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Title: CO-ORBITAL OLIGARCHY

Abstract

We present a systematic examination of the changes in semimajor axis of a protoplanet as it interacts with other protoplanets in the presence of eccentricity dissipation. For parameters relevant to the oligarchic stage of planet formation, dynamical friction keeps the typical eccentricities small and prevents orbit crossing. Interactions at impact parameters greater than several Hill radii cause the protoplanets to repel each other; if the impact parameter is instead much less than the Hill radius, the protoplanets shift slightly in semimajor axis but remain otherwise unperturbed. If the orbits of two or more protoplanets are separated by less than a Hill radius, they are each pushed toward an equilibrium spacing between their neighbors and can exist as a stable co-orbital system. In the shear-dominated oligarchic phase of planet formation, we show that the feeding zones contain several oligarchs instead of only one. Growth of the protoplanets in the oligarchic phase drives the disk to an equilibrium configuration that depends on the mass ratio of protoplanets to planetesimals, {sigma}/{sigma}. Early in the oligarchic phase, when {sigma}/{sigma} is low, the spacing between rows of co-orbital oligarchs are about 5 Hill radii wide, rather than the 10 Hill radii cited in the literature.more » It is likely that at the end of oligarchy, the average number of co-orbital oligarchs is greater than unity. In the outer solar system, this raises the disk mass required to form the ice giants. In the inner solar system, this lowers the mass of the final oligarchs and requires more giant impacts than previously estimated. This result provides additional evidence that Mars is not an untouched leftover from the oligarchic phase, but must be composed of several oligarchs assembled through giant impacts.« less

Authors:
;  [1]
  1. California Institute of Technology, MC 130-33, Pasadena, CA 91125 (United States)
Publication Date:
OSTI Identifier:
21269239
Resource Type:
Journal Article
Journal Name:
Astronomical Journal (New York, N.Y. Online)
Additional Journal Information:
Journal Volume: 137; Journal Issue: 4; Other Information: DOI: 10.1088/0004-6256/137/4/3778; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1538-3881
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; 99 GENERAL AND MISCELLANEOUS//MATHEMATICS, COMPUTING, AND INFORMATION SCIENCE; EQUILIBRIUM; ICE; IMPACT PARAMETER; MASS; ORBITS; PLANETS; PROTOPLANETS; SATELLITES; SOLAR SYSTEM

Citation Formats

Collins, Benjamin F, and Sari, Re'em. CO-ORBITAL OLIGARCHY. United States: N. p., 2009. Web. doi:10.1088/0004-6256/137/4/3778; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
Collins, Benjamin F, & Sari, Re'em. CO-ORBITAL OLIGARCHY. United States. https://doi.org/10.1088/0004-6256/137/4/3778; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)
Collins, Benjamin F, and Sari, Re'em. 2009. "CO-ORBITAL OLIGARCHY". United States. https://doi.org/10.1088/0004-6256/137/4/3778; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA).
@article{osti_21269239,
title = {CO-ORBITAL OLIGARCHY},
author = {Collins, Benjamin F and Sari, Re'em},
abstractNote = {We present a systematic examination of the changes in semimajor axis of a protoplanet as it interacts with other protoplanets in the presence of eccentricity dissipation. For parameters relevant to the oligarchic stage of planet formation, dynamical friction keeps the typical eccentricities small and prevents orbit crossing. Interactions at impact parameters greater than several Hill radii cause the protoplanets to repel each other; if the impact parameter is instead much less than the Hill radius, the protoplanets shift slightly in semimajor axis but remain otherwise unperturbed. If the orbits of two or more protoplanets are separated by less than a Hill radius, they are each pushed toward an equilibrium spacing between their neighbors and can exist as a stable co-orbital system. In the shear-dominated oligarchic phase of planet formation, we show that the feeding zones contain several oligarchs instead of only one. Growth of the protoplanets in the oligarchic phase drives the disk to an equilibrium configuration that depends on the mass ratio of protoplanets to planetesimals, {sigma}/{sigma}. Early in the oligarchic phase, when {sigma}/{sigma} is low, the spacing between rows of co-orbital oligarchs are about 5 Hill radii wide, rather than the 10 Hill radii cited in the literature. It is likely that at the end of oligarchy, the average number of co-orbital oligarchs is greater than unity. In the outer solar system, this raises the disk mass required to form the ice giants. In the inner solar system, this lowers the mass of the final oligarchs and requires more giant impacts than previously estimated. This result provides additional evidence that Mars is not an untouched leftover from the oligarchic phase, but must be composed of several oligarchs assembled through giant impacts.},
doi = {10.1088/0004-6256/137/4/3778; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)},
url = {https://www.osti.gov/biblio/21269239}, journal = {Astronomical Journal (New York, N.Y. Online)},
issn = {1538-3881},
number = 4,
volume = 137,
place = {United States},
year = {Wed Apr 15 00:00:00 EDT 2009},
month = {Wed Apr 15 00:00:00 EDT 2009}
}