Astrophysics in a Nutshell, Second Edition
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Stellar Populations in a Standard ISOGAL Field in the Galactic Disc
A&A 493, 785–807 (2009) Astronomy DOI: 10.1051/0004-6361:200809668 & c ESO 2009 Astrophysics Stellar populations in a standard ISOGAL field in the Galactic disc, S. Ganesh1,2,A.Omont1,U.C.Joshi2,K.S.Baliyan2, M. Schultheis3,1,F.Schuller4,1,andG.Simon5 1 Institut d’Astrophysique de Paris, CNRS and Université Paris 6, 98bis boulevard Arago, 75014 Paris, France e-mail: [email protected] 2 Physical Research Laboratory, Navrangpura, Ahmedabad-380 009, India e-mail: [email protected] 3 Observatoire de Besançon, Besançon, France 4 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany 5 GEPI, UMS-CNRS 2201, Observatoire de Paris, France Received 28 February 2008 / Accepted 3 September 2008 ABSTRACT Aims. We identify the stellar populations (mostly red giants and young stars) detected in the ISOGAL survey at 7 and 15 μmtowards a field (LN45) in the direction = −45, b = 0.0. Methods. The sources detected in the survey of the Galactic plane by the Infrared Space Observatory were characterised based on colour−colour and colour−magnitude diagrams. We combine the ISOGAL catalogue with the data from surveys such as 2MASS and GLIMPSE. Interstellar extinction and distance were estimated using the red clump stars detected by 2MASS in combination with the isochrones for the AGB/RGB branch. Absolute magnitudes were thus derived and the stellar populations identified from their absolute magnitudes and their infrared excess. Results. A standard approach to analysing the ISOGAL disc observations has been established. We identify several hundred RGB/AGB stars and 22 candidate young stellar objects in the direction of this field in an area of 0.16 deg2. -
Chandra Detection of a Pulsar Wind Nebula Associated with Supernova Remnant 3C 396
Chandra Detection of a Pulsar Wind Nebula Associated With Supernova Remnant 3C 396 C.M. Olbert',2, J.W. Keohane'l2v3, K.A. Arnaud4, K.K. Dyer5, S.P. Reynolds', S. Safi-Harb7 ABSTRACT 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 Verp Large Array'. In the Chandra images, a non- thermal 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 (NH = 5.3 f 0.9 x cm-2, r=1.5&0.3) we derive an unabsorbed X-ray flux of SZ=1.62x lo-'* ergcmV2s-l, and from this we estimate the spin-down power of the neutron star to be fi = 7.2 x ergs-'. The central nebula is morphologi- cally 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. Subject headings: ISM: individual (3C396 / G39.2-0.3) - stars: neutron - pulsars: general - supernova remnants lNorth Carolina School of Science and Mathematics, 1219 Broad St., Durham, NC 27705 2Department of Physics and Astronomy, University of North Carolina, Chapel Hill, NC 27599 3Current Address: SIRTF Science Center, California Institute of Technology, MS 220-6, 1200 East Cali- fornia Boulevard, Pasedena, CA 91125 *Goddard Space Flight Center, Code 662, Greenbelt, MD 20771 5National Radio Astronomy Observatory, P.O. -
Exploring CTA Science with Ted and Friends - Activities
Exploring CTA Science with Ted and Friends - Activities This handbook proposes questions and exercises for educators related to the animated series “Exploring CTA Science with Ted and Friends.” The goal is to reinforce the concepts the students learn in each episode about high-energy astrophysics and the future gamma-ray observatory, the Cherenkov Telescope Array (CTA), as well as to develop their scientific thinking and logic. The questions are divided according to each episode - we recommend educators to perform these activities following each episode in order to consolidate new ideas before staring the next episode. Age range: 5-11 years Supplementary material: https://www.cta-observatory.org/outreach-education/ Questions? Contact CTAO Outreach and Education Coordinator, Alba Fernández-Barral ([email protected]) Exploring CTA Science with Ted and Friends EPISODE 1: “CTA: Searching the Skies” How many CTA telescopes