Download or read book Stellar Modeling with Low temperature On the fly Opacity written by Lynn Buchele and published by . This book was released on 2021 with total page 64 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accurate stellar modeling requires using our understanding of phenomena far smaller than humans can observe to study some of the largest objects in the universe. One quantity that bridges this gap is the mean opacity, which uses knowledge about atomic and molecular interactions with light to inform how photons carry energy through a star. As the mean opacity depends on both the quantum mechanics of atoms and molecules and the macroscopic properties of the star (temperature, density, composition) it can be tricky to calculate. Traditionally, stellar modeling programs avoid the time-consuming computation of opacity by interpolating off of pre-made opacity tables. However, this interpolation introduces the possibility of error. In low-temperature areas of a star (less than 10,000K), this error is likely to be largest when the composition of the star differs from the composition used to create the tables. One way to examine this error is to model stars using low-temperature opacity values calculated on-the-fly. In this case, on-the-fly means using opacity calculated as the star is being modeled by a low-temperature opacity code using the exact temperature, density, and composition of each region within the star. This work describes the process of adapting the Atlas Opacity Program (ATOP) for use as an on-the-fly opacity code and discusses the results of using on-the-fly opacity values for several stellar evolution models created with the Modules for Experiments in Stellar Astrophysics (MESA) code. These models show that the effect of using on-the-fly opacity is more pronounced in models where the relative abundance of carbon to oxygen in the outer layers of the star changes significantly over the course of the star’s evolution.
Download or read book Effect of Low temperature Opacities on Stellar Evolution written by Aditya Sharma and published by . This book was released on 2021 with total page 59 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stellar evolution is studied through computational models of stars since any perceived change in the stars can take thousands if not millions of years. One of the physical quantities that defines the evolution of a star is known as the opacity. Opacity of a material determines how much electromagnetic radiation passes through the material. Scattering and absorption processes in the radiative region of the star determine the opacity of that region and regulate radiative energy flow in the star. The mean opacity which is averaged over all wavelengths depends on the temperature, density, and the composition of the material in the star. Currently, tables of mean opacities are used in stellar modeling. These opacities are given as functions of temperature and density and the tables are made for several compositions which changes with evolution of the star. At low temperatures, formation of molecules and dust grains can affect the mean opacity. In this study, low-temperature opacity tables are made with opacity codes ATOP and PHOENIX and stellar models produced with these opacity tables with the stellar evolution code MESA are compared. In addition, the effect of initial elemental abundance sets and molecular data sources on stellar evolution is studied. Finally, the impact of low-temperature opacities on the pace of stellar evolution is analyzed with stellar isochrones. The results show that there is negligible difference between stellar models produced with ATOP and PHOENIX and with different molecular data sources. However, changing the initial elemental abundance set generated significant changes in stellar evolution.
Download or read book Theory of Stellar Atmospheres written by Ivan Hubeny and published by Princeton University Press. This book was released on 2014-10-26 with total page 944 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most authoritative synthesis of the quantitative spectroscopic analysis of stellar atmospheres This book provides an in-depth and self-contained treatment of the latest advances achieved in quantitative spectroscopic analyses of the observable outer layers of stars and similar objects. Written by two leading researchers in the field, it presents a comprehensive account of both the physical foundations and numerical methods of such analyses. The book is ideal for astronomers who want to acquire deeper insight into the physical foundations of the theory of stellar atmospheres, or who want to learn about modern computational techniques for treating radiative transfer in non-equilibrium situations. It can also serve as a rigorous yet accessible introduction to the discipline for graduate students. Provides a comprehensive, up-to-date account of the field Covers computational methods as well as the underlying physics Serves as an ideal reference book for researchers and a rigorous yet accessible textbook for graduate students An online illustration package is available to professors at press.princeton.edu
Download or read book Stellar Interiors written by Carl J. Hansen and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: That trees should have been cut down to provide paper for this book was an ecological afIront. From a book review. - Anthony Blond (in the Spectator, 1983) The first modern text on our subject, Structure and Evolution of the Stars, was published over thirty years ago. In it, Martin Schwarzschild described numerical experiments that successfully reproduced most of the observed properties of the majority of stars seen in the sky. He also set the standard for a lucid description of the physics of stellar interiors. Ten years later, in 1968, John P. Cox's tw~volume monograph Principles of Stellar Structure appeared, as did the more specialized text Principles of Stellar Evolution and Nuc1eosynthesis by Donald D. Clayton-and what a difference ten years had made. The field had matured into the basic form that it remains today. The past twenty-plus years have seen this branch of astrophysics flourish and develop into a fundamental pillar of modern astrophysics that addresses an enormous variety of phenomena. In view of this it might seem foolish to offer another text of finite length and expect it to cover any more than a fraction of what should be discussed to make it a thorough and self-contained reference. Well, it doesn't. Our specific aim is to introduce only the fundamentals of stellar astrophysics. You will find little reference here to black holes, millisecond pulsars, and other "sexy" objects.
