Pre-Supernova Evolution of Massive Stars
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X-Ray Sun SDO 4500 Angstroms: Photosphere
ASTR 8030/3600 Stellar Astrophysics X-ray Sun SDO 4500 Angstroms: photosphere T~5000K SDO 1600 Angstroms: upper photosphere T~5x104K SDO 304 Angstroms: chromosphere T~105K SDO 171 Angstroms: quiet corona T~6x105K SDO 211 Angstroms: active corona T~2x106K SDO 94 Angstroms: flaring regions T~6x106K SDO: dark plasma (3/27/2012) SDO: solar flare (4/16/2012) SDO: coronal mass ejection (7/2/2012) Aims of the course • Introduce the equations needed to model the internal structure of stars. • Overview of how basic stellar properties are observationally measured. • Study the microphysics relevant for stars: the equation of state, the opacity, nuclear reactions. • Examine the properties of simple models for stars and consider how real models are computed. • Survey (mostly qualitatively) how stars evolve, and the endpoints of stellar evolution. Stars are relatively simple physical systems Sound speed in the sun Problem of Stellar Structure We want to determine the structure (density, temperature, energy output, pressure as a function of radius) of an isolated mass M of gas with a given composition (e.g., H, He, etc.) Known: r Unknown: Mass Density + Temperature Composition Energy Pressure Simplifying assumptions 1. No rotation à spherical symmetry ✔ For sun: rotation period at surface ~ 1 month orbital period at surface ~ few hours 2. No magnetic fields ✔ For sun: magnetic field ~ 5G, ~ 1KG in sunspots equipartition field ~ 100 MG Some neutron stars have a large fraction of their energy in B fields 3. Static ✔ For sun: convection, but no large scale variability Not valid for forming stars, pulsating stars and dying stars. 4. -
Introduction to Astronomy from Darkness to Blazing Glory
Introduction to Astronomy From Darkness to Blazing Glory Published by JAS Educational Publications Copyright Pending 2010 JAS Educational Publications All rights reserved. Including the right of reproduction in whole or in part in any form. Second Edition Author: Jeffrey Wright Scott Photographs and Diagrams: Credit NASA, Jet Propulsion Laboratory, USGS, NOAA, Aames Research Center JAS Educational Publications 2601 Oakdale Road, H2 P.O. Box 197 Modesto California 95355 1-888-586-6252 Website: http://.Introastro.com Printing by Minuteman Press, Berkley, California ISBN 978-0-9827200-0-4 1 Introduction to Astronomy From Darkness to Blazing Glory The moon Titan is in the forefront with the moon Tethys behind it. These are two of many of Saturn’s moons Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA 2 Introduction to Astronomy Contents in Brief Chapter 1: Astronomy Basics: Pages 1 – 6 Workbook Pages 1 - 2 Chapter 2: Time: Pages 7 - 10 Workbook Pages 3 - 4 Chapter 3: Solar System Overview: Pages 11 - 14 Workbook Pages 5 - 8 Chapter 4: Our Sun: Pages 15 - 20 Workbook Pages 9 - 16 Chapter 5: The Terrestrial Planets: Page 21 - 39 Workbook Pages 17 - 36 Mercury: Pages 22 - 23 Venus: Pages 24 - 25 Earth: Pages 25 - 34 Mars: Pages 34 - 39 Chapter 6: Outer, Dwarf and Exoplanets Pages: 41-54 Workbook Pages 37 - 48 Jupiter: Pages 41 - 42 Saturn: Pages 42 - 44 Uranus: Pages 44 - 45 Neptune: Pages 45 - 46 Dwarf Planets, Plutoids and Exoplanets: Pages 47 -54 3 Chapter 7: The Moons: Pages: 55 - 66 Workbook Pages 49 - 56 Chapter 8: Rocks and Ice: -
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. -
SHELL BURNING STARS: Red Giants and Red Supergiants
SHELL BURNING STARS: Red Giants and Red Supergiants There is a large variety of stellar models which have a distinct core – envelope structure. While any main sequence star, or any white dwarf, may be well approximated with a single polytropic model, the stars with the core – envelope structure may be approximated with a composite polytrope: one for the core, another for the envelope, with a very large difference in the “K” constants between the two. This is a consequence of a very large difference in the specific entropies between the core and the envelope. The original reason for the difference is due to a jump in chemical composition. For example, the core may have no hydrogen, and mostly helium, while the envelope may be hydrogen rich. As a result, there is a nuclear burning shell at the bottom of the envelope; hydrogen burning shell in our example. The heat generated in the shell is diffusing out with radiation, and keeps the entropy very high throughout the envelope. The core – envelope structure is most pronounced when the core is degenerate, and its specific entropy near zero. It is supported against its own gravity with the non-thermal pressure of degenerate electron gas, while all stellar luminosity, and all entropy for the envelope, are provided by the shell source. A common property of stars with well developed core – envelope structure is not only a very large jump in specific entropy but also a very large difference in pressure between the center, Pc, the shell, Psh, and the photosphere, Pph. Of course, the two characteristics are closely related to each other. -