will be located around the world? More than 100 (Note for educators: specifically, 118 – 19 in La Palma, Spain, and 99 near Paranal, Chile). Where are they going to be located? One group will be in Chile (South America) while the other will be in La Palma (a Spanish island in the Canary Islands, off the coast of west Africa). What do CTA telescopes search for? They search the sky for gamma rays. What are gamma rays? Gamma rays are like X-rays, which are used to see human bones in the hospitals, but much more energetic (Note for educators: gamma rays are the most energetic light -electromagnetic radiation- that exists in the Universe. Light can be classified according to its energy, which is known as the electromagnetic spectrum. -
Squashing and Spaghettification in Newtonian Gravitation
Revista Brasileira de Ensino de F´ısica, vol. 42, e20200278 (2020) Artigos Gerais www.scielo.br/rbef c b DOI: https://doi.org/10.1590/1806-9126-RBEF-2020-0278 Licenc¸aCreative Commons Squashing and spaghettification in Newtonian gravitation R. R. Machado*1 , A. C. Tort2 , C. A. D. Zarro2 1Centro Federal de Educa¸c˜aoTecnol´ogicaCelso Suckow da Fonseca, Rio de Janeiro, RJ, Brasil 2Universidade Federal do Rio de Janeiro, Instituto de F´ısica,Rio de Janeiro, RJ, Brasil Received on July 06, 2020. Revised on September 07, 2020. Accepted on October 08, 2020. Action films and sci-fi novels should be common resources in classrooms since they serve as examples and references involving physical situations. This is due to the abstract nature of many physical concepts, and the lack of references in students’ daily lives makes them more difficult to be visualized or imagined. In this work we bring a discussion of how we can resort to films and literary works in order to elucidate the concepts regarding tidal forces. To this effect, we have used the action film Total Recall (2012) to present the squashing effect and the classic of juvenile literature From Earth to the Moon (1865) to discuss the effect of spaghettification in the context of Newtonian mechanics. Keywords: Newtonian gravitation, non-inertial frames, tidal forces. 1. Introduction Earth to the Moon [3], see Figure 2. On Verne’s chap- ter XXIII, he describes the Projectile-Vehicle, to which Action movies and sci-fi novels can always be resorted to we will refer as Verne’s projectile, designed to trans- whenever we look for situations, or examples, capable of port adventurous people through space; more precisely motivating our students. -
BLACK HOLES: the OTHER SIDE of INFINITY General Information
BLACK HOLES: THE OTHER SIDE OF INFINITY General Information Deep in the middle of our Milky Way galaxy lies an object made famous by science fiction—a supermassive black hole. Scientists have long speculated about the existence of black holes. German astronomer Karl Schwarzschild theorized that black holes form when massive stars collapse. The resulting gravity from this collapse would be so strong that the matter would become more and more dense. The gravity would eventually become so strong that nothing, not even radiation moving at the speed of light, could escape. Schwarzschild’s theories were predicted by Einstein and then borne out mathematically in 1939 by American astrophysicists Robert Oppenheimer and Hartland Snyder. WHAT EXACTLY IS A BLACK HOLE? First, it’s not really a hole! A black hole is an extremely massive concentration of matter, created when the largest stars collapse at the end of their lives. Astronomers theorize that a point with infinite density—called a singularity—lies at the center of black holes. SO WHY IS IT CALLED A HOLE? Albert Einstein’s 1915 General Theory of Relativity deals largely with the effects of gravity, and in essence predicts the existence of black holes and singularities. Einstein hypothesized that gravity is a direct result of mass distorting space. He argued that space behaves like an invisible fabric with an elastic quality. Celestial bodies interact with this “fabric” of space-time, appearing to create depressions termed “gravity wells” and drawing nearby objects into orbit around them. Based on this principle, the more massive a body is in space, the deeper the gravity well it will create. -
A Secondary Clump of Red Giant Stars: Why and Where
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by CERN Document Server A secondary clump of red giant stars: why and where L´eo Girardi Max-Planck-Institut f¨ur Astrophysik, Karl-Schwarzschild-Str. 1, D-85740 Garching bei M¨unchen, Germany E-mail: [email protected] submitted to Monthly Notices of the Royal Astronomical Society Abstract. Based on the results of detailed population synthesis models, Girardi et al. (1998) recently claimed that the clump of red giants in the colour–magnitude diagram (CMD) of composite stellar populations should present an extension to lower luminosities, which goes down to about 0.4 mag below the main clump. This feature is made of stars just massive enough for having ignited helium in non- degenerate conditions, and therefore corresponds to a limited interval of stellar masses and ages. In the present models, which include moderate convective over- shooting, it corresponds to 1 Gyr old populations. In this paper, we go into∼ more details about the origin and properties of this feature. We first compare the clump theoretical models with data for clusters of different ages and metallicities, basically confirming the predicted behaviours. We then refine the previous models in order to show that: (i) The faint extension is expected to be clearly separated from the main clump in the CMD of metal-rich populations, defining a ‘secondary clump’ by itself. (ii) It should be present in all galactic fields containing 1 Gyr old stars and with mean metallicities higher than about Z =0:004. -
Nuclear Astrophysics: the Unfinished Quest for the Origin of the Elements
Nuclear astrophysics: the unfinished quest for the origin of the elements Jordi Jos´e Departament de F´ısica i Enginyeria Nuclear, EUETIB, Universitat Polit`ecnica de Catalunya, E-08036 Barcelona, Spain; Institut d’Estudis Espacials de Catalunya, E-08034 Barcelona, Spain E-mail: [email protected] Christian Iliadis Department of Physics & Astronomy, University of North Carolina, Chapel Hill, North Carolina, 27599, USA; Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA E-mail: [email protected] Abstract. Half a century has passed since the foundation of nuclear astrophysics. Since then, this discipline has reached its maturity. Today, nuclear astrophysics constitutes a multidisciplinary crucible of knowledge that combines the achievements in theoretical astrophysics, observational astronomy, cosmochemistry and nuclear physics. New tools and developments have revolutionized our understanding of the origin of the elements: supercomputers have provided astrophysicists with the required computational capabilities to study the evolution of stars in a multidimensional framework; the emergence of high-energy astrophysics with space-borne observatories has opened new windows to observe the Universe, from a novel panchromatic perspective; cosmochemists have isolated tiny pieces of stardust embedded in primitive meteorites, giving clues on the processes operating in stars as well as on the way matter condenses to form solids; and nuclear physicists have measured reactions near stellar energies, through the combined efforts using stable and radioactive ion beam facilities. This review provides comprehensive insight into the nuclear history of the Universe arXiv:1107.2234v1 [astro-ph.SR] 12 Jul 2011 and related topics: starting from the Big Bang, when the ashes from the primordial explosion were transformed to hydrogen, helium, and few trace elements, to the rich variety of nucleosynthesis mechanisms and sites in the Universe. -
Arxiv:1712.02405V2 [Astro-Ph.SR] 11 Dec 2017
