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The ratio of retrograde to prograde orbits: a test for Kuiper Belt binary formation theories

Schlichting, Hilke E. and Sari, Re'em (2008) The ratio of retrograde to prograde orbits: a test for Kuiper Belt binary formation theories. Astrophysical Journal, 686 (1). pp. 741-747. ISSN 0004-637X.

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With the discovery of Kuiper Belt binaries that have wide separations and roughly equal masses, new theories were proposed to explain their formation. Two formation scenarios were suggested by Goldreich and collaborators. In the first, dynamical friction generated by a sea of small bodies enables a transient binary to become bound (the L^2s mechanism); in the second, a transient binary gets bound by an encounter with a third body (the L^3 mechanism). We show that these different binary formation scenarios leave their own unique signatures in the relative abundance of prograde to retrograde binary orbits. This signature is due to the fact that stable retrograde orbits can exist much further out in the Hill sphere than prograde orbits. This provides an excellent opportunity to distinguish between the different binary formation scenarios observationally. We predict that if binary formation proceeded while sub-Hill velocities prevailed, the vast majority of all binaries with comparable masses would have retrograde orbits. This dominance of retrograde binary orbits is a result of binary formation via the L^2s mechanism, or any other mechanism that dissipates energy in a smooth and gradual manner. For super-Hill velocities, binary formation proceeds via the L^3 mechanism, which produces a roughly equal number of prograde and retrograde binaries. These predictions assume that subsequent orbital evolution due to dynamical friction and dynamical stirring of the Kuiper Belt did not alter the sense of the binary orbit after formation.

Item Type:Article
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Sari, Re'em0000-0002-1084-3656
Additional Information:© 2008 The American Astronomical Society. Received 2008 February 29; accepted 2008 June 12. Some of the numerical calculations presented here were performed on Caltech’s Division of Geological and Planetary Sciences Dell cluster. R. S. is an Alfred P. Sloan Fellow and a Packard Fellow. This research was partially supported by the ERC.
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European Research CouncilUNSPECIFIED
Subject Keywords:Kuiper belt; planets and satellites: formation
Issue or Number:1
Record Number:CaltechAUTHORS:SCHLapj08b
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13410
Deposited By: Tony Diaz
Deposited On:08 May 2009 20:55
Last Modified:03 Mar 2020 13:01

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