DOCSLIB.ORG

Eta Carinae and Its Environment

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Eta Carinae and Its Environment P1: ARK/MBL/plb P2: MBL/plb QC: MBL/agr T1: MBL January 9, 1998 15:7 Annual Reviews AR037-01 Annu. Rev. Astron. Astrophys. 1997. 35:1–32 Copyright c 1997 by Annual Reviews Inc. All rights reserved ETA CARINAE AND ITS ENVIRONMENT Kris Davidson and Roberta M. Humphreys Astronomy Department, University of Minnesota, Minneapolis, Minnesota 55455; e-mail: [email protected] KEY WORDS: massive stars, variable stars, LBVs or luminous blue variables ABSTRACT Eta Carinae (Eta) is one of the most remarkable of all well-studied stars and per- haps the most poorly understood. Observations with the Hubble Space Telescope and other modern instruments have solved a few of the mysteries concerning this object while opening a comparable number of new ones. In this review we first recount some essential background information concerning Eta, then we sketch most of the observational developments of the past few years, related to the star itself and to its ejecta. Throughout, we propose a series of specific unsolved ob- servational and theoretical problems that seem especially interesting or important at this time. 1. INTRODUCTION A strange field of speculation is opened by this phenomenon...here we have a star fitfully variable to an astonishing extent, and whose fluctuations are spread by Deutsche Forschungsgemeinschaft on 07/02/07. For personal use only. over centuries, apparently with no settled period and no regularity of progression. What origin can we ascribe to these sudden flashes and relapses? What conclu- sions are we to draw as to the comfort and habitability of a system depending for Annu. Rev. Astro. Astrophys. 1997.35:1-32. Downloaded from arjournals.annualreviews.org its supply of light and heat on so uncertain a source? —JFW Herschel (1847) Eta Carinae (η Car) is arguably the most remarkable stellar object that is close enough to be observed in great detail. It is so special that enthusiasts often refer simply and familiarly to “Eta”—a usage we would deplore for any other star with a Bayer designation. Eta’s fame and uniqueness rest on a combination of three different but related lists of attributes, which we merely sketch here at the outset of this review, postponing references until later. 1 0066-4146/97/0915-0001$08.00 P1: ARK/MBL/plb P2: MBL/plb QC: MBL/agr T1: MBL January 9, 1998 15:7 Annual Reviews AR037-01 2 DAVIDSON & HUMPHREYS First, a list of superlatives. The most luminous evolved star that can be studied closely, Eta is also the survivor of the greatest well-documented non- terminal stellar explosion. Its mass probably exceeds 100 , which would make it rare even if it were a more stable star near the mainM sequence. For two decades of the nineteenth century, Eta was visually one of the dozen brightest stars in the sky, even at a distance of more than 2 kpc; the total luminous energy radiated during the whole outburst was comparable to that of a supernova event. In recent years, its luminosity has been several million times that of the Sun. Today it is the brightest extra–solar-system infrared source in the sky at λ 20 µm, and it has the brightest known stellar wind at millimeter or centimeter∼ wavelengths. Eta has produced one of the most elegant of all known bipolar nebulae. Second, as John Herschel (1847) wrote with only mild exaggeration, “There is perhaps no other sidereal object which unites more points of interest than this.” Stellar physics?—The interplay of radiation pressure and opacity (maybe rotation too) causes Eta to be irregularly, chaotically unstable, with occasional titanic eruptions. Stellar evolution?—This star appears to be an extreme ex- ample showing how instability limits evolution at the top of the Hertzsprung- Russell (H-R) diagram. Star formation?—Eta was formed in a rich association that includes several other very massive (and therefore very unusual) stars. Gas dynamics?—Bipolar flows created by the aforesaid instability are beautifully symmetric, but at the same time they have conspicuous localized asymmetric features that no one predicted. Microphysics and radiative transfer?—Certain bright emission lines in the ejecta are excited by fluorescent processes that are uniquely effective around Eta. Dust formation? Chemical enrichment of the surrounding medium?—Eta is relevant to these and to other topics as well, in nonroutine largely unexplored ways. Third, this object is very poorly understood. We do not know why or how Eta’s giant eruptions occurred, and its energy budget has never been properly audited. Although we do know that Eta is evolved, we are not sure whether it by Deutsche Forschungsgemeinschaft on 07/02/07. For personal use only. is typical of the most massive stars; it might be a rapid rotator or a close binary system. Some authors suggest that the star exhibits surprising periodicities. Some of the most obvious characteristics of its bipolar ejecta are difficult to Annu. Rev. Astro. Astrophys. 