Draft version October 19, 2018 Typeset using LATEX twocolumn style in AASTeX61 PHOTOSPHERIC DIAGNOSTICS OF CORE HELIUM BURNING IN GIANT STARS Keith Hawkins,1 Yuan-Sen Ting,2, 3, 4, 5 and Hans-Walter Rix6 1Department of Astronomy, Columbia University, 550 W 120th St, New York, NY 10027, USA 2Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, The Australian National University, ACT 2611, Australia 3Institute for Advanced Study, Princeton, NJ 08540, USA 4Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544, USA 5Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101, USA 6Max-Planck-Institut f¨urAstronomie, K¨onigstuhl17, D-69117 Heidelberg, Germany ABSTRACT Core helium burning primary red clump (RC) stars are evolved red giant stars which are excellent standard candles. As such, these stars are routinely used to map the Milky Way or determine the distance to other galaxies among other things. However distinguishing RC stars from their less evolved precursors, namely red giant branch (RGB) stars, is still a difficult challenge and has been deemed the domain of asteroseismology. In this letter, we use a sample of 1,676 RGB and RC stars which have both single epoch infrared spectra from the APOGEE survey and asteroseismic parameters and classification to show that the spectra alone can be used to (1) predict asteroseismic parameters with precision high enough to (2) distinguish core helium burning RC from other giant stars with less than 2% contamination. This will not only allow for a clean selection of a large number of standard candles across our own and other galaxies from spectroscopic surveys, but also will remove one of the primary roadblocks for stellar evolution studies of mixing and mass loss in red giant stars. -
Spacetime Warps and the Quantum World: Speculations About the Future∗
Spacetime Warps and the Quantum World: Speculations about the Future∗ Kip S. Thorne I’ve just been through an overwhelming birthday celebration. There are two dangers in such celebrations, my friend Jim Hartle tells me. The first is that your friends will embarrass you by exaggerating your achieve- ments. The second is that they won’t exaggerate. Fortunately, my friends exaggerated. To the extent that there are kernels of truth in their exaggerations, many of those kernels were planted by John Wheeler. John was my mentor in writing, mentoring, and research. He began as my Ph.D. thesis advisor at Princeton University nearly forty years ago and then became a close friend, a collaborator in writing two books, and a lifelong inspiration. My sixtieth birthday celebration reminds me so much of our celebration of Johnnie’s sixtieth, thirty years ago. As I look back on my four decades of life in physics, I’m struck by the enormous changes in our under- standing of the Universe. What further discoveries will the next four decades bring? Today I will speculate on some of the big discoveries in those fields of physics in which I’ve been working. My predictions may look silly in hindsight, 40 years hence. But I’ve never minded looking silly, and predictions can stimulate research. Imagine hordes of youths setting out to prove me wrong! I’ll begin by reminding you about the foundations for the fields in which I have been working. I work, in part, on the theory of general relativity. Relativity was the first twentieth-century revolution in our understanding of the laws that govern the universe, the laws of physics. -
Stellar Evolution
Stellar Astrophysics: Stellar Evolution 1 Stellar Evolution Update date: December 14, 2010 With the understanding of the basic physical processes in stars, we now proceed to study their evolution. In particular, we will focus on discussing how such processes are related to key characteristics seen in the HRD. 1 Star Formation From the virial theorem, 2E = −Ω, we have Z M 3kT M GMr = dMr (1) µmA 0 r for the hydrostatic equilibrium of a gas sphere with a total mass M. Assuming that the density is constant, the right side of the equation is 3=5(GM 2=R). If the left side is smaller than the right side, the cloud would collapse. For the given chemical composition, ρ and T , this criterion gives the minimum mass (called Jeans mass) of the cloud to undergo a gravitational collapse: 3 1=2 5kT 3=2 M > MJ ≡ : (2) 4πρ GµmA 5 For typical temperatures and densities of large molecular clouds, MJ ∼ 10 M with −1=2 a collapse time scale of tff ≈ (Gρ) . Such mass clouds may be formed in spiral density waves and other density perturbations (e.g., caused by the expansion of a supernova remnant or superbubble). What exactly happens during the collapse depends very much on the temperature evolution of the cloud. Initially, the cooling processes (due to molecular and dust radiation) are very efficient. If the cooling time scale tcool is much shorter than tff , −1=2 the collapse is approximately isothermal. As MJ / ρ decreases, inhomogeneities with mass larger than the actual MJ will collapse by themselves with their local tff , different from the initial tff of the whole cloud. -
(NASA/Chandra X-Ray Image) Type Ia Supernova Remnant – Thermonuclear Explosion of a White Dwarf
Stellar Evolution Card Set Description and Links 1. Tycho’s SNR (NASA/Chandra X-ray image) Type Ia supernova remnant – thermonuclear explosion of a white dwarf http://chandra.harvard.edu/photo/2011/tycho2/ 2. Protostar formation (NASA/JPL/Caltech/Spitzer/R. Hurt illustration) A young star/protostar forming within a cloud of gas and dust http://www.spitzer.caltech.edu/images/1852-ssc2007-14d-Planet-Forming-Disk- Around-a-Baby-Star 3. The Crab Nebula (NASA/Chandra X-ray/Hubble optical/Spitzer IR composite image) A type II supernova remnant with a millisecond pulsar stellar core http://chandra.harvard.edu/photo/2009/crab/ 4. Cygnus X-1 (NASA/Chandra/M Weiss illustration) A stellar mass black hole in an X-ray binary system with a main sequence companion star http://chandra.harvard.edu/photo/2011/cygx1/ 5. White dwarf with red giant companion star (ESO/M. Kornmesser illustration/video) A white dwarf accreting material from a red giant companion could result in a Type Ia supernova http://www.eso.org/public/videos/eso0943b/ 6. Eight Burst Nebula (NASA/Hubble optical image) A planetary nebula with a white dwarf and companion star binary system in its center http://apod.nasa.gov/apod/ap150607.html 7. The Carina Nebula star-formation complex (NASA/Hubble optical image) A massive and active star formation region with newly forming protostars and stars http://www.spacetelescope.org/images/heic0707b/ 8. NGC 6826 (Chandra X-ray/Hubble optical composite image) A planetary nebula with a white dwarf stellar core in its center http://chandra.harvard.edu/photo/2012/pne/ 9. -
Arxiv:1803.04461V1 [Astro-Ph.SR] 12 Mar 2018 (Received; Revised March 14, 2018) Submitted to Apj
Draft version March 14, 2018 Typeset using LATEX preprint style in AASTeX61 CHEMICAL ABUNDANCES OF MAIN-SEQUENCE, TURN-OFF, SUBGIANT AND RED GIANT STARS FROM APOGEE SPECTRA I: SIGNATURES OF DIFFUSION IN THE OPEN CLUSTER M67 Diogo Souto,1 Katia Cunha,2, 1 Verne V. Smith,3 C. Allende Prieto,4, 5 D. A. Garc´ıa-Hernandez,´ 4, 5 Marc Pinsonneault,6 Parker Holzer,7 Peter Frinchaboy,8 Jon Holtzman,9 J. A. Johnson,6 Henrik Jonsson¨ ,10 Steven R. Majewski,11 Matthew Shetrone,12 Jennifer Sobeck,11 Guy Stringfellow,13 Johanna Teske,14 Olga Zamora,4, 5 Gail Zasowski,7 Ricardo Carrera,15 Keivan Stassun,16 J. G. Fernandez-Trincado,17, 18 Sandro Villanova,17 Dante Minniti,19 and Felipe Santana20 1Observat´orioNacional, Rua General Jos´eCristino, 77, 20921-400 S~aoCrist´ov~ao,Rio de Janeiro, RJ, Brazil 2Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721-0065, USA 3National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA 4Instituto de Astrof´ısica de Canarias, E-38205 La Laguna, Tenerife, Spain 5Departamento de Astrof´ısica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain 6Department of Astronomy, The Ohio State University, Columbus, OH 43210, USA 7Department of Physics and Astronomy, The University of Utah, Salt Lake City, UT 84112, USA 8Department of Physics & Astronomy, Texas Christian University, Fort Worth, TX, 76129, USA 9New Mexico State University, Las Cruces, NM 88003, USA 10Lund Observatory, Department of Astronomy and Theoretical Physics, Lund University, Box 43,