Temperature, Mass and Size of Stars
Title Astro100 Lecture 13, March 25 Temperature, Mass and Size of Stars http://www.astro.umass.edu/~myun/teaching/a100/longlecture13.html Also, http://www.astro.columbia.edu/~archung/labs/spring2002/spring2002.html (Lab 1, 2, 3) Goal Goal: To learn how to measure various properties of stars 9 What properties of stars can astronomers learn from stellar spectra? Î Chemical composition, surface temperature 9 How useful are binary stars for astronomers? Î Mass 9 What is Stefan-Boltzmann Law? Î Luminosity, size, temperature 9 What is the Hertzsprung-Russell Diagram? Î Distance and Age Temp1 Stellar Spectra Spectrum: light separated and spread out by wavelength using a prism or a grating BUT! Stellar spectra are not continuous… Temp2 Stellar Spectra Photons from inside of higher temperature get absorbed by the cool stellar atmosphere, resulting in “absorption lines” At which wavelengths we see these lines depends on the chemical composition and physical state of the gas Temp3 Stellar Spectra Using the most prominent absorption line (hydrogen), Temp4 Stellar Spectra Measuring the intensities at different wavelength, Intensity Wavelength Wien’s Law: λpeak= 2900/T(K) µm The hotter the blackbody the more energy emitted per unit area at all wavelengths. The peak emission from the blackbody moves to shorter wavelengths as the T increases (Wien's law). Temp5 Stellar Spectra Re-ordering the stellar spectra with the temperature Temp-summary Stellar Spectra From stellar spectra… Surface temperature (Wien’s Law), also chemical composition in the stellar -
An Overview of New Worlds, New Horizons in Astronomy and Astrophysics About the National Academies
2020 VISION An Overview of New Worlds, New Horizons in Astronomy and Astrophysics About the National Academies The National Academies—comprising the National Academy of Sciences, the National Academy of Engineering, the Institute of Medicine, and the National Research Council—work together to enlist the nation’s top scientists, engineers, health professionals, and other experts to study specific issues in science, technology, and medicine that underlie many questions of national importance. The results of their deliberations have inspired some of the nation’s most significant and lasting efforts to improve the health, education, and welfare of the United States and have provided independent advice on issues that affect people’s lives worldwide. To learn more about the Academies’ activities, check the website at www.nationalacademies.org. Copyright 2011 by the National Academy of Sciences. All rights reserved. Printed in the United States of America This study was supported by Contract NNX08AN97G between the National Academy of Sciences and the National Aeronautics and Space Administration, Contract AST-0743899 between the National Academy of Sciences and the National Science Foundation, and Contract DE-FG02-08ER41542 between the National Academy of Sciences and the U.S. Department of Energy. Support for this study was also provided by the Vesto Slipher Fund. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the authors and do not necessarily reflect the views of the agencies that provided support for the project. 2020 VISION An Overview of New Worlds, New Horizons in Astronomy and Astrophysics Committee for a Decadal Survey of Astronomy and Astrophysics ROGER D. -
The Endpoints of Stellar Evolution Answer Depends on the Star’S Mass Star Exhausts Its Nuclear Fuel - Can No Longer Provide Pressure to Support Itself
The endpoints of stellar evolution Answer depends on the star’s mass Star exhausts its nuclear fuel - can no longer provide pressure to support itself. Gravity takes over, it collapses Low mass stars (< 8 Msun or so): End up with ‘white dwarf’ supported by degeneracy pressure. Wide range of structure and composition!!! Answer depends on the star’s mass Star exhausts its nuclear fuel - can no longer provide pressure to support itself. Gravity takes over, it collapses Higher mass stars (8-25 Msun or so): get a ‘neutron star’ supported by neutron degeneracy pressure. Wide variety of observed properties Answer depends on the star’s mass Star exhausts its nuclear fuel - can no longer provide pressure to support itself. Gravity takes over, it