction with either the rim (Pol IVR) or the cleft (Pol IVC) of the β sliding clamp revealed novel insights into the mechanism of the Pol III-Pol IV switch. Specifically, Pol IV-T120P retained complete catalytic activity in vitro but, like Pol IVR and Pol IVC, failed to support Pol IV TLS function in vivo. Notably, the T120P mutation abrogated a biochemical interaction of Pol IV with Pol III that was required for Pol III-Pol IV switching. Taken together, these results support a model in which Pol III-Pol IV switching involves interaction of Pol IV with Pol III, as well as the β clamp rim and cleft. Moreover, they provide strong support for the view that Pol III-Pol IV switching represents a vitally important mechanism for regulating TLS in vivo by managing access of Pol IV to the DNA.

  14. 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

  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. Far-Infrared Spectroscopy of Planetary Nebulae with the KAO

    NASA Technical Reports Server (NTRS)

    Rubin, Robert H.; Colgan, S.; Haas, M. R.; Lord, S. D.; Simpson, Janet P.

    1996-01-01

    We present new far-infrared line observations of the planetary nebulae (PNs) NGC 7027, NGC 7009, and NGC 6210 obtained with the Kuiper Airborne Observatory (KAO). The bulk of our data are for NGC 7027 and NGC 7009, including [Ne(V)] 24 micrometers, [O(IV)] 26 micrometers, [O(III)] (52, 88) micrometers, and [N(III)] 57 micrometers. Our data for [O(III)] (52, 88) and [N(III)] 57 in NGC 7027 represent the first measurements of these lines in this source. The large [O(III)] 52/88-micrometer flux ratio implies an electron density (cubic cm) of log N(sub e)[O(III)] = 4.19, the largest Ne ever inferred from these lines. We derive N(++)/O(++) = 0.394 +/- 0.062 for NGC 7027 and 0.179 +/- 0.043 for NGC 6210. We are able to infer the O(+3)/O(++) ionic ratio from our data. As gauged by this ionic ratio, NGC 7027 is substantially higher ionization than is NGC 7009 - consistent with our observation that the former produces copious [Ne(V)] emission while the latter does not. These data help characterize the stellar ionizing radiation field. From our [O(IV)] and [O(III)] fluxes, we are able to show that O(++) is by far the dominant oxygen ion in NGC 7009. As a result, the O/H abundance inferred using these data tends to corroborate the value found from UV/optical, collisionally excited lines. We determined accurate rest wavelengths for the [Ne(V)] 2s(2)2p(2)P(sub 1) to 2s(2)2p(2)3P(sub 0) (lambda(sub rest) = 24.316 +/- 0.008 micrometers) and [O(IV)] 2s(2)2p(2)P(sup 0, sub 3/2) to 2s(2)2p(2)P(sup 0, sub 1/2) (lambda(sub rest) = 25.887 +/- 0.007 micrometers) transitions from observations of one or both of the bright PNs NGC 7027 and NGC 7009. Our [O(IV)] value, to the best of our knowledge, is the most accurate direct determination of this lambda(sub rest). These new KAO data will be beneficial for comparison with ISO observations of these PNs.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. 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.).

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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

  17. 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

  18. 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.

  19. 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.

  20. Synthesis, kinetic evaluation, and utilization of a biotinylated dipeptide proline diphenyl phosphonate for the disclosure of dipeptidyl peptidase IV-like serine proteases.

    PubMed

    Gilmore, Brendan F; Carson, Louise; McShane, Laura L; Quinn, Derek; Coulter, Wilson A; Walker, Brian

    2006-08-18

    In this study, we report on the synthesis, kinetic characterisation, and application of a novel biotinylated and active site-directed inactivator of dipeptidyl peptidase IV (DPP-IV). Thus, the dipeptide-derived proline diphenyl phosphonate NH(2)-Glu(biotinyl-PEG)-Pro(P)(OPh)(2) has been prepared by a combination of classical solution- and solid-phase methodologies and has been shown to be an irreversible inhibitor of porcine DPP-IV, exhibiting an over all second-order rate constant (k(i)/K(i)) for inhibition of 1.57 x 10(3) M(-1) min(-1). This value compares favourably with previously reported rates of inactivation of DPP-IV by dipeptides containing a P(1) proline diphenyl phosphonate grouping [B. Boduszek, J. Oleksyszyn, C.M. Kam, J. Selzler, R.E. Smith, J.C. Powers, Dipeptide phophonates as inhibitors of dipeptidyl peptidase IV, J. Med. Chem. 37 (1994) 3969-3976; B.F. Gilmore, J.F. Lynas, C.J. Scott, C. McGoohan, L. Martin, B. Walker, Dipeptide proline diphenyl phosphonates are potent, irreversible inhibitors of seprase (FAPalpha), Biochem, Biophys. Res. Commun. 346 (2006) 436-446.], thus demonstrating that the incorporation of the side-chain modified (N-biotinyl-3-(2-(2-(3-aminopropyloxy)-ethoxy)-ethoxy)-propyl) glutamic acid residue at the P(2) position is compatible with inhibitor efficacy. The utilisation of this probe for the detection of both purified dipeptidyl peptidase IV and the disclosure of a dipeptidyl peptidase IV-like activity from a clinical isolate of Porphyromonas gingivalis, using established electrophoretic and Western blotting techniques previously developed by our group, is also demonstrated.

  1. New Measurements of s-Process Enrichments in Planetary Nebulae from High-Resolution Near-Infrared Spectra

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet L.; Karakas, Amanda; Sterling, Nicholas C.; Kaplan, Kyle

    2017-06-01

    We present preliminary results from a high-spectral resolution survey of near-infrared emission lines of neutron-capture elements in planetary nebulae using the Immersion Grating Infrared Spectrometer, IGRINS (Park et al. 2014, SPIE. 9147, 1), which spans the H- and K-bands at spectral resolving power R ≈ 45,000. Both the [Kr III] and [Se IV] lines identified by Dinerstein (2001, ApJL, 550, L223) are seen in nearly all of an initial sample of ≈ 15 nebulae, with improved accuracy over earlier studies based on lower-resolution data (Sterling & Dinerstein 2008, ApJS, 174, 158; Sterling, Porter, & Dinerstein 2015, ApJS, 218, 25). Several new detections of the [Rb IV], [Cd IV], and [Ge VI] lines identified by Sterling et al. (2016, ApJL, 819, 9), as well as a [Br V] line, were made. About half the objects in this sample descend from stars with [Fe/H] = -0.7 ± 0.2 dex, while the remainder have -0.3 ≤ [Fe/H] ≤ 0. We compare the measured enhancements of Se, Kr, Rb, and Cd with predictions of their production by slow-neutron captures (the s-process) during the AGB from theoretical evolutionary models for the corresponding metallicities and various initial masses. New nucleosynthesis calculations were carried out for [Fe/H] = -0.7 for initial masses between 1.1 and 3 M⊙ using the Monash stellar evolution and post-processing codes described in Karakas & Lugaro (2016, ApJ, 825, 26), which provides the nucleosynthesis predictions for the metal-rich end of our sample. The Monash models predict enrichments larger by factors of two or more than those from FRUITY (Cristallo et al. 2015, ApJS, 219, 40) and NuGRID (Pignatari et al. 2016, ApJS, 225, 24) models for the same masses and metallicities. We find that the Monash models are in substantially better agreement than the others with the abundances derived from the IGRINS observations.This work is based on data taken at the McDonald Observatory of the University of Texas at Austin. IGRINS was developed with support from

  2. 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

  3. 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

  4. 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.

  5. Synthesis and characterization of thorium(IV) sulfates.

    PubMed

    Knope, Karah E; Wilson, Richard E; Skanthakumar, S; Soderholm, L

    2011-09-05

    Three Th(IV) sulfates, two new and one previously reported, have been synthesized from aqueous solution. In all of the compounds, the sulfate anions coordinate the Th(4+) metal center(s) in a monodentate manner with Th-S distances of 3.7-3.8 Å. Th(SO(4))(2)(H(2)O)(7)·2(H(2)O) (1; P2(1)/m, a = 7.224(1) Å, b = 12.151(1) Å, c = 7.989(1) Å, ss =98.289(2)°) and Th(4)(SO(4))(7)(H(2)O)(7)(OH)(2)·H(2)O (2; Pnma, a = 18.139(2) Å, b = 11.173(1) Å, c = 14.391(2) Å) each contain 9-coordinate monomeric (1,2) and dimeric (2) Th(IV) cations in monocapped square antiprism geometry. Alternatively, Th(OH)(2)SO(4) (3; Pnma, a = 11.684(1) Å, b = 6.047(1) Å, c = 7.047(1) Å) is built from chains of hydroxo-bridged, 8-coordinate Th(4+) centers. Whereas 1 adopts a molecular structure, 2 and 3 both exhibit 3D architectures. Differences in the dimensionality and the topology of 1-3 are manifested in the local coordination environment about the Th(IV) centers, the formation of oligomeric Th(4+) species, and the extended connectivity of the sulfate ligands. Herein, we report the syntheses and characterization of 1-3 as well as the atomic correlations of 1 in solution, as determined by high-energy X-ray scattering (HEXS).

  6. 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.

  7. 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.

  8. 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

  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. 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.

  11. 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.

  12. 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

  13. 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

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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

  11. 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.

  12. 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.

  13. 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

  14. Identification of Near-infrared [Se III] and [Kr VI] Emission Lines in Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Sterling, N. C.; Madonna, S.; Butler, K.; García-Rojas, J.; Mashburn, A. L.; Morisset, C.; Luridiana, V.; Roederer, I. U.

    2017-05-01

    We identify [Se III] 1.0994 μm in the planetary nebula (PN) NGC 5315 and [Kr VI] 1.2330 μm in three PNe from spectra obtained with the Folded-Port InfraRed Echellette (FIRE) spectrometer on the 6.5 m Baade Telescope. Se and Kr are the two most widely detected neutron-capture elements in astrophysical nebulae, and can be enriched by s-process nucleosynthesis in PN progenitor stars. The detection of [Se III] 1.0994 μm is particularly valuable when paired with observations of [Se IV] 2.2864 μm, as it can be used to improve the accuracy of nebular Se abundance determinations, and allows Se ionization correction factor (ICF) schemes to be empirically tested for the first time. We present new effective collision strength calculations for Se2+ and Kr5+, which we use to compute ionic abundances. In NGC 5315, we find that the Se abundance computed from Se3+/H+ is lower than that determined with ICFs that incorporate Se2+/H+. We compute new Kr ICFs that take Kr5+/H+ into account, by fitting correlations found in grids of Cloudy models between Kr ionic fractions and those of more abundant elements, and use these to derive Kr abundances in four PNe. Observations of [Se III] and [Kr VI] in a larger sample of PNe, with a range of excitation levels, are needed to rigorously test the ICF prescriptions for Se and our new Kr ICFs. This paper includes data obtained with the 6.5-m Magellan Telescopes at Las Campanas Observatory, Chile.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  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.

    2018-07-01

    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.

  1. 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

  2. Chromogenic Detection of Dipeptidyl Peptidase IV (DPP-IV) Activity using Peptide-Functionalized Gold Nanoparticles

    NASA Astrophysics Data System (ADS)

    Abul-Huda, Yasin Mohammad

    Metal nanoparticles offer a useful platform for a wide range of biological applications especially for biosensing, bioimaging and drug delivery. This thesis presents a body of original research describing the synthesis, characterisation and development of a novel and convenient biosensing assay for detection of dipeptidyl peptidase IV (DPP-IV) enzyme activity using peptide functionalized gold nanoparticles. The distinctive optical and physical properties of gold nanoparticles (Au NP) were harnessed for the development of a colorimetric assay for rapid sensing of DPP-IV activities and screening DPP-IV inhbitors. The citrate reduction method for Au NPs synthesis was optimised and several potential peptide substrates (GPDC, VP-EN-DC, C/G dipeptide, GPG-EN-PEG4-LA, GPDCALNNC) were designed to provide substrates that mimic the DPP-IV natural substrates. The performances of the substrate functionalized Au NPs were assessed for their appropriateness for the detection of the enzyme activity. Addition of DPP-IV to the solutions containing the functionalized Au NPs resulted in cleavage of the substrate and thus causing the aggregation of the Au NPs which in turn led to a shift of the surface plasmon peak toward longer wavelengths, and a change of the colour of the colloidal suspension from red to blue. Overall, real-time detection of DPP-IV activity over a broader range (0-40 U/L) with high selectivity and stability was obtained, thus providing a method that can be used to determine the levels of DPP-IV/CD26 in biological fluids such as serum and plasma. Further assay developments were conducted to overcome limitations encountered with the original Au NP assay, especially the narrow dynamic linear range and stability in high ionic strength solutions. Validation and comparison of the Au NP assay developed has revealed that this method is highly correlated to the gold standard chromogenic Gly-Pro-pNA method for detection of enzyme activity in biological samples. Very good

  3. 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

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. 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

  10. 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

  11. 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.

  12. 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

  13. 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.

  14. Detonative propagation and accelerative expansion of the Crab Nebula shock front.

    PubMed

    Gao, Yang; Law, Chung K

    2011-10-21

    The accelerative expansion of the Crab Nebula's outer envelope is a mystery in dynamics, as a conventional expanding blast wave decelerates when bumping into the surrounding interstellar medium. Here we show that the strong relativistic pulsar wind bumping into its surrounding nebula induces energy-generating processes and initiates a detonation wave that propagates outward to form the current outer edge, namely, the shock front, of the nebula. The resulting detonation wave, with a reactive downstream, then provides the needed power to maintain propagation of the shock front. Furthermore, relaxation of the curvature-induced reduction of the propagation velocity from the initial state of formation to the asymptotic, planar state of Chapman-Jouguet propagation explains the observed accelerative expansion. Potential richness in incorporating reactive fronts in the description of various astronomical phenomena is expected. © 2011 American Physical Society

  15. Evolutionary status of the Of?p star HD 148937 and of its surrounding nebula NGC 6164/5

    NASA Astrophysics Data System (ADS)

    Mahy, L.; Hutsemékers, D.; Nazé, Y.; Royer, P.; Lebouteiller, V.; Waelkens, C.

    2017-03-01

    Aims: The magnetic star HD 148937 is the only Galactic Of?p star surrounded by a nebula. The structure of this nebula is particularly complex and is composed, from the center out outwards, of a close bipolar ejecta nebula (NGC 6164/5), an ellipsoidal wind-blown shell, and a spherically symmetric Strömgren sphere. The exact formation process of this nebula and its precise relation to the star's evolution remain unknown. Methods: We analyzed infrared Spitzer IRS and far-infrared Herschel/PACS observations of the NGC 6164/5 nebula. The Herschel imaging allowed us to constrain the global morphology of the nebula. We also combined the infrared spectra with optical spectra of the central star to constrain its evolutionary status. We used these data to derive the abundances in the ejected material. To relate this information to the evolutionary status of the star, we also determined the fundamental parameters of HD 148937 using the CMFGEN atmosphere code. Results: The Hα image displays a bipolar or "8"-shaped ionized nebula, whilst the infrared images show dust to be more concentrated around the central object. We determine nebular abundance ratios of N/O = 1.06 close to the star, and N/O = 1.54 in the bright lobe constituting NGC 6164. Interestingly, the parts of the nebula located further from HD 148937 appear more enriched in stellar material than the part located closer to the star. Evolutionary tracks suggest that these ejecta have occured 1.2-1.3 and 0.6 Myr ago, respectively. In addition, we derive abundances of argon for the nebula compatible with the solar values and we find a depletion of neon and sulfur. The combined analyses of the known kinematics and of the new abundances of the nebula suggest either a helical morphology for the nebula, possibly linked to the magnetic geometry, or the occurrence of a binary merger. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important

  16. THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

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

    Montez, R. Jr.; Kastner, J. H.; Freeman, M.

    2015-02-10

    We present X-ray spectral analysis of 20 point-like X-ray sources detected in Chandra Planetary Nebula Survey observations of 59 planetary nebulae (PNe) in the solar neighborhood. Most of these 20 detections are associated with luminous central stars within relatively young, compact nebulae. The vast majority of these point-like X-ray-emitting sources at PN cores display relatively ''hard'' (≥0.5 keV) X-ray emission components that are unlikely to be due to photospheric emission from the hot central stars (CSPN). Instead, we demonstrate that these sources are well modeled by optically thin thermal plasmas. From the plasma properties, we identify two classes of CSPN X-raymore » emission: (1) high-temperature plasmas with X-ray luminosities, L {sub X}, that appear uncorrelated with the CSPN bolometric luminosity, L {sub bol} and (2) lower-temperature plasmas with L {sub X}/L {sub bol} ∼ 10{sup –7}. We suggest these two classes correspond to the physical processes of magnetically active binary companions and self-shocking stellar winds, respectively. In many cases this conclusion is supported by corroborative multiwavelength evidence for the wind and binary properties of the PN central stars. By thus honing in on the origins of X-ray emission from PN central stars, we enhance the ability of CSPN X-ray sources to constrain models of PN shaping that invoke wind interactions and binarity.« less

  17. 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.

  18. Million-degree plasma pervading the extended Orion Nebula.

    PubMed

    Güdel, Manuel; Briggs, Kevin R; Montmerle, Thierry; Audard, Marc; Rebull, Luisa; Skinner, Stephen L

    2008-01-18

    Most stars form as members of large associations within dense, very cold (10 to 100 kelvin) molecular clouds. The nearby giant molecular cloud in Orion hosts several thousand stars of ages less than a few million years, many of which are located in or around the famous Orion Nebula, a prominent gas structure illuminated and ionized by a small group of massive stars (the Trapezium). We present x-ray observations obtained with the X-ray Multi-Mirror satellite XMM-Newton, revealing that a hot plasma with a temperature of 1.7 to 2.1 million kelvin pervades the southwest extension of the nebula. The plasma flows into the adjacent interstellar medium. This x-ray outflow phenomenon must be widespread throughout our Galaxy.

  19. A Rapidly Moving Shell in the Orion Nebula

    NASA Technical Reports Server (NTRS)

    Walter, Donald K.; O'Dell, C. R.; Hu, Xihai; Dufour, Reginald J.

    1995-01-01

    A well-resolved elliptical shell in the inner Orion Nebula has been investigated by monochromatic imaging plus high- and low-resolution spectroscopy. We find that it is of low ionization and the two bright ends are moving at -39 and -49 km/s with respect to OMC-1. There is no central object, even in the infrared J bandpass although H2 emission indicates a possible association with the nearby very young pre-main-sequence star J&W 352, which is one of the youngest pre-main-sequence stars in the inner Orion Nebula. Many of the characteristics of this object (low ionization, blue shift) are like those of the Herbig-Haro objects, although the symmetric form would make it an unusual member of that class.

  20. Catalysis by Dust Grains in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Kress, Monika E.; Tielens, Alexander G. G. M.

    1996-01-01

    In order to determine whether grain-catalyzed reactions played an important role in the chemistry of the solar nebula, we have applied our time-dependent model of methane formation via Fischer-Tropsch catalysis to pressures from 10(exp -5) to 1 bar and temperatures from 450 to 650 K. Under these physical conditions, the reaction 3H2 + CO yields CH4 + H2O is readily catalyzed by an iron or nickel surface, whereas the same reaction is kinetically inhibited in the gas phase. Our model results indicate that under certain nebular conditions, conversion of CO to methane could be extremely efficient in the presence of iron-nickel dust grains over timescales very short compared to the lifetime of the solar nebula.

  1. INVESTIGATIONS ON FLARE STARS AND NEBULAE.

    DTIC Science & Technology

    The first part of the report deals with the searching of flare stars in the Pleiades and Praesepe clusters. 13 flares have been found on the... Pleiades and 2 on the Praesepe. Position and characteristics of the flare stars are given. The second part deals with the study of the Orion Nebula with

  2. TeV radiation from the Crab nebula and other matters

    NASA Technical Reports Server (NTRS)

    Lamb, R. C.

    1990-01-01

    The detection of the Crab Nebula via the Cherenkov imaging technique places TeV astronomy on a secure observational footing. The motivation for TeV observations, a discussion of the atmospheric Cherenkov technique, the experimental details of the Crab Nebula detection, and its scientific implications are presented. The present dilemma of VHE/UHE astronomy is that the Crab appears to be the only source whose showers match theoretical expectations. The situation will be clarified as improved ground-based detectors come on-line with sensitivities matching those of the GRO (Gamma Ray Observatory) instruments.

  3. When a Standard Candle Flickers: Crab Nebula Variations in Hard X-rays

    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

    2011-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM) since August 2008, a 7% (70 mcrab) decline was observed in the overall Crab Nebula flux in the 15 - 50 keV band, measured with the Earth occultation technique. This decline is independently confirmed in the 15-50 keV band with four other instruments: Swift/BAT, the RXTE/PCA, INTEGRAL/IBIS, and INTEGRAL/SPI. A similar decline is also observed in the 3-15 keV data from the RXTE/PCA and in the 50-100 keV band with GBM, Swift/BAT, INTEGRAL/IBIS, and INTEGRAL/SPI. The pulsed flux measured with RXTE/PCA since 1999 is consistent with the pulsar spin-down, indicating that the observed changes are nebular. Correlated variations in the Crab Nebula flux on a 3 year timescale are also seen independently with the PCA, BAT, IBIS, and SPI from 2005 to 2008, with a flux minimum in April 2007. As of April 2011, the Crab nebula flux has stopped declining and may be beginning to increase. We will present updated results on our multi-instrument study of long-term Crab nebula variations.

