DOCSLIB.ORG

The Evolution of Red Supergiants to Supernova

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Evolution of Red Supergiants to Supernova THE EVOLUTION OF RED SUPERGIANTS TO SUPERNOVA Emma Beasor NASA Hubble Fellow NOIRLab Ben Davies (LJMU), Nathan Smith (U. Arizona), Nate Bastian (LJMU), Bob Gehrz (U. Minnesota), Don Figer (Rochester), Jacco van Loon (Keele) SOFIA Tele-talk, July 15th 2020 Outline Introduction to RSGs Evolution of RSGs to SN Mass-loss Age determinations Summary !2 RED SUPERGIANTS Evolved massive stars (8-25 M⊙) Direct progenitors to Type II SN - powerful test of stellar evolutionary theory !3 EVOLUTION OF A 15M⊙ STAR H-burning shell H-burning core He-burning core Envelope Envelope Core contracts… star swells up !4 EVOLUTION OF A 15M⊙ STAR H-burning shell H-burning core Envelope He-burning core Envelope Core contracts, star swells up. Lots of convection in the!5 envelope EVOLUTION TO RSG PHASE log(L/L⊙) Main sequence 5.5 Evolutionary tracks…. 30M⊙ Supergiants 20M⊙ 4.5 10M⊙ Red 50,000 20,000 4,000 log(T/K) credit: Ben Davies !6 THE PATH TO SUPERNOVA He-core gets exhausted, fuses into carbon core, which fuses into oxygen, which fuses into neon… Core gets heavier and heavier No more nuclear reactions Star collapses onto the core… Fe Core-collapse supernovae !7 THE PATH TO SUPERNOVA What kind of SN depends on the appearance of the progenitor at core collapse Strong winds peel away H-rich envelope envelope RSGs live ~106 yrs, mass-loss timescale (M/Mdot) is about the same Whole envelope can be peeled off through lifetime !8 TWO OPTIONS… ‘Wolf-Rayet’ (hot RSG/YSG progenitor progenitor) H-rich envelope intact Stripped/H-poor SN (type Unstripped SN (Type II) Ibc) !9 We know RSGs explode as II-P SNe SN —> check archival images —> identify progenitor Pre-explosion photometry + some assumptions allow us to find the terminal luminosity of the progenitor and infer a mass !10 Red supergiant problem… observed… predicted… Maximum IIP progenitor mass ~16Msun? Smartt et al. 2009, updated in Smartt 2015 !11 EVOLUTION FROM MS TO RSG G. Meynet & A. Maeder: Stellar evolution with rotation. V 111 Meynet & Maeder 60M⊙ - skip RSG phase, straight 40M⊙ - short RSG phase, 25M⊙ - RSG phase, dies Fig. 8. Evolutionary tracks for non–rotating (dotted lines) and rotating (continuous lines) models with solar metallicity. The rotat- ing models have an initial velocity vini of 300 km s−1. For purpose of clarity, only the first part of the tracks for the most massive stars (M ≥ 40 M⊙) is shown. Portions of the evolution during the W–R phase for the rotating massive stars are indicated by short– dashed lines. The long–dashed track for the 60 M⊙ model corresponds to a very fast ro- −1 tating star (vini ∼ 400 km s ), which fol- lows a nearly homogeneous evolution. Only the beginning of its evolution is shown. !12 University of Sheffield - Oct as red supergiants at Teff below 4000 K, while the non–rotating 5.3. Masses and mass–luminosity relations models spend a significant part of the He–burning phase in the When rotation increases, the actual masses at the end of both blue part of the HR diagram: for the non–rotating 15 and 20 the MS and the He–burning phases become smaller (cf. Tables 1 M⊙ models, respectively 25 and 20% of the total He–burning and 2). Typically the quantity of mass lost by stellar winds dur- lifetime is spent at log T ≥ 4.0. The behaviour of the rotat- eff ing the MS is enhanced by 60–100% in rotating models with ing models results mainly from the enhancement of the mass v = 200 and 300 km s−1 respectively. For stars which do not loss rates. This effect prevents the formation of a big interme- ini go through a Wolf–Rayet phase, the increase is due mainly to diate convective zone and therefore favours a rapid evolution the direct effect of rotation on the mass loss rates (in the present toward the RSG phase (Stothers & Chin 1979; Maeder 1981). models through the formula proposed by Friend & Abbott 1986) Let us note that the dispersion of the initial rotational velocities and to the higher luminosities reached by the tracks computed produces a certain distribution of the above behaviours. with rotation. The fact that rotation increases the lifetimes also Very interestingly, for the 12 M⊙ model a blue loop appears contributes to produce smaller final masses. For the most mas- when rotation is included. This results from the higher lumi- sive stars (M ≥ 60 M⊙), the present rotating models enter the nosity of the rotating model. The higher luminosity implies that Wolf–Rayet phase already during the H–burning phase (see also the outer envelope is more extended, and is thus characterized Maeder 1987; Fliegner & Langer 1995; Meynet 1999, 