Quasi-Hilda comet 147P/Kushida-Muramatsu

Another long temporary satellite capture by Jupiter

¹ Tokyo Meteor Network, Daisawa 1–27–5, Setagaya-ku, Tokyo 155–0032, Japan e-mail: ohtsuka@jb3.so-net.ne.jp
² National Astronomical Observatory of Japan, Osawa 2–21–1, Mitaka, Tokyo 181–8588, Japan
³ JAXA, Yoshinodai 3–1–1, Sagamihara, Kanagawa 229–8510, Japan
⁴ Armagh Observatory, College Hill, Armagh, BT61 9DG, UK
⁵ Waseda University, Nishi-Waseda 1–6–1, Shinjuku-ku, Tokyo 169–8050, Japan

Received: 3 June 2008
Accepted: 10 August 2008

Abstract

Context. The quasi-Hilda comets (QHCs), being in unstable 3:2 Jovian mean motion resonance, are considered a major cause of temporary satellite capture (TSC) by Jupiter. Although the QHCs may be escaped Hilda asteroids, their origin and nature have not yet been studied in sufficient detail. Of particular interest are long TSCs/orbiters. Orbiters – in which at least one full revolution about the planet is completed – are rare astronomical events, because only four have been known to occur in the last several decades. Every case has been associated with a QHC: 82P/Gehrels 3, 111P/Helin-Roman-Crockett, P/1996 R2 (Lagerkvist), and the possibly QHC-derived D/1993 F2 (Shoemaker-Levy 9, SL9).

Aims. We focus on long TSC/orbiter events involving QHCs and Jupiter. Thus we survey the known QHCs, searching for other long TSCs/orbiters over the past century.

Methods. First, we confirmed the long TSC/orbiter events of 82P, 111P, and 1996 R2 in order to test our method against previous work, applying a general N-body Newtonian code. We then used the same procedure to survey the remaining known QHCs and search for long TSC/orbiter events.

Results. We newly identified another long TSC/orbiter: 147P/Kushida-Muramatsu from 1949 May 14-1961 July 15. Our result is verified by integrations of 243 cloned orbits that take account of the present orbital uncertainty of this comet. The event involves an L₂ L₁ transition as with 82P and 1996 R2. This may represent a distinct subtype of TSCs from QHC-derived (L₁ ) longer captures exemplified by 111P and (probably) SL9, though this classification is still only based on a small database of TSCs.

Conclusions. This is the third long TSC and the fifth orbiter to be found, thus long TSC/orbiter events involving Jupiter have occurred once per decade. Two full revolutions about Jupiter were completed and the capture duration was 12.17 years. Both these numbers rank 147P as third among long TSC/orbiter events, behind SL9 and 111P. This study also confirms the importance of the QHC region as a dynamical route into and out of Jovian TSC, via the Hill's sphere.