collapses Above about 25 Msun: we are left with a ‘black hole’ Black holes are astounding objects because of their simplicity (consider all the complicated physics to set all the macroscopic properties of a star that we have been through) - not unlike macroscopic elementary particles!! According to general relativity, the black hole properties are set by two numbers: mass and spin change of photon energies towards the gravitating mass the opposite when emitted Pound-Rebka experiment used atomic transition of Fe Important physical content for BH studies: general relativity has no intrisic scale instead, all important lengthscales and timescales are set by - and become proportional to the mass. Trick… Examine the energy… Why do we believe that black holes are inevitably created by gravitational collapse? Rather astounding that we go from such complicated initial conditions to such “clean”, simple objects! . -
Stars IV Stellar Evolution Attendance Quiz
Stars IV Stellar Evolution Attendance Quiz Are you here today? Here! (a) yes (b) no (c) my views are evolving on the subject Today’s Topics Stellar Evolution • An alien visits Earth for a day • A star’s mass controls its fate • Low-mass stellar evolution (M < 2 M) • Intermediate and high-mass stellar evolution (2 M < M < 8 M; M > 8 M) • Novae, Type I Supernovae, Type II Supernovae An Alien Visits for a Day • Suppose an alien visited the Earth for a day • What would it make of humans? • It might think that there were 4 separate species • A small creature that makes a lot of noise and leaks liquids • A somewhat larger, very energetic creature • A large, slow-witted creature • A smaller, wrinkled creature • Or, it might decide that there is one species and that these different creatures form an evolutionary sequence (baby, child, adult, old person) Stellar Evolution • Astronomers study stars in much the same way • Stars come in many varieties, and change over times much longer than a human lifetime (with some spectacular exceptions!) • How do we know they evolve? • We study stellar properties, and use our knowledge of physics to construct models and draw conclusions about stars that lead to an evolutionary sequence • As with stellar structure, the mass of a star determines its evolution and eventual fate A Star’s Mass Determines its Fate • How does mass control a star’s evolution and fate? • A main sequence star with higher mass has • Higher central pressure • Higher fusion rate • Higher luminosity • Shorter main sequence lifetime • Larger -
A Stripped Helium Star in the Potential Black Hole Binary LB-1 A
A&A 633, L5 (2020) Astronomy https://doi.org/10.1051/0004-6361/201937343 & c ESO 2020 Astrophysics LETTER TO THE EDITOR A stripped helium star in the potential black hole binary LB-1 A. Irrgang1, S. Geier2, S. Kreuzer1, I. Pelisoli2, and U. Heber1 1 Dr. Karl Remeis-Observatory & ECAP, Astronomical Institute, Friedrich-Alexander University Erlangen-Nuremberg (FAU), Sternwartstr. 7, 96049 Bamberg, Germany e-mail: [email protected] 2 Institut für Physik und Astronomie, Universität Potsdam, Karl-Liebknecht-Str. 24/25, 14476 Potsdam, Germany Received 18 December 2019 / Accepted 1 January 2020 ABSTRACT +11 Context. The recently claimed discovery of a massive (MBH = 68−13 M ) black hole in the Galactic solar neighborhood has led to controversial discussions because it severely challenges our current view of stellar evolution. Aims. A crucial aspect for the determination of the mass of the unseen black hole is the precise nature of its visible companion, the B-type star LS V+22 25. Because stars of different mass can exhibit B-type spectra during the course of their evolution, it is essential to obtain a comprehensive picture of the star to unravel its nature and, thus, its mass. Methods. To this end, we study the spectral energy distribution of LS V+22 25 and perform a quantitative spectroscopic analysis that includes the determination of chemical abundances for He, C, N, O, Ne, Mg, Al, Si, S, Ar, and Fe. Results. Our analysis clearly shows that LS V+22 25 is not an ordinary main sequence B-type star. The derived abundance pattern exhibits heavy imprints of the CNO bi-cycle of hydrogen burning, that is, He and N are strongly enriched at the expense of C and O. -
Stellar Structure and Evolution
