A Caltech Library Service

Formation of Kuiper Belt binaries

Schlichting, Hilke E. and Sari, Re'em (2008) Formation of Kuiper Belt binaries. Astrophysical Journal, 673 (2). pp. 1218-1224. ISSN 0004-637X. doi:10.1086/524930.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


The discovery that a substantial fraction of Kuiper Belt objects (KBOs) exists in binaries with wide separations and roughly equal masses has motivated a variety of new theories explaining their formation. Goldreich and colleagues proposed two formation scenarios: In the first, a transient binary is formed, which becomes bound with the aid of dynamical friction from the sea of small bodies (L^2s mechanism); in the second, a binary is formed by three-body gravitational deflection (L^3 mechanism). Here, we accurately calculate the L^2s and L^3 formation rates for sub-Hill velocities. While the L^2s formation rate is close to previous order of magnitude estimates, the L^3 formation rate is about a factor of 4 smaller. For sub-Hill KBO velocities (v >> v_H) the ratio of the L^3 to the L^2s formation rate is 0.05(v/vH) , independent of the small bodies' velocity dispersion, their surface density, or their mutual collisions. For super-Hill velocities (v>>v_H) the L^3 mechanism dominates over the L^2s mechanism. Binary formation via the L^3 mechanism competes with binary destruction by passing bodies. Given sufficient time, a statistical equilibrium abundance of binaries forms. We show that the frequency of long-lived transient binaries drops exponentially with the system's lifetime and that such transient binaries are not important for binary formation via the L^3 mechanism, contrary to Lee and colleagues. For the L^2s mechanism we find that the typical time that transient binaries must last to form Kuiper Belt binaries (KBBs) for a given strength of dynamical friction, D, increases only logarithmically with D. Longevity of transient binaries (with lifetimes 15Ω^−1 as suggested by Astakhov and colleagues) only becomes important for very weak dynamical friction (i.e., D ≾ 0.002) and is most likely not crucial for KBB formation.

Item Type:Article
Related URLs:
URLURL TypeDescription
Sari, Re'em0000-0002-1084-3656
Additional Information:© 2008 The American Astronomical Society. Received 2007 July 19, accepted for publication 2007 October 25. We thank Peter Goldreich for stimulating discussions and the anonymous referee for valuable comments that helped to clarify the manuscript. 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.
Funding AgencyGrant Number
Alfred P. Sloan FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:Kuiper Belt; planets and satellites: formation
Issue or Number:2
Record Number:CaltechAUTHORS:20090515-093133125
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:14234
Deposited By: Joy Painter
Deposited On:13 Aug 2009 23:08
Last Modified:08 Nov 2021 22:44

Repository Staff Only: item control page