DOCSLIB.ORG

Module 14 H. R. Diagram TABLE of CONTENTS 1. Learning Outcomes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Module 14 H. R. Diagram TABLE of CONTENTS 1. Learning Outcomes Module 14 H. R. Diagram TABLE OF CONTENTS 1. Learning Outcomes 2. Introduction 3. H. R. Diagram 3.1. Coordinates of H. R. Diagram 3.2. Stellar Families 3.3. Hertzsprung Gap 3.4. H. R. Diagram and Stellar Radii 4. Summary 1. Learning Outcomes After studying this module, you should be able to recognize an H. R. Diagram explain the coordinates of an H. R. Diagram appreciate the shape of an H. R. Diagram understand that in this diagram stars appear in distinct families recount the characteristics of these families recognize that there is a real gap in the horizontal branch of the diagram, called the Hertzsprung gap explain that during their evolution stars pass very rapidly through this region and therefore there is a real paucity of stars here derive the shape of the 퐥퐨퐠 푻 − 퐥퐨퐠 푳 plot at a given stellar radius explain that the stellar radius (and mass) increases upwards in the H. R. Diagram 2. Introduction In the last few modules we have discussed the stellar spectra and spectral classification based on stellar spectra. The Harvard system of spectral classification categorized stellar spectra in 7 major classes, from simple spectra containing only a few lines to spectra containing a huge number of lines and molecular bands. The major classes were named O, B, A, F, G, K and M. Each major class was further subdivided into 10 subclasses, running from 0 to 9. Considering the bewildering variety of stellar spectra, classes Q, P and Wolf-Rayet had to be introduced at the top of the classification and classes R and N were introduced at the bottom of the classification scheme. Some prefixes and suffixes were also suggested to be used with the spectral classes to take account of special features of their spectra. Earlier it was thought that the difference in spectra was due to the evolving chemical composition of the stars. However, in 1920 Saha showed that the progression of spectra from class O to M could be explained in terms of the decreasing surface temperature of stars. Saha likened the process of ionization of atoms to a chemical process, and derived what we now call Saha’s ionization formula. This formula gives the fraction of ionized atoms as a function of temperature and pressure in the stellar surface layers. Taking the examples of atoms of hydrogen, helium and calcium, we showed in the last module how the intensities of lines of these atoms vary with temperature, in agreement with the spectral classification. In this module we discuss a type of plot which has become an important diagnostic tool for the astronomers. 3. H. R. Diagram We have already seen that astronomers are always on the lookout for relations which help them to study the objects of their interest. One such relation is the one between some measure of the luminosity of a star and some measure of its surface temperature. The relation, found independently by Hertzsprung and Russell, is named after these astronomers and goes by the name of Hertzsprung – Russell (H. R.) diagram. It is one of the most useful tools for the study of stars and their physical properties. 3.1. Coordinates of an H. R. Diagram Besides luminosity itself, absolute magnitude is measure of luminosity. The measures of surface temperature are spectral class and colour index. Therefore, the coordinates of an H.R. diagram are those shown in Fig. 14.1. Note that the surface temperature increases towards the left while the colour index (퐵 – 푉) increases towards the right. Similarly, the absolute magnitude, being anti-correlated with luminosity, increases downwards. Surface Temperature Absolute Magnitude Absolute y Luminosit O B A F G K M (퐵 − 푉) Fig. 14.1. The coordinates of an H. R. Diagram. Notice that temperature decreases towards right and absolute magnitude decreases towards the top. Fig. 14.2 shows a schematic H. R. diagram. On the 푦-axis are the absolute magnitudes and luminosities; on the 푥-axis are the temperature and spectral class. Separation of stars in neat groups is immediately noticed. Fig. 14.3 shows the Hertzsprung–Russell diagram with 22,000 stars from the Hipparcos Catalogue and 1,000 from the Gliese Catalogue of nearby stars. Fig. 14.2. Schematic H. R. Diagram. Notice that the temperature and luminosity scales are not linear. The density on the Main Sequence is indicative of the actual stellar numbers of stars on it. (Source: http://chandra.harvard.edu/edu/formal/variable_stars/HR_student.html) 3.2. Stellar Families In the H. R. diagrams, the group of stars running from the top left to the bottom right is the most populous