The Evolution Of Circumstellar Disks

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The Evolution Of Circumstellar Disks

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Author : Alexander Richert
language : en
Publisher:
Release Date : 2017

The Evolution Of Circumstellar Disks written by Alexander Richert and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.

Angular momentum conservation during protostellar collapse leads to long-lived, gas-rich circumstellar disks where planets form through the concentration of gas and dust by one or both of gravitational agglomeration and aerodynamic concentration of dust. In this dissertation, I summarize four projects aimed at understanding the evolution of planet-forming disks and the debris-dominated disks that remain after the primordial gas has been depleted. The first two projects make use of X-ray and near-infrared point source data to explore the longevity of young circumstellar disks, providing constraints on the timescales available for planet formation; the first is a study of disk depletion rates in 69 young stellar clusters, while the second examines the role of external photoevaporation by massive stars in accelerating disk depletion. Next, I discuss numerical simulations of planet--disk interactions in gas-rich, optically thick disks, with implications for the observability of newly-formed massive planets. Lastly, I present numerical simulations of gas--dust interactions in optically thin disks in order to explore their effect on disk morphology, with potential consequences for identifying embedded planets.

Structure And Evolution Of Circumstellar Disks A Spitzer View

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Author : Lucas Alejo Cieza-Gonzalez
language : en
Publisher:
Release Date : 2007

Structure And Evolution Of Circumstellar Disks A Spitzer View written by Lucas Alejo Cieza-Gonzalez and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Circumstellar matter categories.

This dissertation is the sum of five studies of the structure and evolution of circumstellar disks, the birthplace of planets. These studies are all based on Infrared data from the Spitzer Space Telescope, and taken together trace the evolution of disks from the optically thick primordial stage to the optically thin debris disk stage. The five projects included in this dissertation are diverse but they are all interconnected and have a common underlying motivation: to impose observational constraints on different aspects of planet formation theories. In the first project, we study the near and mid-IR (1.2-24 [mu]m) emission of Classical T Tauri Star (CTTS), which are low-mass pre-main sequence (PMS) stars that show clear evidence for accretion. We discuss the implications of our results on the structure of their inner disks and their estimated ages. In the second project, we study the incidence as a function of age of disks around weak-line T Tauri stars (low-mass PMS stars that are mostly coeval with CTTS but that do not show clear evidence for accretion) and explore the structure of these disks. We estimate the dissipation timescale of the planet-forming region of primordial disks and discuss the implications for planet formation theories. The third and fourth projects deal with the evolution of angular momentum of PMS stars. We search for observational evidence for the connection between stellar rotation and the presence of a disk predicted by the current disk-braking paradigm, according to which the rotational evolution of PMS stars is regulated through magnetic interactions between the stellar magnetosphere and the inner disk. The last project deals with debris disks, which are second-generation disks where the dust is continuously replenished by collisions between planetesimals. We search for debris disks in the far-IR (24-160 [mu]m) around a sample of Hyades Cluster members. We discuss the implications of our results on the evolution of debris disks and on the Late Heavy Bombardment in the Solar System.

Submillimeter Constraints On The Evolution Of Circumstellar Disks

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Author : Sean M. Andrews
language : en
Publisher:
Release Date : 2007

Submillimeter Constraints On The Evolution Of Circumstellar Disks written by Sean M. Andrews and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with Circumstellar matter categories.

High Angular Resolution Studies Of The Structure And Evolution Of Protoplanetary Disks

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Author : Joshua Eisner
language : en
Publisher: Universal-Publishers
Release Date : 2005

High Angular Resolution Studies Of The Structure And Evolution Of Protoplanetary Disks written by Joshua Eisner and has been published by Universal-Publishers this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with Science categories.

Young stars are surrounded by massive, rotating disks of dust and gas, which supply a reservoir of material that may be incorporated into planets or accreted onto the central star. In this dissertation, I use high angular resolution observations at a range of wavelengths to understand the structure, ubiquity, and evolutionary timescales of protoplanetary disks. First, I describe a study of Class I protostars, objects believed to be at an evolutionary stage between collapsing spherical clouds and fully-assembled young stars surrounded by protoplanetary disks. I use a Monte Carlo radiative transfer code to model new 0.9 micron scattered light images, 1.3 mm continuum images, and broadband spectral energy distributions. This modeling shows that Class I sources are probably surrounded by massive protoplanetary disks embedded in massive infalling envelopes. For the best-fitting models of the circumstellar dust distributions, I determine several important properties, including envelope and disk masses, mass infall rates, and system inclinations, and I use these results to constrain the evolutionary stage of these objects. Second, I discuss observations of the innermost regions of more evolved disks around T Tauri and Herbig Ae/Be stars, obtained with the Palomar Testbed and Keck Interferometers. I constrain the spatial and temperature structure of the circumstellar material at sub-AU radii, and demonstrate that lower-mass stars are surrounded by inclined disks with puffed-up inner edges 0.1-1 AU from the star. In contrast, the truncated inner disks around more massive stars may not puff-up, indicating that disk structure depends on stellar properties. I discuss the implications of these results for disk accretion, terrestrial planet formation and giant planet migration. Finally, I put these detailed studies of disk structure into a broader context by constraining the mass distribution and evolutionary timescales of circumstellar disks. Using the Owens Valley Millimeter Array, I mapped the millimeter continuum emission toward >300 low-mass stars in the NGC 2024 and Orion Nebula clusters. These observations demonstrate that the average disk mass in each cluster is comparable to the "minimum-mass protosolar nebula," and that there may be disk evolution on one million year timescales.