  4. Young stars of low mass in the Gum nebula

    NASA Technical Reports Server (NTRS)

    Graham, J. A.; Heyer, Mark H.

    1989-01-01

    Observations are presented for four recently formed stars in the vicinity of the Gum nebula which are heavily obscured by surrounding dust and are associated with small reflection nebulae. HH46 is the only currently active star of the sample, and it is found to have a spectral type in the range of late G-early K, with superimposed emission lines of H-alpha, Ca II, Fe I, Fe II, and weak He I at near zero velocities. It is suggested that the observed scenario of low-mass stars in an older massive star environment may be analogous to the circumstances surrounding the birth of the sun.

  5. Planetary Nebula Candidates Uncovered with the HASH Research Platform

    NASA Astrophysics Data System (ADS)

    Fragkou, Vasiliki; Bojičić, Ivan; Frew, David; Parker, Quentin

    2017-10-01

    A detailed examination of new high quality radio catalogues (e.g. Cornish) in combination with available mid-infrared (MIR) satellite imagery (e.g. Glimpse) has allowed us to find 70 new planetary nebula (PN) candidates based on existing knowledge of their typical colors and fluxes. To further examine the nature of these sources, multiple diagnostic tools have been applied to these candidates based on published data and on available imagery in the HASH (Hong Kong/ AAO/ Strasbourg Hα planetary nebula) research platform. Some candidates have previously-missed optical counterparts allowing for spectroscopic follow-up. Indeed, the single object spectroscopically observed so far has turned out to be a bona fide PN.

  6. 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

  7. The Helix Nebula: Unraveling at the Seams

    NASA Image and Video Library

    2012-10-03

    This image from NASA Spitzer and GALEX shows the Helix nebula, a dying star throwing a cosmic tantrum. In death, the star dusty outer layers are unraveling into space, glowing from the intense UV radiation being pumped out by the hot stellar core.

  8. 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

  9. 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.

  10. R Coronae Borealis stars and planetary nebulae

    NASA Technical Reports Server (NTRS)

    Schaefer, B. E.

    1986-01-01

    IRAS observations of R Coronae Borealis type stars (R CrB's) suggests that a subset of these is inside planetary nebulae (PNs). In most cases, the PN is confirmed by the finding of a visible nebula around the star. These nebular R CrB's are identified as being the results of a final helium shell flash on the central star of old PNs. The majority of the R CrB's formed after the coalescence of a binary consisting of CO and He white dwarfs. Also presented in this paper are the results of a survey of 52 R CrB's. The normal R CrB's have power-law spectra which imply that the grain absorption coefficient varies linearly with frequency. It is estimated that R CrB's eject about 300 clouds per year, each of which subtend an angle of about 30 sq deg.

  11. 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.

  12. Modeling radio circular polarization in the Crab nebula

    NASA Astrophysics Data System (ADS)

    Bucciantini, N.; Olmi, B.

    2018-03-01

    In this paper, we present, for the first time, simulated maps of the circularly polarized synchrotron emission from the Crab nebula, using multidimensional state of the art models for the magnetic field geometry. Synchrotron emission is the signature of non-thermal emitting particles, typical of many high-energy astrophysical sources, both Galactic and extragalactic ones. Its spectral and polarization properties allow us to infer key information on the particles distribution function and magnetic field geometry. In recent years, our understanding of pulsar wind nebulae has improved substantially thanks to a combination of observations and numerical models. A robust detection or non-detection of circular polarization will enable us to discriminate between an electron-proton plasma and a pair plasma, clarifying once for all the origin of the radio emitting particles, setting strong constraints on the pair production in pulsar magnetosphere, and the role of turbulence in the nebula. Previous attempts at measuring the circular polarization have only provided upper limits, but the lack of accurate estimates, based on reliable models, makes their interpretation ambiguous. We show here that those results are above the expected values, and that current polarimetric techniques are not robust enough for conclusive result, suggesting that improvements in construction and calibration of next generation radio facilities are necessary to achieve the desired sensitivity.

  13. Synthesis, structure, and optoelectronic properties of II-IV-V 2 materials

    DOE PAGES

    Martinez, Aaron D.; Fioretti, Angela N.; Toberer, Eric S.; ...

    2017-03-07

    II-IV-V 2 materials offer the promise of enhanced functionality in optoelectronic devices due to their rich ternary chemistry. In this review, we consider the potential for new optoelectronic devices based on nitride, phosphide, and arsenide II-IV-V 2 materials. As ternary analogs to the III-V materials, these compounds share many of the attractive features that have made the III-Vs the basis of modern optoelectronic devices (e.g. high mobility, strong optical absorption). Control of cation order parameter in the II-IV-V 2 materials can produce significant changes in optoelectronic properties at fixed chemical composition, including decoupling band gap from lattice parameter. Recent progressmore » has begun to resolve outstanding questions concerning the structure, dopability, and optical properties of the II-IV-V 2 materials. Furthermore, remaining research challenges include growth optimization and integration into heterostructures and devices.« less

  14. Inductive Spikes in the Crab Nebula: A Theory of γ-Ray Flares.

    PubMed

    Kirk, John G; Giacinti, Gwenael

    2017-11-24

    We show that the mysterious, rapidly variable emission at ∼400  MeV observed from the Crab Nebula by the AGILE and Fermi satellites could be the result of a sudden drop in the mass loading of the pulsar wind. The current required to maintain wave activity in the wind is then carried by very few particles of a high Lorentz factor. On impacting the nebula, these particles produce a tightly beamed, high-luminosity burst of hard gamma rays, similar to those observed. This implies that (i) the emission is synchrotron radiation in the toroidal field of the nebula and, therefore, linearly polarized and (ii) this mechanism potentially contributes to the gamma-ray emission from other powerful pulsars, such as the Magellanic Cloud objects J0537-6910 and B0540-69.

  15. Inductive Spikes in the Crab Nebula: A Theory of γ -Ray Flares

    NASA Astrophysics Data System (ADS)

    Kirk, John G.; Giacinti, Gwenael

    2017-11-01

    We show that the mysterious, rapidly variable emission at ˜400 MeV observed from the Crab Nebula by the AGILE and Fermi satellites could be the result of a sudden drop in the mass loading of the pulsar wind. The current required to maintain wave activity in the wind is then carried by very few particles of a high Lorentz factor. On impacting the nebula, these particles produce a tightly beamed, high-luminosity burst of hard gamma rays, similar to those observed. This implies that (i) the emission is synchrotron radiation in the toroidal field of the nebula and, therefore, linearly polarized and (ii) this mechanism potentially contributes to the gamma-ray emission from other powerful pulsars, such as the Magellanic Cloud objects J0537-6910 and B0540-69.

  16. High-speed knots in the hourglass-shaped planetary nebula Hubble 12

    NASA Astrophysics Data System (ADS)

    Vaytet, N.; Rushton, A. P.; Lloyd, M.; Lopez, J. A.; Meaburn, J.; O'Brien, T. J.; Mitchell, D. L.; Pollacco, D.

    We present a detailed kinematical analysis of the young compact hourglass-shaped planetary nebula Hb 12. We performed optical imaging and longslit spectroscopy of Hb 12 using the Manchester echelle spectrometer with the 2.1-m San Pedro Martir telescope. We reveal, for the first time, the presence of end caps (or knots) aligned with the bipolar lobes of the planetary nebula shell in a deep [N ii] 6584 image of Hb 12. We measured from our spectroscopy radial velocities of about 120 km s-1 for these knots. We have derived the inclination angle of the hourglass shaped nebular shell to be 65° to the line of sight. It has been suggested that Hb 12's central star system is an eclipsing binary which would imply a binary inclination of at least 80°. However, if the central binary has been the major shaping influence on the nebula then both nebula and binary would be expected to share a common inclination angle. Finally, we report the discovery of high-velocity knots with Hubble-type velocities, close to the core of Hb 12, observed in HA and oriented in the same direction as the end caps. Very different velocities and kinematical ages were calculated for the outer and inner knots showing that they may originate from different outburst events.

  17. Identification of the Gum nebula as the fossil Stroemgren sphere of the Vela X supernova

    NASA Technical Reports Server (NTRS)

    Brandt, J. C.

    1971-01-01

    Evidence is presented for the production of the Gum nebula by the Vela X supernova, as opposed to its ionization by gamma Velorum and zeta Puppis. A model for the excitation of the nebula is proposed.

  18. Nebulae: Not as Close as They Appear

    NASA Image and Video Library

    2011-05-05

    This image from NASA Wide-field Infrared Survey Explorer, shows three different nebulae located in the constellation of Perseus. NGC 1491 is seen on the right side of the image, SH 2-209 is on the left side and BFS 34 lies in between.

  19. The Emerging Population of Pulsar Wind Nebulae in Hard X-rays

    NASA Astrophysics Data System (ADS)

    Mattana, F.; Götz, D.; Terrier, R.; Renaud, M.; Falanga, M.

    2009-05-01

    The hard X-ray synchrotron emission from Pulsar Wind Nebulae probes energetic particles, closely related to the pulsar injection power at the present time. INTEGRAL has disclosed the yet poorly known population of hard X-ray pulsar/PWN systems. We summarize the properties of the class, with emphasys on the first hard X-ray bow-shock (CTB 80 powered by PSR B1951+32), and highlight some prospects for the study of Pulsar Wind Nebulae with the Simbol-X mission.

  20. 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

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

    NASA Technical Reports Server (NTRS)

    Pham, Long; Chen, Aijun; Kempler, Steven; Lynnes, Christopher; Theobald, Michael; Asghar, Esfandiari; Campino, Jane; Vollmer, Bruce

    2011-01-01

    Cloud Computing has been implemented in several commercial arenas. The NASA Nebula Cloud Computing platform is an Infrastructure as a Service (IaaS) built in 2008 at NASA Ames Research Center and 2010 at GSFC. Nebula is an open source Cloud platform intended to: a) Make NASA realize significant cost savings through efficient resource utilization, reduced energy consumption, and reduced labor costs. b) Provide an easier way for NASA scientists and researchers to efficiently explore and share large and complex data sets. c) Allow customers to provision, manage, and decommission computing capabilities on an as-needed bases

  2. Young stars of low mass in the Gum nebula

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

    Graham, J.A.; Heyer, M.H.

    1989-06-01

    Observations are presented for four recently formed stars in the vicinity of the Gum nebula which are heavily obscured by surrounding dust and are associated with small reflection nebulae. HH46 is the only currently active star of the sample, and it is found to have a spectral type in the range of late G-early K, with superimposed emission lines of H-alpha, Ca II, Fe I, Fe II, and weak He I at near zero velocities. It is suggested that the observed scenario of low-mass stars in an older massive star environment may be analogous to the circumstances surrounding the birthmore » of the sun. 53 refs.« less

  3. Cosmic-ray effects in the Gum nebula

    NASA Technical Reports Server (NTRS)

    Ramaty, R.; Boldt, E. A.

    1971-01-01

    The effects of low energy heavy nuclei from the supernova explosion on nearby interstellar space were investigated. In addition to the ionization and heating of the Gum nebula, these particles may produce detectable fluxes of X-rays and gamma rays, both as continuum radiation and line emission.

  4. When a Standard Candle Flickers: Crab Nebula Variations in Hard X-rays

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Collen 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

    2012-01-01

    RXTE played a crucial role in our surprising discovery that the Crab Nebula is variable in hard X-rays. In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008-2010, 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 in the 15-50 keV band 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 and Swift/BAT starting in 2005. Before 2001 and since 2010, the Crab nebula 15-50 keV flux measured with RXTE/PCA appeared more stable, varying by less than 2% per year. In this talk I will present Crab light curves including RXTE data for the entire 16-year mission in multiple energy bands.

  5. 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

  6. Formation of iron sulphide in solar nebula

    NASA Technical Reports Server (NTRS)

    Kerridge, J. F.

    1976-01-01

    Noting that the iron sulfide in the Orgueil carbonaceous meteorite is an Fe-deficient monosulfide (pyrrhotite), it is suggested that such mineral chemistry is inconsistent with equilibrium condensation of the solar nebula and that the course of condensation may have been modified by kinetic effects. The effect of Ni on the reaction between Fe and S to produce FeS is examined, and possible reasons are considered for the fact that the cited meteorite differs in both crystal structure and Ni content from the predictions of equilibrium condensation. It is proposed that sulfide formation in the solar nebula may have been inhibited by sluggish diffusion, so that sulfur began to react with previously condensed troilite to form pyrrhotite. On this basis, observations of the Orgueil sulfides are shown to suggest that the course of solar-system condensation was modified by kinetic effects below about 700 K and that equilibrium may not have been achieved.

  7. Isotopic homogeneity of iron in the early solar nebula.

    PubMed

    Zhu, X K; Guo, Y; O'Nions, R K; Young, E D; Ash, R D

    2001-07-19

    The chemical and isotopic homogeneity of the early solar nebula, and the processes producing fractionation during its evolution, are central issues of cosmochemistry. Studies of the relative abundance variations of three or more isotopes of an element can in principle determine if the initial reservoir of material was a homogeneous mixture or if it contained several distinct sources of precursor material. For example, widespread anomalies observed in the oxygen isotopes of meteorites have been interpreted as resulting from the mixing of a solid phase that was enriched in 16O with a gas phase in which 16O was depleted, or as an isotopic 'memory' of Galactic evolution. In either case, these anomalies are regarded as strong evidence that the early solar nebula was not initially homogeneous. Here we present measurements of the relative abundances of three iron isotopes in meteoritic and terrestrial samples. We show that significant variations of iron isotopes exist in both terrestrial and extraterrestrial materials. But when plotted in a three-isotope diagram, all of the data for these Solar System materials fall on a single mass-fractionation line, showing that homogenization of iron isotopes occurred in the solar nebula before both planetesimal accretion and chondrule formation.

  8. 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.

  9. Detection of gamma-ray emission from the Vela pulsar wind nebula with AGILE.

    PubMed

    Pellizzoni, A; Trois, A; Tavani, M; Pilia, M; Giuliani, A; Pucella, G; Esposito, P; Sabatini, S; Piano, G; Argan, A; Barbiellini, G; Bulgarelli, A; Burgay, M; Caraveo, P; Cattaneo, P W; Chen, A W; Cocco, V; Contessi, T; Costa, E; D'Ammando, F; Del Monte, E; De Paris, G; Di Cocco, G; Di Persio, G; Donnarumma, I; Evangelista, Y; Feroci, M; Ferrari, A; Fiorini, M; Fuschino, F; Galli, M; Gianotti, F; Hotan, A; Labanti, C; Lapshov, I; Lazzarotto, F; Lipari, P; Longo, F; Marisaldi, M; Mastropietro, M; Mereghetti, S; Moretti, E; Morselli, A; Pacciani, L; Palfreyman, J; Perotti, F; Picozza, P; Pittori, C; Possenti, A; Prest, M; Rapisarda, M; Rappoldi, A; Rossi, E; Rubini, A; Santolamazza, P; Scalise, E; Soffitta, P; Striani, E; Trifoglio, M; Vallazza, E; Vercellone, S; Verrecchia, F; Vittorini, V; Zambra, A; Zanello, D; Giommi, P; Colafrancesco, S; Antonelli, A; Salotti, L; D'Amico, N; Bignami, G F

    2010-02-05

    Pulsars are known to power winds of relativistic particles that can produce bright nebulae by interacting with the surrounding medium. These pulsar wind nebulae are observed by their radio, optical, and x-ray emissions, and in some cases also at TeV (teraelectron volt) energies, but the lack of information in the gamma-ray band precludes drawing a comprehensive multiwavelength picture of their phenomenology and emission mechanisms. Using data from the AGILE satellite, we detected the Vela pulsar wind nebula in the energy range from 100 MeV to 3 GeV. This result constrains the particle population responsible for the GeV emission and establishes a class of gamma-ray emitters that could account for a fraction of the unidentified galactic gamma-ray sources.

  10. Synthesis of guanosine and its derivatives from 5-amino-1-beta-D-ribofuranosyl-e-imidazolecarboxamide. IV. A new route to guanosine via cyanamide derivative.

    PubMed Central

    Yamazaki, A; Okutsu, M; Yamada, Y

    1976-01-01

    4-Cyanamido-5-imidazolecarboxamide (IV) was prepared by brief treatment of 5-(S-methylisothiocarbamoyl) amino-4-imidazolecarboxamide (V) with alkali. Compound VI was converted in an alkaline solution to either guanine (VII) or isoguanine (VIII), depending on the concentration of alkali. This procedure was applied to the synthesis of 2',3'-0-isopropylideneguanosine (XVI) from the riboside of 5-(N'-benzoyl-S-methylthiocarbamoyl) amino-4-imidazolecarboxamide (IX), PROviding a new route to XVI. PMID:1250702

  11. 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.

  12. Synthesis, structure, and thermal properties of soluble hydrazinium germanium(IV) and tin(IV) selenide salts.

    PubMed

    Mitzi, David B

    2005-05-16

    The crystal structures of two hydrazinium-based germanium(IV) and tin(IV) selenide salts are determined. (N(2)H(5))(4)Ge(2)Se(6) (1) [I4(1)cd, a = 12.708(1) Angstroms, c = 21.955(2) Angstroms, Z = 8] and (N(2)H(4))(3)(N(2)H(5))(4)Sn(2)Se(6) (2) [P, a = 6.6475(6) Angstroms, b = 9.5474(9) Angstroms, c = 9.8830(10) Angstroms, alpha = 94.110(2) degrees, beta = 99.429(2) degrees, gamma = 104.141(2) degrees, Z = 1] each consist of anionic dimers of edge-sharing metal selenide tetrahedra, M(2)Se(6)(4-) (M = Ge or Sn), separated by hydrazinium cations and, for 2, additional neutral hydrazine molecules. Substantial hydrogen bonding exists among the hydrazine/hydrazinium molecules as well as between the hydrazinium cations and the selenide anions. Whereas the previously reported tin(IV) sulfide system, (N(2)H(5))(4)Sn(2)S(6), decomposes cleanly to microcrystalline SnS(2) when heated to 200 degrees C in an inert atmosphere, higher temperatures (>300 degrees C) are required to dissociate selenium from 1 and 2 for the analogous preparations of single-phase metal selenides. The metal chalcogenide salts are highly soluble in hydrazine, as well as in a variety of amines and DMSO, highlighting the potential usefulness of these compounds as precursors for the solution deposition of the corresponding metal chalcogenide films.

  13. Probing the Molecular Outflows of the Coldest Known Object in the Universe: The Boomerang Nebula

    NASA Astrophysics Data System (ADS)

    Sahai, Raghvendra; Vlemmings, W.; Nyman, L. A.; Huggins, P.

    2012-05-01

    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 AGB and Planetary Nebula evolutionary stages. The Boomerang's estimated prodigious mass-loss rate (0.001 solar masses/year) and low-luminosity (300 Lsun) lack an explanation in terms of current paradigms for dusty mass-loss and standard evolutionary theory of intermediate-mass stars. Single-dish CO J=1-0 observations (with a 45 arcsec beam) show that the high-speed outflow in this object has cooled to a temperature significantly below the temperature of the cosmic background radiation. We report on our high-resolution ALMA mapping of the CO lines in this ultra-cold nebula to determine the origin of these extreme conditions and robustly confirm current estimates of the fundamental physical properties of its ultra-cold outflow.

  14. 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 composite image of the Crab Nebula, a supernova remnant, 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. Credits: NASA, ESA, NRAO/AUI/NSF and G. Dubner (University of Buenos Aires) #nasagoddard #space #science

  15. 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.

  16. Dust in emission nebulae of the LMC derived from photometric reddening of stars

    NASA Astrophysics Data System (ADS)

    Greve, A.; van Genderen, A. M.; Laval, A.

    1990-10-01

    VBLUW photometric observations of stars in emission nebulae of the LMC are reported. The luminosities and extinctions of the stars are derived. Agreement is found between the average photometric extinctions of the nebulae and the extinctions derived from the Balmer line decrement measured by Caplan and Deharveng (1985 and 1986). The photometric extinctions are shown in the CO map of the LMC (Cohen et al., 1988).

  17. Rapid X-Ray Variations of the Geminga Pulsar Wind Nebula

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

    Hui, C. Y.; Lee, Jongsu; Kong, A. K. H.

    A recent study by Posselt et al. reported the deepest X-ray investigation of the Geminga pulsar wind nebula (PWN) by using Chandra X-ray Observatory . In comparison with previous studies of this system, a number of new findings have been reported, and we found that these suggest the possible variabilities in various components of this PWN. This motivates us to carry out a dedicated search for the morphological and spectral variations of this complex nebula. We have discovered variabilities on timescales from a few days to a few months from different components of the nebula. The fastest change occurred inmore » the circumstellar environment at a rate of 80% of the speed of light. One of the most spectacular results is the wiggling of a half light-year long tail as an extension of the jet, which is significantly bent by the ram pressure. The jet wiggling occurred at a rate of about 20% of the speed of light. This twisted structure could possibly be a result of a propagating torsional Alfv́en wave. We have also found evidence of spectral hardening along this tail for a period of about nine months.« less

  18. The Formation of Graphite Whiskers in the Primitive Solar Nebula

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Kimura, Yuki; Lucas, Christopher; Ferguson, Frank; Johnson, Natasha M.