group. This group is called the Main Sequence. On the Main Sequence the luminosity steadily decreases as we go from the early to the late spectral classes. The lower region of the Main Sequence is more crowded than the upper region. The stars at the lower end are red in colour (because of the low surface temperature) and are very small in size. These stars are therefore called Red Dwarf stars. These are the most abundant stars in the Galaxy. Another group of stars is situated below the Main Sequence, occupying the left bottom corner. The stars in this group have luminosities like those of the Red Dwarfs, but their surface temperatures are much higher. These stars are known as White Dwarf stars. In abundance, they are next only to the red dwarfs. That their name is descriptive of their size is clear from the fact that the white dwarfs are about 10 magnitudes fainter than the Main Sequence stars of the same surface temperature, and so must have very small surface area (and radius). Fig. 14.3. H–R diagram with 22,000 stars plotted from the Hipparcos Catalogue and 1,000 from the Gliese Catalogue of nearby stars. Notice the use of colour index (퐵 − 푉), surface temperature and the spectral class along the 푥- axis. (Source: https://en.wikipedia.org/wiki/Hertzsprung%E2%80%93Russell_diagram. Diagram made by Richard Powell.) Next in abundance are the stars called Giant Stars, lying above the Main Sequence. These stars are much brighter than their surface temperatures would suggest, indicating that they are large in size. The giant branch is almost horizontal, the luminosity of giants changing little with their surface temperature. These stars belong mostly to spectral classes F, G, K and M. Brighter than the giant stars by about 5 magnitudes (a factor of hundred in luminosity) are the Supergiant Stars having radii of about 100 푅⨀. In this group, too, luminosity does not change much with spectral class. These stars are the least abundant stars. Between giants and the Main Sequence is a group of stars called the Subgiant stars. These belong mostly to the latter spectral classes. Finally, between the Main Sequence and the White Dwarf stars are the Subdwarf stars. If we plot apparent magnitude instead of the absolute magnitude, no such correlation with the surface temperature is found (Fig. 14.4). There is no separation into families either. Fig. 14.4. Lack of correlation between the apparent magnitude and the spectral class. (Source: http://spiff.rit.edu/classes/phys230/lectures/hr/hr.html) 3.3. Hertzsprung Gap 4. Following comments are called for about the H. R. diagram: Fig. 14.5. An HR diagram with the instability strip and its components highlighted. (Source: Wikipedia) 1. The stars are found all over the diagram; the groups simply define the locations where the stars tend to congregate. 2. There is a real paucity of supergiant stars of spectral classes A, F and G. This defines a real gap in the supergiant branch, called the Hertzsprung gap (Fig. 14.5). The reason for the presence of this gap is that during their evolution stars stay at this location for a very, very short time. 3. The H. R. diagrams shown above feature the stars found in the spiral arms of our galaxy and other galaxies. These stars are the so-called Population I stars. These are young stars. The stars found in the globular clusters and in the central bulge of the Galaxy and other galaxies are generally old stars (Fig. 14.6). These are known as Population II stars. The H. R. diagram of the Population II stars is quite different from that of the Population I stars (Fig. 14.7). Fig. 14.6. The Messier 80 globular cluster contains hundreds of thousands of stars (Source: NASA/ESA). The density of stars in a globular cluster is so large that the cluster appears almost spherical. All these stars are old Population II stars. Since the stars in globular clusters can be assumed to be of the same age (born at the same time), though different in masses, H.R. diagrams of these clusters throw a lot of light on stellar evolution. Typical H. R. Diagram of a Globular Cluster Horizontal Branch ) 4 Hertzsprung Gap 10 ⨀ 퐿 1 Luminosity ( Luminosity Main −4 Sequence 10 40000 20000 10000 5000 2500 Temperature (K) Fig. 14.7. A typical globular cluster H. R. Diagram. H. R. diagram of globular cluster M3 is shown in Fig. 14.8. 3.4. Importance of H. R. Diagram The importance of H. R. diagram to astronomers can hardly be overstated. It is an important tool for them since all physical properties of a star can be read from its location on the H. R. diagram. The diagram has been called the horoscope of stars, because astrologers claim that they can read the events of the entire life of a person from birth to death from her horoscope.