Evolution Of Circumstellar Disks In Binary Star Systems

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Author : Charles Guo
language : en
Publisher:
Release Date : 2015

Evolution Of Circumstellar Disks In Binary Star Systems written by Charles Guo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.

Physical Processes In Circumstellar Disks Around Young Stars

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Author : Paulo J. V. Garcia
language : en
Publisher: University of Chicago Press
Release Date : 2011-05-15

Physical Processes In Circumstellar Disks Around Young Stars written by Paulo J. V. Garcia and has been published by University of Chicago Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-05-15 with Science categories.

Circumstellar disks are vast expanses of dust that form around new stars in the earliest stages of their birth. Predicted by astronomers as early as the eighteenth century, they weren’t observed until the late twentieth century, when interstellar imaging technology enabled us to see nascent stars hundreds of light years away. Since then, circumstellar disks have become an area of intense study among astrophysicists, largely because they are thought to be the forerunners of planetary systems like our own—the possible birthplaces of planets. This volume brings together a team of leading experts to distill the most up-to-date knowledge of circumstellar disks into a clear introductory volume. Understanding circumstellar disks requires a broad range of scientific knowledge, including chemical processes, the properties of dust and gases, hydrodynamics and magnetohydrodynamics, radiation transfer, and stellar evolution—all of which are covered in this comprehensive work, which will be indispensable for graduate students, seasoned researchers, or even advanced undergrads setting out on the study of planetary evolution.

From Disks To Planets

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Author : Michel Blanc
language : en
Publisher: Springer
Release Date : 2019-01-30

From Disks To Planets written by Michel Blanc and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-01-30 with Science categories.

This volume discusses the evolutionary paths linking planets and their atmospheres to their origin within circumstellar disks. It reviews the main phases of this evolution, summarizes what we understand and what are the important open questions, and suggests ways towards solutions. Dust accretion within disks generates planet cores, while gas accretion on these cores leads to the diversity of their fluid envelopes. The formation of planetary proto-atmospheres and oceans is an essential product of planet formation. A fraction of the planets retain their primary proto-atmosphere, while others lose it and may form a “secondary” atmosphere. When the disk finally dissipates, it leaves us with the combination of a planetary system and a debris disk. Using the next generation of observing facilities, we will be able to reconstruct more accurately the evolutionary paths linking stellar genesis to the possible emergence of habitable worlds. Originally published in Space Science Reviews, Volume 205, Issue 1-4, December 2016

The Evolution Of Dust In The Terrestrial Planet Region Of Circumstellar Disks Around Young Stars

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Author : Diane Dutkevitch
language : en
Publisher:
Release Date : 1995

The Evolution Of Dust In The Terrestrial Planet Region Of Circumstellar Disks Around Young Stars written by Diane Dutkevitch and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1995 with Circumstellar matter categories.

Properties And Evolution Of Circumstellar Disks And Envelopes Around Young Low Mass Stars In The Taurus Star Forming Region

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Author : Elise Furlan
language : en
Publisher:
Release Date : 2006

Properties And Evolution Of Circumstellar Disks And Envelopes Around Young Low Mass Stars In The Taurus Star Forming Region written by Elise Furlan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2006 with categories.

Circumstellar Disk Structure And Evolution Through Resolved Submillimeter Observations

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Author : Alanna Meredith Hughes
language : en
Publisher:
Release Date : 2010

Circumstellar Disk Structure And Evolution Through Resolved Submillimeter Observations written by Alanna Meredith Hughes and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.

Circumstellar disks provide the reservoirs of raw material and determine conditions for the formation of nascent planetary systems. This thesis presents observations from millimeter-wavelength interferometers, particularly the Submillimeter Array, that address the following outstanding problems in the study of protoplanetary disks: (1) constraining the physical mechanisms driving the viscous transport of material through the disk, and (2) carrying out detailed studies of "transitional" objects between the gas-rich protoplanetary and tenuous, dusty debris disk phases to better understand how gas and dust are cleared from the system. We study accretion processes in three complementary ways: using spatially resolved observations of molecular gas lines at high spectral resolution to determine the magnitude and spatial distribution of turbulence in the disk; using polarimetry to constrain the magnetic properties of the outer disk in order to evaluate whether the MRI is a plausible origin for this turbulence and investigating the gas and dust distribution at the outer disk edge in the context of self-similar models of accretion disk structure and evolution. The studies of transition disks use spatially resolved observations to study the detailed structure of the gas and dust in systems that are currently in the process of clearing material. We obtain snapshots of the inside-out clearing of gas and dust in several systems, and compare our observations with the theoretical predictions generated for different disk clearing mechanisms. Our observations are generally consistent with the characteristics predicted for viscous transport driven by the magnetorotational instability and disk clearing accomplished through the dual action of giant planet formation and photoevaporation by energetic radiation from the star.