1997.35:1-32. Downloaded from arjournals.annualreviews.org explain, as are the brightnesses and ratios of some of its most conspicuous emis- sion lines. As new instruments have settled particular observational questions about Eta, they have opened new questions to replace the old ones—a classic tendency shared with other unusually interesting astrophysical topics. We recommend Eta as a subject for all sorts of theoretical and observational research projects. Therefore, throughout the review we mark some of the most crucial or interesting questions with Q labels, e.g. Herschel’s classic mystery that still deserves top billing: { } P1: ARK/MBL/plb P2: MBL/plb QC: MBL/agr T1: MBL January 9, 1998 15:7 Annual Reviews AR037-01 ETA CARINAE 3 Q1 What origin can we ascribe to these sudden flashes and relapses? { } Eta and its vicinity were the topics of a meeting held in 1993, whose pro- ceedings contain many useful papers (see Niemela et al 1995). For a review of the class of star to which Eta most likely belongs, see Humphreys & Davidson (1994). 2. AN UPPER-CLASS NEIGHBORHOOD From our vantage point, the constellation Carina marks the most spectacular direction in the Milky Way. There our line of sight passes along the Carina spiral arm, which can be traced to distances of more than 10 kpc at visual wavelengths (Humphreys 1976) and as far as 23 kpc with CO observations (Grabelsky et al 1988). This major Galactic feature is defined by large numbers of massive stars and prominent star-formation regions, such as the Carina Nebula (NGC 3372) and its surrounding association Car OB1 (` 284.2 to 288.3 , b 2.2 to ≈ ◦ ◦ ≈− ◦ 0.9◦, D 2.5 kpc). With a more impressive concentration of very luminous +stars than any≈ other place within a few kiloparsecs of the Sun, the Carina Nebula is one of the best available sites for studying the formation and evolution of the most massive stars. Its two central clusters, Trumpler 14 and Trumpler 16 (Tr 14 and Tr 16), are particularly unusual. When we refer here to Tr 16, we also include a set of stars called Collinder 228 (Cr 228). Together these are now considered to be a single cluster, with an illusory separation between Tr 16 and Cr 228 caused by a superimposed dust lane (see Walborn 1995). A census of hot stars in Tr 14 and Tr 16, based on the work of Walborn (1982a,b), Morrell et al (1988), Levato & Malaroda (1981, 1982), and Massey & Johnson (1993), includes 36 stars earlier than spectral type B0 and 3 WN-A stars. These provide enough ultraviolet (UV) photons to ionize the large nebula and to heat the dust seen in infrared observations (Harvey et al 1979; Ghosh et al 1988). Far more remarkably, Tr 14 and Tr 16 contain 6 of the 17 known O3-type stars in our by Deutsche Forschungsgemeinschaft on 07/02/07. For personal use only. Galaxy; because O3 stars are at the hot end of the normal spectral sequence, they are very massive and quite rare. Knowing this, perhaps one is not very surprised to learn that Eta is a member of Tr 16. Annu. Rev. Astro. Astrophys. 1997.35:1-32. Downloaded from arjournals.annualreviews.org The larger association Car OB1 and the outer clusters IC 2581, NGC 3293, and NGC 3324 contain numerous OB stars and evolved supergiants, including many M supergiants, whose presence implies an age of about 10 million years for the oldest massive stars in this stellar complex. Published distance moduli for the outer clusters range from 11.9–12.5 mag, and the distance to the as- sociation is usually quoted as 2.5 kpc (see Humphreys 1978). The clusters Bochum 10 and 11 are apparently∼ close to the Carina Nebula and contain sev- eral OB stars; Fitzgerald & Mehta (1987) derived ages of 7 and 3 million years P1: ARK/MBL/plb P2: MBL/plb QC: MBL/agr T1: MBL January 9, 1998 15:7 Annual Reviews AR037-01 4 DAVIDSON & HUMPHREYS and distance moduli of 12.2 and 12.7 mag for Bo 10 and Bo 11, respectively. Tr 15 is usually considered to be behind the H II region (Walborn 1995). Distances to Tr 14 and Tr 16 have been made more uncertain by anomalous extinction within or near the Carina Nebula. Feinstein et al (1973), Herbst (1976), and Forte (1978) reported abnormally high ratios of extinction to red- dening there, i.e. the wavelength dependence of the obscuration is relatively weaker than it is in the normal interstellar medium. In a multiwavelength study, Th´e et al (1980) found that the wavelength dependence of the extinction varies from star to star in the vicinity of the Carina Nebula.
