Aerodynamics of solid bodies in the solar nebula.

doi:10.1093/MNRAS/180.2.57

Journal Article•DOI•

Aerodynamics of solid bodies in the solar nebula.

Stuart J. Weidenschilling¹•Institutions (1)

01 Sep 1977-Monthly Notices of the Royal Astronomical Society (Oxford University Press)-Vol. 180, Iss: 2, pp 57-70

About: This article is published in Monthly Notices of the Royal Astronomical Society.The article was published on 1977-09-01 and is currently open access. It has received 2001 citations till now. The article focuses on the topics: Planetesimal & Formation and evolution of the Solar System.

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Journal Article•DOI•

Protoplanetary Disks and Their Evolution

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Jonathan Williams¹, Lucas A. Cieza¹•Institutions (1)

University of Hawaii¹

18 Aug 2011-Annual Review of Astronomy and Astrophysics

TL;DR: A review of the outer parts, beyond 1 AU, of protoplanetary disks with a focus on recent IR and (sub)millimeter results can be found in this paper.

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Abstract: Flattened, rotating disks of cool dust and gas extending for tens to hundreds of astronomical units are found around almost all low-mass stars shortly after their birth. These disks generally persist for several million years, during which time some material accretes onto the star, some is lost through outflows and photoevaporation, and some condenses into centimeter- and larger-sized bodies or planetesimals. Through observations mainly at IR through millimeter wavelengths, we can determine how common disks are at different ages; measure basic properties including mass, size, structure, and composition; and follow their varied evolutionary pathways. In this way, we see the first steps toward exoplanet formation and learn about the origins of the Solar System. This review addresses observations of the outer parts, beyond 1 AU, of protoplanetary disks with a focus on recent IR and (sub)millimeter results and an eye to the promise of new facilities in the immediate future.

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1,366 citations

Cites background or methods from "Aerodynamics of solid bodies in the..."

...Further, the fraction of disks with at least a MMSN, 10MJup, within 60AU is similar, ∼ 11 − 13%, in Taurus, Ophiuchus, and Orion and, incidentally, comparable to the detection rate of Jupiter mass extrasolar planets (Mann & Williams 2009b)....
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...As a fiducial comparison, we use the MinimumMass Solar Nebula (MMSN), the lowest mass primordial disk that formed the Solar System inferred from scaling planetary compositions to cosmic abundances at each orbital radius (Kusaka, Nakano & Hayashi 1970; Weidenschilling 1977)....
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...Andrews et al. (2009, 2010b) infer surface densities, Σ ≈ 10 − 100 g cm−2 at 20AU, in their sample of Ophiuchus disks that are in good agreement with the MMSN (Figure 2)....
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...For disks, β ≈ 1 so κ(1mm) = 0.03 cm2 g−1 which implies τ(1mm) = 1 at a surface density of Σ ≈ 30 g cm−2, corresponding to about 10AU in the MMSN (Davis 2005) and an angular scale of 0....
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...Andrews & Williams (2005) also show that for a 100AU disk with the mass and surface density profile of the MMSN, about one third of the emission by mass is optically thick at 850µm....
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Journal Article•DOI•

Rapid planetesimal formation in turbulent circumstellar disks

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Anders Johansen¹, Jeffrey S. Oishi², Jeffrey S. Oishi³, Mordecai-Mark Mac Low³, Mordecai-Mark Mac Low¹, Hubert Klahr¹, Thomas Henning¹, Andrew N. Youdin⁴ - Show less +4 more•Institutions (4)

Max Planck Society¹, University of Virginia², American Museum of Natural History³, University of Toronto⁴

30 Aug 2007-Nature

TL;DR: It is reported that boulders can undergo efficient gravitational collapse in locally overdense regions in the midplane of the disk, and it is found that gravitationally bound clusters form with masses comparable to dwarf planets and containing a distribution of boulder sizes.

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Abstract: During the initial stages of planet formation in circumstellar gas disks, dust grains collide and build up larger and larger bodies. How this process continues from metre-sized boulders to kilometre-scale planetesimals is a major unsolved problem: boulders are expected to stick together poorly, and to spiral into the protostar in a few hundred orbits owing to a 'headwind' from the slower rotating gas. Gravitational collapse of the solid component has been suggested to overcome this barrier. But even low levels of turbulence will inhibit sedimentation of solids to a sufficiently dense midplane layer, and turbulence must be present to explain observed gas accretion in protostellar disks. Here we report that boulders can undergo efficient gravitational collapse in locally overdense regions in the midplane of the disk. The boulders concentrate initially in transient high pressure regions in the turbulent gas, and these concentrations are augmented a further order of magnitude by a streaming instability driven by the relative flow of gas and solids. We find that gravitationally bound clusters form with masses comparable to dwarf planets and containing a distribution of boulder sizes. Gravitational collapse happens much faster than radial drift, offering a possible path to planetesimal formation in accreting circumstellar disks.