Download or read book Stellar Atmosphere Modeling written by Ivan Hubený and published by . This book was released on 2003 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stellar Opacity written by and published by . This book was released on 1999 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt: The monochromatic opacity, [kappa]{sub v}, quantifies the property of a material to remove energy of frequency v from a radiation field. A harmonic average of [kappa]{sub v}, known as the Rosseland mean, [kappa]{sub R}, is frequently used to simplify the calculation of energy transport in stars. The term ''opacity'' is commonly understood to refer to [kappa]{sub R}. Opacity plays an important role in stellar modeling because for most stars radiation is the primary mechanism for transporting energy from the nuclear burning region in the core to the surface. Depending on the mass, convection and electron thermal conduction can also be important modes of stellar energy transport. The efficiency of energy transport is related to the temperature gradient, which is directly proportional to the mean radiative opacity in radiation dominated regions. When the radiative opacity is large, convection can become the more efficient energy transport mechanism. Electron conductive opacity, the resistance of matter to thermal conduction, is inversely proportional to electron thermal conductivity. Thermal conduction becomes the dominant mode of energy transport at high density and low temperature.
Download or read book Radiative Transfer in Stellar and Planetary Atmospheres written by Lucio Crivellari and published by Cambridge University Press. This book was released on 2020-01-09 with total page 251 pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiative transfer is essential for obtaining information from the spectra of astrophysical objects. This volume provides an overview of the physical and mathematical background of radiative transfer, and its applications to stellar and planetary atmospheres. It covers the phenomenology and physics of early-type and late-type stars, as well as ultra-cool dwarf stars and extrasolar planets. Importantly, it provides a bridge between classical radiative transfer and stellar atmosphere modelling and novel approaches, from both theoretical and computational standpoints. With new fields of application and a dramatic improvement in both observational and computational facilities, it also discusses the future outlook for the field. Chapters are written by eminent researchers from across the astronomical disciplines where radiative transfer is employed. Using the most recent observations, this is a go-to resource for graduate students and researchers in astrophysics.
Download or read book Astrophysical Flows written by James E. Pringle and published by Cambridge University Press. This book was released on 2007-04-26 with total page 217 pages. Available in PDF, EPUB and Kindle. Book excerpt: Almost all conventional matter in the Universe is fluid, and fluid dynamics plays a crucial role in astrophysics. This graduate textbook, first published in 2007, provides a basic understanding of the fluid dynamical processes relevant to astrophysics. The mathematics used to describe these processes is simplified to bring out the underlying physics. The authors cover many topics, including wave propagation, shocks, spherical flows, stellar oscillations, the instabilities caused by effects such as magnetic fields, thermal driving, gravity, shear flows, and the basic concepts of compressible fluid dynamics and magnetohydrodynamics. The authors are Directors of the UK Astrophysical Fluids Facility (UKAFF) at the University of Leicester, and editors of the Cambridge Astrophysics Series. This book has been developed from a course in astrophysical fluid dynamics taught at the University of Cambridge. It is suitable for graduate students in astrophysics, physics and applied mathematics, and requires only a basic familiarity with fluid dynamics.
Download or read book Stellar Structure and Evolution written by Rudolf Kippenhahn and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: A complete and comprehensive treatment of the physics of the stellar interior and the underlying fundamental processes and parameters. The text presents an overview of the models developed to explain the stability, dynamics and evolution of the stars, and great care is taken to detail the various stages in a star's life. The authors have succeeded in producing a unique text based on their own pioneering work in stellar modeling. Since its publication, this textbook has come to be considered a classic by both readers and teachers in astrophysics. This study edition is intended for students in astronomy and physics alike.
Download or read book The Equation of State in Astrophysics written by G. CHABRIER (Ed) and published by Cambridge University Press. This book was released on 1994-08-11 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt: A unique review of our understanding of dense ionised matter in astrophysical contexts - essential reading for graduate students and researchers.
Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1975 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stellar Populations written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2010 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: IAU Symposium 262 presents reviews on the current understanding of the theories of stellar evolution, galaxy formation and galaxy evolution. It emphasises what we have learned in the past few years from massive surveys covering large portions of the sky (e.g. SDSS, HDF, UDF, GOODS, COSMOS). Several critical aspects of research on stellar populations deserve further effort in order to be brought in tune with other areas of astrophysical research. The next ten years will see the opening of major observatories that will increase the quality and quantity of astronomical data by orders of magnitude. The expected benefits from these instruments for the study of stellar populations are explored. This critical review of state of the art observational and theoretical work will appeal to all those working on stellar populations, from distant galaxies to local resolved galaxies and galactic star clusters.
Download or read book Theoretical Astrophysics Volume 2 Stars and Stellar Systems written by T. Padmanabhan and published by Cambridge University Press. This book was released on 2001-04-23 with total page 596 pages. Available in PDF, EPUB and Kindle. Book excerpt: This authoritative textbook - the second volume of a comprehensive three-volume course on theoretical astrophysics - deals with stellar physics. Designed to help graduate students and researchers develop an understanding of the key physical processes governing stars and stellar systems, it teaches the fundamentals, and then builds on them to give the reader an in-depth understanding of advanced topics. The book's modular design allows the chapters to be approached individually, yet seamless transitions create a coherent and connected whole. It can be used alone or in conjunction with Volume I, which covers a wide range of astrophysical processes, and the forthcoming Volume III, on galaxies and cosmology. After reviewing the key observational results and nomenclature used in stellar astronomy, the book develops a solid understanding of central concepts including stellar structure and evolution, the physics of stellar remnants, pulsars, binary stars, the sun and planetary systems, interstellar medium and globular clusters. Throughout, the reader's comprehension is developed and tested with more than seventy-five exercises. This indispensable volume provides graduate students with a self-contained introduction to stellar physics, and will allow them to master the material sufficiently to read and engage in research with heightened understanding.