Load more

Recommended publications
  • FY08 Technical Papers by GSMTPO Staff
    AURA/NOAO ANNUAL REPORT FY 2008 Submitted to the National Science Foundation July 23, 2008 Revised as Complete and Submitted December 23, 2008 NGC 660, ~13 Mpc from the Earth, is a peculiar, polar ring galaxy that resulted from two galaxies colliding. It consists of a nearly edge-on disk and a strongly warped outer disk. Image Credit: T.A. Rector/University of Alaska, Anchorage NATIONAL OPTICAL ASTRONOMY OBSERVATORY NOAO ANNUAL REPORT FY 2008 Submitted to the National Science Foundation December 23, 2008 TABLE OF CONTENTS EXECUTIVE SUMMARY ............................................................................................................................. 1 1 SCIENTIFIC ACTIVITIES AND FINDINGS ..................................................................................... 2 1.1 Cerro Tololo Inter-American Observatory...................................................................................... 2 The Once and Future Supernova η Carinae...................................................................................................... 2 A Stellar Merger and a Missing White Dwarf.................................................................................................. 3 Imaging the COSMOS...................................................................................................................................... 3 The Hubble Constant from a Gravitational Lens.............................................................................................. 4 A New Dwarf Nova in the Period Gap............................................................................................................
    [Show full text]
  • Luminous Blue Variables
    Review Luminous Blue Variables Kerstin Weis 1* and Dominik J. Bomans 1,2,3 1 Astronomical Institute, Faculty for Physics and Astronomy, Ruhr University Bochum, 44801 Bochum, Germany 2 Department Plasmas with Complex Interactions, Ruhr University Bochum, 44801 Bochum, Germany 3 Ruhr Astroparticle and Plasma Physics (RAPP) Center, 44801 Bochum, Germany Received: 29 October 2019; Accepted: 18 February 2020; Published: 29 February 2020 Abstract: Luminous Blue Variables are massive evolved stars, here we introduce this outstanding class of objects. Described are the specific characteristics, the evolutionary state and what they are connected to other phases and types of massive stars. Our current knowledge of LBVs is limited by the fact that in comparison to other stellar classes and phases only a few “true” LBVs are known. This results from the lack of a unique, fast and always reliable identification scheme for LBVs. It literally takes time to get a true classification of a LBV. In addition the short duration of the LBV phase makes it even harder to catch and identify a star as LBV. We summarize here what is known so far, give an overview of the LBV population and the list of LBV host galaxies. LBV are clearly an important and still not fully understood phase in the live of (very) massive stars, especially due to the large and time variable mass loss during the LBV phase. We like to emphasize again the problem how to clearly identify LBV and that there are more than just one type of LBVs: The giant eruption LBVs or h Car analogs and the S Dor cycle LBVs.
    [Show full text]
  • A Basic Requirement for Studying the Heavens Is Determining Where In
    Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun­ damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short).