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1,238 citations

Journal Article•DOI•

Protoplanet Migration by Nebula Tides

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William R. Ward¹•Institutions (1)

California Institute of Technology¹

01 Apr 1997-Icarus

1,086 citations

Journal Article•DOI•

A terrestrial planet candidate in a temperate orbit around Proxima Centauri

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Guillem Anglada-Escudé¹, Pedro J. Amado², John R. Barnes³, Z. M. Berdiñas², R. Paul Butler⁴, Gavin A. L. Coleman¹, Ignacio de la Cueva, Stefan Dreizler⁵, Michael Endl⁶, Benjamin Giesers⁵, Sandra V. Jeffers⁵, James S. Jenkins⁷, Hugh R. A. Jones⁸, Marcin Kiraga⁹, Martin Kürster¹⁰, Marίa J. López-González², Christopher Marvin⁵, Nicolás Morales², Julien Morin¹¹, Richard P. Nelson¹, Jose Luis Ortiz², Aviv Ofir¹², Sijme-Jan Paardekooper¹, Ansgar Reiners⁵, E. Rodriguez², Cristina Rodrίguez-López², L. F. Sarmiento⁵, J. B. P. Strachan¹, Yiannis Tsapras¹³, Mikko Tuomi⁸, Mathias Zechmeister⁵ - Show less +27 more•Institutions (13)

Queen Mary University of London¹, Spanish National Research Council², Open University³, Carnegie Institution for Science⁴, University of Göttingen⁵, University of Texas at Austin⁶, University of Chile⁷, University of Hertfordshire⁸, University of Warsaw⁹, Max Planck Society¹⁰, University of Montpellier¹¹, Weizmann Institute of Science¹², Heidelberg University¹³

25 Aug 2016-Nature

TL;DR: Observations reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units.

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Abstract: At a distance of 1.295 parsecs, the red dwarf Proxima Centauri (α Centauri C, GL 551, HIP 70890 or simply Proxima) is the Sun's closest stellar neighbour and one of the best-studied low-mass stars. It has an effective temperature of only around 3,050 kelvin, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun and a mass of about 12 per cent of the mass of the Sun. Although Proxima is considered a moderately active star, its rotation period is about 83 days (ref. 3) and its quiescent activity levels and X-ray luminosity are comparable to those of the Sun. Here we report observations that reveal the presence of a small planet with a minimum mass of about 1.3 Earth masses orbiting Proxima with a period of approximately 11.2 days at a semi-major-axis distance of around 0.05 astronomical units. Its equilibrium temperature is within the range where water could be liquid on its surface.

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1,052 citations

Journal Article•DOI•

The Growth Mechanisms of Macroscopic Bodies in Protoplanetary Disks

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Jürgen Blum¹, Gerhard Wurm²•Institutions (2)

Braunschweig University of Technology¹, University of Münster²

15 Aug 2008-Annual Review of Astronomy and Astrophysics

TL;DR: In this article, a review examines the experimental achievements and puts them into the context of the dust processes in protoplanetary disks, concluding that the formation of planetesimals starts with the growth of fractal dust aggregates, followed by compaction processes.

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Abstract: The formation of planetesimals, the kilometer-sized planetary precursors, is still a puzzling process. Considerable progress has been made over the past years in the physical description of the first stages of planetesimal formation, owing to extensive laboratory work. This review examines the experimental achievements and puts them into the context of the dust processes in protoplanetary disks. It has become clear that planetesimal formation starts with the growth of fractal dust aggregates, followed by compaction processes. As the dust-aggregate sizes increase, the mean collision velocity also increases, leading to the stalling of the growth and possibly to fragmentation, once the dust aggregates have reached decimeter sizes. A multitude of hypotheses for the further growth have been proposed, such as very sticky materials, secondary collision processes, enhanced growth at the snow line, or cumulative dust effects with gravitational instability. We will also critically review these ideas.

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892 citations

Cites background from "Aerodynamics of solid bodies in the..."

...…to the gas motion the dust particles are, they always possess a relative velocity to the gas, caused either by Brownian motion (for very small dust grains), by a systematic motion due to vertical settling or due to the sub-Keplerian motion of the gas, or by gas turbulence (Weidenschilling 1977)....
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...Hence, differential settling is not the main driver for mutual collisions among the grains (Weidenschilling 1977)....
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...However done, the formation of kilometer-sized planetesimals has to happen fast, as large bodies possess a rather short lifetime owing to their effective inward drift motion (Weidenschilling 1977)....
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Aerodynamics of solid bodies in the solar nebula.

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