2000b). by lower temperatures and higher opacities at a given mass co- This reduces significantly the mass at the end of the H–burning ordinate. As a consequence, in the rotating model during the phase. first dredge–up, the outer convective zone proceeds much more As indicated in Sect. 5.1, the initial distribution of the ro- deeply in mass than in the non–rotating star. Typically in the tational velocities implies a dispersion of the luminosities at non–rotating model the minimum mass coordinate reached by the end of the MS. This effect introduces a significant scatter the outer convective zone is 6.6 M⊙ while in the rotating model in the mass–luminosity relation (Langer 1992; Meynet 1998), it is 2.6 M⊙. This prevents temporarily the extension in mass of in the sense that fast rotators are overluminous with respect to the He–core and enables the apparition of a blue loop. Indeed their actual masses. This is especially true in the high mass star the lower the mass of the He–core is, the lower its gravitational range in which the luminosity versus mass relation flattens. This potential. According to Lauterborn et al. (1971, see also the dis- may explain some of the discrepancies between the evolutionary cussion in Maeder & Meynet 1989), a blue loop appears when masses and the direct mass estimates in some binaries (Penny the gravitational potential of the core Φ is inferior to a crit- c et al. 1999). ical potential Φ depending only on the actual mass of the crit Let us end this section by saying a few words about the star which is about the same for the rotating and non–rotating mass discrepancy problem (see e.g. Herrero et al. 2000). For model. This explains the appearance of a blue loop in the 12 some stars, the evolutionary masses (i.e. determined from the M⊙ rotating model. For the 9 M⊙ model, the minimum mass theoretical evolutionary tracks) are greater that the spectroscop- coordinate reached by the outer convective zone is not much ically determined masses. Interestingly, according to Herrero et affected by rotation and the models with and without rotation al. (2000), only the low gravity objects present (if any) a mass present very similar blue loops. discrepancy. Even if most of the problem has collapsed and was …MODEL DEPENDENT what changed..? abundances, opacities, overshooting… mass-loss rate implementation !13 MASS-LOSS RATE IMPLEMENTATION log(L/L⊙) in addition, in Ekstrom+ 2012: if L > 5LEdd, Ṁ = Ṁx3 (kicks in at ~20M⊙) Ṁ : Main sequence Ṁ : Vink / de Jager / Nugis & Lamers / van Loon Kudritzki 5.5 30M⊙ Supergiants 20M⊙ 4.5 10M⊙ Red Yellow Supergiants Yellow 50,000 20,000 4,000 log(T/K) credit: Ben Davies !14 EMPIRICAL MASS-LOSS RELATIONS Mass-loss rates are not calculated from first principles !15 Mauron & Josselin 2010 EMPIRICAL MASS-LOSS RELATIONS Mass-loss rates are not calculated from Reid+ 1990 first principles dusty RSGs van Loon+ Lots of internal 2005 scatter ± x10 Groenewegen+ 2009 de Jager Bonanos+ !16 1988A&AS...72..259D Needs a bit of an update… ̣ Highly heterogeneous sample (masses, metallicities…) ̣ Highly heterogeneous methodologies (mid-IR excesses, abs line analysis, radio…) ̣ No longer used for OBA !17 REAPPRAISAL OF RSG MASS-LOSS By targeting RSGs in clusters, we can assume all RSGs are the same Z and Late stage same Mini RSGs We can use L as a proxy for evolution evolution Early stage RSGs NGC 2100 !18 SOFIA - new data (PI N Smith) WISE - archival MSX - archival SPITZER - archival !19 HOW DO WE MEASURE MASS-LOSS RATES? Dust layer Dust layer absorbs and re-emits photons Mass-loss can be RSG measured by modeling mid-IR excess !20 HOW DO WE MEASURE MASS-LOSS RATES? The shape of this bump tells us about the dust composition, for RSGs it’s silicate rich dust Light absorbed by dust here Flux Re-emitted here Wavelength !21 HOW DO WE MEASURE MASS-LOSS RATES? We model this emission using a radiative transfer code (DUSTY), and derive a mass-lossflux rate for each RSG in the cluster wavelength !22 NGC2100 Dust shell mass increases with Tight correlation… evolution Fixed initial mass and Z Beasor & Davies 2016 !23 HOW DO MASS-LOSS RATES CHANGE WITH INITIAL MASS? χ Per NGC 2100 RSGC1 Repeat for clusters of different ages (and hence RSGs of different initial masses..) NGC 7419 NGC 2004 !24 A MASS-DEPENDENT MASS-LOSS RATE PRESCRIPTION Same gradient to within the errors… Beasor et al. (2020) !25 A MASS-DEPENDENT MASS-LOSS RATE PRESCRIPTION increasing initial mass Beasor et al. 2020 !26 COMPARISON TO OTHER PRESCRIPTIONS Our prescription de Jager Offset = 1.4 RMS = 0.45 RMS = 0.52 Residuals [ log(Mdot/Msun) ] Lower scatter Scatter slightly higher No offset Avg offset = 0.13 BUT much worse for higher luminosity stars… Beasor et al.