    [Show full text]
  • Astronomy 2008 Index
    Astronomy Magazine Article Title Index 10 rising stars of astronomy, 8:60–8:63 1.5 million galaxies revealed, 3:41–3:43 185 million years before the dinosaurs’ demise, did an asteroid nearly end life on Earth?, 4:34–4:39 A Aligned aurorae, 8:27 All about the Veil Nebula, 6:56–6:61 Amateur astronomy’s greatest generation, 8:68–8:71 Amateurs see fireballs from U.S. satellite kill, 7:24 Another Earth, 6:13 Another super-Earth discovered, 9:21 Antares gang, The, 7:18 Antimatter traced, 5:23 Are big-planet systems uncommon?, 10:23 Are super-sized Earths the new frontier?, 11:26–11:31 Are these space rocks from Mercury?, 11:32–11:37 Are we done yet?, 4:14 Are we looking for life in the right places?, 7:28–7:33 Ask the aliens, 3:12 Asteroid sleuths find the dino killer, 1:20 Astro-humiliation, 10:14 Astroimaging over ancient Greece, 12:64–12:69 Astronaut rescue rocket revs up, 11:22 Astronomers spy a giant particle accelerator in the sky, 5:21 Astronomers unearth a star’s death secrets, 10:18 Astronomers witness alien star flip-out, 6:27 Astronomy magazine’s first 35 years, 8:supplement Astronomy’s guide to Go-to telescopes, 10:supplement Auroral storm trigger confirmed, 11:18 B Backstage at Astronomy, 8:76–8:82 Basking in the Sun, 5:16 Biggest planet’s 5 deepest mysteries, The, 1:38–1:43 Binary pulsar test affirms relativity, 10:21 Binocular Telescope snaps first image, 6:21 Black hole sets a record, 2:20 Black holes wind up galaxy arms, 9:19 Brightest starburst galaxy discovered, 12:23 C Calling all space probes, 10:64–10:65 Calling on Cassiopeia, 11:76 Canada to launch new asteroid hunter, 11:19 Canada’s handy robot, 1:24 Cannibal next door, The, 3:38 Capture images of our local star, 4:66–4:67 Cassini confirms Titan lakes, 12:27 Cassini scopes Saturn’s two-toned moon, 1:25 Cassini “tastes” Enceladus’ plumes, 7:26 Cepheus’ fall delights, 10:85 Choose the dome that’s right for you, 5:70–5:71 Clearing the air about seeing vs.
    [Show full text]
  • Stats2010 E Final.Pdf
    Imprint Publisher: Max-Planck-Institut für extraterrestrische Physik Editors and Layout: W. Collmar und J. Zanker-Smith Personnel 1 PERSONNEL 2010 Directors Min. Dir. J. Meyer, Section Head, Federal Ministry of Prof. Dr. R. Bender, Optical and Interpretative Astronomy, Economics and Technology also Professorship for Astronomy/Astrophysics at the Prof. Dr. E. Rohkamm, Thyssen Krupp AG, Düsseldorf Ludwig-Maximilians-University Munich Prof. Dr. R. Genzel, Infrared- and Submillimeter- Scientifi c Advisory Board Astronomy, also Prof. of Physics, University of California, Prof. Dr. R. Davies, Oxford University (UK) Berkeley (USA) (Managing Director) Prof. Dr. R. Ellis, CALTECH (USA) Prof. Dr. Kirpal Nandra, High-Energy Astrophysics Dr. N. Gehrels, NASA/GSFC (USA) Prof. Dr. G. Morfi ll, Theory, Non-linear Dynamics, Complex Prof. Dr. F. Harrison, CALTECH (USA) Plasmas Prof. Dr. O. Havnes, University of Tromsø (Norway) Prof. Dr. G. Haerendel (emeritus) Prof. Dr. P. Léna, Université Paris VII (France) Prof. Dr. R. Lüst (emeritus) Prof. Dr. R. McCray, University of Colorado (USA), Prof. Dr. K. Pinkau (emeritus) Chair of Board Prof. Dr. J. Trümper (emeritus) Prof. Dr. M. Salvati, Osservatorio Astrofi sico di Arcetri (Italy) Junior Research Groups and Minerva Fellows Dr. N.M. Förster Schreiber Humboldt Awardee Dr. S. Khochfar Prof. Dr. P. Henry, University of Hawaii (USA) Prof. Dr. H. Netzer, Tel Aviv University (Israel) MPG Fellow Prof. Dr. V. Tsytovich, Russian Academy of Sciences, Prof. Dr. A. Burkert (LMU) Moscow (Russia) Manager’s Assistant Prof. S. Veilleux, University of Maryland (USA) Dr. H. Scheingraber A. v. Humboldt Fellows Scientifi c Secretary Prof. Dr. D. Jaffe, University of Texas (USA) Dr.