Load more

Recommended publications
  • Hertzsprung-Russell Diagram and Mass Distribution of Barium Stars ? A
    Astronomy & Astrophysics manuscript no. HRD_Ba c ESO 2019 May 14, 2019 Hertzsprung-Russell diagram and mass distribution of barium stars ? A. Escorza1; 2, H.M.J. Boffin3, A.Jorissen2, S. Van Eck2, L. Siess2, H. Van Winckel1, D. Karinkuzhi2, S. Shetye2; 1, and D. Pourbaix2 1 Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium 2 Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, ULB, Campus Plaine C.P. 226, Boulevard du Triomphe, B-1050 Bruxelles, Belgium 3 ESO, Karl Schwarzschild Straße 2, D-85748 Garching bei München, Germany Received; Accepted ABSTRACT With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H] = −0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5 M with a tail at higher masses up to 4.5 M . This peak is also seen in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1 – 2 M ) barium giants.
    [Show full text]
  • Structure and Evolution of FK Comae Corona
    A&A 383, 919–932 (2002) Astronomy DOI: 10.1051/0004-6361:20011810 & c ESO 2002 Astrophysics Structure and evolution of FK Comae corona P. Gondoin, C. Erd, and D. Lumb Space Science Department, European Space Agency – Postbus 299, 2200 AG Noordwijk, The Netherlands Received 16 October 2001 / Accepted 17 December 2001 Abstract. FK Comae (HD 117555) is a rapidly rotating single G giant whose distinctive characteristics include a quasisinusoidal optical light curve and high X-ray luminosity. FK Comae was observed twice at two weeks interval in January 2001 by the XMM-Newton space observatory. Analysis results suggest a scenario where the corona of FK Comae is dominated by large magnetic structures similar in size to interconnecting loops between solar active regions but significantly hotter. The interaction of these structures themselves could explain the permanent flaring activity on large scales that is responsible for heating FK Comae plasma to high temperatures. During our observations, these flares were not randomly distributed on the star surface but were partly grouped within a large compact region of about 30 degree extent in longitude reminiscent of a large photospheric spot. We argue that the α − Ω dynamo driven activity on FK Comae will disappear in the future with the effect of suppressing large scale magnetic structures in its corona. Key words. stars: individual: FK Comae – stars: activity – stars: coronae – stars: evolution – stars: late-type – X-ray: stars 1. Introduction ments and their temporal behaviour during the observa- tions. Sections 5 and 6 describe the spectral analysis of the FK Comae (HD 117555) is the prototype of a small group EPIC and RGS datasets.
    [Show full text]
  • Post-Main Sequence Evolution – Low and Intermediate Mass Stars
    Post-Main Sequence Evolution – Low and Intermediate Mass Stars Pols 10, 11 Prialnik 9 Glatzmaier and Krumholz 16 • Once hydrogen is exhausted in the inner part of the star, it is no longer a main What happens when sequence star. It continues to burn the sun runs out of hydrogen in a thick shell around the helium hydrogen in its center? core, and actually grows more luminous. • Once the SC mass is exceeded, the contraction of the H-depleted core takes the hydrogen burning shell to H greater depth and higher temperature. He it burns very vigorously with a luminosity set more by the properties of the helium core than the unburned “envelope” of the star. The shell becomes thin in response to a reduced pressure scale height at the core’s edge because of its high gravity. L • The evolution differs for stars below about 2 solar masses and above. The helium core becomes degenerate as T ← it contracts for the lower mass stars • H shell burning is by the CNO cycle and What happens when therefore very temperature sensitive. the sun runs out of hydrogen in its center? • In stars lighter than the sun where a large fraction of the outer mass was already convective on the main sequence, the increased luminosity is transported quickly to the surface and the stars luminosity rises at nearly H constant photospheric temperature He (i.e., the star is already on the Hayashi strip) • For more massive stars, the surface remains radiative for a time and the luminosity continues to be set by the L mass of the star (i.e., is constant).