    2010-01-01

    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from proto stellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H2, CO, and N2 reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H2, CO, and N2 at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.

  19. Rapid X-Ray Variations of the Geminga Pulsar Wind Nebula

    NASA Astrophysics Data System (ADS)

    Hui, C. Y.; Lee, Jongsu; Kong, A. K. H.; Tam, P. H. T.; Takata, J.; Cheng, K. S.; Ryu, Dongsu

    2017-09-01

    A recent study by Posselt et al. reported the deepest X-ray investigation of the Geminga pulsar wind nebula (PWN) by using Chandra X-ray Observatory. In comparison with previous studies of this system, a number of new findings have been reported, and we found that these suggest the possible variabilities in various components of this PWN. This motivates us to carry out a dedicated search for the morphological and spectral variations of this complex nebula. We have discovered variabilities on timescales from a few days to a few months from different components of the nebula. The fastest change occurred in the circumstellar environment at a rate of 80% of the speed of light. One of the most spectacular results is the wiggling of a half light-year long tail as an extension of the jet, which is significantly bent by the ram pressure. The jet wiggling occurred at a rate of about 20% of the speed of light. This twisted structure could possibly be a result of a propagating torsional Alfv´en wave. We have also found evidence of spectral hardening along this tail for a period of about nine months.

  20. Chemical fractionation in the solar nebula

    NASA Technical Reports Server (NTRS)

    Grossman, L.

    1977-01-01

    The sequence of condensation of minerals from a cooling gas of solar composition has been calculated from thermodynamic data over the pressure range 0.001-0.00001 atm, assuming that complete chemical equilibrium is maintained. The results suggest that the Ca-Al-rich inclusions Allende and other carbonaceous chondrites are aggregates of the highest temperature condensates. Complete condensation of these elements is followed, 100 deg later, by the onset of the crystallization of nickel-iron, forsterite and enstatite. Transport of Ca-Al-rich refractory condensates from one part of the nebula to another before the condensation of these lower-temperature phases may have been responsible for the refractory element fractionations between the different classes of chondrites and possibly for the inferred refractory element enrichment of the Moon. The temperature gap between the condensation temperatures of nickel-iron and forsterite increases with increasing total pressure. Because pressure and temperature probably increased with decreasing heliocentric distance in the solar nebula, Mercury may have accreted from a condensate assemblage having a higher metal/silicate ratio than Venus or Earth which may, in turn, have formed from less oxidized material than Mars.

  1. A Spatially Resolved Plerionic X-Ray Nebula around PSR B0540-69.

    PubMed

    Gotthelf; Wang

    2000-04-01

    We present a high-resolution Chandra X-ray observation of PSR B0540-69, the Crab-like 50 ms pulsar in the Large Magellanic Cloud. We use phase-resolved imaging to decompose the extended X-ray emission, as expected of a synchrotron nebula, from the pointlike emission of the pulsar. The image of the pulsed X-ray emission shows a well-defined point-spread function of the observation, while the resolved nebula has a morphology and size remarkably similar to the Crab nebula, including evidence for a jetlike feature from PSR B0540-69. The patchy outer shell, which most likely represents the expanding blast wave of the supernova, is reminiscent of that seen in radio. Based on morphology, size, and energetics, there can be little doubt that SNR B0540-69 is an analogous system to the Crab but located in our neighboring galaxy.

  2. Far-infrared line observations of planetary nebulae. 1: The O 3 spectrum

    NASA Technical Reports Server (NTRS)

    Dinerstein, H. L.; Lester, D. F.; Werner, M. W.

    1985-01-01

    Observations of the far-infrared fine structure lines of O III have been obtained for six planetary nebulae. The infrared measurements are combined with optical O III line fluxes to probe physical conditions in the gas. From the observed line intensity ratios, a simultaneous solution was obtained for electron temperature and density, as well as means of evaluating the importance of inhomogeneities. Densities determined from the far-infrared O III lines agree well density diagnostics from other ions, indicating a fairly homogeneous density in the emitting gas. Temperatures are determined separately from the O III 4363/5007 A and 5007 A/52 micron intensity ratios and compared. Systematically higher values are derived from the former ratio, which is expected from a nebula which is not isothermal. Allowance for the presence of temperature variations within these nebulae raises their derived oxygen abundances, determinations to be reconciled with the solar value.

  3. A survey of nebulae around Galactic Wolf-Rayet stars in the southern sky, 1

    NASA Technical Reports Server (NTRS)

    Marston, A. P.; Chu, Y.-H.; Garcia-Segura, G.

    1994-01-01

    Images are presented from the first half of a survey of all Galactic Wolf-Rayet stars in the catalog of van der Hucht et al. (1981) residing in the southern skies. Previous surveys used only existing broad-band photographic plates. Encouraged by successes using CCD imaging with interference filters of the LMC and northern Galaxy (Miller & Chu 1993), we have expanded the survey to the southern hemisphere. In the first half of our southern survey, H alpha and (O III) narrow-band CCD images of fields centered on known Wolf-Rayet stars have indicated the existence of six new ring nebulae as well as revealing previously unobserved morphological features in the known ring nebulae. An example of this is an almost perfect ring of (O III) emission residing interior to the previously observed H alpha filaments of the Wolf-Rayet ring nebulae RCW 104. Our surveys to date indicate that 21% of all Wolf-Rayet stars have ring nebulae, with WN-type Wolf-Rayet stars having a greater likelihood for an associated ring.

  4. 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

  5. Revealing the velocity structure of the filamentary nebula in NGC 1275 in its entirety

    NASA Astrophysics Data System (ADS)

    Gendron-Marsolais, M.; Hlavacek-Larrondo, J.; Martin, T. B.; Drissen, L.; McDonald, M.; Fabian, A. C.; Edge, A. C.; Hamer, S. L.; McNamara, B.; Morrison, G.

    2018-05-01

    We have produced for the first time a detailed velocity map of the giant filamentary nebula surrounding NGC 1275, the Perseus cluster's brightest galaxy, and revealed a previously unknown rich velocity structure across the entire nebula. These new observations were obtained with the optical imaging Fourier transform spectrometer SITELLE at CFHT. With its wide field of view (˜11'×11'), SITELLE is the only integral field unit spectroscopy instrument able to cover the 80 kpc×55 kpc (3.8'×2.6') large nebula in NGC 1275. Our analysis of these observations shows a smooth radial gradient of the [N II]λ6583/Hα line ratio, suggesting a change in the ionization mechanism and source across the nebula. The velocity map shows no visible general trend or rotation, indicating that filaments are not falling uniformly onto the galaxy, nor being uniformly pulled out from it. Comparison between the physical properties of the filaments and Hitomi measurements of the X-ray gas dynamics in Perseus are also explored.

  6. FAR-ULTRAVIOLET OBSERVATIONS OF THE SPICA NEBULA AND THE INTERACTION ZONE

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

    Choi, Yeon-Ju; Min, Kyoung-Wook; Lim, Tae-Ho

    2013-09-01

    We report the analysis results of far-ultraviolet (FUV) observations, made for a broad region around {alpha} Vir (Spica) including the interaction zone of Loop I and the Local Bubble. The whole region was optically thin and a general correlation was seen between the FUV continuum intensity and the dust extinction, except in the neighborhood of the bright central star, indicating the dust scattering nature of the FUV continuum. We performed Monte Carlo radiative transfer simulations to obtain the optical parameters related to the dust scattering as well as to the geometrical structure of the region. The albedo and asymmetry factormore » were found to be 0.38 {+-} 0.06 and 0.46 {+-} 0.06, respectively, in good agreement with the Milky Way dust grain models. The distance to and the thickness of the interaction zone were estimated to be 70{sup +4}{sub -8} pc and 40{sup +8}{sub -10} pc, respectively. The diffuse FUV continuum in the northern region above Spica was mostly the result of scattering of the starlight from Spica, while that in the southern region was mainly due to the background stars. The C IV {lambda}{lambda}1548, 1551 emission was found throughout the whole region, in contrast to the Si II* {lambda}1532 emission which was bright only within the H II region. This indicates that the C IV line arises mostly at the shell boundaries of the bubbles, with a larger portion likely from the Loop I than from the Local Bubble side, whereas the Si II* line is from the photoionized Spica Nebula.« less

  7. 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

  8. 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

  9. Blowing in the Wind: II. Creation and Redistribution of Refractory Inclusions in a Turbulent Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Davis, Sanford S.; Dobrovolskis, Anthony R.

    2003-01-01

    Ca-A1 rich refractory mineral inclusions (CAIs) found at 1-6% mass fraction in primitive chondrites appear to be 1-3 million years older than the dominant (chondrule) components which were accreted into 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 reassess the situation in terms of 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 overwhelm inward drift, and prevent significant numbers of CAI-size particles from being lost into the sun for times on the order of 10(exp 6) years. CAIs can form early, when the inner nebula was hot, and persist in sufficient abundance to be incorporated into primitive planetesimals at a much later time. Small (less than or approximately 0.1 mm diameter) CAIs persist for longer times than large (greater than or approximately 5mm diameter ones. To obtain a quantitative match to the observed volume fractions of CAIs in chondrites, another process must be allowed for: a substantial enhancement of the inner hot nebula in silicate-forming material, which we suggest was caused by rapid inward drift of meter-sized objects. This early in nebula history, the drifting rubble would have a carbon content probably an order of magnitude larger than even the most primitive (CI) carbonaceous chondrites. Abundant carbon in the evaporating material would help keep the nebula oxygen fugacity low, plausibly solar; as inferred for the formation environment of CAIs. The associated production of a larger than canonical amount of CO2 might also play a role in mass-independent fractionation of oxygen isotopes, leaving the gas rich in O-16 as inferred from CAIs and other high temperature condensates.

  10. 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.

  11. Festive Nebulas Light Up Milky Way Galaxy Satellite

    NASA Image and Video Library

    2017-12-08

    NASA’s Hubble Space Telescope captured two festive-looking nebulas, situated so as to appear as one. They reside in the Small Magellanic Cloud, a dwarf galaxy that is a satellite of our Milky Way galaxy. Intense radiation from the brilliant central stars is heating hydrogen in each of the nebulas, causing them to glow red. The nebulas, together, are called NGC 248. They were discovered in 1834 by the astronomer Sir John Herschel. NGC 248 is about 60 light-years long and 20 light-years wide. It is among a number of glowing hydrogen nebulas in the dwarf satellite galaxy, which is located approximately 200,000 light-years away in the southern constellation Tucana. The image is part of a study called Small Magellanic Cloud Investigation of Dust and Gas Evolution (SMIDGE). Astronomers are using Hubble to probe the Milky Way satellite to understand how dust is different in galaxies that have a far lower supply of heavy elements needed to create dust. The Small Magellanic Cloud has between a fifth and a tenth of the amount of heavy elements that the Milky Way does. Because it is so close, astronomers can study its dust in great detail, and learn about what dust was like earlier in the history of the universe. “It is important for understanding the history of our own galaxy, too,” explained the study’s principal investigator, Dr. Karin Sandstrom of the University of California, San Diego. Most of the star formation happened earlier in the universe, at a time where there was a much lower percentage of heavy elements than there is now. “Dust is a really critical part of how a galaxy works, how it forms stars,” said Sandstrom. Credit: NASA, ESA, STScI, K. Sandstrom (University of California, San Diego), and the SMIDGE team 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

  12. 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.

  13. Ionized magnesium in the planetary nebula NGC 7027

    NASA Technical Reports Server (NTRS)

    Evans, N. J., II; Natta, A.; Russell, R. W.; Wyant, J.; Beckwith, S.

    1984-01-01

    Observations of NGC 7027 are presented for six ionic lines: Mg(+3) (4.48 microns), Mg(+4) (5.61 microns), H(0) (4.05 and 7.46 microns), Ne(+5) (7.64 microns), and Ar(+5) (4.53 microns). The magnesium lines are consistent with the measurements of Russell, Soifer, and Willner (1977), and the hydrogen lines are consistent with the line strengths predicted from the radio flux. Upper limits were obtained for the neon and argon lines. The abundance of magnesium in the central part of the nebula is highly uncertain because the fine-structure collision strengths are poorly known. The strong gradient of magnesium abundance from the inner to the outer portions of the nebula derived by Pequignot and Stasinska (1980) could be an artifact of this uncertainty. A brief analysis of the effective stellar temperature derived from the magnesium line ratios is given.

  14. Pyrolysis-GCMS Analysis of Solid Organic Products from Catalytic Fischer-Tropsch Synthesis Experiments

    NASA Technical Reports Server (NTRS)

    Locke, Darren R.; Yazzie, Cyriah A.; Burton, Aaron S.; Niles, Paul B.; Johnson, Natasha M.

    2015-01-01

    Abiotic synthesis of complex organic compounds in the early solar nebula that formed our solar system is hypothesized to occur via a Fischer-Tropsch type (FTT) synthesis involving the reaction of hydrogen and carbon monoxide gases over metal and metal oxide catalysts. In general, at low temperatures (less than 200 C), FTT synthesis is expected to form abundant alkane compounds while at higher temperatures (greater than 200 C) it is expected to product lesser amounts of n-alkanes and greater amounts of alkene, alcohol, and polycyclic aromatic hydrocarbons (PAHs). Experiments utilizing a closed-gas circulation system to study the effects of FTT reaction temperature, catalysts, and number of experimental cycles on the resulting solid insoluble organic products are being performed in the laboratory at NASA Goddard Space Flight Center. These experiments aim to determine whether or not FTT reactions on grain surfaces in the protosolar nebula could be the source of the insoluble organic matter observed in meteorites. The resulting solid organic products are being analyzed at NASA Johnson Space Center by pyrolysis gas chromatography mass spectrometry (PY-GCMS). PY-GCMS yields the types and distribution of organic compounds released from the insoluble organic matter generated from the FTT reactions. Previously, exploratory work utilizing PY-GCMS to characterize the deposited organic materials from these reactions has been reported. Presented here are new organic analyses using magnetite catalyst to produce solid insoluble organic FTT products with varying reaction temperatures and number of experimental cycles.

  15. Anomalous cosmic ray fluxes in diffusive shock acceleration processes in the heliosphere and in planetary and WR-nebulae

    NASA Astrophysics Data System (ADS)

    Yeghikyan, Ararat

    2018-04-01

    Based on the analogy between interacting stellar winds of planetary nebulae and WR-nebulae, on the one hand, and the heliosphere and the expanding envelopes of supernovae, on the other, an attempt is made to calculate the differential intensity of the energetic protons accelerated to energies of 100 MeV by the shock wave. The proposed one-parameter formula for estimating the intensity at 1-100 MeV, when applied to the heliosphere, shows good agreement with the Voyager-1 data, to within a factor of less than 2. The same estimate for planetary (and WR-) nebulae yields a value 7-8 (3-4) orders of magnitude higher than the mean galactic intensity value. The obtained estimate of the intensity of energetic protons in mentioned kinds of nebulae was used to estimate the doses of irradiation of certain substances, in order to show that such accelerated particles play an important role in radiation-chemical transformations in such nebulae.

  16. DISCOVERY OF COLLIMATED BIPOLAR OUTFLOWS IN THE PLANETARY NEBULA TH 2-A

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

    Danehkar, A., E-mail: ashkbiz.danehkar@cfa.harvard.edu

    We present a comprehensive set of spatially resolved, integral field spectroscopic mapping of the Wolf–Rayet planetary nebula Th 2-A, obtained using the Wide Field Spectrograph on the Australian National University 2.3-m telescope. Velocity-resolved Hα channel maps with a resolution of 20 km s{sup −1} allow us to identify different kinematic components within the nebula. This information is used to develop a three-dimensional morpho-kinematic model of the nebula using the interactive kinematic modeling tool shape. These results suggest that Th 2-A has a thick toroidal shell with an expansion velocity of 40 ± 10 km s{sup −1}, and a thin prolate ellipsoid withmore » collimated bipolar outflows toward its axis reaching velocities in the range of 70–110 km s{sup −1}, with respect to the central star. The relationship between its morpho-kinematic structure and peculiar [WO]-type stellar characteristics deserves further investigation.« less

  17. 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

  18. 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.

  19. Crab Nebula Variations in Hard X-rays

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen A.

    2012-01-01

    The Crab Nebula was surprisingly variable from 2001-2010, with less variability before 2001 and since mid-2010. We presented evidence for spectral softening from RXTE, Swift/BAT, and Fermi GBM during the mid-2008-2010 flux decline. We see no clear connections between the hard X-ray variations and the GeV flares

  20. X-ray Emission from Hot Bubbles in nebulae around Evolved Stars

    NASA Astrophysics Data System (ADS)

    Toalá Sánz, Jesús Alberto

    This thesis presents an observational and numerical study on the X-ray emission related to the formation and evolution from hot bubbles in nebulae around evolved stars. The observational part of this study consists mainly in observations obtained from the X-ray satellites X-ray Multi Mirror Mission (XMM-Newton) and Chandra X-ray Observatory (CXO). We have made use of optical, infrared, and ultraviolet observations that have complemented our results and analysis. These observations have allowed us to study the Wolf-Rayet (WR) nebulae S 308 and NGC 6888 and that around the WR star WR 16. We have also studied the planetary nebulae (PNe) NGC 6543 and Abell 78 (A 78). The X-ray telescopes, XMM-Newton and CXO, have allowed us to study the distribution and physical characteristics of the hot and diffuse gas in the WR nebulae S 308 and NGC 6888 with exquisite detail. Even though the CXO observations do not map entirely NGC 6888, we are able to estimate global parameters of the X-ray emission making use of ROSAT observations. Previous observations performed with were hampered by Suzaku, ROSAT, and ASCA were hampered by a large number of point sources in the line of sight of the nebulae. S 308 was observed with XMM-Newton with four pointings. We have made use of the most up-to-date tools for the analysis of soft and diffuse X-ray emission (the ESAS tasks). We found that in both nebulae the hot gas has a plasma temperature of 1-1.5×10^6 K and it is delineated by the [O III] emission and not the Hα as stated in previous studies. A notable difference between these two WR nebulae is that S 308 has a limb-brightened morphology in the distribution of its hot gas, while NGC 6888 displays three maxima. We have studied the WR nebula around WR 16 with archived XMM-Newton observations. Even though it was expected that diffuse X-ray emission should be detected from a spherical, non-disrupted WR nebula, by comparison with S 308 and NGC 6888, we are not able to detect such emission

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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

  6. 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.

  7. Synthesis, Spectral, and In Vitro Antibacterial Studies of Organosilicon(IV) Complexes with Schiff Bases Derived from Amino Acids.

    PubMed

    Singh, Har Lal; Singh, Jangbhadur; Mukherjee, A

    2013-01-01

    The present work stems from our interest in the synthesis, characterization, and antibacterial evaluation of organosilicon(IV) complexes of a class of amino-acid-based Schiff base which have been prepared by the interaction of ethoxytrimethylsilane with the Schiff bases (N OH) in 1 : 1 molar ratio. These complexes have been characterized by elemental analysis, molar conductance, and spectroscopic studies including electronic IR and NMR ((1)H, (13)C, and (29)Si) spectroscopy. The analytical and spectral data suggest trigonal bipyramidal geometry around the silicon atom in the resulting complexes. The ligands and their organosilicon complexes have also been evaluated for in vitro antimicrobial activity against bacteria (Bacillus cereus, Nocardia spp., E. aerogenes, Escherichia coli, Klebsiella spp., and Staphylococcus spp.). The complexes were found to be more potent as compared to the ligands.

  8. Solar nebula heterogeneity in p-process samarium and neodymium isotopes.

    PubMed

    Andreasen, Rasmus; Sharma, Mukul

    2006-11-03

    Bulk carbonaceous chondrites display a deficit of approximately 100 parts per million (ppm) in 144Sm with respect to other meteorites and terrestrial standards, leading to a decrease in their 142Nd/144Nd ratios by approximately 11 ppm. The data require that samarium and neodymium isotopes produced by the p process associated with photodisintegration reactions in supernovae were heterogeneously distributed in the solar nebula. Other samarium and neodymium isotopes produced by rapid neutron capture (r process) in supernovae and by slow neutron capture (s process) in red giants were homogeneously distributed. The supernovae sources supplying the p- and r-process nuclides to the solar nebula were thus disconnected or only weakly connected.

  9. 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

  10. 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.

  11. PHOTOMETRY OF THE STINGRAY NEBULA (V839 ARA) FROM 1889 TO 2015 ACROSS THE IONIZATION OF ITS PLANETARY NEBULA

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

    Schaefer, Bradley E.; Edwards, Zachary I.