Download or read book Astrophysical Jets and Their Engines written by Wolfgang Kundt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 265 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is the documentation of the first Course on 'Neutron Stars, Active Galactic Nuclei and Jets', of an Erice School with a wide astro physical scope. The choice of the subject was made because of an apparent similari ty - stressed already at earlier meetings - of four classes of astrophy sical jet sources: Active Galactic Nuclei, Young Stellar Objects, Binary Neutron Stars and Binary White Dwarfs. They share important properties such as their morphology, high variability and large veloci ty gradients as well as - with some inference - their broad spectrum, hypersonic outflow and core/lobe power ratio. Despite this apparent similarity of the four source classes, quite different models have been put forward for their description: (i) The central engine of active galactic nuclei has been generally thought to be a black hole, in contrast to the central engine of young stellar objects and cometary nebulae which apparently is a pre-T-Tauri star, some six orders of magnitude less compact, and to the central engine of planetary nebulae which mayor may not be a binary white dwarf. (ii) The elongated lobes, or flow patterns, have been often interpreted as highly directional stellar wind outflows whereas in a few well mapped cases, the elongated flow appears to be 'pumped up' through a much narrower channel, or jet, both in the extragalactic and stellar sources.
Download or read book Solar Phenomena in Stars and Stellar Systems written by R.M. Bonnet and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book represents the proceedings of a NATO Advanced Study Institute which was held at Bonas from August 25 till Sep tember 5, 1980 and was devoted to the study of "Solar Phenomena in Stars and Stellar Systems". It is intended for a broad audi ence. Students and post-doctoral scientists for example can dis cover new aspects of astrophysics. The general spirit of the ASI was aimed at presenting a unified aspect of astrophysical phenomena which can be studied intensively on the Sun although they are of a much more general nature. On the other hand, spe cialists in solar or stellar physics will find here the latest theoretical developments and/or the most recent observations made in their own field of research. An extensive bibliography will be found throughout the various sections, to which the reader may refer, for more detailed developments in various specific areas. In the past, stellar and solar astrophysics have more or less followed their own independent tracks. However, with the rapid development of modern techniques, in particular artificial satellites like the International Ultraviolet Explorer and the Einstein Observatory, which provide a new wealth of data, it appears that chromospheres, coronae, magnetic fields, mass loss and stellar winds, etc . . . . , are found not only in the Sun but occur also in other stars. Frequently these other stars represent quite different conditions of gravity, lumino~ity, and other parameters from those occurring in the Sun.
Download or read book Nature s Third Cycle written by Arnab Rai Choudhuri and published by OUP Oxford. This book was released on 2015-01-29 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cycle of day and night and the cycle of seasons are two familiar natural cycles around which many human activities are organized. But is there a third natural cycle of importance for us humans? On 13 March 1989, six million people in Canada went without electricity for many hours: a large explosion on the sun was discovered as the cause of this blackout. Such explosions occur above sunspots, dark features on the surface of the Sun that have been observed through telescopes since the time of Galileo. The number of sunspots has been found to wax and wane over a period of 11 years. Although this cycle was discovered less than two centuries ago, it is becoming increasingly important for us as human society becomes more dependent on technology. For nearly a century after its discovery, the cause of the sunspot cycle remained completely shrouded in mystery. The 1908 discovery of strong magnetic fields in sunspots made it clear that the 11-year cycle is the magnetic cycle of the sun. It is only during the last few decades that major developments in plasma physics have at last given us the clue to the origins of the cycle and how the large explosions affecting the earth arise. Nature's Third Cycle discusses the fascinating science behind the sunspot cycle, and gives an insider's perspective of this cutting-edge scientific research from one of the leaders of the field.
Download or read book Astronomy written by Michael Zeilik and published by . This book was released on 1988-01-26 with total page 576 pages. Available in PDF, EPUB and Kindle. Book excerpt: This new edition of the classic astronomy text contains new information on the Voyager 2 mission to Uranus, Halley's Comet, superclusters and voids, and the inflationary universe model. Other new material covers image processing, solar activity and seismic studies, and high-energy astrophysics. Chapters have been carefully revised and there is much new artwork. Style is informal and non-mathematical, and development of the material progresses smoothly from the concrete to the abstract. The main theme of cosmic evolution and the sub-theme of scientific model-building are carried through the book's four parts: a history of cosmology, the solar system, stars and steller systems, and current speculations. Chapters include new lists of key terms, new problems incorporating algebra, and multiple-choice questions keyed to learning-objectives. A seasonal star chart has also been added.
