Observational Signatures From Self Gravitating Protostellar Disks

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Observational Signatures from Self-gravitating Protostellar Disks

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Author : Alexander Leonard DeSouza
Publisher :
ISBN 13 :
Total Pages : 232 pages
Book Rating : 4.:/5 (17 download)

Book Synopsis Observational Signatures from Self-gravitating Protostellar Disks by : Alexander Leonard DeSouza

Download or read book Observational Signatures from Self-gravitating Protostellar Disks written by Alexander Leonard DeSouza and published by . This book was released on 2014 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Protostellar disks are the ubiquitous corollary outcome of the angular momentum con-serving, gravitational collapse of molecular cloud cores into stars. Disks are an essential component of the star formation process, mediating the accretion of material onto the pro-tostar, and redistributing excess angular momentum during the collapse. We present a model to explain the observed correlation between mass accretion rates Ṁ and stellar mass M ∗ that has been inferred from the observations of intermediate to upper mass T Tauri stars--that is Ṁ ∝ M 1 . 3 ± 0 . 3 ∗ . We explain this correlation within the framework of gravit ationally driven torques parameterized in terms of Toomre's Q criterion. Our models reproduce both the ob- served correlation and spread in the Ṁ − M ∗ relation as has been observed for protostars with masses of 0 . 2 M ⊙ ≤ M ∗ ≤ 3 . 0 M ⊙ , such as those found in the Ophiuchus and Taurus star forming regions. We also examine the formation and long-term evolution of pri mordial protostellar disks har- bored by the first stars (Population III stars), using 2+1D nu merical hydrodynamics simulations in the thin-disk limit. The disks that form in the primordial environment are very massive and subject to vigorous fragmentation. Fragments torqued inward due to gravitational interactions with sub-structure within the disk give rise to accretion an d luminosity bursts several orders of magnitude above the mean rate--the first evidence for the burs t mode of accretion among Pop- ulation III stars. By considering the cosmological landscape in this epoch, we argue from the Jeans criterion for the existence of clusters of Population III stars. A simultaneity of burst mode accretion events among several cluster members results in fluctuations that are nearly 1000 × greater than the mean cluster luminosity, resulting in a total luminosity above 10 8 L ⊙ . This phenomenon arises solely as a result of the gravitational-instability-driven episodic fragmen- tation and accretion that characterizes this early stage of protostellar evolution. We speculate as to how these extrema may provide a window through which next-generation telescopes will be able to gather observational evidence for the existence of the first stars.

Using Numerical Simulations to Identify Observational Signatures of Self-gravitating Protostellar Discs

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Author : Cassandra Hall
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)

Book Synopsis Using Numerical Simulations to Identify Observational Signatures of Self-gravitating Protostellar Discs by : Cassandra Hall

Download or read book Using Numerical Simulations to Identify Observational Signatures of Self-gravitating Protostellar Discs written by Cassandra Hall and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Probing Self-gravitating Protostellar Discs Using Smoothed Particle Hydrodynamics and Radiative Transfer

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Author : Duncan Hugh Forgan
Publisher :
ISBN 13 :
Total Pages : 263 pages
Book Rating : 4.:/5 (781 download)

Book Synopsis Probing Self-gravitating Protostellar Discs Using Smoothed Particle Hydrodynamics and Radiative Transfer by : Duncan Hugh Forgan