Lecture Notes on Stellar Structure and Evolution Jørgen Christensen-Dalsgaard Institut for Fysik og Astronomi, Aarhus Universitet Sixth Edition Fourth Printing March 2008 ii Preface The present notes grew out of an introductory course in stellar evolution which I have given for several years to third-year undergraduate students in physics at the University of Aarhus. The goal of the course and the notes is to show how many aspects of stellar evolution can be understood relatively simply in terms of basic physics. Apart from the intrinsic interest of the topic, the value of such a course is that it provides an illustration (within the syllabus in Aarhus, almost the first illustration) of the application of physics to “the real world” outside the laboratory. I am grateful to the students who have followed the course over the years, and to my colleague J. Madsen who has taken part in giving it, for their comments and advice; indeed, their insistent urging that I replace by a more coherent set of notes the textbook, supplemented by extensive commentary and additional notes, which was originally used in the course, is directly responsible for the existence of these notes. Additional input was provided by the students who suffered through the first edition of the notes in the Autumn of 1990. I hope that this will be a continuing process; further comments, corrections and suggestions for improvements are most welcome. I thank N. Grevesse for providing the data in Figure 14.1, and P. E. Nissen for helpful suggestions for other figures, as well as for reading and commenting on an early version of the manuscript. -
Part V Stellar Spectroscopy
Part V Stellar spectroscopy 53 Chapter 10 Classification of stellar spectra Goal-of-the-Day To classify a sample of stars using a number of temperature-sensitive spectral lines. 10.1 The concept of spectral classification Early in the 19th century, the German physicist Joseph von Fraunhofer observed the solar spectrum and realised that there was a clear pattern of absorption lines superimposed on the continuum. By the end of that century, astronomers were able to examine the spectra of stars in large numbers and realised that stars could be divided into groups according to the general appearance of their spectra. Classification schemes were developed that grouped together stars depending on the prominence of particular spectral lines: hydrogen lines, helium lines and lines of some metallic ions. Astronomers at Harvard Observatory further developed and refined these early classification schemes and spectral types were defined to reflect a smooth change in the strength of representative spectral lines. The order of the spectral classes became O, B, A, F, G, K, and M; even though these letter designations no longer have specific meaning the names are still in use today. Each spectral class is divided into ten sub-classes, so that for instance a B0 star follows an O9 star. This classification scheme was based simply on the appearance of the spectra and the physical reason underlying these properties was not understood until the 1930s. Even though there are some genuine differences in chemical composition between stars, the main property that determines the observed spectrum of a star is its effective temperature. -
Evolution of Helium Star Plus Carbon-Oxygen White Dwarf Binary Systems and Implications for Diverse Stellar Transients and Hypervelocity Stars
A&A 627, A14 (2019) https://doi.org/10.1051/0004-6361/201935322 Astronomy c ESO 2019 & Astrophysics Evolution of helium star plus carbon-oxygen white dwarf binary systems and implications for diverse stellar transients and hypervelocity stars P. Neunteufel1, S.-C. Yoon2, and N. Langer1 1 Argelander Institut für Astronomy (AIfA), University of Bonn, Auf dem Hügel 71, 53121 Bonn, Germany e-mail: [email protected] 2 Department of Physics and Astronomy, Seoul National University, 599 Gwanak-ro, Gwanak-gu, Seoul 151-742, Korea Received 20 February 2019 / Accepted 28 April 2019 ABSTRACT Context. Helium accretion induced explosions in CO white dwarfs (WDs) are considered promising candidates for a number of observed types of stellar transients, including supernovae (SNe) of Type Ia and Type Iax. However, a clear favorite outcome has not yet emerged. Aims. We explore the conditions of helium ignition in the WD and the final fates of helium star-WD binaries as functions of their initial orbital periods and component masses. Methods. We computed 274 model binary systems with the Binary Evolution Code, in which both components are fully resolved. Both stellar and orbital evolution were computed including mass and angular momentum transfer, tides, gravitational wave emission, differential rotation, and internal hydrodynamic and magnetic angular momentum transport. We worked out the parts of the parameter space leading to detonations of the accreted helium layer on the WD, likely resulting in the complete disruption of the WD to deflagrations, where the CO core of the WD may remain intact and where helium ignition in the WD is avoided.