    [Show full text]
  • Hertzsprung-Russell Diagram and Mass Distribution of Barium Stars? A
    A&A 608, A100 (2017) Astronomy DOI: 10.1051/0004-6361/201731832 & c ESO 2017 Astrophysics Hertzsprung-Russell diagram and mass distribution of barium stars? A. Escorza1; 2, H. M. J. Boffin3, A. Jorissen2, S. Van Eck2, L. Siess2, H. Van Winckel1, D. Karinkuzhi2, S. Shetye2; 1, and D. Pourbaix2 1 Institute of Astronomy, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium e-mail: [email protected] 2 Institut d’Astronomie et d’Astrophysique, Université Libre de Bruxelles, ULB, Campus Plaine C.P. 226, Boulevard du Triomphe, 1050 Bruxelles, Belgium 3 ESO, Karl Schwarzschild Straße 2, 85748 Garching bei München, Germany Received 25 August 2017 / Accepted 25 September 2017 ABSTRACT With the availability of parallaxes provided by the Tycho-Gaia Astrometric Solution, it is possible to construct the Hertzsprung-Russell diagram (HRD) of barium and related stars with unprecedented accuracy. A direct result from the derived HRD is that subgiant CH stars occupy the same region as barium dwarfs, contrary to what their designations imply. By comparing the position of barium stars in the HRD with STAREVOL evolutionary tracks, it is possible to evaluate their masses, provided the metallicity is known. We used an average metallicity [Fe/H] = −0.25 and derived the mass distribution of barium giants. The distribution peaks around 2.5 M with a tail at higher masses up to 4.5 M . This peak is also seen in the mass distribution of a sample of normal K and M giants used for comparison and is associated with stars located in the red clump. When we compare these mass distributions, we see a deficit of low-mass (1 – 2 M ) barium giants.
    [Show full text]
  • Origin of Spin-Orbit Misalignments: the Microblazar V4641 Sgr
    Draft version June 29, 2020 Typeset using LATEX twocolumn style in AASTeX62 Origin of Spin-Orbit Misalignments: The Microblazar V4641 Sgr Greg Salvesen1, 2, 3, ∗ and Supavit Pokawanvit3 1CCS-2, Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545, USA. 2Center for Theoretical Astrophysics, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. 3Department of Physics, University of California, Santa Barbara, CA 93106, USA. (Received November 05, 2019; Accepted April 22, 2020; Published June 2020) Submitted to Monthly Notices of the Royal Astronomical Society ABSTRACT Of the known microquasars, V4641 Sgr boasts the most severe lower limit (> 52◦) on the misalign- ment angle between the relativistic jet axis and the binary orbital angular momentum. Assuming the jet and black hole spin axes coincide, we attempt to explain the origin of this extreme spin-orbit misalignment with a natal kick model, whereby an aligned binary system becomes misaligned by a supernova kick imparted to the newborn black hole. The model inputs are the kick velocity distri- bution, which we measure customized to V4641 Sgr, and the immediate pre/post-supernova binary system parameters. Using a grid of binary stellar evolution models, we determine post-supernova configurations that evolve to become consistent with V4641 Sgr today and obtain the corresponding pre-supernova configurations by using standard prescriptions for common envelope evolution. Using each of these potential progenitor system parameter sets as inputs, we find that a natal kick strug- gles to explain the origin of the V4641 Sgr spin-orbit misalignment. Consequently, we conclude that evolutionary pathways involving a standard common envelope phase followed by a supernova kick are highly unlikely for V4641 Sgr.