Download or read book Probing Self-gravitating Protostellar Discs Using Smoothed Particle Hydrodynamics and Radiative Transfer written by Duncan Hugh Forgan and published by . This book was released on 2011 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stars are likely to form with non-zero initial angular momentum, and will consequently possess a substantial gaseous protostellar disc in the early phases of their evolution. At this early stage, the disc mass is expected to be comparable to the mass of the protostar. The disc's self-gravity therefore plays an important role in the subsequent evolution of the system, regulating the accretion of matter onto the protostar, as well as being potentially capable of forming low mass stars and massive planets by disc fragmentation. The protostellar disc may later evolve into a protoplanetary disc, providing the feedstock for planet formation. Therefore, if the current stellar populations and exoplanetary systems are to be understood, an understanding of the evolution of protostellar discs is crucial, especially their earliest self-gravitating phases. I have used various methods of numerical simulation to probe the physics of self-gravitating protostellar discs and their constituents. When constructing a model for self-gravitating protostellar discs, including detailed thermodynamics and radiative transfer is essential. I have developed two distinct numerical techniques for incorporating radiative transfer into Smoothed Particle Hydrodynamics (SPH) simulations. The first allows the modelling of frequency-averaged radiative transfer during the SPH simulation, in effect approximating radiative SPH (RSPH) with only a marginal increase in runtime (around 6%). The second takes the output from SPH simulations, and creates synthetic, wavelength-dependent telescope images and spectra of SPH systems. This allows the direct construction of observables from SPH simulations, providing, for the first time, a direct connection between the output of SPH simulations and observations. I have used these numerical methods to analyse, in detail, the local angular momentum transport induced by self-gravity in protostellar discs, testing the robustness of the "pseudo-viscous" analytical approximation for local disc stresses. I confirm that semi-analytical disc modellers are justified in using the pseudo-viscous approximation in some cases, but I also outline the limits in which non-local transport effects causes the approximation to fail. Also, I have investigated the evolution of protostellar discs when perturbed by a secondary companion, in particular identifying whether such events will in general trigger a) a disc fragmentation event, or b) a stellar outburst event. For case a), I found no significant evidence that perturbation by a companion improves the possibility of disc fragmentation in compact discs - in case b), I found that stellar outburst events do indeed occur, but they are unlikely to be seen by observers due to their rare occurrence, as well as due to self-obscuration effects.

Theory of Accretion Disks

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Author : F. Meyer
Publisher : Springer Science & Business Media
ISBN 13 : 9400910371
Total Pages : 471 pages
Book Rating : 4.4/5 (9 download)

Book Synopsis Theory of Accretion Disks by : F. Meyer

Download or read book Theory of Accretion Disks written by F. Meyer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 471 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the advent of space observatories and modern developments in ground based astronomy and concurrent progress in the theoretical understanding of these observations it has become clear that accretion of material on to compact objects is an ubiquitous mechanism powering very diverse astrophysical sources ranging in size and luminosity by many orders of magnitude. A problem common to these systems is that the material accreted must in general get rid of its angular momentum and this leads to the formation of an Accretion Disk which allows angular momentum re-distribution and converts potential energy into radiation with an efficiency which can be higher than the nuclear burning yield. These systems range in size from quasars and active galactic nuclei to accretion disks around forming stars and the early solar system and to compact binaries such as cataclysmic variables and low-mass X-ray binaries. Other objects that should be mentioned in this context are 88433, the black hole binary candidates, and possibly gamma-ray burst sources. Observations of these systems have provided important constraints for theoretical accretion disk models on widely differing scales, lumi nosities, mass-transfer rates and physical environments.

Protostars and Planets V

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Author : Bo Reipurth
Publisher : University of Arizona Press
ISBN 13 : 9780816526543
Total Pages : 994 pages
Book Rating : 4.5/5 (265 download)

Book Synopsis Protostars and Planets V by : Bo Reipurth

Download or read book Protostars and Planets V written by Bo Reipurth and published by University of Arizona Press. This book was released on 2007 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'Protostars and Planets V' builds on the latest results from recent advances in ground and space-based astronomy and in numerical computing techniques to offer the most detailed and up-to-date picture of star and planet formation - including the formation and early evolution of our own solar system.