Load more

Recommended publications
  • Astronomie in Theorie Und Praxis 8. Auflage in Zwei Bänden Erik Wischnewski
    Astronomie in Theorie und Praxis 8. Auflage in zwei Bänden Erik Wischnewski Inhaltsverzeichnis 1 Beobachtungen mit bloßem Auge 37 Motivation 37 Hilfsmittel 38 Drehbare Sternkarte Bücher und Atlanten Kataloge Planetariumssoftware Elektronischer Almanach Sternkarten 39 2 Atmosphäre der Erde 49 Aufbau 49 Atmosphärische Fenster 51 Warum der Himmel blau ist? 52 Extinktion 52 Extinktionsgleichung Photometrie Refraktion 55 Szintillationsrauschen 56 Angaben zur Beobachtung 57 Durchsicht Himmelshelligkeit Luftunruhe Beispiel einer Notiz Taupunkt 59 Solar-terrestrische Beziehungen 60 Klassifizierung der Flares Korrelation zur Fleckenrelativzahl Luftleuchten 62 Polarlichter 63 Nachtleuchtende Wolken 64 Haloerscheinungen 67 Formen Häufigkeit Beobachtung Photographie Grüner Strahl 69 Zodiakallicht 71 Dämmerung 72 Definition Purpurlicht Gegendämmerung Venusgürtel Erdschattenbogen 3 Optische Teleskope 75 Fernrohrtypen 76 Refraktoren Reflektoren Fokus Optische Fehler 82 Farbfehler Kugelgestaltsfehler Bildfeldwölbung Koma Astigmatismus Verzeichnung Bildverzerrungen Helligkeitsinhomogenität Objektive 86 Linsenobjektive Spiegelobjektive Vergütung Optische Qualitätsprüfung RC-Wert RGB-Chromasietest Okulare 97 Zusatzoptiken 100 Barlow-Linse Shapley-Linse Flattener Spezialokulare Spektroskopie Herschel-Prisma Fabry-Pérot-Interferometer Vergrößerung 103 Welche Vergrößerung ist die Beste? Blickfeld 105 Lichtstärke 106 Kontrast Dämmerungszahl Auflösungsvermögen 108 Strehl-Zahl Luftunruhe (Seeing) 112 Tubusseeing Kuppelseeing Gebäudeseeing Montierungen 113 Nachführfehler
    [Show full text]
  • "#$%&'() + '', %-./0$%)%1 2 ()3 4&(5' 456')5'
    rs uvvwxyuzyws { yz|z|} rsz}~suzywsu}u~w vz~wsw 456789@A C 99D 7EFGH67A7I P @AQ R8@S9 RST9AS9 UVWUX `abcdUVVe fATg96GTHP7Eh96HE76QGiT69pf q rAS76876@HTAs tFR u Fv wxxy @AQ 4FR 4u Fv wxxy UVVe abbc d dbdc e f gc hi` ij ad bch dgcadabdddc c d ac k lgbc bcgb dmg agd g` kg bdcd dW dd k bg c ngddbaadgc gabmob nb boglWad g kdcoddog kedgcW pd gc bcogbpd kb obpcggc dd kfq` UVVe c iba ! " #$%& $' ())01023 Book of Abstracts – Table of Contents Welcome to the European Week of Astronomy & Space Science ...................................................... iii How space, and a few stars, came to Hatfield ............................................................................... v Plenary I: UK Solar Physics (UKSP) and Magnetosphere, Ionosphere and Solar Terrestrial (MIST) ....... 1 Plenary II: European Organisation for Astronomical Research in the Southern Hemisphere (ESO) ....... 2 Plenary III: European Space Agency (ESA) .................................................................................. 3 Plenary IV: Square Kilometre Array (SKA), High-Energy Astrophysics, Asteroseismology ................... 4 Symposia (1) The next era in radio astronomy: the pathway to SKA .............................................................. 5 (2) The standard cosmological models - successes and challenges .................................................. 17 (3) Understanding substellar populations and atmospheres: from brown dwarfs to exo-planets .......... 28 (4) The life cycle of dust ...........................................................................................................