    Up until around 1980, the Stingray was an ordinary B1 post-AGB star, but then it suddenly sprouted bright emission lines like in a planetary nebula (PN), and soon after this the Hubble Space Telescope (HST) discovered a small PN around the star, so apparently we have caught a star in the act of ionizing a PN. We report here on a well-sampled light curve from 1889 to 2015, with unique coverage of the prior century plus the entire duration of the PN formation plus three decades of its aftermath. Surprisingly, the star anticipated the 1980s ionization event by declining frommore » B = 10.30 in 1889 to B = 10.76 in 1980. Starting in 1980, the central star faded fast, at a rate of 0.20 mag year{sup −1}, reaching B = 14.64 in 1996. This fast fading is apparently caused by the central star shrinking in size. From 1994 to 2015, the V-band light curve is almost entirely from the flux of two bright [O iii] emission lines from the unresolved nebula, and it shows a consistent decline at a rate of 0.090 mag year{sup −1}. This steady fading (also seen in the radio and infrared) has a timescale equal to that expected for ordinary recombination within the nebula, immediately after a short-duration ionizing event in the 1980s. We are providing the first direct measure of the rapidly changing luminosity of the central star on both sides of a presumed thermal pulse in 1980, with this providing a strong and critical set of constraints, and these are found to sharply disagree with theoretical models of PN evolution.« less

  12. CTIO Image of Carina Nebula

    NASA Image and Video Library

    2017-12-08

    NASA image release April 22, 2010 Object Names: Carina Nebula, NGC 3372 Image Type: Astronomical Credit: NASA/N. Smith (University of California, Berkeley) and NOAO/AURA/NSF 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 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.

  13. Ultraviolet observations of close-binary and pulsating nuclei of planetary nebulae; Winds and shells around low-mass supergiants; The close-binary nucleus of the planetary nebula HFG-1; A search for binary nuclei of planetary nebulae; UV monitoring of irregularly variable planetary nuclei; and The pulsating nucleus of the planetary nebula Lo 4

    NASA Technical Reports Server (NTRS)

    Bond, Howard E.

    1992-01-01

    A brief summary of the research highlights is presented. The topics covered include the following: binary nuclei of planetary nebulae; other variable planetary nuclei; low-mass supergiants; and other IUE-related research.

  14. William Herschel's 'Hole in the Sky' and the discovery of dark nebulae

    NASA Astrophysics Data System (ADS)

    Steinicke, Wolfgang

    2016-12-01

    In 1785 William Herschel published a paper in the Philosophical Transactions containing the remarkable section "An opening or hole". It describes an unusual vacant place in Scorpius. This matter falls into oblivion until Caroline Herschel initiated a correspondence with her nephew John in 1833. It contains Herschel's spectacular words "Hier ist wahrhaftig ein Loch im Himmel" ("Here truly is a hole in the sky"). About a hundred years later, Johann Georg Hagen, Director of the Vatican Observatory, presented a spectacular candidate for the 'hole', discovered in 1857 by Angelo Secchi in Sagittarius and later catalogued by Edward E. Barnard as the dark nebula B 86. Hagen's claim initiated a debate, mainly in the Journal of the British Astronomical Association, about the identity of Herschel's 'object'. Though things could be partly cleared up, unjustified claims still remain. This is mainly due to the fact that original sources were not consulted. A comprehensive study of the curious 'hole' is presented here. It covers major parts of the epochal astronomical work of William, Caroline and John Herschel. This includes a general study of 'vacant places', found by William Herschel and others, and the speculations about their nature, eventually leading to the finding that dark nebulae are due to absorbing interstellar matter. Some of the 'vacant places' could be identified in catalogues of dark nebulae and this leads to a 'Herschel Catalogue of Dark Nebulae' - the first historic catalogue of its kind.

  15. A Large Bubble External to the Wolf-Rayet Ring Nebula NGC 6888

    NASA Astrophysics Data System (ADS)

    Marston, A. P.

    1995-05-01

    We present high spatial resolution IRAS images (HIRES) of a 2° field surrounding the Wolf-Rayet ring nebula NGC 6888. This shows the presence of an elliptical shell 1.7° × 1.4° in size and with a position angle at 45° relative to that of NGC 6888 which is also observed in our images. IRAS fluxes indicate the outer large bubble has a cooler dust temperature than NGC 6888 and has an implied gas mass of approximately 8000 Msun. It is proposed that the outer shell represents the extent of a bubble 19 pc across created in the O star phase of the Wolf-Rayet star WR 136 (HD 192163), presently at the center of NGC 6888. This bubble is estimated as being 1.9 × 106 yr old with an associated O star phase of 1.6-1.9 × 106 yr. The high spatial resolution in our IRAS images has also allowed better fluxes to be determined for the ring nebula NGC 6888 which are consistent with the previous results of Marston & Meaburn (1988). We illustrate how the nebulae around the star WR 136 are consistent with a three phase evolution for Wolf-Rayet stars. With the large mass lost in the ring nebula we suggest that a massive (>40 Msun) O star has evolved through a luminous blue variable phase before becoming the Wolf-Rayet star WR 136.

  16. 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

    Protostellar systems are variable on many timescales. One of the most dramatic forms of variability known to occur in low mass stellar systems is the FU Orionis outburst (Herbig 1977). Throughout a typical outburst lasting several decades, system luminosities may be a hundred times what is typical of the quiesent state. FU Orionis outburst events are thought to have significant impact on the thermal structure of the protosolar nebula; their existence has been used to explain features in the meteoritic record from thermally induced homogenization to the formation of chondrules. Until recently, the magnitude of the likely effect from such outbursts has been largely speculative due to the lack of a detailed understanding of the outburst mechanism. Recent numerical models (Bell\\& Lin 1994) have demonstrated the viability of the observational hypothesis (Hartmann\\& Kenyon 1985) that the radiation observed during outburst is emitted by a luminous circumstellar disk transporting mass at a thousand times the quiesent rate. Light curves and color and line width evolution observed in FU Orionis systems are naturally explained by time dependent outbursting model disks (Bell et al. 1995). The radial temperature structure and shape of the disk during outburst derived from these models may be used to calculate the outburst's expected impact on primitive material at various radii throughout the disk. In this review, we will begin by discussing what is known about the FU Orionis outburst phenomenon from recent observations and theory including statistically deduced outburst timescales and observed peak temperatures. Unless covered by another author, we will discuss the evidence which suggests that outburst radiation is emitted by a circumstellar disk rather than by the star and will briefly review the thermal instability as a mechanism for outburst. We will then report on recent work which investigates the likely heating of solar nebula material due to FU Orionis outbursts

  17. Ionized haloes in planetary nebulae: new discoveries, literature compilation and basic statistical properties

    NASA Astrophysics Data System (ADS)

    Corradi, R. L. M.; Schönberner, D.; Steffen, M.; Perinotto, M.

    2003-04-01

    We present a comprehensive observational study of haloes around planetary nebulae (PNe). Deep Hα+[NII] and/or [OIII] narrow-band images have been obtained for 35 PNe, and faint extended haloes have been newly discovered in the following 10 objects: Cn 1-5, IC 2165, IC 2553, NGC 2792, NGC 2867, NGC 3918, NGC 5979, NGC 6578, PB 4, and possibly IC 1747. New deep images have also been obtained of other known or suspected haloes, including the huge extended emission around NGC 3242 and Sh 2-200. In addition, the literature was searched, and together with the new observations an improved data base containing some 50 PN haloes has been compiled. The halo sample is illustrated in an image atlas contained in this paper, and the original images are made available for use by the scientific community at http://www.ing. iac.es/~rcorradi/HALOES/. The haloes have been classified following the predictions of modern radiation-hydrodynamical simulations that describe the formation and evolution of ionized multiple shells and haloes around PNe. According to the models, the observed haloes have been divided into the following groups: (i) circular or slightly elliptical asymptotic giant branch (AGB) haloes, which contain the signature of the last thermal pulse on the AGB; (ii) highly asymmetrical AGB haloes; (iii) candidate recombination haloes, i.e. limb-brightened extended shells that are expected to be produced by recombination during the late post-AGB evolution, when the luminosity of the central star drops rapidly by a significant factor; (iv) uncertain cases which deserve further study for a reliable classification; (v) non-detections, i.e. PNe in which no halo is found to a level of <~10-3 the peak surface brightness of the inner nebulae. We discuss the properties of the haloes: detection rate, morphology, location of the central stars in the Hertzsprung-Russell diagram, sizes, surface brightness profiles, and kinematical ages. Among the most

  18. Crab Nebula

    NASA Image and Video Library

    2017-12-08

    The Crab Nebula is a supernova remnant, all that remains of a tremendous stellar explosion. Observers in China and Japan recorded the supernova nearly 1,000 years ago, in 1054. Credit: NASA, ESA, J. Hester and A. Loll (Arizona State University) 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 Institute conducts Hubble science operations. Goddard is responsible for HST project management, including mission and science operations, servicing missions, and all associated development activities. To learn more about the Hubble Space Telescope go here: www.nasa.gov/mission_pages/hubble/main/index.html 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. Follow us on Twitter Join us on Facebook

  19. Double Engine for a Nebula

    NASA Astrophysics Data System (ADS)

    2009-08-01

    ESO has just released a stunning new image of a field of stars towards the constellation of Carina (the Keel). This striking view is ablaze with a flurry of stars of all colours and brightnesses, some of which are seen against a backdrop of clouds of dust and gas. One unusual star in the middle, HD 87643, has been extensively studied with several ESO telescopes, including the Very Large Telescope Interferometer (VLTI). Surrounded by a complex, extended nebula that is the result of previous violent ejections, the star has been shown to have a companion. Interactions in this double system, surrounded by a dusty disc, may be the engine fuelling the star's remarkable nebula. The new image, showing a very rich field of stars towards the Carina arm of the Milky Way, is centred on the star HD 87643, a member of the exotic class of B[e] stars [1]. It is part of a set of observations that provide astronomers with the best ever picture of a B[e] star. The image was obtained with the Wide Field Imager (WFI) attached to the MPG/ESO 2.2-metre telescope at the 2400-metre-high La Silla Observatory in Chile. The image shows beautifully the extended nebula of gas and dust that reflects the light from the star. The central star's wind appears to have shaped the nebula, leaving bright, ragged tendrils of gas and dust. A careful investigation of these features seems to indicate that there are regular ejections of matter from the star every 15 to 50 years. A team of astronomers, led by Florentin Millour, has studied the star HD 87643 in great detail, using several of ESO's telescopes. Apart from the WFI, the team also used ESO's Very Large Telescope (VLT) at Paranal. At the VLT, the astronomers used the NACO adaptive optics instrument, allowing them to obtain an image of the star free from the blurring effect of the atmosphere. To probe the object further, the team then obtained an image with the Very Large Telescope Interferometer (VLTI). The sheer range of this set of observations

  20. Helix Nebula: Enabling federation of existing data infrastructures and data services to an overarching cross-domain e-infrastructure

    NASA Astrophysics Data System (ADS)

    Lengert, Wolfgang; Farres, Jordi; Lanari, Riccardo; Casu, Francesco; Manunta, Michele; Lassalle-Balier, Gerard

    2014-05-01

    so called "Supersite Exploitation Platform" (SSEP) provides scientists an overarching federated e-infrastructure with a very fast access to (i) large volume of data (EO/non-space data), (ii) computing resources (e.g. hybrid cloud/grid), (iii) processing software (e.g. toolboxes, RTMs, retrieval baselines, visualization routines), and (iv) general platform capabilities (e.g. user management and access control, accounting, information portal, collaborative tools, social networks etc.). In this federation each data provider remains in full control of the implementation of its data policy. This presentation outlines the Architecture (technical and services) supporting very heterogeneous science domains as well as the procedures for new-comers to join the Helix Nebula Market Place. Ref.1 http://cds.cern.ch/record/1374172/files/CERN-OPEN-2011-036.pdf

  1. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Weisskopf, M.; Hester, J. J.; Tennant, A. F.; Elsner, R. F.; Schulz, N. S.; Marshall, H. L.; Karovska, M.; Nichols, J. S.; Swartz, D. A.; Kolodziejczak, J. J.

    2000-01-01

    The Chandra X-ray Observatory observed the Crab Nebula and Pulsar During orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) read-out by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure, at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the Nebula.

  2. 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

  3. 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.

  4. THE BALMER-DOMINATED BOW SHOCK AND WIND NEBULA STRUCTURE OF {gamma}-RAY PULSAR PSR J1741-2054

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

    Romani, Roger W.; Shaw, Michael S.; Camilo, Fernando

    2010-12-01

    We have detected an H{alpha} bow shock nebula around PSR J1741-2054, a pulsar discovered through its GeV {gamma}-ray pulsations. The pulsar is only {approx}1.''5 behind the leading edge of the shock. Optical spectroscopy shows that the nebula is non-radiative, dominated by Balmer emission. The H{alpha} images and spectra suggest that the pulsar wind momentum is equatorially concentrated and implies a pulsar space velocity {approx}150 km s{sup -1}, directed 15{sup 0} {+-} 10{sup 0} out of the plane of the sky. The complex H{alpha} profile indicates that different portions of the post-shock flow dominate line emission as gas moves along themore » nebula and provide an opportunity to study the structure of this unusual slow non-radiative shock under a variety of conditions. CXO ACIS observations reveal an X-ray pulsar wind nebula within this nebula, with a compact {approx}2.''5 equatorial structure and a trail extending several arcminutes behind. Together these data support a close ({<=}0.5 kpc) distance, a spin geometry viewed edge-on, and highly efficient {gamma}-ray production for this unusual, energetic pulsar.« less

  5. 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.

  6. 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.

  7. The extinction and dust-to-gas structure of the planetary nebula NGC 7009 observed with MUSE

    NASA Astrophysics Data System (ADS)

    Walsh, J. R.; Monreal-Ibero, A.; Barlow, M. J.; Ueta, T.; Wesson, R.; Zijlstra, A. A.

    2016-04-01

    Context. Dust plays a significant role in planetary nebulae. Dust ejected with the gas in the asymptotic giant branch (AGB) phase is subject to the harsh environment of the planetary nebula (PN) while the star is evolving towards a white dwarf. Dust surviving the PN phase contributes to the dust content of the interstellar medium. Aims: The morphology of the internal dust extinction has been mapped for the first time in a PN, the bright nearby Galactic nebula NGC 7009. The morphologies of the gas, dust extinction and dust-to-gas ratio are compared to the structural features of the nebula. Methods: Emission line maps in H Balmer and Paschen lines were formed from analysis of MUSE cubes of NGC 7009 observed during science verification of the instrument. The measured electron temperature and density from the same cube were employed to predict the theoretical H line ratios and derive the extinction distribution across the nebula. After correction for the interstellar extinction to NGC 7009, the internal AV/NH has been mapped for the first time in a PN. Results: The extinction map of NGC 7009 has considerable structure, broadly corresponding to the morphological features of the nebula. The dust-to-gas ratio, AV/NH, increases from 0.7 times the interstellar value to >5 times from the centre towards the periphery of the ionized nebula. The integrated AV/NH is about 2× the mean ISM value. A large-scale feature in the extinction map is a wave, consisting of a crest and trough, at the rim of the inner shell. The nature of this feature is investigated and instrumental and physical causes considered; no convincing mechanisms were identified to produce this feature, other than AGB mass loss variations. Conclusions: Extinction mapping from H emission line imaging of PNe with MUSE provides a powerful tool for revealing the properties of internal dust and the dust-to-gas ratio. Based on observations collected at the European Organisation for Astronomical Research in the Southern

  8. Blowing in the Wind: II. Creation and Redistribution of Refractory Inclusions in a Turbulent Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Cuzzi, Jeffrey N.; Davis, Sanford S.; Dobrovolskis, Anthony R.

    2003-01-01

    Ca-Al rich refractory mineral inclusions (CAIs) found at 1-6% mass fraction in primitive chondrites appear to be 1-3 million years older than the dominant (chondrule) components which were accreted into 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 reassess the situation in terms of 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 overwhelm inward drift, and prevent significant numbers of CAI-size particles from being lost into the sun for times on the order of 10(exp 6) years. CAIs can form early, when the inner nebula was hot, and persist in sufficient abundance to be incorporated into primitive planetesimals at a much later time. Small (less than or approx. equal to 0.1 mm diameter) CAIs persist for longer times than large (greater than or approx. equal to 5mm diameter ones). To obtain a quantitative match t o the observed volume fractions of CAIs in chondrites, another process must be allowed for: a substantial enhancement of the inner hot nebula in silicate-forming material, which we suggest was caused by rapid inward drift of meter-sized objects. This early in nebula history, the drifting rubble would have a carbon content probably an order of magnitude larger than even the most primitive (CI) carbonaceous chondrites. Abundant carbon in the evaporating material would help keep the nebula oxygen fugacity low, plausably solar, as inferred for the formation environment of CAIs. The associated production of a larger than canonical amount of CO2 might also play a role in mass-independent fractionation of oxygen isotopes, leaving the gas rich in l60 as inferred from CAIs and other high temperature condensates.

  9. Unsymmetric Mono- and Dinuclear Platinum(IV) Complexes Featuring an Ethylene Glycol Moiety: Synthesis, Characterization, and Biological Activity

    PubMed Central

    Pichler, Verena; Heffeter, Petra; Valiahdi, Seied M.; Kowol, Christian R.; Egger, Alexander; Berger, Walter; Jakupec, Michael A.; Galanski, Markus; Keppler, Bernhard K.

    2014-01-01

    Eight novel mononuclear and two dinuclear platinum(IV) complexes were synthesized and characterized by elemental analysis, one- and two-dimensional NMR spectroscopy, mass spectrometry, and reversed-phase HPLC (log kw) and in one case by X-ray diffraction. Cytotoxicity of the compounds was studied in three human cancer cell lines (CH1, SW480, and A549) by means of the MTT assay, featuring IC50 values to the low micromolar range. Furthermore a selected set of compounds was investigated in additional cancer cell lines (P31 and P31/cis, A2780 and A2780/cis, SW1573, 2R120, and 2R160) with regard to their resistance patterns, offering a distinctly different scheme compared to cisplatin. To gain further insights into the mode of action, drug uptake, DNA synthesis inhibition, cell cycle effects, and induction of apoptosis were determined for two characteristic substances. PMID:23194425

  10. Imaging the Crab nebula when it is flaring in gamma-rays

    NASA Astrophysics Data System (ADS)

    De Luca, Andrea

    2013-10-01

    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. Such events, detected roughly once per year, can be very spectacular. Indeed, in April 2011, for a few days the Crab was by far the brightest source in the gamma-ray sky. Such a dramatic variability challenges our understanding of how pulsar wind nebulae work and defies current astrophysical models for particle acceleration. With the aim of locating the site{s} of the flares, an ad hoc HST strategy must be put in place to be prepared and react promptly in case of a new brightening in gamma rays. We ask here 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. This is a crucial part of a multiwavelength program that we are organizing, based on lessons learnt from our follow-up observations of previous flares, including a regular {monthly} monitoring of the source both in X-ray and optical through a joint Chandra-HST proposal.

  11. Imaging the Crab nebula when it is flaring in gamma-rays

    NASA Astrophysics Data System (ADS)

    De Luca, Andrea

    2014-10-01

    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. Such events, with a recurrence time of about once per year, can be so dramatic to make the system the brightest source in the gamma-ray sky, as it occurred in April 2011. Such a discovery challenges our understanding of how pulsar wind nebulae work and defies current astrophysical models for particle acceleration. With the aim of locating the site(s) of the flares, an ad hoc HST strategy have been put in place to be prepared and react promptly in case of a new brightening in gamma rays. We ask here 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 the Fermi missions. This TOO is crucial part of a multiwavelength program that we have organized, based on lessons learnt from our follow-up observations of previous flares, including a regular (quarterly) monitoring of the source both in X-rays and optical through a joint Chandra-HST proposal.

  12. Implementing an ADA Kernel on NEBULA.

    DTIC Science & Technology

    1983-08-01

    physical address(es). No instruction supports directly semaphore operations , or spin-locks, or other entities used in the synchronisation of tasks...these operations It is found that NEBULA supports admirably the control structures oil Ada, but its Memory Mamagement system is not very suitable. Entry... operating system . With the advent of Ada, in theory at least, the whole program can be written in Ada in a manner that is independent of the computer and of

  13. HUBBLE'S PLANETARY NEBULA GALLERY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [Top left] - IC 3568 lies in the constellation Camelopardalis at a distance of about 9,000 light-years, and has a diameter of about 0.4 light-years (or about 800 times the diameter of our solar system). It is an example of a round planetary nebula. Note the bright inner shell and fainter, smooth, circular outer envelope. Credits: Howard Bond (Space Telescope Science Institute), Robin Ciardullo (Pennsylvania State University) and NASA [Top center] - NGC 6826's eye-like appearance is marred by two sets of blood-red 'fliers' that lie horizontally across the image. The surrounding faint green 'white' of the eye is believed to be gas that made up almost half of the star's mass for most of its life. The hot remnant star (in the center of the green oval) drives a fast wind into older material, forming a hot interior bubble which pushes the older gas ahead of it to form a bright rim. (The star is one of the brightest stars in any planetary.) NGC 6826 is 2,200 light- years away in the constellation Cygnus. The Hubble telescope observation was taken Jan. 27, 1996 with the Wide Field and Planetary Camera 2. Credits: Bruce Balick (University of Washington), Jason Alexander (University of Washington), Arsen Hajian (U.S. Naval Observatory), Yervant Terzian (Cornell University), Mario Perinotto (University of Florence, Italy), Patrizio Patriarchi (Arcetri Observatory, Italy) and NASA [Top right ] - NGC 3918 is in the constellation Centaurus and is about 3,000 light-years from us. Its diameter is about 0.3 light-year. It shows a roughly spherical outer envelope but an elongated inner balloon inflated by a fast wind from the hot central star, which is starting to break out of the spherical envelope at the top and bottom of the image. Credits: Howard Bond (Space Telescope Science Institute), Robin Ciardullo (Pennsylvania State University) and NASA [Bottom left] - Hubble 5 is a striking example of a 'butterfly' or bipolar (two-lobed) nebula. The heat generated by fast winds causes

  14. (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.