Dynamics of Astrophysical Discs

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Author : J. A. Sellwood
Publisher : Cambridge University Press
ISBN 13 : 9780521548144
Total Pages : 280 pages
Book Rating : 4.5/5 (481 download)

Book Synopsis Dynamics of Astrophysical Discs by : J. A. Sellwood

Download or read book Dynamics of Astrophysical Discs written by J. A. Sellwood and published by Cambridge University Press. This book was released on 2004-01-22 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Covers recent developments in both theory and observations of discs in a wide variety of astrophysical contexts. The volume is based on a conference held at the University of Manchester in 1988, which brought together an international group of experts in a wide range of fields. The papers cover planetary ring systems, discs in star-forming regions, protoplanetary discs, accretion and galaxy discs--areas related by the remarkable similarity between the dynamical problems posed by each type of disc. This will be a valuable reference work for researchers and postgraduate students in many branches of astronomy.

Formation, Evolution, and Dynamics of Young Solar Systems

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Author : Martin Pessah
Publisher : Springer
ISBN 13 : 3319606093
Total Pages : 383 pages
Book Rating : 4.3/5 (196 download)

Book Synopsis Formation, Evolution, and Dynamics of Young Solar Systems by : Martin Pessah

Download or read book Formation, Evolution, and Dynamics of Young Solar Systems written by Martin Pessah and published by Springer. This book was released on 2017-12-04 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book's interdisciplinary scope aims at bridging various communities: 1) cosmochemists, who study meteoritic samples from our own solar system, 2) (sub-) millimetre astronomers, who measure the distribution of dust and gas of star-forming regions and planet-forming discs, 3) disc modellers, who describe the complex photo-chemical structure of parametric discs to fit these to observation, 4) computational astrophysicists, who attempt to decipher the dynamical structure of magnetised gaseous discs, and the effects the resulting internal structure has on the aerodynamic re-distribution of embedded solids, 5) theoreticians in planet formation theory, who aim to piece it all together eventually arriving at a coherent holistic picture of the architectures of planetary systems discovered by 6) the exoplanet observers, who provide us with unprecedented samples of exoplanet worlds. Combining these diverse fields the book sheds light onto the riddles that research on planet formation is currently confronted with, and paves the way for a comprehensive understanding of the formation, evolution, and dynamics of young solar systems. The chapters ‘Chondrules – Ubiquitous Chondritic Solids Tracking the Evolution of the Solar Protoplanetary Disk’, ‘Dust Coagulation with Porosity Evolution’ and ‘The Emerging Paradigm of Pebble Accretion’ are published open access under a CC BY 4.0 license via link.springer.com.

International Aerospace Abstracts

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Author :
Publisher :
ISBN 13 :
Total Pages : 940 pages
Book Rating : 4.3/5 (91 download)

Book Synopsis International Aerospace Abstracts by :

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1996 with total page 940 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Physics of Gravitating Systems I

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Author : A.M. Fridman
Publisher : Springer Science & Business Media
ISBN 13 : 364287830X
Total Pages : 480 pages
Book Rating : 4.6/5 (428 download)

Book Synopsis Physics of Gravitating Systems I by : A.M. Fridman

Download or read book Physics of Gravitating Systems I written by A.M. Fridman 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: It would seem that any specialist in plasma physics studying a medium in which the interaction between particles is as distance-dependent as the inter action between stars and other gravitating masses would assert that the role of collective effects in the dynamics of gravitating systems must be decisive. However, among astronomers this point of view has been recog nized only very recently. So, comparatively recently, serious consideration has been devoted to theories of galactic spiral structure in which the dominant role is played by the orbital properties of individual stars rather than collec tive effects. In this connection we would like to draw the reader's attention to a difference in the scientific traditions of plasma physicists and astrono mers, whereby the former have explained the delay of the onset of controlled thermonuclear fusion by the "intrigues" of collective processes in the plasma, while many a generation of astronomers were calculating star motions, solar and lunar eclipses, and a number of other fine effects for many years ahead by making excellent use of only the laws of Newtonian mechanics. Therefore, for an astronomer, it is perhaps not easy to agree with the fact that the evolution of stellar systems is controlled mainly by collective effects, and the habitual methods of theoretical mechanics III astronomy must make way for the method of self-consistent fields.