    [Show full text]
  • The Search for Exomoons and the Characterization of Exoplanet Atmospheres
    Corso di Laurea Specialistica in Astronomia e Astrofisica The search for exomoons and the characterization of exoplanet atmospheres Relatore interno : dott. Alessandro Melchiorri Relatore esterno : dott.ssa Giovanna Tinetti Candidato: Giammarco Campanella Anno Accademico 2008/2009 The search for exomoons and the characterization of exoplanet atmospheres Giammarco Campanella Dipartimento di Fisica Università degli studi di Roma “La Sapienza” Associate at Department of Physics & Astronomy University College London A thesis submitted for the MSc Degree in Astronomy and Astrophysics September 4th, 2009 Università degli Studi di Roma ―La Sapienza‖ Abstract THE SEARCH FOR EXOMOONS AND THE CHARACTERIZATION OF EXOPLANET ATMOSPHERES by Giammarco Campanella Since planets were first discovered outside our own Solar System in 1992 (around a pulsar) and in 1995 (around a main sequence star), extrasolar planet studies have become one of the most dynamic research fields in astronomy. Our knowledge of extrasolar planets has grown exponentially, from our understanding of their formation and evolution to the development of different methods to detect them. Now that more than 370 exoplanets have been discovered, focus has moved from finding planets to characterise these alien worlds. As well as detecting the atmospheres of these exoplanets, part of the characterisation process undoubtedly involves the search for extrasolar moons. The structure of the thesis is as follows. In Chapter 1 an historical background is provided and some general aspects about ongoing situation in the research field of extrasolar planets are shown. In Chapter 2, various detection techniques such as radial velocity, microlensing, astrometry, circumstellar disks, pulsar timing and magnetospheric emission are described. A special emphasis is given to the transit photometry technique and to the two already operational transit space missions, CoRoT and Kepler.
    [Show full text]
  • A Blast Wave from the 1843 Eruption of Eta Carinae
    1 A Blast Wave from the 1843 Eruption of Eta Carinae Nathan Smith* *Astronomy Department, University of California, 601 Campbell Hall, Berkeley, CA 94720-3411 Very massive stars shed much of their mass in violent precursor eruptions [1] as luminous blue variables (LBVs) [2] before reaching their most likely end as supernovae, but the cause of LBV eruptions is unknown. The 19th century eruption of Eta Carinae, the prototype of these events [3], ejected about 12 solar masses at speeds of 650 km/s, with a kinetic energy of almost 1050ergs[4]. Some faster material with speeds up to 1000-2000 km/s had previously been reported [5,6,7,8] but its full distribution was unknown. Here I report observations of much faster material with speeds up to 3500-6000 km/s, reaching farther from the star than the fastest material in earlier reports [5]. This fast material roughly doubles the kinetic energy of the 19th century event, and suggests that it released a blast wave now propagating ahead of the massive ejecta. Thus, Eta Carinae’s outer shell now mimics a low-energy supernova remnant. The eruption has usually been discussed in terms of an extreme wind driven by the star’s luminosity [2,3,9,10], but fast material reported here suggests that it was powered by a deep-seated explosion rivalling a supernova, perhaps triggered by the pulsational pair instability[11]. This may alter interpretations of similar events seen in other galaxies. Eta Carinae [3] is the most luminous and the best studied among LBVs [1,2].
