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The Early Evolution of Solids in Protoplanetary Disks By Carey Louise Weisberg Observations at millimeter wavelengths can directly probe the existence of mm/ cm-sized pebbles in the disks around forming stars and thereby reveal information about the dust evolution that leads to planet formation. 24 disks in the Upper Scorpius starforming region were observed at a wavelength of 2.87 mm with the Atacama Large Millimeter/Submillilmeter Array (ALMA) of radio antennas. Disk images were analyzed with the Common Astronomy Software Application (CASA) to determine the amount of radiation per unit area. By combining these observations with the detections obtained for the same disks at a wavelength of 0.88 mm, we measured for the first time the amount of radiation per unit wavelength of disks toward the end of their lifetime, i.e. 5-10 million years. This wavelength-dependence of dust emissivity depends on the size of the particles. Mm/cm-sized particles have been observed in the outer regions of younger disks. These observations will reveal whether these particles are still present near the end of a disk's lifetime, which would indicate that some kind of trapping mechanism is preventing them from accreting inwards.
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.
Is the Sun and its planetary system special? How did the Solar system form? Are there similar systems in the Galaxy? How common are habitable planets? What processes take place in the early life of stars and in their surrounding circumstellar disks that could impact whether life emerges or not? This book is based on the lectures by Philip Armitage and Wilhelm Kley presented at 45th Saas-Fee Advanced Course „From Protoplanetary Disks to Planet Formation“ of the Swiss Society for Astrophysics and Astronomy. The first part deals with the physical processes occurring in proto-planetary disks starting with the observational context, structure and evolution of the proto-planetary disk, turbulence and accretion, particle evolution and structure formation. The second part covers planet formation and disk-planet interactions. This includes in detail dust and planetesimal formation, growth to protoplanets, terrestrial planet formation, giant planet formation, migration of planets, multi-planet systems and circumbinary planets. As Saas-Fee advanced course this book offers PhD students an in-depth treatment of the topic enabling them to enter on a research project in the field.
Starburst regions in nearby and distant galaxies have a profound impact on our understanding of the early universe. This new, substantially updated and extended edition of Norbert Schulz’s unique book "From Dust to Stars" describes complex physical processes involved in the creation and early evolution of stars. It illustrates how these processes reveal themselves from radio wavelengths to high energy X-rays and gamma–rays, with special reference towards high energy signatures. Several sections devoted to key analysis techniques demonstrate how modern research in this field is pursued and new chapters are introduced on massive star formation, proto-planetary disks and observations of young exoplanets. Recent advances and contemporary research on the theory of star formation are explained, as are new observations, specifically from the three great observatories of the Spitzer Space Telescope, the Hubble Space Telescope and the Chandra X-Ray Observatory which all now operate at the same time and make high resolution space based observing in its prime. As indicated by the new title two new chapters have been included on proto-planetary disks and young exoplanets. Many more colour images illustrate attractive old and new topics that have evolved in recent years. The author gives updates in theory, fragmentation, dust, and circumstellar disks and emphasizes and strengthens the targeting of graduate students and young researchers, focusing more on computational approaches in this edition.
The first comprehensive overview of planet formation for students and researchers in astronomy, cosmochemistry, laboratory astrophysics and planetary sciences.
Starburst regions in nearby and distant galaxies have a profound impact on our understanding of the early universe. This new, substantially updated and extended edition of Norbert Schulz’s unique book "From Dust to Stars" describes complex physical processes involved in the creation and early evolution of stars. It illustrates how these processes reveal themselves from radio wavelengths to high energy X-rays and gamma–rays, with special reference towards high energy signatures. Several sections devoted to key analysis techniques demonstrate how modern research in this field is pursued and new chapters are introduced on massive star formation, proto-planetary disks and observations of young exoplanets. Recent advances and contemporary research on the theory of star formation are explained, as are new observations, specifically from the three great observatories of the Spitzer Space Telescope, the Hubble Space Telescope and the Chandra X-Ray Observatory which all now operate at the same time and make high resolution space based observing in its prime. As indicated by the new title two new chapters have been included on proto-planetary disks and young exoplanets. Many more colour images illustrate attractive old and new topics that have evolved in recent years. The author gives updates in theory, fragmentation, dust, and circumstellar disks and emphasizes and strengthens the targeting of graduate students and young researchers, focusing more on computational approaches in this edition.
The Early Earth: Accretion and Differentiation provides a multidisciplinary overview of the state of the art in understanding the formation and primordial evolution of the Earth. The fundamental structure of the Earth as we know it today was inherited from the initial conditions 4.56 billion years ago as a consequence of planetesimal accretion, large impacts among planetary objects, and planetary-scale differentiation. The evolution of the Earth from a molten ball of metal and magma to the tectonically active, dynamic, habitable planet that we know today is unique among the terrestrial planets, and understanding the earliest processes that led to Earth’s current state is the essence of this volume. Important results have emerged from a wide range of disciplines including cosmochemistry, geochemistry, experimental petrology, experimental and theoretical mineral physics and geodynamics. The topics in this volume include: Condensation of primitive objects in the solar nebula, planetary building blocks Early and late accretion and planetary dynamic modeling Primordial differentiation, core formation, Magma Ocean evolution and crystallization This volume will be a valuable resource for graduate students, academics, and researchers in the fields of geophysics, geochemistry, cosmochemistry, and planetary science.
Astronomy and Astrophysics Abstracts is devoted to the recording, summarizing and indexing of astronomical publications throughout the world. Two volumes are scheduled to appear per year. Volume 67 records 10,903 papers covering besides the classical fields of astronomy and astrophysics such matters as space flights related to astronomy, lunar and planetary probes and satellites, meteorites and interplanetary matter, X rays and cosmic rays, quasars and pulsars. The abstracts are classified under more than one hundred subject categories thus permitting quick surveying of the bulk of material published on the same topic within six months. For instance, this volume records 119 papers on minor planets, 155 papers on supernovae, and 554 papers on cosmology.