    [Show full text]
  • This Online Essay Is an Extended Version of the Essay in the Printed-Edition Handbook, Containing All the Material of Its Print
    This online essay is an extended version of the essay in the printed-edition Handbook, containing all the material of its printed- edition accompaniment, but adding material of its own. The accompanying online table is likewise an extended version of the printed-edition table, (a) with extra stars (the brightest 313, allowing for variability, where the printed edition has almost 30 fewer, allowing for variability), and (b) with additional remarks for most of the duplicated stars. The online essay and table try to address the needs of three kinds of serious amateur: amateurs who are also astrophysics students (whether or not enrolled formally at some campus); amateurs who, like many in RASC, assist in public outreach, through some form of lecturing; and amateurs who are planning their own private citizen-science observing runs, in the spirit of such “pro-am” organizations as AAVSO. Our online project, now a couple of years old, must be considered still in its early stages. We cannot claim to have fully satisfied the needs of our three constituencies. Above all, we cannot claim to have covered all the appropriate points from stellar- astronomy news in our “Remarks” column, important though news is to amateurs of all three types. We would hope in coming years to remedy our deficiencies in several ways, above all by relying more in our writing on recent primary-literature journal articles, and by making appropriate citations of the primary literature. Already at this early stage, we have tried to pick out a few tens of the more important recent journal articles.
    [Show full text]
  • Stars, Galaxies, and Beyond, 2012
    Stars, Galaxies, and Beyond Summary of notes and materials related to University of Washington astronomy courses: ASTR 322 The Contents of Our Galaxy (Winter 2012, Professor Paula Szkody=PXS) & ASTR 323 Extragalactic Astronomy And Cosmology (Spring 2012, Professor Željko Ivezić=ZXI). Summary by Michael C. McGoodwin=MCM. Content last updated 6/29/2012 Rotated image of the Whirlpool Galaxy M51 (NGC 5194)1 from Hubble Space Telescope HST, with Companion Galaxy NGC 5195 (upper left), located in constellation Canes Venatici, January 2005. Galaxy is at 9.6 Megaparsec (Mpc)= 31.3x106 ly, width 9.6 arcmin, area ~27 square kiloparsecs (kpc2) 1 NGC = New General Catalog, http://en.wikipedia.org/wiki/New_General_Catalogue 2 http://hubblesite.org/newscenter/archive/releases/2005/12/image/a/ Page 1 of 249 Astrophysics_ASTR322_323_MCM_2012.docx 29 Jun 2012 Table of Contents Introduction ..................................................................................................................................................................... 3 Useful Symbols, Abbreviations and Web Links .................................................................................................................. 4 Basic Physical Quantities for the Sun and the Earth ........................................................................................................ 6 Basic Astronomical Terms, Concepts, and Tools (Chapter 1) ............................................................................................. 9 Distance Measures ......................................................................................................................................................
    [Show full text]
  • Post Main Sequence Evolution
    Post Main Sequence evolution Contents 1 Introduction1 2 Main sequence evolution and lifetime2 2.1 Main sequence duration..............................2 2.2 Evolution along the main sequence........................3 3 Evolutionary tracks and isochrones5 4 Red giant phase5 4.1 The turn-off point.................................5 4.2 From H burning to He burning: overview....................6 4.3 Giant stars: red or blue..............................7 4.4 Hydrogen shell burning and helium core growth.................7 4.5 The Schonberg-Chandrasekhar¨ limit and the Hertzprung gap..........9 4.6 Low-mass stars: degenerate core and the Helium flash.............. 10 4.7 Horizontal branch: low-mass. core helium burning, stars............ 10 4.8 Sub Giant Branch................................. 10 4.9.......................................... 11 5 Cepheids 11 6 The Asymptotic Giant Branch 11 1 Introduction The density of stars in the HR diagram (or simply HRD) directly tells us where stars spend significant amounts of time. After the main sequence, which is the densest part of the HRD, high density of points in the HRD are found in regions above the MS, namely where the radius is increased. These stars are in the giant region which, as we will see, can be divived into the red giant branch (RGB), the horizontal branch (HB), and the asymptotic giant branch (AGB). The evolution of stars beyond the main sequence is much more complex than that on the main sequence, essentially because the timescale separation not always applies. Nevertheless, some of the basic features of the evolutionary path in the HRD can still be understood using 2 4 simple equations, one of the most useful being L = 4πR σTeff .
