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Stsci Newsletter: 1997 Volume 014 Issue 01
January 1997 • Volume 14, Number 1 SPACE TELESCOPE SCIENCE INSTITUTE Highlights of this issue: • AURA science and functional awards to Leitherer and Hanisch — pages 1 and 23 • Cycle 7 to be extended — page 5 • Cycle 7 approved Newsletter program listing — pages 7-13 Astronomy with HST Climbing the Starburst Distance Ladder C. Leitherer Massive stars are an important and powerful star formation events in sometimes dominant energy source for galaxies. Even the most luminous star- a galaxy. Their high luminosity, both in forming regions in our Galaxy are tiny light and mechanical energy, makes on a cosmic scale. They are not them detectable up to cosmological dominated by the properties of an distances. Stars ~100 times more entire population but by individual massive than the Sun are one million stars. Therefore stochastic effects times more luminous. Except for stars prevail. Extinction represents a severe of transient brightness, like novae and problem when a reliable census of the supernovae, hot, massive stars are Galactic high-mass star-formation the most luminous stellar objects in history is atempted, especially since the universe. massive stars belong to the extreme Massive stars are, however, Population I, with correspondingly extremely rare: The number of stars small vertical scale heights. Moreover, formed per unit mass interval is the proximity of Galactic regions — roughly proportional to the -2.35 although advantageous for detailed power of mass. We expect to find very studies of individual stars — makes it few massive stars compared to, say, difficult to obtain integrated properties, solar-type stars. This is consistent with such as total emission-line fluxes of observations in our solar neighbor- the ionized gas. -
Filter Performance Comparisons for Some Common Nebulae
Filter Performance Comparisons For Some Common Nebulae By Dave Knisely Light Pollution and various “nebula” filters have been around since the late 1970’s, and amateurs have been using them ever since to bring out detail (and even some objects) which were difficult to impossible to see before in modest apertures. When I started using them in the early 1980’s, specific information about which filter might work on a given object (or even whether certain filters were useful at all) was often hard to come by. Even those accounts that were available often had incomplete or inaccurate information. Getting some observational experience with the Lumicon line of filters helped, but there were still some unanswered questions. I wondered how the various filters would rank on- average against each other for a large number of objects, and whether there was a “best overall” filter. In particular, I also wondered if the much-maligned H-Beta filter was useful on more objects than the two or three targets most often mentioned in publications. In the summer of 1999, I decided to begin some more comprehensive observations to try and answer these questions and determine how to best use these filters overall. I formulated a basic survey covering a moderate number of emission and planetary nebulae to obtain some statistics on filter performance to try to address the following questions: 1. How do the various filter types compare as to what (on average) they show on a given nebula? 2. Is there one overall “best” nebula filter which will work on the largest number of objects? 3. -
198 7Apj. . .312L. .11J the Astrophysical Journal, 312:L11-L15
.11J The Astrophysical Journal, 312:L11-L15,1987 January 1 .312L. © 1987. The American Astronomical Society. All rights reserved. Printed in U.S.A. 7ApJ. 198 INTERSTELLAR DUST IN SHAPLEY-AMES ELLIPTICAL GALAXIES M. Jura and D. W. Kim Department of Astronomy, University of California, Los Angeles AND G. R. Knapp and P. Guhathakurta Princeton University Observatory Received 1986 August 11; accepted 1986 September 30 ABSTRACT We have co-added the IRAS survey data at the positions of the brightest elliptical galaxies in the Revised Shapley-Ames Catalog to increase the sensitivity over that of the IRAS Point Source Catalog. More than half of 7 8 the galaxies (with Bj< \\ mag) are detected at 100 /xm with flux levels indicating, typically, 10 or 10 M0 of cold interstellar matter. The presence of cold gas in ellipticals thus appears to be the rule rather than the exception. Subject headings: galaxies: general — infrared: sources I. INTRODUCTION infrared emission from the elliptical galaxy in the line of sight. The traditional view of early-type galaxies is that they are Our criteria for a real detection are as follows: essentially free of interstellar matter. However, with advances 1. The optical position of the galaxy and the position of the in instrumental sensitivity, it has become possible to observe IRAS source agree to better than V. (The agreement is usually 21 cm emission (Knapp, Turner, and Cunniffe 1985; Wardle much better than T.) and Knapp 1986), optical dust patches (Sadler and Gerhard 2. The flux is at least 3 times the r.m.s. noise. -
New Herbig±Haro Objects and Giant Outflows in Orion
Mon. Not. R. Astron. Soc. 310, 331±354 (1999) New Herbig±Haro objects and giant outflows in Orion S. L. Mader,1 W. J. Zealey,1 Q. A. Parker2 and M. R. W. Masheder3,4 1Department of Engineering Physics, University of Wollongong, Northfields Avenue, Wollongong, NSW 2522, Australia 2Anglo-Australian Observatory, Coonabarabran, NSW 2357, Australia 3Department of Physics, University of Bristol, Bristol BS8 1TL 4Netherlands Foundation for Research in Astronomy, PO Box 2, 7990 AA Dwingeloo, the Netherlands Accepted 1999 June 29. Received 1999 May 11; in original form 1998 June 25 ABSTRACT We present the results of a photographic and CCD imaging survey for Herbig±Haro (HH) objects in the L1630 and L1641 giant molecular clouds in Orion. The new HH flows were initially identified from a deep Ha film from the recently commissioned AAO/UKST Ha Survey of the southern sky. Our scanned Ha and broad-band R images highlight both the improved resolution of the Ha survey and the excellent contrast of the Ha flux with respect to the broad-band R. Comparative IVN survey images allow us to distinguish between emission and reflection nebulosity. Our CCD Ha,[Sii], continuum and I-band images confirm the presence of a parsec-scale HH flow associated with the Ori I-2 cometary globule, and several parsec-scale strings of HH emission centred on the L1641-N infrared cluster. Several smaller outflows display one-sided jets. Our results indicate that, for declinations south of 268 in L1641, parsec-scale flows appear to be the major force in the large-scale movement of optical dust and molecular gas. -
Planetary Nebulae
Planetary Nebulae A planetary nebula is a kind of emission nebula consisting of an expanding, glowing shell of ionized gas ejected from old red giant stars late in their lives. The term "planetary nebula" is a misnomer that originated in the 1780s with astronomer William Herschel because when viewed through his telescope, these objects appeared to him to resemble the rounded shapes of planets. Herschel's name for these objects was popularly adopted and has not been changed. They are a relatively short-lived phenomenon, lasting a few tens of thousands of years, compared to a typical stellar lifetime of several billion years. The mechanism for formation of most planetary nebulae is thought to be the following: at the end of the star's life, during the red giant phase, the outer layers of the star are expelled by strong stellar winds. Eventually, after most of the red giant's atmosphere is dissipated, the exposed hot, luminous core emits ultraviolet radiation to ionize the ejected outer layers of the star. Absorbed ultraviolet light energizes the shell of nebulous gas around the central star, appearing as a bright colored planetary nebula at several discrete visible wavelengths. Planetary nebulae may play a crucial role in the chemical evolution of the Milky Way, returning material to the interstellar medium from stars where elements, the products of nucleosynthesis (such as carbon, nitrogen, oxygen and neon), have been created. Planetary nebulae are also observed in more distant galaxies, yielding useful information about their chemical abundances. In recent years, Hubble Space Telescope images have revealed many planetary nebulae to have extremely complex and varied morphologies. -
Long-Period Variables in NGC 147 and NGC 185⋆
A&A 532, A78 (2011) Astronomy DOI: 10.1051/0004-6361/201116951 & c ESO 2011 Astrophysics Long-period variables in NGC 147 and NGC 185 D. Lorenz1, T. Lebzelter1,W.Nowotny1, J. Telting2, F. Kerschbaum1,H.Olofsson3,4, and H. E. Schwarz 1 University of Vienna, Department of Astronomy, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: [email protected] 2 Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de La Palma, Spain 3 Department of Astronomy, Stockholm University, AlbaNova University Center, 10691 Stockholm, Sweden 4 Onsala Space Observatory, 43992 Onsala, Sweden Received 24 March 2011 / Accepted 25 May 2011 ABSTRACT Context. Previous studies on the stellar content of the two nearby dwarf galaxies NGC 147 and NGC 185 reveal a rich population of late-type giants in both systems, including a large number of carbon-rich objects. These stars are known to show pronounced photo- metric variability, which can be used for a more detailed characterisation of these highly evolved stars. Owing to their well-studied parameters, these Local Group members are ideal candidates for comparative studies. Aims. Through photometric monitoring, we attempt to provide a catalogue of long-period variables (LPVs), including Mira variables, semi-regular variables, and even irregular variables in NGC 147 and NGC 185. We investigate the light variations and compare the characteristics of these two LPV populations with the results found for other galaxies, such as the LMC. Methods. We carried out time-series photometry in the i-band of the two target galaxies with the Nordic Optical Telescope (NOT), covering a time span of ≈2.5 years. -
Chapter 16 the Sun and Stars
Chapter 16 The Sun and Stars Stargazing is an awe-inspiring way to enjoy the night sky, but humans can learn only so much about stars from our position on Earth. The Hubble Space Telescope is a school-bus-size telescope that orbits Earth every 97 minutes at an altitude of 353 miles and a speed of about 17,500 miles per hour. The Hubble Space Telescope (HST) transmits images and data from space to computers on Earth. In fact, HST sends enough data back to Earth each week to fill 3,600 feet of books on a shelf. Scientists store the data on special disks. In January 2006, HST captured images of the Orion Nebula, a huge area where stars are being formed. HST’s detailed images revealed over 3,000 stars that were never seen before. Information from the Hubble will help scientists understand more about how stars form. In this chapter, you will learn all about the star of our solar system, the sun, and about the characteristics of other stars. 1. Why do stars shine? 2. What kinds of stars are there? 3. How are stars formed, and do any other stars have planets? 16.1 The Sun and the Stars What are stars? Where did they come from? How long do they last? During most of the star - an enormous hot ball of gas day, we see only one star, the sun, which is 150 million kilometers away. On a clear held together by gravity which night, about 6,000 stars can be seen without a telescope. -
NIR High-Resolution Imaging and Radiative Transfer Modeling of the Frosty Leo Nebula
Planetary Nebulae in our Galaxy and Beyond Proceedings IAU Symposium No. 234, 2006 c 2006 International Astronomical Union M. J. Barlow & R. H. M´endez, eds. doi:10.1017/S1743921306003802 NIR high-resolution imaging and radiative transfer modeling of the Frosty Leo nebula K. Murakawa1, K. Ohnaka1, T. Driebe1, K.-H. Hofmann1, D. Schertl1,S.Oya2, and G. Weigelt1 1Max-Planck-Institut f¨ur Radioastronomie, Auf dem H¨ugel 69, D-53121 Bonn, Germany email: [email protected] 2Subaru telescope, 650 North A’ohoku Place, Hilo, HI 96720, USA Abstract. We present a K-band speckle image and HK-band polarimetric images of the proto- planetary nebula Frosty Leo obtained using the 6 m SAO telescope and the 8 m Subaru telescope, respectively. Our speckle image revealed clumpy structures in the hourglass-like bipolar nebula. The polarimetric data, for the first time, detected an elongated region with small polarizations and polarization vector alignment on the east side of the central star. We have performed radiative transfer calculations to model the dust shell of Frosty Leo. We found that micron-size grains in the equatorial dense region and small grains in the bipolar lobes are required to explain the total intensity images, the polarization images, and the spectral energy distribution. Keywords. speckle imaging, polarimetry, radiative transfer modeling, Frosty Leo, PPN 1. Introduction Frosty Leo is a well-studied oxygen-rich proto-planetary nebula (PPN). The deep wa- ter ice absorption feature at 3.1 µm(τ3.1µm∼3.3) was detected in the L-band spectrum (Rouan et al. -
The Evolutionary Status of the Frosty Leo Nebula
Asymmetrical Planetary Nebulae II: From Origins to Microstructures ASP Conference Series, Vol. 199, 2000 J.H. Kastner, N. Soker, & S. Rappaport, eds. The evolutionary status of The Frosty Leo Nebula Tyler Bourke1, A. R. Hyland2, Garry Robinson3, & Kevin Luhman1 1Harvard-Smithsonian Center for Astrophysics, Cambridge MA, USA 2Southern Cross University, Lismore NSW, Australia 3University College, UNSW-ADFA, Canberra ACT, Australia Abstract. We present new observational data for IRAS 09371+1212, the Frosty Leo Nebula, in the form of infrared spectra from 2.2–2.5µm which reveal photospheric bands of CO. The 12CO/13CO band ratio deter- mined is similar to those exhibited by evolved K giant stars, and supports the proposal that the object is highly evolved. The equivalent width of the CO bands implies, however, that the spectral type lies in the range G5III to K0III, somewhat earlier than K7III, as derived from colours and optical spectra. The smaller equivalent widths of the CO bands may re- flect a low metal abundance which could fit well with the considerable height of the source above the galactic plane (>0.9kpc). 1. Introduction The Frosty Leo Nebula, IRAS 09371+1212, remains unique with its extremely deep 3.1µm absorption feature, almost two decades in depth, its twin far-infrared emission features at 44 and 62µm, and its abnormal location, >0.9kpc from the plane of the Galaxy. Forveille et al. (1987; hereafter FMOL) concluded, primarily on the basis of its 2.6mm CO emission spectrum, that it is a post-AGB star with a bipolar circumstellar envelope, and suggested water ice mantles around the grains as the source of the excess emission in the 60µm IRAS band. -
Nightwatch Club Events Calendar President's Message
Henry Wadsworth Longfellow Henry Wadsworth Thewithfilled skyby day. is stars, invisible Volume 32 Number 06 nightwatch June 2012 President's Message Club Events Calendar Busy days right now, both in the heavens and here on Earth. June 8 - General Meeting – Speaker Robert Stephens - I've heard lots of good reports of people successfully viewing the “A Journey Through the Asteroid Belt” eclipse on May 20. My own eclipse trip to Page, Arizona, was a June 16 - Star Party - White Mountain smashing success. The lunar eclipse early in the morning on June 22 - Star Party - Cottonwood Springs - joint with June 4 was clouded out, at least here in Claremont. By the time Palm Springs Braille Institute you read this, the transit of Venus across the face of the sun on June 5 will already have happened. I hope you got a chance to July 2 - School Star Party - Colony High School, Ontario see it—it won't happen again until 2117. July 5 - Board Meeting, 6:15 We also have some great club events coming up. Our speaker July 13 - General Meeting for the June 8 general meeting is Robert Stephens July 21 – Star Party – Cottonwood Springs (http://planetarysciences.org/stephens.html), who will give us “A July 24 - Ontario Library Main Branch - Dark to 9pm Journey Through the Asteroid Belt”. On June 16 we'll have a star July 25 – Star Party – Orange County Braille Institute, party at White Mountain. My annual curse has struck again—I'll Anaheim be in New York looking at fossils instead of on White Mountain looking at stars, but I hope you all have fun without me. -
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). -
Eagle Nebula Star Formation Region
Eagle Nebula Star Formation Region AST 303: Chapter 17 1 The Formation of Stars (2) • A cloud of gas and dust must collapse if stars are to be formed. • The self-gravity of the cloud will tend to cause it to collapse. • Radiation pressure from nearby hot stars may do the same. • The passage of a shock wave from a nearby supernova blast or some other source (such as galactic shock waves) may do the same. – Note: The “sonic boom” of a jet plane is an example of a shock wave. • When two clouds collide, they may cause each other to collapse. AST 303: Chapter 17 2 Trifid Nebula AST 303: Chapter 17 3 Trifid Nebula Stellar Nursery Revealed AST 303: Chapter 17 4 Young Starburst Cluster Emerges from Cloud AST 303: Chapter 17 5 The Formation of Stars (3) • The gas in the collapsing cloud probably becomes turbulent. • This would tend to fragment the collapsing gas, producing condensations that would be the nuclei of new stars. • There is abundant evidence that shows that the stars in a cluster are all about the same age. For a young cluster, many stars have not yet reached the main sequence: ! Isochron Luminosity "Temperature AST 303: Chapter 17 6 The Formation of Stars (4) • The evolutionary paths of young stars on the H-R diagram look like this. Note the T Tauri stars, long thought to be young stars. • Theory says that these stars use convection as the main method of transporting energy to their surfaces. ! T Tauri Stars Luminosity "Temperature AST 303: Chapter 17 7 The Search for Stellar Precursors • Astronomers have long been fascinated by very dark, dense regions seen outlined against bright gas, called globules.