    [Show full text]
  • Unlocking Galactic Wolf-Rayet Stars with $\Textit {Gaia} $ DR2 II: Cluster
    MNRAS 000,1{19 (2019) Preprint 7 May 2020 Compiled using MNRAS LATEX style file v3.0 Unlocking Galactic Wolf-Rayet stars with Gaia DR2 II: Cluster and Association membership Gemma Rate,? Paul A. Crowther, Richard J. Parkery Department of Physics and Astronomy, University of Sheffield, Sheffield, S3 7RH, UK Accepted XXX. Received YYY; in original form ZZZ ABSTRACT Galactic Wolf-Rayet (WR) star membership of star forming regions can be used to constrain the formation environments of massive stars. Here, we utilise Gaia DR2 parallaxes and proper motions to reconsider WR star membership of clusters and associations in the Galactic disk, supplemented by recent near-IR studies of young massive clusters. We find that only 18{36% of 553 WR stars external to the Galac- tic Centre region are located in clusters, OB associations or obscured star-forming regions, such that at least 64% of the known disk WR population are isolated, in contrast with only 13% of O stars from the Galactic O star Catalogue. The fraction located in clusters, OB associations or star-forming regions rises to 25{41% from a global census of 663 WR stars including the Galactic Centre region. We use simu- lations to explore the formation processes of isolated WR stars. Neither runaways, nor low mass clusters, are numerous enough to account for the low cluster member- ship fraction. Rapid cluster dissolution is excluded as mass segregation ensures WR stars remain in dense, well populated environments. Only low density environments consistently produce WR stars that appeared to be isolated during the WR phase.
    [Show full text]
  • The Low-Mass Stellar Content of Westerlund 1
    The low-mass stellar content of Westerlund 1 Morten Andersen (Gemini South) Galactic young massive star clusters • Connection between local and global SF. • Can resolve the stellar populations to low masses • Star counts instead of integrated properties • Directly measure the IMF The IMF in resolved massive clusters Only scale-free part probed Westerlund 1 • Distance of ~4 Kpc, age 3-5 Myr • Total mass estimated to be 50000 Msun • High foreground extinction • Best opportunity for resolving the low mass content in a young massive cluster • HST J (F125W) and H (F160W) band imaging Westerlund 1 from ground 5pc 4.5’ SOfI JHK, Brandner et al. 2007, Gennaro et al. Early lessons • Probe down to ~3 Msun, normal (Salpeter) IMF • Total mass of ~50000 Msun assuming standard IMF • Mass segregated, at least for high masses • Elliptical cluster • Currently difficult to improve from the ground Westerlund 1 with HST 5pc 4.5’ WFC3 F125W, F160W. Andersen et al. 2016 Color-magnitude diagrams Andersen et al. 2016 Foreground population Andersen et al. 2016 Red Clump Andersen et al. 2016 Background contamination Andersen et al. 2016 Cluster main sequence MS/PMS turn-on Andersen et al. 2016 Field star subtraction Andersen et al. 2016 Mass Functions Log-normal fit below 1 Msun to the 50% completeness limit. Power-law fit above 1 Msun (Siess 4 Myr isochrone) Change of fit parameters as a function of radius M < 1 Msun, log-normal fits Comparable peak mass as the field. More narrow distribution Change of fit parameters as a function of radius M > 1 Msun Evidence for mass segregation out to 1.5-2 pc Andersen et al.
    [Show full text]
  • Spatial Distribution of Galactic Wolf–Rayet Stars and Implications for the Global Population
    MNRAS 447, 2322–2347 (2015) doi:10.1093/mnras/stu2525 Spatial distribution of Galactic Wolf–Rayet stars and implications for the global population C. K. Rosslowe‹ andP.A.Crowther Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, S3 7RH, UK Accepted 2014 November 26. Received 2014 November 26; in original form 2014 September 5 ABSTRACT We construct revised near-infrared absolute magnitude calibrations for 126 Galactic Wolf– Rayet (WR) stars at known distances, based in part upon recent large-scale spectroscopic surveys. Application to 246 WR stars located in the field permits us to map their Galactic distribution. As anticipated, WR stars generally lie in the thin disc (∼40 pc half-width at half- maximum) between Galactocentric radii 3.5–10 kpc, in accordance with other star formation tracers. We highlight 12 WR stars located at vertical distances of ≥300 pc from the mid-plane. Analysis of the radial variation in WR subtypes exposes a ubiquitously higher NWC/NWN ratio than predicted by stellar evolutionary models accounting for stellar rotation. Models for non- rotating stars or accounting for close binary evolution are more consistent with observations. We consolidate information acquired about the known WR content of the Milky Way to build a simple model of the complete population. We derive observable quantities over a range of wavelengths, allowing us to estimate a total number of 1900 ± 250 Galactic WR stars, implying an average duration of ∼ 0.4 Myr for the WR phase at the current Milky Way star formation rate. Of relevance to future spectroscopic surveys, we use this model WR population to predict follow-up spectroscopy to KS 17.5 mag will be necessary to identify 95 per cent of Galactic WR stars.
    [Show full text]
  • Resolving the Low-Mass Content of Westerlund 1 Using MCAO
    Resolving the low-mass content of Westerlund 1 using MCAO M. Andersena, B. Neichelb, A. Bernardb, and V. Garrela aGemini Observatories, Casilla 603 La Silla, Chile bAix Marseille Universit´e,CNRS, LAM (Laboratoire d'Astrophysique de Marseille) UMR 7326, 13388 Marseille, France ABSTRACT We present deep Ks band Gemini GeMS/GSAOI observations of Westerlund 1, the most massive young Galactic star cluster known. The high spatial resolution combined with a relatively stable point spread function across a large field of view provide unique possibilities to resolve the low-mass content of the cluster. We show that the clean point spread function is crucial in handling the source detection in this crowded field suffering extremely high contrast from the brightest hypergiants in the cluster to faint brown dwarfs. Keywords: star clusters: Westerlund 1, Initial Mass Function, Photometry, MCAO, Laser Guide Star Systems 1. INTRODUCTION Much progress has been made in the last decades in our understanding of low-mass star forming regions. Detailed observations of individual objects have made it possible to characterise them in detail and to determine the star formation history and the impact of environment. 4 Similar studies of massive star clusters (more than 10 M ) are much less detailed. However, they differ fundamentally from nearby regions in terms of their central densities and large content of massive stars that may have influenced the star formation process within the cluster. These clusters are rare and the nearest ones known are an order of magnitude more distant than the nearby low-mass regions. This, together with their higher densities, means that high spatial resolution observations are necessary to resolve the low-mass content of the clusters.
    [Show full text]
  • Study of Globular Cluster Sources Using Erass1 Data
    Study of Globular Cluster Sources using eRASS1 data Bachelorarbeit aus der Physik Vorgelegt von Roman Laktionov 27. April 2021 Dr. Karl Remeis-Sternwarte Friedrich-Alexander-Universit¨at Erlangen-Nu¨rnberg Betreuerin: Prof. Dr. Manami Sasaki Abstract Due to the high stellar density in globular clusters (GCs), they provide an ideal envi- ronment for the formation of X-ray luminous objects, e.g. cataclysmic variables and low-mass X-ray binaries. Those X-ray sources have, in the advent of ambitious observa- tion campaigns like the eROSITA mission, become accessible for extensive population studies. During the course of this thesis, X-ray data in the direction of the Milky Way's GCs was extracted from the eRASS1 All-Sky Survey and then analyzed. The first few chap- ters serve to provide an overview on the physical properties of GCs, the goals of the eROSITA mission and the different types of X-ray sources. Afterwards, the methods and results of the analysis will be presented. Using data of the eRASS1 survey taken between December 13th, 2019 and June 11th, 2020, 113 X-ray sources were found in the field of view of 39 GCs, including Omega Cen- tauri, 47 Tucanae and Liller 1. A Cross-correlation with optical/infrared catalogs and the subsequent analysis of various diagrams enabled the identification of 6 foreground stars, as well as numerous background candidates and stellar sources. Furthermore, hardness ratio diagrams were used to select 16 bright sources, possibly of GC origin, for a spectral analysis. By marking them in X-ray and optical images, it was concluded that 6 of these sources represent the bright central emission of their host GC, while 10 are located outside of the GC center.
    [Show full text]
  • A 3Mm ALMA Census of the Massive Cluster Westerlund 1 1 2 1 3 4 5 6 2 D
    A 3mm ALMA census of the massive cluster Westerlund 1 D. Fenech1, J. Clark2, R. Prinja1, S. Dougherty3, F. NaJarro4, I. Negueruela5, A. Richards6 and B. Ritchie2 1Department of Physics and Astronomy, University College London, U.K.; 2School of Physical Science, The Open University, UK; 3Dominion Radio Astrophysical Observatory, National Research Council Canada; 4Departamento de Física, Ingenaría de Sistemas y Teoría de la Señal, Universidad de Alicante, Spain; 5Departamento de Astrofísica, Centro de Astrobiología, (CSIC-INTA) Spain; 6JBCA, University of Manchester & MERLIN/VLBI National Facility, JBO,U.K. Westerlund 1 Massive stars Cool super-/hypergiants Westerlund 1 (Wd1) is one of the first examples of a super star cluster within our Despite their rarity, massive stars play a major role in galactic evolution. They deposit large amounts of Galaxy and contains a population of co-eval massive stars. Located at a distance of Yellow hypergiants (YHGs) and red supergiants (RSGs) are of particular chemically enriched material, energy and ionising radiation into their environment and dominate the ~5 kpc, Wd1 was discovered by Westerlund in 1961 (Westerlund, 1961,PASP, 73, interest as they are believed to shed mass at suffucent rates to profoundly integrated galactic spectra in the UV and IR regimes (via re-radiation). However, the lives of massive stars 51). However, the large extinction towards Wd1 (Av~11 mag) meant that few affect a stars evolution in spite of spending relatively little time in this are still poorly understood. observations were made of the cluster until relatively recently when radio images phase. Mass-loss is considered a critical factor in the evolutionary pathway of massive stars and consequently the revealed a large number of radio sources (Dougherty et al.
    [Show full text]
  • Annual Report 2007 ESO
    ESO European Organisation for Astronomical Research in the Southern Hemisphere Annual Report 2007 ESO European Organisation for Astronomical Research in the Southern Hemisphere Annual Report 2007 presented to the Council by the Director General Prof. Tim de Zeeuw ESO is the pre-eminent intergovernmental science and technology organisation in the field of ground-based astronomy. It is supported by 13 countries: Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. Further coun- tries have expressed interest in member- ship. Created in 1962, ESO provides state-of- the-art research facilities to European as- tronomers. In pursuit of this task, ESO’s activities cover a wide spectrum including the design and construction of world- class ground-based observational facili- ties for the member-state scientists, large telescope projects, design of inno- vative scientific instruments, developing new and advanced technologies, further- La Silla. ing European cooperation and carrying out European educational programmes. One of the most exciting features of the In 2007, about 1900 proposals were VLT is the possibility to use it as a giant made for the use of ESO telescopes and ESO operates the La Silla Paranal Ob- optical interferometer (VLT Interferometer more than 700 peer-reviewed papers servatory at several sites in the Atacama or VLTI). This is done by combining the based on data from ESO telescopes were Desert region of Chile. The first site is light from several of the telescopes, al- published. La Silla, a 2 400 m high mountain 600 km lowing astronomers to observe up to north of Santiago de Chile.
    [Show full text]
  • Magnetars Unleash Mammoth Bursts of Energy, but How and Why? Astronomers Are Working to Understand These Bizarre Stellar Objects
    In search of the galaxy’s magnetic Magnetars unleash mammoth bursts of energy, but how and why? Astronomers are working to understand these bizarre stellar objects. By Steve Nadis monsters n 1987, when Robert Duncan and Chris- the 5-day event, seemingly lumped in the objects constitute a distinct class of pul- Blasts from beyond IN a magNetar’S gIaNt flareS, magnetic field lines break and reconnect, releasing a burst of topher Thompson first contemplated the fringe category. sars. They are rapidly spinning, intensely Scientists’ now believe magnetars exist energy. This process resembles solar-flare formation, except magnetars’ flares are much more existence of ultramagnetized neutron Six years later, in 2004, colleagues magnetic neutron stars — dense remnants because of a confluence of theory and obser- powerful. Don Dixon for Astronomy stars (later dubbed “magnetars”), they finally recognized Duncan and Thompson of massive stars that expired in fiery vational data from some of nature’s most had a hard time convincing themselves (now at the University of Texas and the supernova blasts. impressive high-energy displays. For astron- magnetic field of about a million billion powerful flare from outside our solar sys- I that the notion made sense. Five years University of Toronto, respectively) for Armed with this knowledge, researchers omers, says Thompson, the turning point (1015) gauss. (Earth’s magnetic field reaches tem astronomers had ever recorded. In later, when they got their first opportunity their theoretical work on magnetars.
    [Show full text]
  • January 2019 BRAS Newsletter
    Monthly Meeting January 14th at 7PM at HRPO (Monthly meetings are on 2nd Mondays, Highland Road Park Observatory). Speaker: Jim Gutierrez, Sunspots, Hot Spots and Relativity What's In This Issue? President’s Message Secretary's Summary Outreach Report Astrophotography Group Comet and Asteroid News Light Pollution Committee Report “Free The Milky Way” Campaign Recent BRAS Forum Entries Messages from the HRPO Science Academy Friday Night Lecture Series Globe at Night Adult Astronomy Courses Total Lunar Eclipse Observing Notes – Ara – The Alter & Mythology Like this newsletter? See PAST ISSUES online back to 2009 Visit us on Facebook – Baton Rouge Astronomical Society Newsletter of the Baton Rouge Astronomical Society January 2019 © 2019 President’s Message First off, I thank you for placing your trust in me for another year. Another thanks goes out to Scott Cadwallader and John R. Nagle for fixing the Library Telescope. The telescope was missing a thumbnut witch Orion Telescope replaced, Scott and John, put the thumbnut back on and reset the collimation. Let’s don’t forget the Total Lunar Eclipse coming up this January 20th. See HRPO announcement below. We are planning 2019 and hope to have an enjoyable year for our members. I’d like to find more opportunity to point our telescopes at the night sky. If there is anything you’d like to see, do, or wish to offer let us know. Our webmaster has set up a private forum: "BRAS Members Only" Group/Section to the "Baton Rouge Astronomical Society Forum" (http://www.brastro.org/phpBB3/). The plan is to use this Group/Section to get additional information to members and get feedback from members without the need of flooding everyone's inbox.
    [Show full text]
  • Miljenko Čemeljić, CAMK, Warsaw & ASIAA, Taiwan
    arXiv:2012.08550 Miljenko Čemeljić, CAMK, Warsaw & ASIAA, Taiwan Miljenko Čemeljić, CAMK Journal Club, March, 2021, Warsaw Outline -Hypergiants? -VY Canis Majoris -Possible implications on the explanation of the recent dimming of Betelgeuse. Miljenko Čemeljić, CAMK Journal Club, March, 2021, Warsaw Hypergiants -Hypergiants: how giant are they? -At the beginning of the article is written that if VY Cma, with radius about 1420 R_sun, would be in place of our Sun, it would reach to Jupiter. Jupiter? I remembered “giants, e.g. Antares, would reach to Mars”, this one ... Jupiter?! Other supergiants are Westerlund 1-26, WOH G64, with about 1200 and 1500 R_sun, and Stephenson 2-18 with about 2500 R_sun-it would reach to Saturn! Light travelling around the equator of VY CMa star would take 6 hours, compared to 14.5 seconds for the Sun. It is not at all that “obvious” for me that gaseous spheres can be THAT big. I did not remember it from the HR diagrams I saw. “Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist's, but that's just peanuts to space.” ― Douglas Adams, “The Hitchhiker's Guide to the Galaxy” Supergiants in HR diagram Radius of the Sun is about 695,700 km --> diameter is of the order of 1 million km. Distance Earth-Moon is 384 000 km. Hypergiants? Supergiants in HR diagram About 90 percent of the stars in the universe exist along Main sequence line at one time in their lives, when they still fuse hydrogen to helium.
    [Show full text]