    [Show full text]
  • Rotation and Magnetic Activity of the Hertzsprung-Gap Giant 31 Comae,
    A&A 520, A52 (2010) Astronomy DOI: 10.1051/0004-6361/201015023 & c ESO 2010 Astrophysics Rotation and magnetic activity of the Hertzsprung-gap giant 31 Comae, K. G. Strassmeier1, T. Granzer1,M.Kopf1, M. Weber1,M.Küker1,P.Reegen2,J.B.Rice3,J.M.Matthews4, R. Kuschnig2,J.F.Rowe5, D. B. Guenther6,A.F.J.Moffat7,S.M.Rucinski8, D. Sasselov9, and W. W. Weiss2 1 Astrophysical Institute Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany e-mail: [email protected] 2 Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria e-mail: [email protected] 3 Department of Physics, Brandon University, Brandon, Manitoba R7A 6A9, Canada e-mail: [email protected] 4 Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, Canada, V6T 1Z1 5 NASA Ames Research Center, Moffett Field, CA 94035, USA 6 Department of Astronomy and Physics, St. Mary’s University Halifax, NS B3H 3C3, Canada 7 Département de Physique, Université de Montréal C.P. 6128, Succ. Centre-Ville, Montréal, QC H3C 3J7, Canada 8 Department of Astronomy & Astrophysics, University of Toronto, 50 St. George Str., Toronto, OM5S 3H4, Canada 9 Harvard-Smithsonian Center for Astrophysics 60 Garden Street, Cambridge, MA 02138, USA Received 20 May 2010 / Accepted 15 July 2010 ABSTRACT Context. The single rapidly-rotating G0 giant 31 Comae has been a puzzle because of the absence of photometric variability despite its strong chromospheric and coronal emissions. As a Hertzsprung-gap giant, it is expected to be at the stage of rearranging its moment of inertia, hence likely also its dynamo action, which could possibly be linked with its missing photospheric activity.
    [Show full text]
  • Stellar Structure and Evolution: Syllabus 3.3 the Virial Theorem and Its Implications (ZG: P5-2; CO: 2.4) Ph
    Page 2 Stellar Structure and Evolution: Syllabus 3.3 The Virial Theorem and its Implications (ZG: P5-2; CO: 2.4) Ph. Podsiadlowski (MT 2006) 3.4 The Energy Equation and Stellar Timescales (CO: 10.3) (DWB 702, (2)73343, [email protected]) (www-astro.physics.ox.ac.uk/˜podsi/lec mm03.html) 3.5 Energy Transport by Radiation (ZG: P5-10, 16-1) and Con- vection (ZG: 16-1; CO: 9.3, 10.4) Primary Textbooks 4. The Equations of Stellar Structure (ZG: 16; CO: 10) ZG: Zeilik & Gregory, “Introductory Astronomy & Astro- • 4.1 The Mathematical Problem (ZG: 16-2; CO: 10.5) physics” (4th edition) 4.1.1 The Vogt-Russell “Theorem” (CO: 10.5) CO: Carroll & Ostlie, “An Introduction to Modern Astro- • 4.1.2 Stellar Evolution physics” (Addison-Wesley) 4.1.3 Convective Regions (ZG: 16-1; CO: 10.4) also: Prialnik, “An Introduction to the Theory of Stellar Struc- • 4.2 The Equation of State ture and Evolution” 4.2.1 Perfect Gas and Radiation Pressure (ZG: 16-1: CO: 1. Observable Properties of Stars (ZG: Chapters 11, 12, 13; CO: 10.2) Chapters 3, 7, 8, 9) 4.2.2 Electron Degeneracy (ZG: 17-1; CO: 15.3) 1.1 Luminosity, Parallax (ZG: 11; CO: 3.1) 4.3 Opacity (ZG: 10-2; CO: 9.2) 1.2 The Magnitude System (ZG: 11; CO: 3.2, 3.6) 5. Nuclear Reactions (ZG: P5-7 to P5-9, P5-12, 16-1D; CO: 10.3) 1.3 Black-Body Temperature (ZG: 8-6; CO: 3.4) 5.1 Nuclear Reaction Rates (ZG: P5-7) 1.4 Spectral Classification, Luminosity Classes (ZG: 13-2/3; CO: 5.2 Hydrogen Burning 5.1, 8.1, 8.3) 5.2.1 The pp Chain (ZG: P5-7, 16-1D) 1.5 Stellar Atmospheres (ZG: 13-1; CO: 9.1, 9.4) 5.2.2 The CN Cycle (ZG: P5-9; 16-1D) 1.6 Stellar Masses (ZG: 12-2/3; CO: 7.2, 7.3) 5.3 Energy Generation from H Burning (CO: 10.3) 1.7 Stellar Radii (ZG: 12-4/5; CO: 7.3) 5.4 Other Reactions Involving Light Elements (Supplementary) 2.