    [Show full text]
  • Publications of the Astronomical Society of the Pacific 108: 8-34, 1996 January
    Publications of the Astronomical Society of the Pacific 108: 8-34, 1996 January Invited Review Paper Astrophysics in 1995 Virginia Trimble Department of Astronomy, University of Maryland, College Park, Maryland 20742-2421 and Department of Physics, University of California, Irvine, California 92717-4575 Peter J. T. Leonard Department of Astronomy, University of Maryland, College Park, Maryland 20742-2421 Received 1995 October 26; accepted 1995 October 27 ABSTRACT. Ap95 differs from Ap91 to Ap94 primarily in Ap number. That is, it once again attempts to highlight some areas of our mutual science where a major event has occurred during the year (a possible solution of the Type II supernova problem, the faintness of quasar host galaxies, the collision of Shoemaker-Levy 9 with Jupiter), but also to focus on some topics where dogged determination is producing more gradual advances (dense star clusters, the second-parameter problem, inventories of nearby objects, and dark-matter candidates). In moderate departure from the rules of Ap92-94, there has been some deliberate up-dating of topics discussed previously. The topics are only partly ordered from nearby to far away. 1. INTRODUCTION Journal. Another, less publicized, change of editors has "For crying out loud," we can hear you saying, "is it modified the journal so much that Vinod Krishan's Bulletin them again!" Well, yes. This is the fifth annual mustering of of the Astronomical Society of India (BASI in the references) the sheep and goats of astronomical/astrophysical research, has been added to the list of journals to be scanned regularly. based on journals that reached library shelves between 1 Oc- Last year, we worried a bit about paying too much atten- tober 1994 and 30 September 1995.
    [Show full text]
  • NASA's Goddard Space Flight Center Laboratory for Astronomy & Solar Physics Greenbelt, Maryland, 20771
    NASA’s Goddard Space Flight Center Laboratory for Astronomy & Solar Physics Greenbelt, Maryland, 20771 The following report covers the period from Septem- istrator announced the cancellation of the next servicing ber 2003 through September 2004. mission (SM4) to the Hubble Space Telescope (HST), citing safety concerns about sending the Shuttle into an 1 INTRODUCTION orbit that did not have a “safe haven” (namely, the Inter- The Laboratory for Astronomy & Solar Physics national Space Station). Subsequently, the Administra- (LASP) is a Division of the Space Sciences Directorate tor authorized GSFC to begin study of a robotic repair at NASA’s Goddard Space Flight Center (GSFC). Mem- of HST, which would add new batteries, gyroscopes, and bers of LASP conduct a broad program of observational install both of the new instruments intended for installa- and theoretical scientific research. Observations are car- tion on SM4 – the Cosmic Origins Spectrograph (COS) ried out from space-based observatories, balloons, and and the Wide Field Camera 3 (WFC3). An intensive ground-based telescopes at wavelengths extending from engineering effort in the HST Project at Goddard is cur- the EUV to the sub-millimeter. Research projects cover rently underway to determine if this robotic repair is the fields of solar and stellar astrophysics, extrasolar technically possible within the allowed time-fame (be- planets, the interstellar and intergalactic medium, ac- fore the HST batteries die). WFC3 has completed a tive galactic nuclei, and the evolution of structure in the successful initial thermal vacuum test at Goddard under universe. the leadership of Instrument Scientist Randy Kimble. Studies of the sun are carried out in the gamma- However, on a decidedly sad note for LASP, the Space ray, x-ray, EUV/UV and visible portions of the spec- Telescope Imaging Spectrograph (STIS; Woodgate, PI), trum from space and the ground.
