The catastrophic fragmentation of Comet 332P (Ikeya-Murakami)

TL;DR

This study documents the fragmentation of Comet 332P, analyzing its breakup timeline, fragment properties, and suggesting a crystallization-driven splitting process based on observations and simulations.

Contribution

It provides detailed photometric analysis and simulations of the comet's fragmentation, revealing the timing and mechanisms behind the breakup, which were previously not well understood.

Findings

Fragments emitted after 2010 outburst, with some splitting years later.

The original nucleus likely corresponds to the rapidly brightening fragment F4.

Non-gravitational parameters are consistent with zero, indicating minimal non-gravitational forces.

Abstract

We describe 2016 January to April observations of the fragments of 332P/Ikeya-Murakami, a comet earlier observed in a 2010 October outburst (Ishiguro et al 2014). We present photometry of the fragments, and perform simulations to infer the time of breakup. We argue that the eastern-most rapidly brightening fragment ($F4$) best corresponds to the original nucleus, rather than the initial bright fragment $F1$. We compute radial and tangential non-gravitational parameters, $A_1 = (1.5 \pm 0.4) \times 10^{-8}$ AU day$^{-2}$ and $(7.2 \pm 1.9) \times 10^{-9}$ AU day$^{-2}$; both are consistent with zero at the $4\sigma$ level. Monte Carlo simulations indicate that the fragments were emitted on the outbound journey well after the 2010 outburst, with bright fragment $F1$ splitting in mid--2013 and the fainter fragments within months of the 2016 January recovery. Western fragment $F7$ is the oldest, dating from 2011. We suggest that the delayed onset of the splitting is consistent with a self-propagating crystallization of water ice.