The Exoplanet Handbook

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Author : Michael Perryman
Publisher : Cambridge University Press
ISBN 13 : 1108329667
Total Pages : 973 pages
Book Rating : 4.1/5 (83 download)

Book Synopsis The Exoplanet Handbook by : Michael Perryman

Download or read book The Exoplanet Handbook written by Michael Perryman and published by Cambridge University Press. This book was released on 2018-08-30 with total page 973 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the discovery of planets beyond our solar system 25 years ago, exoplanet research has expanded dramatically, with new state-of-the-art ground-based and space-based missions dedicated to their discovery and characterisation. With more than 3,500 exoplanets now known, the complexity of the discovery techniques, observations and physical characterisation have grown exponentially. This Handbook ties all these avenues of research together across a broad range of exoplanet science. Planet formation, exoplanet interiors and atmospheres, and habitability are discussed, providing in-depth coverage of our knowledge to date. Comprehensively updated from the first edition, it includes instrumental and observational developments, in-depth treatment of the new Kepler mission results and hot Jupiter atmospheric studies, and major updates on models of exoplanet formation. With extensive references to the research literature and appendices covering all individual exoplanet discoveries, it is a valuable reference to this exciting field for both incoming and established researchers.

Astrophysics of Planet Formation

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Author : Philip J. Armitage
Publisher : Cambridge University Press
ISBN 13 : 1108356117
Total Pages : 345 pages
Book Rating : 4.1/5 (83 download)

Book Synopsis Astrophysics of Planet Formation by : Philip J. Armitage

Download or read book Astrophysics of Planet Formation written by Philip J. Armitage and published by Cambridge University Press. This book was released on 2020-01-30 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt: Concise and self-contained, this textbook gives a graduate-level introduction to the physical processes that shape planetary systems, covering all stages of planet formation. Writing for readers with undergraduate backgrounds in physics, astronomy, and planetary science, Armitage begins with a description of the structure and evolution of protoplanetary disks, moves on to the formation of planetesimals, rocky, and giant planets, and concludes by describing the gravitational and gas dynamical evolution of planetary systems. He provides a self-contained account of the modern theory of planet formation and, for more advanced readers, carefully selected references to the research literature, noting areas where research is ongoing. The second edition has been thoroughly revised to include observational results from NASA's Kepler mission, ALMA observations and the JUNO mission to Jupiter, new theoretical ideas including pebble accretion, and an up-to-date understanding in areas such as disk evolution and planet migration.

Planets in Binary Star Systems

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Author : Nader Haghighipour
Publisher : Springer Science & Business Media
ISBN 13 : 9048186870
Total Pages : 334 pages
Book Rating : 4.0/5 (481 download)

Book Synopsis Planets in Binary Star Systems by : Nader Haghighipour

Download or read book Planets in Binary Star Systems written by Nader Haghighipour and published by Springer Science & Business Media. This book was released on 2010-06-03 with total page 334 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 1988, in an article on the analysis of the measurements of the variations in the radial velocities of a number of stars, Campbell, Walker, and Yang reported an - teresting phenomenon;the radial velocity variations of Cephei seemed to suggest the existence of a Jupiter-like planet around this star. This was a very exciting and, at the same time, very surprising discovery. It was exciting because if true, it would have marked the detection of the ?rst planet outside of our solar system. It was surprising because the planet-hosting star is the primary of a binary system with a separation less than 19 AU, a distance comparable to the planetary distances in our solar system. The moderatelyclose orbit of the stellar companionof Cephei raised questions about the reality of its planet. The skepticism over the interpretation of the results (which was primarily based on the idea that binary star systems with small sepa- tions would not be favorable places for planet formation) became so strong that in a subsequent paper in 1992, Walker and his colleagues suggested that the planet in the Cephei binary might not be real, and the variations in the radial velocity of this star might have been due to its chromospheric activities.