  15. When a Standard Candle Flickers: 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.; Camaro-Arranz, A.; Connaughton, V.; Diehl, R.; hide

    2014-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, an 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. At higher energies, above 50 keV, the Crab flux appears to be slowly recovering to its 2008 levels. I will present updated light curves in multiple energy bands for the Crab nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL, MAXI, and NuSTAR and a 16-year long light curve from RXTE/PCA.

  16. 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

  17. UV lines in spectra of planetary nebulae.

    NASA Astrophysics Data System (ADS)

    Milanova, Yu.; Kholtygin, A.

    2008-12-01

    The modern observations of planetary nebulae (PNe) are used to create a new catalogue of element abundances for galactic and extragalac- tic PNe. Some of these abundances, especially C ones, need to be refined. Using in the PNe's models the UV line intensities, planned to be obtained with a help of WSO-UV observatory let us to determine the precision element abundances.

  18. The Wolf-Rayet nebula NGC 3199 - an interstellar snow plough?

    NASA Astrophysics Data System (ADS)

    Dyson, J. E.; Ghanbari, J.

    1989-12-01

    The Wolf-Rayet nebula NGC 3199 has a highly asymmetric morphology, with a very bright hemisphere near the exciting star HD 89358 and a much fainter and more extended other hemisphere. This nebula is modeled in terms of the distorted bubble produced by a moving star blowing a strong stellar wind into a surrounding uniform interstellar medium; this model is fitted to the morphology and observed kinematic data. The exciting star appears to be moving at about 60 km/s into local interstellar gas of density of about 10/cu cm, and has a mass-loss rate of about 0.000027 solar mass/yr. This latter mass-loss rate is in excellent agreement with observed mass-loss rates from Wolf-Rayet stars.

  19. Observations of the Gum Nebula with a Fabry-Perot spectrometer

    NASA Technical Reports Server (NTRS)

    Reynolds, R. J.

    1976-01-01

    Scans have been made of H-alpha, 6584-A forbidden N II, 5007-A forbidden O III, and 5876-A He I emissions in selected directions in the Gum Nebula. Analyses of the line profiles and line intensities indicate that much of the emitting gas in the Gum Nebula is confined to an expanding shell which has a radius of about 125 pc, an expansion velocity of approximately 20 km/s, an emission measure which ranges from about 15 units to about 500 units, and a temperature near 11,000 K. The ultraviolet flux from zeta Pup and gamma-2 Vel appears to be capable of producing most of the observed ionization, although the origin of the shell structure and high expansion velocity is not certain.-

  20. Mono- and di-bromo platinum(IV) prodrugs via oxidative bromination: synthesis, characterization, and cytotoxicity.

    PubMed

    Xu, Zoufeng; Wang, Zhigang; Yiu, Shek-Man; Zhu, Guangyu

    2015-12-14

    Platinum(IV)-based anticancer prodrugs have attracted much attention due to their relative inertness under physiological conditions, being activated inside cells, and their capacity for functionalization with a variety of small-molecule or macromolecule moieties. Novel asymmetric platinum(IV) compounds synthesized through expedient and unique methods are desired. Here we utilize N-bromosuccinimide (NBS) and carry out oxidative bromination on platinum(II) drugs, namely cisplatin, carboplatin, and oxaliplatin, to obtain asymmetric and mono-bromo platinum(IV) prodrugs. Different solvents are used to obtain various compounds, and the compounds are further functionalized. Di-bromo compounds are also obtained through NBS-directed oxidative bromination in ethanol. The crystal structures of representative compounds are discussed, and the reduction potentials of some compounds are examined. A cytotoxicity test shows that the mono- and di-bromo platinum(IV) compounds are active against human ovarian cancer cells. Our study enriches the family of asymmetric platinum(IV) prodrugs and provides with a convenient strategy to obtain brominated platinum(IV) complexes.

  1. 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

  2. Method of synthesis of anhydrous thorium(IV) complexes

    DOEpatents

    Kiplinger, Jaqueline L; Cantat, Thibault

    2013-04-30

    Method of producing anhydrous thorium(IV) tetrahalide complexes, utilizing Th(NO.sub.3).sub.4(H.sub.2O).sub.x, where x is at least 4, as a reagent; method of producing thorium-containing complexes utilizing ThCl.sub.4(DME).sub.2 as a precursor; method of producing purified ThCl.sub.4(ligand).sub.x compounds, where x is from 2 to 9; and novel compounds having the structures: ##STR00001##

  3. Close-up of M27, the Dumbbell Nebula

    NASA Image and Video Library

    2003-02-11

    An aging star last hurrah creates a flurry of glowing knots of gas that appear to be streaking through space. This closeup image of the Dumbbell Nebula was taken by the JPL-built and designed WFC3 camera, onboard NASA's Hubble Space Telescope. http://photojournal.jpl.nasa.gov/catalog/PIA04249

  4. Synthesis, spectral, DFT modeling, cytotoxicity and microbial studies of novel Zr(IV), Ce(IV) and U(VI) piroxicam complexes

    NASA Astrophysics Data System (ADS)

    El-Shwiniy, Walaa H.; Zordok, Wael A.

    2018-06-01

    The Zr(IV), Ce(IV) and U(VI) piroxicam anti-inflammatory drug complexes were prepared and characterized using elemental analyses, conductance, IR, UV-Vis, magnetic moment, IHNMR and thermal analysis. The ratio of metal: Pir is found to be 1:2 in all complexes estimated by using molar ratio method. The conductance data reveal that Zr(IV) and U(VI) chelates are non-electrolytes except Ce(IV) complex is electrolyte. Infrared spectroscopic confirm that the Pir behaves as a bidentate ligand co-ordinated to the metal ions via the oxygen and nitrogen atoms of ν(Cdbnd O)carbonyl and ν(Cdbnd N)pyridyl, respectively. The kinetic parameters of thermogravimetric and its differential, such as activation energy, entropy of activation, enthalpy of activation, and Gibbs free energy evaluated using Coats-Redfern and Horowitz-Metzger equations for Pir and complexes. The geometry of the piroxicam drug in the Free State differs significantly from that in the metal complex. In the time of metal ion-drug bond formation the drug switches-on from the closed structure (equilibrium geometry) to the open one. The antimicrobial tests were assessed towards some types of bacteria and fungi. The in vitro cell cytotoxicity of the complexes in comparison with Pir against colon carcinoma (HCT-116) cell line was measured. Optimized geometrical structure of piroxicam ligand by using DFT calculations.

  5. Spectral Analysis, Synthesis, & Energy Distributions of Nearby E+A Galaxies Using SDSS-IV MaNGA

    NASA Astrophysics Data System (ADS)

    Weaver, Olivia A.; Anderson, Miguel Ricardo; Wally, Muhammad; James, Olivia; Falcone, Julia; Liu, Allen; Wallack, Nicole; Liu, Charles; SDSS Collaboration

    2017-01-01

    Utilizing data from the Mapping Nearby Galaxies at APO (MaNGA) Survey (MaNGA Product Launch-4, or MPL-4), of the latest generation of the Sloan Digital Sky Survey (SDSS-IV), we identified nine post-starburst (E+A) systems that lie within the Green Valley transition zone. We identify the E+A galaxies by their SDSS single fiber spectrum and u-r color, then confirmed their classification as post-starburst by coding/plotting methods and spectral synthesis codes (FIREFLY and PIPE3D), as well as with their Spectral Energy Distributions (SEDs) from 0.15 µm to 22 µm, using GALEX, SDSS, 2MASS, and WISE data. We produced maps of gaussian-fitted fluxes, equivalent widths, stellar velocities, metallicities and age. We also produced spectral line ratio diagrams to classify regions of stellar populations of the galaxies. We found that our sample of E+As retain their post-starburst properties across the entire galaxy, not just at their center. We detected matching a trend line in the ultraviolet and optical bands, consistent with the expected SEDs for an E+A galaxy, and also through the J, H and Ks bands, except for one object. We classified one of the nine galaxies as a luminous infrared galaxy, unusual for a post-starburst object. Our group seeks to further study stellar population properties, spectral energy distributions and quenching properties in E+A galaxies, and investigate their role in galaxy evolution as a whole. This work was supported by the Alfred P. Sloan Foundation via the SDSS-IV Faculty and Student Team (FAST) initiative, ARC Agreement #SSP483 to the CUNY College of Staten Island. This work was also supported by grants to The American Museum of Natural History, and the CUNY College of Staten Island through from National Science Foundation.

  6. The Lighthouse nebula: a run-away pulsar, its PWN, jets and parent SNR

    NASA Astrophysics Data System (ADS)

    Pavan, L.; Bordas, P.; Puhlhofer, G.; et al.

    2016-06-01

    Some 10-20 kyr ago a pulsar was born from a core collapse event, receiving right away a strong kick. Nowadays this pulsar is powering the Lighthouse Nebula (IGR J11014-6103): a complex system of outflows comprising the bow-shock PWN, and two well collimated jets extending perpendicularly to the pulsar's direction of motion. Whereas sharing some clear commonalities with the well known Guitar Nebula, the Lighthouse nebula is the only such system where the parent supernova remnant is well visible and bright in X-rays. I will describe the results from our recent Chandra X-ray campaign, and follow-up optical and radio observations, analyse the properties of the PWN, and possible interpretations on the nature of the long helicoidal jets and of the other outflows that we identified. I will also discuss the link between this system and its parent supernova remnant MSH 11-61A, which could help shedding a light on the processes that give birth to such peculiar systems.

  7. 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.

  8. 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

  9. Kinetics of Methane Clathrate Formation in the Presolar Nebula

    NASA Astrophysics Data System (ADS)

    Vu, Tuan; Choukroun, Mathieu

    2016-10-01

    Clathrate hydrates are a distinct form of water ice wherein the crystal lattice of the host water molecules forms symmetric, polyhedral cages that trap volatile guest species under appropriate pressures and temperatures. These materials are an abundant source of hydrocarbons on Earth, and have been expected to be present on a number of icy celestial bodies, including Mars, Europa, Titan, and Enceladus. Clathrates are also thought to be one of the most likely traps for volatiles during the condensation of the protostellar nebulae. Prior to the Voyager mission, the prevailing expectation was that the elemental composition of the giant planets would reflect the composition of the solar nebula and therefore be similar to solar abundances. However, spacecraft observations by Voyager, Galileo, and Cassini-Huygens, as well as ground-based observations, have revealed unexpected elemental enrichment, relative to solar abundances, of C, N, S, As, P, and noble gases in the giant planets and in comets. One of the contending explanations is the retention of these volatiles as clathrate hydrates, which may have enabled their capture early in the history of the Solar System.While the formation and stability of clathrates have been addressed theoretically and, to some extent, experimentally at relatively high pressures (10-7-10-3 bar), there is a scarcity of experimental undertaking on the kinetics of clathrate formation and their stability at the low pressures relevant to the early outer solar nebula (~10-11 bar). This study seeks to elucidate the clathrate formation kinetics under nebula-relevant conditions via a series of optical Raman experiments on ice/gas mixtures over a range of pressures and temperatures. Our work on the methane gas/ice system shows that clathrate formation occurs on a rather fast timescale (typically within minutes at 223-253 K and 30-50 bar CH4). In addition, the rate of enclathration increases with pressures and temperatures, and the activation energy

  10. Hopkins Ultraviolet Telescope observations of H2 toward the planetary nebula NGC 1535

    NASA Technical Reports Server (NTRS)

    Bowers, Charles W.; Blair, William P.; Long, Knox S.; Davidsen, Arthur F.

    1995-01-01

    We have observed the far-ultraviolet spectrum (912-1860 A) of the bright high-excitation planetary nebula NGC 1535 with approximately 3 A resolution using the Hopkins Ultraviolet Telescope (HUT) aboard the Astro-1 space shuttle pmission in 1990 December. We see strong continuum emission down to the Lyman limit and strong P Cygni profiles from high-excitation lines such as C IV wavelength 1549, N V wavelength 1240, O V wavelength 1371, and O VI wavelength 1035. Below 1150 A strong absorption bands of H2 are seen, which were unanticipated by us because of the low reddening and high galactic latitude of the object and the absence of detected H2 emission in the infrared. We construct model H2 spectra and convolve them to the HUT resolution for comparison with the NGC 1535 data. We find good agreement with a population distribution characterized by a single temperature (T = 300 K) or a two-temperature model (T = 144/500 K), and determine limits on the H2 column density. While both inter-stellar and circumstellar origins for the observed H2 absorption are plausible, we ascribe the material to the planetary nebula in order to estimate the conditions of excitation and place upper limits on the mass of both H2 and H1 in this system. Because the UV transitions are ground-state connected, we determine a stringent upper limit of 0.03 d(sup 2)(sub 1.6) solar mass on the mass of H2, where d(sub 1.6) is the distance relative to an assumed distance of 1.6 kpc. This value is less model-dependent than IR estimates. Along with the central star and nebular masses, these estimates allow us to limit the main-sequence mass of the progenitor star to less than 1.8 solar mass. This upper limit is consistent with a relatively low-mass extended thick disk or Population II progenitor, as expected for an object approximately 1 kpc off the galactic plane.

  11. Dynamos in asymptotic-giant-branch stars as the origin of magnetic fields shaping planetary nebulae.

    PubMed

    Blackman, E G; Frank, A; Markiel, J A; Thomas, J H; Van Horn, H M

    2001-01-25

    Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary nebulae are not spherical; rather, they are elliptical or bipolar in shape. A magnetic field could launch and collimate a bipolar outflow, but the origin of such a field has hitherto been unclear, and some previous work has even suggested that a field could not be generated. Here we show that an asymptotic-giant-branch (AGB) star can indeed generate a strong magnetic field, having as its origin a dynamo at the interface between the rapidly rotating core and the more slowly rotating envelope of the star. The fields are strong enough to shape the bipolar outflows that produce the observed bipolar planetary nebulae. Magnetic braking of the stellar core during this process may also explain the puzzlingly slow rotation of most white dwarf stars.

  12. PAHs in the Ices of Saturn's Satellites: Connections to the Solar Nebula and the Interstellar Medium

    NASA Technical Reports Server (NTRS)

    Cruikshank, Dale P.; Pendleton, Yvonne J.

    2015-01-01

    Aliphatic hydrocarbons and PAHs have been observed in the interstellar medium (e.g., Allamandola et al. 1985, Pendleton et al. 1994, Pendleton & Allamandola 2002, Tielens 2013, Kwok 2008, Chiar & Pendleton 2008) The inventory of organic material in the ISM was likely incorporated into the molecular cloud in which the solar nebula condensed, contributing to 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). Additional organic synthesis occurred in the solar nebula (Ciesla & Sandford 2012). 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 Saturn (Johnson & Lunine 2005). VIMS spectral maps of Phoebe's surface reveal a complex organic spectral signature consisting of prominent aromatic (CH) and aliphatic 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 ((is) approximately 5-20 micrometers size) spiral inward toward Saturn (Verbiscer et al. 2009). They encounter Iapetus and Hyperion 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, and in carbonaceous meteorites (Cruikshank et al. 2014). 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 (is) approximately 4, which is larger than the value found in the diffuse ISM ((is) approximately 2

  13. A convenient synthesis of 1,1-disubstituted 1,2,3,4-tetrahydroisoquinolines via Pictet-Spengler reaction using titanium(IV) isopropoxide and acetic-formic anhydride.

    PubMed

    Horiguchi, Yoshie; Kodama, Hirokazu; Nakamura, Masayoshi; Yoshimura, Tsuyoshi; Hanezi, Kaori; Hamada, Hiroko; Saitoh, Toshiaki; Sano, Takehiro

    2002-02-01

    A synthesis of 1,1-disubstituted 1,2,3,4-tetrahydroisoquinolines (6) was achieved in a highly efficient manner via Pictet-Spengler reaction of arylethylamines (1) and acyclic and cyclic ketones (2) using titanium (IV) isopropoxide and acetic-formic anhydride. The cyclization of the in situ formed acyliminium ion (4) to N-formyl 1,2,3,4-tetrahydroisoquinoline (5) was greatly facilitated by using trifluoroacetic acid as an additional reagent. The Pictet-Spengler reaction was carried out by one pot procedure, providing a convenient and effective method for preparing various 1,2,3,4-tetrahydroisoquinolines.

  14. Nebula observations. Catalogues and archive of photoplates

    NASA Astrophysics Data System (ADS)

    Shlyapnikov, A. A.; Smirnova, M. A.; Elizarova, N. V.

    2017-12-01

    A process of data systematization based on "Academician G.A. Shajn's Plan" for studying the Galaxy structure related to nebula observations is considered. The creation of digital versions of catalogues of observations and publications is described, as well as their presentation in HTML, VOTable and AJS formats and basic principles of work in the interactive application of International Virtual Observatory the Aladin Sky Atlas.

  15. Synthesis and reactivity of a mononuclear non-haem cobalt(IV)-oxo complex

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Lee, Yong-Min; Tcho, Woon-Young; Tussupbayev, Samat; Kim, Seoung-Tae; Kim, Yujeong; Seo, Mi Sook; Cho, Kyung-Bin; Dede, Yavuz; Keegan, Brenna C.; Ogura, Takashi; Kim, Sun Hee; Ohta, Takehiro; Baik, Mu-Hyun; Ray, Kallol; Shearer, Jason; Nam, Wonwoo

    2017-03-01

    Terminal cobalt(IV)-oxo (CoIV-O) species have been implicated as key intermediates in various cobalt-mediated oxidation reactions. Herein we report the photocatalytic generation of a mononuclear non-haem [(13-TMC)CoIV(O)]2+ (2) by irradiating [CoII(13-TMC)(CF3SO3)]+ (1) in the presence of [RuII(bpy)3]2+, Na2S2O8, and water as an oxygen source. The intermediate 2 was also obtained by reacting 1 with an artificial oxidant (that is, iodosylbenzene) and characterized by various spectroscopic techniques. In particular, the resonance Raman spectrum of 2 reveals a diatomic Co-O vibration band at 770 cm-1, which provides the conclusive evidence for the presence of a terminal Co-O bond. In reactivity studies, 2 was shown to be a competent oxidant in an intermetal oxygen atom transfer, C-H bond activation and olefin epoxidation reactions. The present results lend strong credence to the intermediacy of CoIV-O species in cobalt-catalysed oxidation of organic substrates as well as in the catalytic oxidation of water that evolves molecular oxygen.

  16. Turbulence in the ionized gas of the Orion nebula

    NASA Astrophysics Data System (ADS)

    Arthur, S. J.; Medina, S.-N. X.; Henney, W. J.

    2016-12-01

    In order to study the nature, origin, and impact of turbulent velocity fluctuations in the ionized gas of the Orion nebula, we apply a variety of statistical techniques to observed velocity cubes. The cubes are derived from high resolving power (R ≈ 40 000) longslit spectroscopy of optical emission lines that span a range of ionizations. From velocity channel analysis (VCA), we find that the slope of the velocity power spectrum is consistent with predictions of Kolmogorov theory between scales of 8 and 22 arcsec (0.02 to 0.05 pc). The outer scale, which is the dominant scale of density fluctuations in the nebula, approximately coincides with the autocorrelation length of the velocity fluctuations that we determine from the second-order velocity structure function. We propose that this is the principal driving scale of the turbulence, which originates in the autocorrelation length of dense cores in the Orion molecular filament. By combining analysis of the non-thermal linewidths with the systematic trends of velocity centroid versus ionization, we find that the global champagne flow and smaller scale turbulence each contribute in equal measure to the total velocity dispersion, with respective root-mean-square widths of 4-5 km s-1. The turbulence is subsonic and can account for only one half of the derived variance in ionized density, with the remaining variance provided by density gradients in photoevaporation flows from globules and filaments. Intercomparison with results from simulations implies that the ionized gas is confined to a thick shell and does not fill the interior of the nebula.

  17. Discovery of a radio nebula around PSR J0855-4644

    NASA Astrophysics Data System (ADS)

    Maitra, C.; Roy, S.; Acero, F.; Gupta, Y.

    2018-06-01

    We report the discovery of a diffuse radio emission around PSR J0855-4644 using an upgraded GMRT (uGMRT) observation at 1.35 GHz. The radio emission is spatially coincident with the diffuse X-ray pulsar wind nebula (PWN) seen with XMM-Newton but is much larger in extent compared to the compact axisymmetric PWN seen with Chandra. The morphology of the emission, with a bright partial ring-like structure and two faint tail-like features strongly resembles a bow shock nebula, and indicates a velocity of 100 km s-1 through the ambient medium. We conclude that the emission is most likely to be associated with the radio PWN of PSR J0855-4644. From the integrated flux density, we estimate the energetics of the PWN.

  18. When a Standard Candle Flickers: Hard X-ray Variations in the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Wilson-Hodge, Colleen; Cherry, Michael L.; Case, Gary L.; Baumgartner, Wayne H.; Beklen, Elif; Bhat, Narayana P.; Briggs, Michael S.; Buehler, Rolf; Camero-Arranz, Ascension; Connaughton, Valerie; hide

    2014-01-01

    In the first two years of science operations of the Fermi Gamma-ray Burst Monitor (GBM), August 2008 to August 2010, an 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 approximately3.5% 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. At higher energies, above 50 keV, the Crab flux appears to be slowly recovering to its 2008 levels. I will present updated light curves in multiple energy bands for the Crab nebula, including recent data from Fermi GBM, Swift/BAT, INTEGRAL, MAXI, and NuSTAR and a 16-year long light curve from RXTE/PCA. We will compare these variations to higher energies as well, e.g. Fermi LAT.

  19. Crystal chemistry of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} double monophosphates

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

    Bregiroux, Damien, E-mail: damien.bregiroux@upmc.fr; Popa, Karin; Wallez, Gilles

    2015-10-15

    M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds have been extensively studied for several decades for their potential applications in the field of several domains such as matrices for actinides conditioning, phosphors etc. In this paper, the relationships between composition and crystal structure of these compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. M{sup II}M′{sup IV}(PO{sub 4}){sub 2} structures stem from two different archetypes: the cheralite and the yavapaiite structures, with some exceptions that are also described in this article. The ratio of themore » cations radii appears to be the most relevant parameter. The high ratio between the ionic radii of the divalent and tetravalent cations in yavapaiite derivates results in the ordering of these cations into well-differentiated polyhedra whereas cheralite is the only non-ordered structure encountered for M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds. - Graphical abstract: In this paper, the relationships between composition and crystal structure of M{sup II}M′{sup IV}(PO{sub 4}){sub 2} compounds are established. A review of the various processes used for the synthesis of these compounds is also proposed, as well as their most reported properties. - Highlights: • Crystal structure–composition relationships of MIIM′IV(PO4)2 compounds. • Review of the various processes used for the synthesis of these compounds. • Their most reported properties are described and discussed.« less

  20. 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.

  1. 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

  2. The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. II. Evidence for High Luminosity in Holmberg II ULX

    NASA Technical Reports Server (NTRS)

    Berghea, C. T.; Dudik, R. P.; Weaver, K. A.; Kallman, T. R.

    2009-01-01

    This is the second of two papers examining Spitzer Infrared Spectrograph (IRS) observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here we perform detailed photoionization modeling of they infrared lines. Our analysis suggests that the luminosity and morphology of the [O IV] 25.89 micron emission line is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is matter-bounded both in the line of sight direction and to the east, and probably radiation-bounded to the west. A bolometric luminosity in excess of 1040 erg per second would be needed to produce the measured [O IV] flux. We use modeling and previously published studies to conclude that shacks likely contribute very little, if at all, to the high excitation line fluxes observed in the Holmberg II ULX. Additionally, we find that the spectral type of the companion star has a surprisingly strong effect on they predicted strength of the [O IV] emission. This finding could explain the origin of [O IV] hi some starburst systems containing black hole binaries.

  3. The First Detection of [O IV] from an Ultraluminous X-ray Source with Spitzer. 2; Evidence for High Luminosity in Holmberg II ULX

    NASA Technical Reports Server (NTRS)

    Berghea, C. T.; Dudik, R. P.; Weaver, K. A.; Kallman, T. R.

    2009-01-01

    This is the second of two papers examining Spitzer Infrared Spectrograph (IRS) observations of the ultraluminous X-ray source (ULX) in Holmberg II. Here we perform detailed photoionization modeling of the infrared lines. Our analysis suggests that the luminosity and morphology of the [O IV] 25.89 micron emission line is consistent with photoionization by the soft X-ray and far ultraviolet (FUV) radiation from the accretion disk of the binary system and inconsistent with narrow beaming. We show that the emission nebula is matter-bounded both in the line of sight direction and to the east, and probably radiation-bounded to the west. A bolometric luminosity in excess of 10(exp 40) erg/s would be needed to produce the measured [O IV] flux. We use modeling and previously published studies to conclude that shocks likely contribute very little, if at all, to the high-excitation line fluxes observed in the Holmberg II ULX. Additionally, we find that the spectral type of the companion star has a surprisingly strong effect on the predicted strength of the [O IV] emission. This finding could explain the origin of [O IV] in some starburst systems containing black hole binaries.

  4. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Weisskopf, Martin C.; Hester, J. Jeff; Tennant, Allyn F.; Elsner, Ronald F.; Schulz, Norbert S.; Marshall, Herman L.; Karovska, Margarita; Nichols, Joy S.; Swartz, Douglas A.; Kolodziejczak, Jeffery J.

    2000-01-01

    The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced Charge Coupled Devices (CCD) Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.

  5. An X-ray look at the first head-trail nebula in an X-ray binary

    NASA Astrophysics Data System (ADS)

    Soleri, Paolo

    2011-09-01

    Head-tail trails are a common feature in active galactic nuclei and pulsar bow-shocks. Heinz et al. (2008) suggested that also X-ray binaries, being jet sources moving with high velocities in dense media, can leave trails of highly ionized plasma that should be detectable at radio frequencies. During bservations of faint-persistent X-ray binaries, we discovered an optical nebula around the X-ray binary SAX J1712.6-3739, consisting of a bow-shock ring-like nebula in front of the binary and two trails originating close to it. This is the first detection of such structure in a X-ray binary and it opens a new sub-field in the study of these objects. Observations with XMM-Newton and Chandra are now needed to investigate the properties of the surrounding nebula.

  6. An X-ray look at the first head-trail nebula in an X-ray binary

    NASA Astrophysics Data System (ADS)

    Soleri, Paolo

    2010-10-01

    Head-tail trails are a common feature in active galactic nuclei and pulsar bow-shocks. Heinz et al. (2008) suggested that also X-ray binaries, being jet sources moving with high velocities in dense media, can leave trails of highly ionized plasma that should be detectable at radio frequencies. During observations of faint-persistent X-ray binaries, we discovered an optical nebula around the X-ray binary SAX J1712.6-3739, consisting of a bow-shock ring-like nebula ``in front'' of the binary and two trails originating close to it. This is the first detection of such structure in a X-ray binary and it opens a new sub-field in the study of these objects. Observations with XMM-Newton and Chandra are now needed to investigate the properties of the surrounding nebula.

  7. The Eclipsing Central Stars of the Planetary Nebulae Lo 16 and PHR J1040-5417

    NASA Astrophysics Data System (ADS)

    Hillwig, Todd C.; Frew, David; Jones, David; Crispo, Danielle

    2017-01-01

    Binary central stars of planetary nebula are a valuable tool in understanding common envelope evolution. In these cases both the resulting close binary system and the expanding envelope (the planetary nebula) can be studied directly. In order to compare observed systems with common envelope evolution models we need to determine precise physical parameters of the binaries and the nebulae. Eclipsing central stars provide us with the best opportunity to determine high precision values for mass, radius, and temperature of the component stars in these close binaries. We present photometry and spectroscopy for two of these eclipsing systems; the central stars of Lo 16 and PHR 1040-5417. Using light curves and radial velocity curves along with binary modeling we provide physical parameters for the stars in both of these systems.

  8. Discovery of Spatial and Spectral Structure in the X-Ray Emission from the Crab Nebula.

    PubMed

    Weisskopf; Hester; Tennant; Elsner; Schulz; Marshall; Karovska; Nichols; Swartz; Kolodziejczak; O'Dell

    2000-06-20

    The Chandra X-Ray Observatory observed the Crab Nebula and pulsar during orbital calibration. Zeroth-order images with the High-Energy Transmission Grating (HETG) readout by the Advanced CCD Imaging Spectrometer spectroscopy array (ACIS-S) show a striking richness of X-ray structure at a resolution comparable to that of the best ground-based visible-light observations. The HETG-ACIS-S images reveal, for the first time, an X-ray inner ring within the X-ray torus, the suggestion of a hollow-tube structure for the torus, and X-ray knots along the inner ring and (perhaps) along the inward extension of the X-ray jet. Although complicated by instrumental effects and the brightness of the Crab Nebula, the spectrometric analysis shows systematic variations of the X-ray spectrum throughout the nebula.

  9. Photoionization modeling of Magellanic Cloud planetary nebulae. I

    NASA Technical Reports Server (NTRS)

    Dopita, M. A.; Meatheringham, S. J.

    1991-01-01

    The results of self-consistent photoionization modeling of 38 Magellanic Cloud PNe are presented and used to construct an H-R diagram for the central stars and to obtain both the nebular chemical abundances and the physical parameters of the nebulae. T(eff)s derived from nebular excitation analysis are in agreement with temperatures derived by the classical Zanstra method. There is a linear correlation between log T(eff) and the excitation class. The majority of the central stars in the sample with optically thick nebulae have masses between 0.55 and 0.7 solar mass and are observed during their hydrogen-burning excursion toward high temperatures. Optically thin objects are found scattered throughout the H-R diagram, but tend to have a somewhat smaller mean mass. Type I PN are found to have high core masses and to lie on the descending branch of the evolutionary tracks. The nebular mass of the optically thick objects is closely related to the nebular radius, and PN with nebular masses over one solar are observed.

  10. Pulsar Wind Nebulae, Space Velocities and Supernova Remnant

    NASA Technical Reports Server (NTRS)

    2005-01-01

    The original proposal for this LTSA grant was for X-ray studies of pulsars, and especially pulsar wind nebulae and what they could tell us about pulsar properties, especially their space velocities. By any metric, this program has been very successful. No fewer than 14 papers on directly related topics (and several dozen more on related topics) have been published in refereed journals with the PI as lead or co-author, all observational results that have had significant impact on the field. These include the first X-ray detection of the "Duck" pulsar, a clear demonstration that estimated pulsar ages can be off by over an order of magnitude (via observations of the young supernova remnant G11.2-0.3) and the detection of the first pulsar wind nebula around a millisecond pulsar. These publications have also resulted in 4 press releases. Moreover, they also represent the thesis work of two PhD students at MIT (Froney Crawford and Mike Pivovaroff) and one postdoctoral fellow, Bryan Gaensler, now Assistant Professor at Harvard.

  11. Structural and thermochemical Aspects of (III-V)IV3 Material Assembly from First Principles

    NASA Astrophysics Data System (ADS)

    Chizmeshya, Andrew; Kouvetakis, John

    2014-03-01

    Alloys with (III-V)-(IV) compositions, including Si3(AlP), Si5-2y(AlP)y, Si3Al(As1-xNx), Si5-2yAl(P1-xNx)y and Ge5-2y(InP)y and have recently been synthesized as mono-crystalline films on Si substrates, using a synthesis route specifically designed to avoid phase separation between the III-V and IV constituents. Molecular ``building blocks'' containing group-V-centered III-V-IV3 cores, formed via interactions of group-III atoms and reactive silyly/germyl hydride precursors of desired composition (e.g, P(SiH3)3 , P(GeH3)3 , etc), assemble to form stable, covalent, diamond-like materials with the inherent tetrahedral symmetry and composition of the III-V-IV3 units. The resulting systems may provide access to a broad range of new semiconductor systems with extended optoelectronic properties, provided that the required molecular sources are available, the thermodynamic processes are viable, and the resulting alloy composition can be tuned to lattice-match the growth substrate. Molecular/solid-state simulations are used to identify promising synthetic pathways and guide the epitaxial creation of new (III-V)-(IV) materials. The thermodynamics of gas phase synthesis reactions, energetic stability of the alloys, and their epitaxial/chemical compatibility with the substrate are combined to form a global figure of merit. The latter corroborates the synthesis of known systems and predicts that formation of GaPSi3/Si(100), GaAsSi3/SiGe(100), AlPGe3/Ge(100) and InAsSi3/Ge(100) may also be favorable. Supported by NSF-DMR under SusChEM award #1309090.

  12. Fermi-LAT Constraints on the Pulsar Wind Nebula Nature of HESS J1857+026

    NASA Technical Reports Server (NTRS)

    Rousseau, R.; Grondin, M.-H.; VanEtten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.; hide

    2012-01-01

    Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857+026 is a spatially extended gamma-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856+0245. Aims. We search for -ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Methods. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase.fold 36 months of gamma-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete gamma-ray spectral and morphological analysis. Results. No pulsation was detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857+026. The gamma-ray spectrum is well described by a simple power law with a spectral index of Gamma = 1.53 +/- 0.11(sub stat) +/- 0.55(sub syst) and an energy flux of G(0.1 C100 GeV) = (2.71 +/- 0.52(sub stat) +/- 1.51(sub syst) X 10(exp -11) ergs/ sq cm/s. This implies a gamma.ray efficiency of approx 5 %, assuming a distance of 9 kpc, the gamma-ray luminosity of L(sub gamma) (sub PWN) (0.1 C100 GeV) = (2.5 +/- 0.5(sub stat) +/- 1.5(sub syst)) X 10(exp 35)(d/(9kpc))(exp 2) ergs/s and E-dot = 4.6 X 10(exp 36) erg /s, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

  13. Fermi-LAT constraints on the pulsar wind nebula nature of HESS J1857+026

    NASA Astrophysics Data System (ADS)

    Rousseau, R.; Grondin, M.-H.; Van Etten, A.; Lemoine-Goumard, M.; Bogdanov, S.; Hessels, J. W. T.; Kaspi, V. M.; Arzoumanian, Z.; Camilo, F.; Casandjian, J. M.; Espinoza, C. M.; Johnston, S.; Lyne, A. G.; Smith, D. A.; Stappers, B. W.; Caliandro, G. A.

    2012-08-01

    Context. Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857 + 026 is a spatially extended γ-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856 + 0245. Aims: We search for γ-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Methods: Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of γ-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete γ-ray spectral and morphological analysis. Results: No γ-ray pulsations were detected from PSR J1856+0245. However, significant emission is detected at a position coincident with the TeV source HESS J1857 + 026. The γ-ray spectrum is well described by a simple power-law with a spectral index of Γ = 1.53 ± 0.11stat ± 0.55syst and an energy flux of G(0.1-100 GeV) = (2.71 ± 0.52stat ± 1.51syst) × 10-11 erg cm-2 s-1. The γ-ray luminosity is LPWNγ (0.1-100 GeV)=(2.5 ± 0.5stat ± 1.5syst) × 1035 (d/9 kpc)2 erg s-1, assuming a distance of 9 kpc. This implies a γ-ray efficiency of ~5% for Ė = 4.6 × 1036 erg s-1, in the range expected for pulsar wind nebulae. Detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.

  14. Fermi -LAT constraints on the pulsar wind nebula nature of HESS J1857+026

    DOE PAGES

    Rousseau, R.; Grondin, M. -H.; Van Etten, A.; ...

    2012-07-17

    Since its launch, the Fermi satellite has firmly identified 5 pulsar wind nebulae plus a large number of candidates, all powered by young and energetic pulsars. HESS J1857 + 026 is a spatially extended γ-ray source detected by H.E.S.S. and classified as a possible pulsar wind nebula candidate powered by PSR J1856 + 0245. Here, we search for γ-ray pulsations from PSR J1856+0245 and explore the characteristics of its associated pulsar wind nebula. Using a rotational ephemeris obtained from the Lovell telescope at Jodrell Bank Observatory at 1.5 GHz, we phase-fold 36 months of γ-ray data acquired by the Large Area Telescope (LAT) aboard Fermi. We also perform a complete γ-ray spectral and morphological analysis. No γ-ray pulsations were detected from PSR J1856+0245. But, significant emission is detected at a position coincident with the TeV source HESS J1857 + 026. The γ-ray spectrum is well described by a simple power-law with a spectral index of Γ = 1.53 ± 0.11 stat ± 0.55 syst and an energy flux of G(0.1–100 GeV) = (2.71 ± 0.52 stat ± 1.51 syst) × 10 -11 erg cm -2 s -1. The γ-ray luminosity is L PWN γ (0.1–100 GeV)=(2.5 ± 0.5 stat ± 1.5 syst) × 10 35 (d/9 kpc) 2 erg s -1, assuming a distance of 9 kpc. This implies a γ-ray efficiency of ~5% formore » $$\\dot{E}$$ = 4.6 × 10 36 erg s -1, in the range expected for pulsar wind nebulae. This detailed multi-wavelength modeling provides new constraints on its pulsar wind nebula nature.« less

  15. Meteoritic Constraints on Models of the Solar Nebula: The Abundances of Moderately Volatile Elements

    NASA Technical Reports Server (NTRS)

    Cassen, Patrick; Cuzzi, Jeff (Technical Monitor)

    1994-01-01

    The "moderately volatile" elements are those which condense (or evaporate) in the temperature range 650 - 1350 K, as a mix of material with solar abundances is cooled (or heated) tinder equilibrium conditions. Their relative abundances in chondritic meteorites are solar (or "cosmic", as defined by the composition of Cl meteorites) to within a factor of several, but vary within that range in a way that correlates remarkably well with condensation temperature, independent of chemical affinity. It has been argued that this correlation reflects a systematically selective process which favored the accretion of refractory material over volatile material from a cooling nebula. Wasson and Chou (Meteoritics 9, 69-94, 1974, and Wasson and co-authors in subsequent papers) suggested that condensation and settling of solids contemporaneously with the cooling and removal of nebular gas could produce the observed abundance patterns, but a quantitative model has been lacking. We show that the abundance patterns of the moderately volatile elements in chondritic meteorites can be produced, in some degree of quantitative detail, by models of the solar nebula that are designed to conform to observations of T Tauri stars and the global conservation laws. For example, even if the local surface density of the nebula is not decreasing, condensation and accretion of solids from radially inflowing gas in a cooling nebula can result in depletions of volatiles, relative to refractories, like those observed, The details of the calculated abundance patterns depend on (but are not especially sensitive to) model parameters, and can exhibit the variations that distinguish the meteorite classes. Thus it appears that nebula characteristics such as cooling rates, radial flow velocities, and particle accumulation rates can be quantitatively constrained by demanding that they conform to meteoritic data; and the models, in turn, can produce testable hypotheses regarding the time and location of the

  16. Structural studies of a bifunctional inhibitor of neprilysin and DPP-IV.

    PubMed

    Oefner, Christian; Pierau, Sabine; Schulz, Henk; Dale, Glenn E

    2007-09-01

    Neutral endopeptidase (NEP) is the major enzyme involved in the metabolic inactivation of a number of bioactive peptides including the enkephalins, substance P, endothelin, bradykinin and atrial natriuretic factor, as well as the incretin hormone glucagon-like peptide 1 (GLP-1), which is a potent stimulator of insulin secretion. The activity of GLP-1 is also rapidly abolished by the serine protease dipeptidyl peptidase IV (DPP-IV), which led to an elevated interest in inhibitors of this enzyme for the treatment of type II diabetes. A dual NEP/DPP-IV inhibitor concept is proposed, offering an alternative strategy for the treatment of type 2 diabetes. Here, the synthesis and crystal structures of the soluble extracellular domain of human NEP (residues 52-749) complexed with the NEP, competitive and potent dual NEP/DPP-IV inhibitor MCB3937 are described.

  17. GBT, VLA Team Up to Produce New Image of Orion Nebula

    NASA Astrophysics Data System (ADS)

    2002-01-01

    Combining the best features of the National Science Foundation's (NSF) new Robert C. Byrd Green Bank Telescope (GBT) in West Virginia with those of the NSF's Very Large Array (VLA) in New Mexico, astronomers have produced a vastly improved radio image of the Orion Nebula and developed a valuable new technique for studying star formation and other astrophysical processes. GBT-VLA Image of Orion Nebula GBT-VLA Image of Orion Nebula "Our GBT image of the Orion Nebula is the best image ever produced with a single-dish radio telescope and it illustrates the superb performance of this new telescope," said Debra Shepherd, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM. "By combining data from the GBT with that from the VLA, we get an image that reflects reality far better than images from the separate telescopes could do," she added. Shepherd worked with Ron Maddalena from NRAO in Green Bank and Joe McMullin, from NRAO in Socorro. The astronomers presented their work to the American Astronomical Society meeting in Washington, DC. Single-dish radio telescopes such as the GBT, dedicated in 2000, are able to capture the large-scale structure of objects such as the Orion Nebula. However, they are unable to discern the fine detail revealed by multi-antenna arrays such as the VLA. Conversely, a VLA-like array is "blind" to the larger-scale structures. Combining the data from both types of radio telescopes to produce an image showing both large- and small-scale structures in the same celestial object has been a difficult, laborious task. "We are developing new observing techniques and software to make this task much easier and quicker," said McMullin. "We now have achieved in hours what used to take months or even longer to do, but we are producing an observational tool that will allow astronomers to make much higher-fidelity images that will greatly improve our understanding of several important astronomical processes," McMullin added. For this observation

  18. 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

  19. 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

  20. 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

  1. Chandra Detection of a Pulsar Wind Nebula Associated With Supernova Remnant 3C 396

    NASA Technical Reports Server (NTRS)

    Olbert, C. M.; Keohane, J. W.; Arnaud, K. A.; Dyer, K. K.; Reynolds, S. P.; Safi-Harb, S.