    [Show full text]
  • ESO Annual Report 2004 ESO Annual Report 2004 Presented to the Council by the Director General Dr
    ESO Annual Report 2004 ESO Annual Report 2004 presented to the Council by the Director General Dr. Catherine Cesarsky View of La Silla from the 3.6-m telescope. ESO is the foremost intergovernmental European Science and Technology organi- sation in the field of ground-based as- trophysics. It is supported by eleven coun- tries: Belgium, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Sweden, Switzerland and the United Kingdom. Created in 1962, ESO provides state-of- the-art research facilities to European astronomers and astrophysicists. In pur- suit of this task, ESO’s activities cover a wide spectrum including the design and construction of world-class ground-based observational facilities for the member- state scientists, large telescope projects, design of innovative scientific instruments, developing new and advanced techno- logies, furthering European co-operation and carrying out European educational programmes. ESO operates at three sites in the Ataca- ma desert region of Chile. The first site The VLT is a most unusual telescope, is at La Silla, a mountain 600 km north of based on the latest technology. It is not Santiago de Chile, at 2 400 m altitude. just one, but an array of 4 telescopes, It is equipped with several optical tele- each with a main mirror of 8.2-m diame- scopes with mirror diameters of up to ter. With one such telescope, images 3.6-metres. The 3.5-m New Technology of celestial objects as faint as magnitude Telescope (NTT) was the first in the 30 have been obtained in a one-hour ex- world to have a computer-controlled main posure.
    [Show full text]
  • The Binarity of Eta Carinae Revealed from Photoionization Modeling of The
    The Binarity of Eta Carinae Revealed from Photoionization Modeling of the Spectral Variability of the Weigelt Blobs B and D 1 Short title: Eta Carinae Binarity E. Verner2,3, F. Bruhweiler2,3, and T. Gull3 [email protected], [email protected], and [email protected] 1 Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555 2 Institute for Astrophysics and Computational Science, Department of Physics, Catholic University of America, 200 Hannan Hall, Washington, DC 20064 3 Laboratory of Astronomy and Solar Physics, NASA Goddard Space, Flight Center, Greenbelt, MD 20771 Abstract We focus on two Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS) spectra of the Weigelt Blobs B&D, extending from 1640 to 10400Å; one recorded during the 1998 minimum (March 1998) and the other recorded in February 1999, early in the following broad maximum. The spatially-resolved spectra suggest two distinct ionization regions. One structure is the permanently low ionization cores of the Weigelt Blobs, B&D, located several hundred AU from the ionizing source. Their spectra are dominated by emission from H I, [N II], Fe II, [Fe II], Ni II, [Ni II], Cr II and Ti II. The second region, relatively diffuse in character and located between the ionizing source and the Weigelt Blobs, is more highly ionized with emission from [Fe III], [Fe IV], N III], [Ne III], [Ar III], [Si III], [S III] and He I.
    [Show full text]
  • Eta Carinae Eta Carinae’S Vibrant Fireworks Show in the 1840S, Astronomers Saw a Star Flare up to Become the Second Brightest Star in the Sky for More Than a Decade
    National Aeronautics and Space Administration Eta Carinae Eta Carinae’s Vibrant Fireworks Show In the 1840s, astronomers saw a star flare up to become the second brightest star in the sky for more than a decade. The star, named Eta Carinae, was so bright that mariners sailing the southern seas used it for navigation. Astronomers now know that the suddenly luminous star is actually a pair of stars with a combined mass of more than 100 times that of our Sun. The brightening during the mid-1800s was a signal that the system’s most massive star had undergone a titanic outburst, which astronomers call the “Great Eruption.” During this violent event, the giant star ejected material into space at 1.5 million miles per hour, creating an expanding cloud of gas and dust. Some of the material formed twin bubbles of gas on opposite sides of the hefty stars. Although Eta Carinae has faded since the Great Eruption, it is still the brightest star system in the Carina Nebula. Observations by ground- and space- based telescopes, including the Hubble Space Telescope, reveal that the stellar fireworks aren’t over yet. The Hubble image on the front of this lithograph shows Eta Carinae’s hot, expanding, twin bubbles of glowing gas. The image is a blend of visible and ultraviolet light. The outer nitrogen-rich filaments are red. The blue color is the ultraviolet glow of magnesium within warm gas. The gas inside and between the twin bubbles appears white, showing that the material radiates strongly This image of the heart of the Carina Nebula shows the location of the at ultraviolet and visible wavelengths.
    [Show full text]