    [Show full text]
  • Stellar Structure and Evolution
    Stellar structure and evolution Warrick Ball November 3 & 4, 2014 Contents 1 Stellar modelling 4 1.1 Basic assumptions . 4 1.1.1 Mass conservation . 6 1.1.2 Hydrostatic equilibrium . 6 1.1.3 Energy generation (and conservation) . 7 1.1.4 Energy transport . 7 1.2 Composition equations . 10 1.3 Matter equations . 11 1.3.1 Opacity . 12 1.3.2 Nuclear reactions . 13 1.3.3 Neutrino loss rates . 15 1.3.4 Equation of state . 16 1.4 Boundary conditions . 18 1.4.1 Centre . 18 1.4.2 Surface . 18 1.4.3 Composition . 18 1.4.4 Initial models . 19 2 Stellar evolution 20 2.1 Characterizing stellar evolution . 20 2.1.1 The Hertzsprung{Russell diagram . 20 2.1.2 Colour{magnitude diagrams . 22 2.1.3 The ρ-T diagram . 23 2.1.4 Kippenhahn diagrams . 23 2.2 Evolution of a Sun-like star . 25 2.2.1 The main sequence . 25 2.2.2 The red giant branch . 25 2.2.3 The helium flash and core helium burning . 27 2.2.4 Thermal pulses and the asymptotic giant branch . 28 2.2.5 Envelope expulsion and the white dwarf cooling track . 29 2.3 More massive stars . 30 2.3.1 Convective cores on the main sequence . 30 2.3.2 Non-degenerate helium ignition . 30 1 2.3.3 Mass loss on the main sequence . 31 2.3.4 Carbon burning and beyond . 34 2.4 Parting thoughts . 34 2 Prologue About the course These lecture notes are from the two lectures I gave at the DWIH Winter School in 2014.
    [Show full text]
  • Extended Table
    PREFACE: Scope and purpose of this essay This online essay is an extended version of the essay in the printed-edition Handbook, containing all the material of its printed-edition accompaniment, but adding material of its own. The accompanying online table is likewise an extended version of the printed-edition table, (a) with extra stars (after providing for multiplicity, as we explain below, the brightest MK-classified 322, allowing for variability, where the printed edition has almost 30 fewer, allowing for variability: our cutoff is mag. ~3.55), and (b) with additional remarks for most of the duplicated stars. We use a dagger superscript (†) to mark data cells for which the online table supplies some additional information, some context, or a caveat. The online essay and table try to address the needs of three kinds of serious amateur: amateurs who are also astrophysics students (whether or not enrolled formally at some campus); amateurs who, like many in RASC, assist in public outreach, through some form of lecturing; and amateurs who are planning their own private citizen-science observing runs, in the spirit of such “pro-am” organizations as AAVSO. Additionally, we would hope that the online project will help serve a constituency of sky-lovers, whether professional or amateur, who work with the heavens in an unambitious and contemplative spirit, seeking to understand at the eyepiece, or even with the naked eye, the realities behind the little that their limited circumstances may allow them to see. (This is the same contemplative exercise as is proposed for the Cyg X-1 black hole, with its gas-dumping supergiant companion HD226868, in the Handbook printed-editions “Expired Stars” essay: with a small telescope, or even with binoculars, we first find HD226868, and then take a moment to ponder in awe the accompanying unobserved realities of gas-fed hot accretion disk, event horizon, and spacetime singularity.) Our online project, started as a supplement to the 2017 Handbook, must be considered still in its rather early stages.
    [Show full text]