    2003-01-01

    We present a 100 ks observation of the Galactic supernova remnant 3C396 (G39.2-0.3) with the Chandra X-Ray Observatory that we compare to a 20cm map of the remnant from the Very Large Array. In the Chandra images, a nonthermal nebula containing an embedded pointlike source is apparent near the center of the remnant which we interpret as a synchrotron pulsar wind nebula surrounding a yet undetected pulsar. From the 2-10 keV spectrum for the nebula (N(sub H) = 5.3 plus or minus 0.9 x 10(exp 22) per square centimeter, GAMMA =1.5 plus or minus 0.3) we derive an unabsorbed x-ray flux of S(sub z)=1.62 x 10(exp -12) erg per square centimeter per second, and from this we estimate the spin-down power of the neutron star to be E(sup dot) = 7.2 x 10(exp 36) ergs per second. The central nebula is morphologically complex, showing bent, extended structure. The radio and X-ray shells of the remnant correlate poorly on large scales, particularly on the eastern half of the remnant, which appears very faint in X-ray images. At both radio and X-ray wavelengths the western half of the remnant is substantially brighter than the east.

  2. Vorticity Transport and Wave Emission in the Protoplanetary Nebula

    NASA Technical Reports Server (NTRS)

    Davis, S. S.; DeVincenzi, Donald (Technical Monitor)

    2001-01-01

    Higher order numerical algorithms (4th order in time, 3rd order in space) are applied to the Euler/Energy equations and are used to examine vorticity transport and wave motion in a non-self gravitating, initially isentropic Keplerian disk. In this talk we will examine the response of the nebula to an isolated vortex with a circulation about equal to the rotation rate of Jupiter. The vortex is located on the 4 AU circle and the nebula is simulated from 1 to 24 AU. We show that the vortex emits pressure-supported density and Rossby-type wave packets before it decays within a few orbits. The acoustic density waves evolve into weak (non entropy preserving) shock waves that propagate over the entire disk. The Rossby waves remain in the vicinity of the initial vortex disturbance, but are rapidly damped. Temporal frequencies and spatial wavenumbers are derived using the simulation data and compared with analytical dispersion relations from the linearized Euler/Energy equations.

  3. A D'-type symbiotic binary in the planetary nebula SMP LMC 88

    NASA Astrophysics Data System (ADS)

    Iłkiewicz, Krystian; Mikołajewska, Joanna; Miszalski, Brent; Kozłowski, Szymon; Udalski, Andrzej

    2018-05-01

    SMP LMC 88 is one of the planetary nebulae (PNe) in the Large Magellanic Cloud. We identify in its spectrum Raman scattered O VI lines at 6825 and 7083 Å. This unambiguously classifies the central object of the nebula as a symbiotic star (SySt). We identified the cold component to be a K-type giant, making this the first D'-type (yellow) SySt discovered outside the Galaxy. The photometric variability in SMP LMC 88 resembles the orbital variability of Galactic D'-type SySt with its low amplitude and sinusoidal light-curve shape. The SySt classification is also supported by the He I diagnostic diagram.

  4. Condensation Time of the Solar Nebula from Extinct 129I in Primitive Meteorites

    PubMed Central

    Lewis, Roy S.; Anders, Edward

    1975-01-01

    Mineral separates from five carbonaceous chondrites were dated by extinct 16 million year 129I, in an attempt to establish the condensation time of the solar nebula. Two Fe3O4 or Fe3O4-FeS samples from the Murchison and Orgueil meteorites are older than any other material dated thus far, and apparently formed within 2 × 105 years of each other. The great age, close isochronism, and primitive nature of the samples suggest that the event recorded was the condensation stage of the solar nebula. It provides a suitable zero point for the chronology of the early solar system. The 129I/127I ratio during condensation of the nebula was (1.46 ± 0.04) × 10-4. The recrystallized C4 chondrite Karoonda began to retain 129Xe 1.8 ± 0.5 million years after the above event. This short cooling time implies rapid aceretion (≤1 million years) and a shallow origin (≤10 km) below the surface of its parent body. Images PMID:16592213

  5. An Analysis and Classification of Dying AGB Stars Transitioning to Pre-Planetary Nebulae

    NASA Technical Reports Server (NTRS)

    Blake, Adam C.

    2011-01-01

    The principal objective of the project is to understand part of the life and death process of a star. During the end of a star's life, it expels its mass at a very rapid rate. We want to understand how these Asymptotic Giant Branch (AGB) stars begin forming asymmetric structures as they start evolving towards the planetary nebula phase and why planetary nebulae show a very large variety of non-round geometrical shapes. To do this, we analyzed images of just-forming pre-planetary nebula from Hubble surveys. These images were run through various image correction processes like saturation correction and cosmic ray removal using in-house software to bring out the circumstellar structure. We classified the visible structure based on qualitative data such as lobe, waist, halo, and other structures. Radial and azimuthal intensity cuts were extracted from the images to quantitatively examine the circumstellar structure and measure departures from the smooth spherical outflow expected during most of the AGB mass-loss phase. By understanding the asymmetrical structure, we hope to understand the mechanisms that drive this stellar evolution.

  6. Spatially extended K Iλ7699 emission in the nebula of VY CMa: kinematics and geometry

    NASA Astrophysics Data System (ADS)

    Smith, Nathan

    2004-04-01

    Long-slit echelle spectra reveal bright extended emission from the K Iλ7699 resonance line in the reflection nebula surrounding the extreme red supergiant VY Canis Majoris. The central star has long been known for its unusually bright K I emission lines, but this is the first report of intrinsic emission from K I in the nebula. The extended emission is not just a reflected spectrum of the star, but is due to resonant scattering by K atoms in the outer nebula itself, and is therefore a valuable probe of the kinematics and geometry of the circumstellar environment of VY CMa. Dramatic velocity structure is seen in the long-slit spectra, and most lines of sight through the nebula intersect multiple distinct velocity components. A faint `halo' at large distances from the star does appear to show a reflected spectrum, however, and suggests a systemic velocity of +40 km s-1 with respect to the Sun. The most striking feature is blueshifted emission from the filled interior of a large shell seen in images; the kinematic structure is reminiscent of a Hubble flow, and provides strong evidence for asymmetric and episodic mass loss due to localized eruptions on the stellar surface.

  7. 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.

  8. Interaction of Particles and Turbulence in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Dacles-Mariani, Jennifer S.; Dobrovolskis, A. R.; Cuzzi, J. N.; DeVincenzi, Donald L. (Technical Monitor)

    1996-01-01

    The most widely accepted theories for the formation of the Solar system claim that small solid particles continue to settle into a thin layer at the midplane of the Solar nebula until it becomes gravitationally unstable and collapses directly into km-sized planetesimals. This scenario has been challenged on at least two grounds: (1) due to turbulence, the particles may not settle into a thin layer, and (2) a thin layer may not be unstable. The Solar nebula contains at least three sources of turbulence: radial shear, vertical shear, and thermal convection. The first of these is small and probably negligible, while the last is poorly understood. However, the second contribution is likely to be substantial. The particle-rich layer rotates at nearly the Keplerian speed, but the surrounding gaseous nebula rotates slower because it is partly supported by pressure. The resulting shear generates a turbulent boundary layer which stirs the particles away from the midplane, and forestalls gravitational instability. Our previous work used a 'zero-equation' (Prandtl) model to predict the intensity of shear-generated turbulence, and enabled us to demonstrate numerically that settling of particles to the midplane is self-limiting. However, we neglected the possibility that mass loading by particles might damp the turbulence. To explore this, we have developed a more sophisticated 'one-equation' model which incorporates local generation, transport, and dissipation of turbulence, as well as explicit damping of turbulence by particles. We also include a background level of global turbulence to represent other sources. Our results indicate that damping flattens the distribution of particles somewhat, but that background turbulence thickens the particle layer.

  9. Confinement of the Crab Nebula with tangled magnetic field by its supernova remnant

    NASA Astrophysics Data System (ADS)

    Tanaka, Shuta J.; Toma, Kenji; Tominaga, Nozomu

    2018-05-01

    A pulsar wind is a relativistic outflow dominated by Poynting energy at its base. Based on the standard ideal magnetohydrodynamic (MHD) model of pulsar wind nebulae (PWNe) with the ordered magnetic field, the observed slow expansion vPWN ≪ c requires the wind to be dominated by kinetic energy at the upstream of its termination shock, which conflicts with the pulsar wind theory (σ-problem). In this paper, we extend the standard model of PWNe by phenomenologically taking into account conversion of the ordered to turbulent magnetic field and dissipation of the turbulent magnetic field. Disordering of the magnetic structure is inferred from the recent three-dimensional relativistic ideal MHD simulations, while magnetic dissipation is a non-ideal MHD effect requiring a finite resistivity. We apply this model to the Crab Nebula and find that the conversion effect is important for the flow deceleration, while the dissipation effect is not. Even for Poynting-dominated pulsar wind, we obtain the Crab Nebula's vPWN by adopting a finite conversion time-scale of ˜0.3 yr. Magnetic dissipation primarily affects the synchrotron radiation properties. Any values of the pulsar wind magnetization σw are allowed within the present model of the PWN dynamics alone, and even a small termination shock radius of ≪0.1 pc reproduces the observed dynamical features of the Crab Nebula. In order to establish a high-σw model of PWNe, it is important to extend the present model by taking into account the broadband spectrum and its spacial profiles.

  10. 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

  11. 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

  12. Global Modeling of Nebulae with Particle Growth, Drift, and Evaporation Fronts. I. Methodology and Typical Results

    NASA Astrophysics Data System (ADS)

    Estrada, Paul R.; Cuzzi, Jeffrey N.; Morgan, Demitri A.

    2016-02-01

    We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplane temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 105 years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core.

  13. Registration of H2O and SiO masers in the Calabash Nebula to confirm the planetary nebula paradigm

    NASA Astrophysics Data System (ADS)

    Dodson, R.; Rioja, M.; Bujarrabal, V.; Kim, J.; Cho, S. H.; Choi, Y. K.; Youngjoo, Y.

    2018-05-01

    We report on the astrometric registration of very long baseline interferometry images of the SiO and H2O masers in OH 231.8+4.2, the iconic proto-planetary nebula also known as the Calabash nebula, using the Korean VLBI Network and source frequency phase referencing. This, for the first time, robustly confirms the alignment of the SiO masers, close to the asymptotic giant branch star, driving the bilobe structure with the water masers in the outflow. We are able to trace the bulk motions for the H2O masers over the last few decades to be 19 km s-1 and deduce that the age of this expansion stage is 38 ± 2 yr. The combination of this result with the distance allows a full 3D reconstruction and confirms that the H2O masers lie on and expand along the known large-scale symmetry axis and that the outflow is only a few decades old, so mass loss is almost certainly ongoing. Therefore, we conclude that the SiO emission marks the stellar core of the nebular, the H2O emission traces the expansion, and there must be multiple epochs of ejection to drive the macro-scale structure.

  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. The Orion Nebula: The Jewel in the Sword

    NASA Astrophysics Data System (ADS)

    2001-01-01

    Orion the Hunter is perhaps the best known constellation in the sky, well placed in the evening at this time of the year for observers in both the northern and southern hemispheres, and instantly recognisable. And for astronomers, Orion is surely one of the most important constellations, as it contains one of the nearest and most active stellar nurseries in the Milky Way, the galaxy in which we live. Here tens of thousands of new stars have formed within the past ten million years or so - a very short span of time in astronomical terms. For comparison: our own Sun is now 4,600 million years old and has not yet reached half-age. Reduced to a human time-scale, star formation in Orion would have been going on for just one month as compared to the Sun's 40 years. Just below Orion's belt, the hilt of his sword holds a great jewel in the sky, the beautiful Orion Nebula . Bright enough to be seen with the naked eye, a small telescope or even binoculars show the nebula to be a few tens of light-years' wide complex of gas and dust, illuminated by several massive and hot stars at its core, the famous Trapezium stars . However, the heart of this nebula also conceals a secret from the casual observer. There are in fact about one thousand very young stars about one million years old within the so-called Trapezium Cluster , crowded into a space less than the distance between the Sun and its nearest neighbour stars. The cluster is very hard to observe in visible light, but is clearly seen in the above spectacular image of this area ( ESO PR 03a/01 ), obtained in December 1999 by Mark McCaughrean (Astrophysical Institute Potsdam, Germany) and his collaborators [1] with the infrared multi-mode ISAAC instrument on the ESO Very Large Telescope (VLT) at Paranal (Chile). Many details are seen in the new ISAAC image ESO PR Photo 03b/01 ESO PR Photo 03b/01 [Preview - JPEG: 400 x 589 pix - 62k] [Normal - JPEG: 800 x 1178 pix - 648k] [Hires - JPEG: 1957 x 2881 pix - 2.7M] ESO PR Photo 03c

  16. 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

  17. The evolved central star of the planetary nebula ESO 166-PN 21.

    NASA Astrophysics Data System (ADS)

    Pena, M.; Ruiz, M. T.; Bergeron, P.; Torres-Peimbert, S.; Heathcote, S.

    1997-02-01

    Optical and UV spectrophotometric data of the nebula and the central star of the planetary nebula ESO 166-PN 21 are presented. The analysis of the nebular lines confirms that it is a He- and N-rich PN, with He/H=0.138+/-0.005 and N/O=0.58+/-0.08. The oxygen abundance is 12+logO/H=8.60+/-0.10. A distance of 1.2+/-0.2 kpc is derived for the nebula. The central star is very faint and blue, with an apparent magnitude V=17.94+/-0.03mag and a dereddened color index (B-V)_0_=-0.38mag. It shows faint wide H and He absorption lines typical of a DAO star. By modeling the line profiles we derived T_eff_=69200+/-8700K, logg=7.14+/-0.39 and logHe/H=-1.50+/-0.49 for the star. The position of the star in a HR diagram compared with evolutionary tracks indicates a stellar mass of ~0.55Msun_. The bolometric correction derived from the model atmosphere is -5.6mag which, combined with the mass, yields an absolute visual magnitude M_V_=6.95, a luminosity of 22Lsun_ and a distance of 1185+/-700pc, in good agreement with the nebular distance. Therefore, ESO 166-PN 21 central star is among the hottest and most helium-rich DAO stars and it is one of the most evolved PN nuclei known, similar to the central stars of S216 and NGC7293. A kinematical age of 16100yr is deduced for the nebula which is lower by about two orders of magnitude than the age of the central star. The possibility that this object is a member of a close binary system is suggested.

  18. Facile synthesis of titanium (IV) ion immobilized adenosine triphosphate functionalized silica nanoparticles for highly specific enrichment and analysis of intact phosphoproteins.

    PubMed

    Wang, Hao; Tian, Zhixin

    2018-06-06

    Analysis of phosphoproteins always faces the challenge of low stoichiometry, which demands highly selective and efficient enrichment in the initial sample preparation. Here we report our synthesis of the novel titanium (IV) ion immobilized adenosine triphosphate functionalized silica nanoparticles (Ti 4+ -ATP-NPs) for efficient enrichment of intact phosphoproteins. The average diameter of Ti 4+ -ATP-NPs was about 128 nm with good dispersibility and the saturated adsorption capacity for β-casein was 1046.5 mg/g. In addition, Ti 4+ -ATP-NPs exhibited high specificity and selectivity in enriching phosphoproteins from both standard protein mixtures and complex biological samples (non-fat milk, chicken egg white and mouse heart tissue extract) as demonstrated by SDS-PAGE. Copyright © 2018 Elsevier B.V. All rights reserved.

  19. NASA SOFIA Captures Images of the Planetary Nebula M2-9

    NASA Image and Video Library

    2012-03-29

    Researchers using NASA Stratospheric Observatory for Infrared Astronomy SOFIA have captured infrared images of the last exhalations of a dying sun-like star. This image is of the planetary Nebula M2-9.

  20. 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

  1. ELEMENT MASSES IN THE CRAB NEBULA

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

    Sibley, Adam R.; Katz, Andrea M.; Satterfield, Timothy J.

    Using our previously published element abundance or mass-fraction distributions in the Crab Nebula, we derived actual mass distributions and estimates for overall nebular masses of hydrogen, helium, carbon, nitrogen, oxygen and sulfur. As with the previous work, computations were carried out for photoionization models involving constant hydrogen density and also constant nuclear density. In addition, employing new flux measurements for [Ni ii]  λ 7378, along with combined photoionization models and analytic computations, a nickel abundance distribution was mapped and a nebular stable nickel mass estimate was derived.

  2. H2 Imaging of Three Proto-Planetary and Young Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Volk, Kevin; Hrivnak, Bruce J.; Kwok, Sun

    2004-12-01

    High-resolution (0.15") 2.12 μm H2 and narrowband K images have been obtained of one cool proto-planetary nebula, IRAS 20028+3910, and two hot proto-planetary/young planetary nebulae, IRAS 19306+1407 and IRAS 22023+5249. The observations were made with an adaptive optics system and near-infrared imager on the Gemini North 8 m telescope. All three nebulae are seen to be extended, and in two and possibly all three of them H2 is found to be emitting from bipolar lobes. In IRAS 19306+1407, H2 emission is seen arising from a ring close to the star and from the edges of emerging bipolar lobes. In IRAS 20028+3910, one bright lobe and a very faint second lobe are seen in the H2 and K-band images, similar to the published visible images, but in the H2 and K-band images a faint filament appears to connect the two lobes. The central star is not seen in IRAS 20028+3910, indicating that the nebula is optically thick even at 2 μm, which is unusual. The images suggest that extended H2 emission is often the manifestation of fast-slow wind interactions in the bipolar lobes. The paper is based on observations obtained at the Gemini Observatory with the Adaptive Optics System Hokupa'a/QUIRC, developed and operated by the University of Hawaii Adaptive Optics Group, with support from the National Science Foundation. The Gemini Observatory is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), the Particle Physics and Astronomy Research Council (United Kingdom), the National Research Council (Canada), Comisión Nacional de Investigación Científica y Tecnológica (CONICYT; Chile), the Australian Research Council (Australia), Laboratório Nacional de Astrofísica (CNPq; Brazil), and Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET; Argentina).

  3. 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.

  4. Oxygen isotope exchange between refractory inclusion in Allende and solar nebula gas.

    PubMed

    Yurimoto, H; Ito, M; Nagasawa, H

    1998-12-04

    A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope composition (approximately 5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). Some of the melilite is also anomalously enriched in oxygen-16 compared with oxygen isotopes measured in other CAIs. The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI. Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula.

  5. Oxygen isotope exchange between refractory inclusion in allende and solar nebula Gas

    PubMed

    Yurimoto; Ito; Nagasawa

    1998-12-04

    A calcium-aluminum-rich inclusion (CAI) from the Allende meteorite was analyzed and found to contain melilite crystals with extreme oxygen-isotope compositions ( approximately 5 percent oxygen-16 enrichment relative to terrestrial oxygen-16). Some of the melilite is also anomalously enriched in oxygen-16 compared with oxygen isotopes measured in other CAIs. The oxygen isotopic variation measured among the minerals (melilite, spinel, and fassaite) indicates that crystallization of the CAI started from oxygen-16-rich materials that were probably liquid droplets in the solar nebula, and oxygen isotope exchange with the surrounding oxygen-16-poor nebular gas progressed through the crystallization of the CAI. Additional oxygen isotope exchange also occurred during subsequent reheating events in the solar nebula.

  6. 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.

  7. A possible line feature at 73 keV from the Crab Nebula

    NASA Technical Reports Server (NTRS)

    Ling, J. C.; Mahoney, W. A.; Willett, J. B.; Jacobson, A. S.

    1979-01-01

    Evidence is reported for a possible line feature at 73 keV from the Crab Nebula. The experiment was conducted with a balloon-borne high-resolution gamma-ray spectrometer on June 10, 1974, over Palestine, Texas. The intensity and the width of the line derived from the fitting of these data are approximately 0.0038 photon per (sq cm-sec) and less than 4.9 keV FWHM, respectively. The line is superposed on a power-law continuum of 11.2 E to the -2.16 photons per (sq cm-keV) in the energy range from 53 to 300 keV, which is consistent with other measurements of the Crab Nebula spectrum.

  8. A guide to the use of theoretical models of the solar nebula for the interpretation of the meteoritic record

    NASA Technical Reports Server (NTRS)

    Cassen, Pat

    1991-01-01

    Attempts to derive a theoretical framework for the interpretation of the meteoritic record have been frustrated by our incomplete understanding of the fundamental processes that controlled the evolution of the primitive solar nebula. Nevertheless, it is possible to develop qualitative models of the nebula that illuminate its dynamic character, as well as the roles of some key parameters. These models draw on the growing body of observational data on the properties of disks around young, solar-type stars, and are constructed by applying the results of known solutions of protostellar collapse problems; making simple assumptions about the radial variations of nebular variables; and imposing the integral constraints demanded by conservation of mass, angular momentum, and energy. The models so constructed are heuristic, rather than predictive; they are intended to help us think about the nebula in realistic ways, but they cannot provide a definitive description of conditions in the nebula.

  9. 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

  10. 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.

  11. The Geminga pulsar wind nebula in the mid-infrared and submillimetre

    NASA Astrophysics Data System (ADS)

    Greaves, J. S.; Holland, W. S.

    2017-10-01

    The nearby middle-aged Geminga pulsar has crossed the Galactic plane within the last ∼0.1 Myr. We present archival data from Wide-field Infrared Survey Explorer and from SCUBA and SCUBA-2 on the James Clerk Maxwell Telescope to assess whether any mid-infrared and submillimetre emission arises from interaction of the pulsar wind nebula with the interstellar medium. A candidate shell and bow shock are reported. Given the low pulsar velocity and local density, dust grains appear able to penetrate into the nebula. A compact source seen towards the pulsar is fitted with a dust spectrum. If confirmed as a real association at higher resolution, this could be a circum-pulsar disc of at least a few Earth-masses, in which future planets could form.