Dust-Gas Instabilities in Protoplanetary Disks

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Author : Ryosuke Tominaga
Publisher : Springer
ISBN 13 : 9789811917677
Total Pages : 0 pages
Book Rating : 4.9/5 (176 download)

Book Synopsis Dust-Gas Instabilities in Protoplanetary Disks by : Ryosuke Tominaga

Download or read book Dust-Gas Instabilities in Protoplanetary Disks written by Ryosuke Tominaga and published by Springer. This book was released on 2023-04-27 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: How planets form is one of the long-standing questions in astrophysics. In particular, formation scenarios of planetesimals which are kilometer-sized bodies and a precursor of planets are still unclear and under debate although some promising mechanisms have been proposed. This book highlight disk instabilities that have the potential to explain the origin of planetesimals. Using linear analyses and numerical simulations, it addresses how a disk evolves through the development of instabilities, and also presents a new instability driven by dust coagulation. As a result, the simulation demonstrates a scenario of planetesimal formation: A successive development of multiple instabilities triggers planetesimal formation in resulting dusty rings.

Stars and Stellar Processes

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Author : Mike Guidry
Publisher : Cambridge University Press
ISBN 13 : 1107197880
Total Pages : 573 pages
Book Rating : 4.1/5 (71 download)

Book Synopsis Stars and Stellar Processes by : Mike Guidry

Download or read book Stars and Stellar Processes written by Mike Guidry and published by Cambridge University Press. This book was released on 2019-02-07 with total page 573 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents the physics of stars in relation to modern topics such as neutrino oscillations, supernovae, black holes, and gravitational waves.

Planetary Astrobiology

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Author : Victoria Meadows
Publisher : University of Arizona Press
ISBN 13 : 0816540063
Total Pages : 593 pages
Book Rating : 4.8/5 (165 download)

Book Synopsis Planetary Astrobiology by : Victoria Meadows

Download or read book Planetary Astrobiology written by Victoria Meadows and published by University of Arizona Press. This book was released on 2020-07-07 with total page 593 pages. Available in PDF, EPUB and Kindle. Book excerpt: Are we alone in the universe? How did life arise on our planet? How do we search for life beyond Earth? These profound questions excite and intrigue broad cross sections of science and society. Answering these questions is the province of the emerging, strongly interdisciplinary field of astrobiology. Life is inextricably tied to the formation, chemistry, and evolution of its host world, and multidisciplinary studies of solar system worlds can provide key insights into processes that govern planetary habitability, informing the search for life in our solar system and beyond. Planetary Astrobiology brings together current knowledge across astronomy, biology, geology, physics, chemistry, and related fields, and considers the synergies between studies of solar systems and exoplanets to identify the path needed to advance the exploration of these profound questions. Planetary Astrobiology represents the combined efforts of more than seventy-five international experts consolidated into twenty chapters and provides an accessible, interdisciplinary gateway for new students and seasoned researchers who wish to learn more about this expanding field. Readers are brought to the frontiers of knowledge in astrobiology via results from the exploration of our own solar system and exoplanetary systems. The overarching goal of Planetary Astrobiology is to enhance and broaden the development of an interdisciplinary approach across the astrobiology, planetary science, and exoplanet communities, enabling a new era of comparative planetology that encompasses conditions and processes for the emergence, evolution, and detection of life.

Protostars and Planets VI

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Author : Henrik Beuther
Publisher : University of Arizona Press
ISBN 13 : 0816531242
Total Pages : 945 pages
Book Rating : 4.8/5 (165 download)

Book Synopsis Protostars and Planets VI by : Henrik Beuther

Download or read book Protostars and Planets VI written by Henrik Beuther and published by University of Arizona Press. This book was released on 2014-12-18 with total page 945 pages. Available in PDF, EPUB and Kindle. Book excerpt: Proceedings of a conference held in Heidelberg, Germany, July 15-20, 2013.

Circumstellar Disks, Outflows and Star Formation

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Author :
Publisher :
ISBN 13 :
Total Pages : 416 pages
Book Rating : 4.F/5 ( download)

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Download or read book Circumstellar Disks, Outflows and Star Formation written by and published by . This book was released on 1995 with total page 416 pages. Available in PDF, EPUB and Kindle. Book excerpt: