Fragment Dynamics in Active Asteroid 331P/Gibbs

TL;DR

This study analyzes the fragmentation history of active asteroid 331P/Gibbs using Hubble data, revealing recent breakup events and supporting rotational disruption as the cause, thus offering insights into asteroid cluster formation.

Contribution

It provides the first detailed dynamical analysis of 331P/Gibbs fragments, estimating their separation times and velocities, and links the fragmentation to rotational disruption.

Findings

Fragments separated at low velocities (~0.7-8 cm/s).

Fragmentation occurred between 2011 and 2014.

The asteroid's breakup is consistent with rotational disruption.

Abstract

We present a dynamical analysis of the fragmented active asteroid 331P/Gibbs. Using archival images taken by the Hubble Space Telescope from 2015 to 2018, we measured the astrometry of the primary and the three brightest (presumably the largest) components. Conventional orbit determination revealed a high-degree of orbital similarity between the components. We then applied a fragmentation model to fit the astrometry, obtaining key parameters including the fragmentation epochs and separation velocities. Our best-fit models show that Fragment B separated from the primary body at a speed of $\sim$1 cm s$^{-1}$ between 2011 April and May, whereas two plausible scenarios were identified for Fragments A and C. The former split either from the primary or from Fragment B, in 2011 mid-June at a speed of $\sim$8 cm s$^{-1}$, and the latter split from Fragment B either in late 2011 or between late 2013 and early 2014, at a speed of $\sim$0.7-0.8 cm s$^{-1}$. The results are consistent with rotational disruption as the mechanism causing the cascading fragmentation of the asteroid, as suggested by the rapid rotation of the primary. The fragments constitute the youngest known asteroid cluster, providing us with a great opportunity to study asteroid fragmentation and formation of asteroid clusters.