  12. Carina Nebula Detail

    NASA Image and Video Library

    2017-12-08

    Carina Nebula Details: Great Clouds Credit for Hubble Image: NASA, ESA, N. Smith (University of California, Berkeley), and The Hubble Heritage Team (STScI/AURA) Credit for CTIO Image: N. Smith (University of California, Berkeley) and NOAO/AURA/NSF 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 Institute conducts Hubble science operations. Goddard is responsible for HST project management, including mission and science operations, servicing missions, and all associated development activities. To learn more about the Hubble Space Telescope go here: www.nasa.gov/mission_pages/hubble/main/index.html 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. Follow us on Twitter Join us on Facebook

  13. 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.

  14. 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

  15. 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.

  16. 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.

  17. Determining the Location of the Snowline in an Externally-Photoevaporated Solar Nebula

    NASA Astrophysics Data System (ADS)

    Kalyaan, Anusha; Desch, Steven

    2015-11-01

    The water snowline in the solar nebula, the point beyond which water exists abundantly as ice, is often taken to lie at 2.7 AU from the Sun, where temperatures are ~170 K, the sublimation point of water [1,2]. While superficially consistent with the spatial distribution of (wet) C-type and (dry) S-type asteroids between 2-3AU [3], most disk models place the snowline closer to ~1AU [4]. Aside from temperature, radial transport and outward diffusion of water vapor, and the inward drift of ices also determine where the snowline is [5,6]. Over many Myr, a steady cycling of water inward and outward across the T=170 K line balance out, with an enhanced ice abundance outside creating the ‘snowline’[2]. But external effects like photoevaporation of the nebula by nearby massive stars can potentially shift this balance, lead to net outward water vapor transport from the inner nebula [7,8], pushing the snowline beyond T=170 K, thus giving rise to water-poor planets.To test this hypothesis, we have first built a 1+1D protoplanetary disk evolution model, incorporating viscosity due to the magnetorotational instability with a non-uniform turbulent viscosity α across disk radius r, ionization equilibrium with dust, and external photoevaporation [8]. Our simulation results suggest that the structure of the photoevaporated solar nebula with a non-uniform α(r) was more complex than previously thought, with the following features: (i) very steep Σ profile (Σ(r)=Σ0 r-p, where slope p = 3-5, > pMMSN=1.5) due to the varying α(r), that is further steepened by the effect of dust and photoevaporation, and (ii) transition radius (where net disk mass flow changes from inward flow to outward) that is present very close to the star (~3AU). We apply these new results to study the distribution of water in the solar nebula. References: [1] Hayashi, C., (1981) PThP.Supp. 70, 35-53 [2] Stevenson,D., & Lunine,J., (1988) Icarus 75, 146-155 [3] Gradie, J., & Tedesco, E.,(1982) Science 216

  18. GLOBAL MODELING OF NEBULAE WITH PARTICLE GROWTH, DRIFT, AND EVAPORATION FRONTS. I. METHODOLOGY AND TYPICAL RESULTS

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

    Estrada, Paul R.; Cuzzi, Jeffrey N.; Morgan, Demitri A., E-mail: Paul.R.Estrada@nasa.gov

    2016-02-20

    We model particle growth in a turbulent, viscously evolving protoplanetary nebula, incorporating sticking, bouncing, fragmentation, and mass transfer at high speeds. We treat small particles using a moments method and large particles using a traditional histogram binning, including a probability distribution function of collisional velocities. The fragmentation strength of the particles depends on their composition (icy aggregates are stronger than silicate aggregates). The particle opacity, which controls the nebula thermal structure, evolves as particles grow and mass redistributes. While growing, particles drift radially due to nebula headwind drag. Particles of different compositions evaporate at “evaporation fronts” (EFs) where the midplanemore » temperature exceeds their respective evaporation temperatures. We track the vapor and solid phases of each component, accounting for advection and radial and vertical diffusion. We present characteristic results in evolutions lasting 2 × 10{sup 5} years. In general, (1) mass is transferred from the outer to the inner nebula in significant amounts, creating radial concentrations of solids at EFs; (2) particle sizes are limited by a combination of fragmentation, bouncing, and drift; (3) “lucky” large particles never represent a significant amount of mass; and (4) restricted radial zones just outside each EF become compositionally enriched in the associated volatiles. We point out implications for millimeter to submillimeter SEDs and the inference of nebula mass, radial banding, the role of opacity on new mechanisms for generating turbulence, the enrichment of meteorites in heavy oxygen isotopes, variable and nonsolar redox conditions, the primary accretion of silicate and icy planetesimals, and the makeup of Jupiter’s core.« less

  19. The nebula around the post-AGB star 89 Herculis

    NASA Astrophysics Data System (ADS)

    Bujarrabal, V.; van Winckel, H.; Neri, R.; Alcolea, J.; Castro-Carrizo, A.; Deroo, P.

    2007-06-01

    Aims:We aim to study the structure of the nebula around the post-AGB, binary star 89 Her. The presence of a rotating disk around this star had been proposed but not been yet confirmed by observations. Methods: We present high-resolution PdBI maps of CO J=2-1 and 1-0. Properties of the nebula are directly derived from the data and model fitting. We also present N-band interferometric data on the extent of the hot dust emission, obtained with the VLTI. Results: Two nebular components are found: (a) an extended hour-glass-like structure, with expansion velocities of 7 km s-1 and a total mass 3× 10-3 M{⊙}, and (b) an unresolved very compact component, smaller than 0.4 arcsec and with a low total velocity dispersion of 5 km s-1. We cannot determine the velocity field in the compact component, but we argue that it can hardly be in expansion, since this would require too recent and too sudden an ejection of mass. On the other hand, assuming that this component is a Keplerian disk, we derive disk properties that are compatible with expectations for such a structure; in particular, the size of the rotating gas disk should be very similar to the extent of the hot dust component from our VLTI data. Assuming that the equator of the extended nebula coincides with the binary orbital plane, we provide new results on the companion star mass and orbit. Based on observations carried out with the IRAM Plateau de Bure Interferometer, as well as on observations of the Belgian Guaranteed time on VISA (ESO). IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  20. 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

  1. Planets, Planetary Nebulae, and Intermediate Luminosity Optical Transients (ILOTs)

    NASA Astrophysics Data System (ADS)

    Soker, Noam

    2018-05-01

    I review some aspects related to the influence of planets on the evolution of stars before and beyond the main sequence. Some processes include the tidal destruction of a planet on to a very young main sequence star, on to a low mass main sequence star, and on to a brown dwarf. This process releases gravitational energy that might be observed as a faint intermediate luminosity optical transient (ILOT) event. I then summarize the view that some elliptical planetary nebulae are shaped by planets. When the planet interacts with a low mass upper asymptotic giant branch (AGB) star it both enhances the mass loss rate and shapes the wind to form an elliptical planetary nebula, mainly by spinning up the envelope and by exciting waves in the envelope. If no interaction with a companion, stellar or sub-stellar, takes place beyond the main sequence, the star is termed a Jsolated star, and its mass loss rates on the giant branches are likely to be much lower than what is traditionally assumed.

  2. 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.

  3. 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.

  4. sNebula, a network-based algorithm to predict binding between human leukocyte antigens and peptides

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

    Luo, Heng; Ye, Hao; Ng, Hui Wen

    Understanding the binding between human leukocyte antigens (HLAs) and peptides is important to understand the functioning of the immune system. Since it is time-consuming and costly to measure the binding between large numbers of HLAs and peptides, computational methods including machine learning models and network approaches have been developed to predict HLA-peptide binding. However, there are several limitations for the existing methods. We developed a network-based algorithm called sNebula to address these limitations. We curated qualitative Class I HLA-peptide binding data and demonstrated the prediction performance of sNebula on this dataset using leave-one-out cross-validation and five-fold cross-validations. Furthermore, this algorithmmore » can predict not only peptides of different lengths and different types of HLAs, but also the peptides or HLAs that have no existing binding data. We believe sNebula is an effective method to predict HLA-peptide binding and thus improve our understanding of the immune system.« less

  5. sNebula, a network-based algorithm to predict binding between human leukocyte antigens and peptides

    PubMed Central

    Luo, Heng; Ye, Hao; Ng, Hui Wen; Sakkiah, Sugunadevi; Mendrick, Donna L.; Hong, Huixiao

    2016-01-01

    Understanding the binding between human leukocyte antigens (HLAs) and peptides is important to understand the functioning of the immune system. Since it is time-consuming and costly to measure the binding between large numbers of HLAs and peptides, computational methods including machine learning models and network approaches have been developed to predict HLA-peptide binding. However, there are several limitations for the existing methods. We developed a network-based algorithm called sNebula to address these limitations. We curated qualitative Class I HLA-peptide binding data and demonstrated the prediction performance of sNebula on this dataset using leave-one-out cross-validation and five-fold cross-validations. This algorithm can predict not only peptides of different lengths and different types of HLAs, but also the peptides or HLAs that have no existing binding data. We believe sNebula is an effective method to predict HLA-peptide binding and thus improve our understanding of the immune system. PMID:27558848

  6. sNebula, a network-based algorithm to predict binding between human leukocyte antigens and peptides

    DOE PAGES

    Luo, Heng; Ye, Hao; Ng, Hui Wen; ...

    2016-08-25

    Understanding the binding between human leukocyte antigens (HLAs) and peptides is important to understand the functioning of the immune system. Since it is time-consuming and costly to measure the binding between large numbers of HLAs and peptides, computational methods including machine learning models and network approaches have been developed to predict HLA-peptide binding. However, there are several limitations for the existing methods. We developed a network-based algorithm called sNebula to address these limitations. We curated qualitative Class I HLA-peptide binding data and demonstrated the prediction performance of sNebula on this dataset using leave-one-out cross-validation and five-fold cross-validations. Furthermore, this algorithmmore » can predict not only peptides of different lengths and different types of HLAs, but also the peptides or HLAs that have no existing binding data. We believe sNebula is an effective method to predict HLA-peptide binding and thus improve our understanding of the immune system.« less

  7. 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.

  8. Coordination Chemistry of Homoleptic Actinide(IV)-Thiocyanate Complexes

    DOE PAGES

    Carter, Tyler J.; Wilson, Richard E.

    2015-09-10

    Here, the synthesis, X-ray crystal structure, vibrational and optical spectroscopy for the eight-coordinate thiocyanate compounds, [Et 4N] 4[Pu IV(NCS) 8], [Et 4N] 4[Th IV(NCS) 8], and [Et 4N] 4[Ce III(NCS) 7(H 2O)] are reported. Thiocyanate was found to rapidly reduce plutonium to Pu III in acidic solutions (pH<1) in the presence of NCS –. The optical spectrum of [Et 4N][SCN] containing Pu III solution was indistinguishable from that of aquated Pu III suggesting that inner-sphere complexation with [Et 4N][SCN] does not occur in water. However, upon concentration, the homoleptic thiocyanate complex [Et 4N] 4[Pu IV(NCS) 8] was crystallized when amore » large excess of [Et 4N][NCS] was present. This compound, along with its U IV analogue, maintains inner-sphere thiocyanate coordination in acetonitrile based on the observation of intense ligand-to-metal charge-transfer bands. Spectroscopic and crystallographic data do not support the interaction of the metal orbitals with the ligand π system, but support an enhanced An IV–NCS interaction, as the Lewis acidity of the metal ion increases from Th to Pu.« less

  9. 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.

  10. Contribution of alpha3(IV)alpha4(IV)alpha5(IV) Collagen IV to the Mechanical Properties of the Glomerular Basement Membrane

    NASA Astrophysics Data System (ADS)

    Gyoneva, Lazarina

    The glomerular basement membrane (GBM) is a vital part of the blood-urine filtration barrier in the kidneys. In healthy GBMs, the main tension-resisting component is alpha3(IV)alpha4(IV)alpha5(IV) type IV collagen, but in some diseases it is replaced by other collagen IV isoforms. As a result, the GBM becomes leaky and disorganized, ultimately resulting in kidney failure. Our goal is to understanding the biomechanical aspects of the alpha3(IV)alpha4(IV)alpha5(IV) chains and how their absence could be responsible for (1) the initial injury to the GBM and (2) progression to kidney failure. A combination of experiments and computational models were designed for that purpose. A model basement membrane was used to compare experimentally the distensibility of tissues with the alpha3(IV)alpha4(IV)alpha5(IV) chains present and missing. The experiments showed basement membranes containing alpha3(IV)alpha4(IV)alpha5(IV) chains were less distensible. It has been postulated that the higher level of lateral cross-linking (supercoiling) in the alpha3(IV)alpha4(IV)alpha5(IV) networks contributes additional strength/stability to basement membranes. In a computational model of supercoiled networks, we found that supercoiling greatly increased the stiffness of collagen IV networks but only minimally decreased the permeability, which is well suited for the needs of the GBM. It is also known that the alpha3(IV)alpha4(IV)alpha5(IV) networks are more protected from enzymatic degradation, and we explored their significance in GBM remodeling. Our simulations showed that the more protected network was needed to prevent the system from entering a dangerous feedback cycle due to autoregulation mechanisms in the kidneys. Overall, the work adds to the evidence of biomechanical differences between the alpha3(IV)alpha4(IV)alpha5(IV) networks and other collagen IV networks, points to supercoiling as the main source of biomechanical differences, discusses the suitability of alpha3(IV)alpha4(IV

  11. Astrometry With the Hubble Space Telescope: Trigonometric Parallaxes of Planetary Nebula Nuclei NGC 6853, NGC 7293, ABELL 31, and DeHt 5

    DTIC Science & Technology

    2009-12-01

    reserved. Printed in the U.S.A. ASTROMETRY WITH THE HUBBLE SPACE TELESCOPE: TRIGONOMETRIC PARALLAXES OF PLANETARY NEBULA NUCLEI NGC 6853, NGC 7293, ABELL 31...present absolute parallaxes and relative proper motions for the central stars of the planetary nebulae NGC 6853 (The Dumbbell), NGC 7293 (The Helix...Abell 31, and DeHt 5. This paper details our reduction and analysis using DeHt 5 as an example. We obtain these planetary nebula nuclei (PNNi

  12. Fermi Detection Of The Pulsar Wind Nebula Hess J1640–465

    DOE PAGES

    Slane, P.; Castro, D.; Funk, S.; ...

    2010-08-09

    We present observations of HESS J1640–465 with the Fermi-Large Area Telescope. The source is detected with high confidence as an emitter of high-energy gamma-rays. The spectrum lacks any evidence for the characteristic cutoff associated with emission from pulsars, indicating that the emission arises primarily from the pulsar wind nebula (PWN). Broadband modeling implies an evolved nebula with a low magnetic field resulting in a high γ-ray to X-ray flux ratio. The Fermi emission exceeds predictions of the broadband model, and has a steeper spectrum, possibly resulting from a distinct excess of low energy electrons similar to what is inferred formore » both the Vela X and Crab PWNe.« less

  13. Wolf-Rayet nebulae - Chemical enrichment and effective temperatures of the exciting stars

    NASA Technical Reports Server (NTRS)

    Rosa, Michael R.; Mathis, John S.

    1990-01-01

    Extensive new spectrophotometric observations of five Wolf-Rayet nebulas are analyzed by means of models photoionized by plane-parallel and also WR atmosphere models. Abundance ratios O/H and Ne, S, Cl, and Ar relative to O are close to solar. N/H is enriched relative to solar and variable over the faces of the nebulas. He/H varies from one to three times solar. The O(+)/O - S(+)/S(2+) diagram is used in estimating T(eff) for the exciting stars. It indicates that S 308, NGC 3199, NGC 6888, and NGC 2359 are ionized by hot stars. RCW 58, RCW 104, MR 26, and MR 100 have such low-excitation spectra that their stellar T(eff) and nebular He/H cannot be reliably determined.

  14. 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.

  15. The ALMA early science view of FUor/EXor objects - IV. Misaligned outflows in the complex star-forming environment of V1647 Ori and McNeil's Nebula

    NASA Astrophysics Data System (ADS)

    Principe, David A.; Cieza, Lucas; Hales, Antonio; Zurlo, Alice; Williams, Jonathan; Ruíz-Rodríguez, Dary; Canovas, Hector; Casassus, Simon; Mužić, Koraljka; Perez, Sebastian; Tobin, John J.; Zhu, Zhaohuan

    2018-01-01

    We present Atacama Large Millimeter/sub-millimeter Array (ALMA) observations of the star-forming environment surrounding V1647 Ori, an outbursting FUor/EXor pre-main sequence star. Dust continuum and the (J = 2 - 1) 12CO, 13CO, C18O molecular emission lines were observed to characterize the V1647 Ori circumstellar disc and any large scale molecular features present. We detect continuum emission from the circumstellar disc and determine a radius r = 40 au, inclination i = 17°+6-9 and total disc mass of Mdisc of ∼0.1 M⊙. We do not identify any disc structures associated with nearby companions, massive planets or fragmentation. The molecular cloud environment surrounding V1647 Ori is both structured and complex. We confirm the presence of an excavated cavity north of V1647 Ori and have identified dense material at the base of the optical reflection nebula (McNeil's Nebula) that is actively shaping its surrounding environment. Two distinct outflows have been detected with dynamical ages of ∼11 700 and 17 200 yr. These outflows are misaligned suggesting disc precession over ∼5500 yr as a result of anisotropic accretion events is responsible. The collimated outflows exhibit velocities of ∼2 km s-1, similar in velocity to that of other FUor objects presented in this series, but significantly slower than previous observations and model predictions. The V1647 Ori system is seemingly connected by an 'arm' of material to a large unresolved structure located ∼20 arcsec to the west. The complex environment surrounding V1647 Ori suggests it is in the early stages of star formation, which may relate to its classification as both a FUor and EXor type object.

  16. KINEMATIC DISTANCES OF GALACTIC PLANETARY NEBULAE

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

    Yang, A. Y.; Tian, W. W.; Zhu, H.

    2016-03-15

    We construct H i absorption spectra for 18 planetary nebulae (PNs) and their background sources using data from the International Galactic Plane Survey. We estimate the kinematic distances of these PNs, among which 15 objects’ kinematic distances are obtained for the first time. The distance uncertainties of 13 PNs range from 10% to 50%, which is a significant improvement with uncertainties of a factor of two or three smaller than most previous distance measurements. We confirm that PN G030.2−00.1 is not a PN because of its large distance found here.

  17. 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.

  18. Synthesis and Analysis of the Structure, Diffusion and Cytotoxicity of Heterocyclic Platinum(IV) Complexes.

    PubMed

    Macias, Freddy J; Deo, Krishant M; Pages, Benjamin J; Wormell, Paul; Clegg, Jack K; Zhang, Yingjie; Li, Feng; Zheng, Gang; Sakoff, Jennette; Gilbert, Jayne; Aldrich-Wright, Janice R

    2015-11-16

    We have developed six dihydroxidoplatinum(IV) compounds with cytotoxic potential. Each derived from active platinum(II) species, these complexes consist of a heterocyclic ligand (HL) and ancillary ligand (AL) in the form [Pt(HL)(AL)(OH)2](2+), where HL is a methyl-functionalised variant of 1,10-phenanthroline and AL is the S,S or R,R isomer of 1,2-diaminocyclohexane. NMR characterisation and X-ray diffraction studies clearly confirmed the coordination geometry of the octahedral platinum(IV) complexes. The self-stacking of these complexes was determined using pulsed gradient stimulated echo nuclear magnetic resonance. The self-association behaviour of square planar platinum(II) complexes is largely dependent on concentration, whereas platinum(IV) complexes do not aggregate under the same conditions, possibly due to the presence of axial ligands. The cytotoxicity of the most active complex, exhibited in several cell lines, has been retained in the platinum(IV) form. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. BROADBAND X-RAY IMAGING AND SPECTROSCOPY OF THE CRAB NEBULA AND PULSAR WITH NuSTAR

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

    Madsen, Kristin K.; Harrison, Fiona; Grefenstette, Brian W.

    We present broadband (3-78 keV) NuSTAR X-ray imaging and spectroscopy of the Crab nebula and pulsar. We show that while the phase-averaged and spatially integrated nebula + pulsar spectrum is a power law in this energy band, spatially resolved spectroscopy of the nebula finds a break at ∼9 keV in the spectral photon index of the torus structure with a steepening characterized by ΔΓ ∼ 0.25. We also confirm a previously reported steepening in the pulsed spectrum, and quantify it with a broken power law with break energy at ∼12 keV and ΔΓ ∼ 0.27. We present spectral maps ofmore » the inner 100'' of the remnant and measure the size of the nebula as a function of energy in seven bands. These results find that the rate of shrinkage with energy of the torus size can be fitted by a power law with an index of γ = 0.094 ± 0.018, consistent with the predictions of Kennel and Coroniti. The change in size is more rapid in the NW direction, coinciding with the counter-jet where we find the index to be a factor of two larger. NuSTAR observed the Crab during the latter part of a γ-ray flare, but found no increase in flux in the 3-78 keV energy band.« less

  20. 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.