Fragmentation Kinematics in Comet 332P/Ikeya-Murakami

Abstract

We present initial time-resolved observations of the split comet 332P/Ikeya-Murakami taken using the Hubble Space Telescope. Our images reveal a dust-bathed cluster of fragments receding from their parent nucleus at projected speeds in the range 0.06 to 3.5 m s${}^{-1}$ from which we estimate ejection times from October to December 2015. The number of fragments with effective radii $\gtrsim$20 m follows a differential power law with index $\gamma$ = -3.6$\pm$0.6, while smaller fragments are less abundant than expected from an extrapolation of this power-law. We argue that, in addition to losses due to observational selection, torques from anisotropic outgassing are capable of destroying the small fragments by driving them quickly to rotational instability. Specifically, the spin-up times of fragments $\lesssim$20 m in radius are shorter than the time elapsed since ejection from the parent nucleus. The effective radius of the parent nucleus is $r_e\le$ 275 m (geometric albedo 0.04 assumed). This is about seven times smaller than previous estimates and results in a nucleus mass at least 300 times smaller than previously thought. The mass in solid pieces, $2\times 10^9$ kg, is about 4% of the mass of the parent nucleus. As a result of its small size, the parent nucleus also has a short spin-up time. Brightness variations in time-resolved nucleus photometry are consistent with rotational instability playing a role in the release of fragments.

19 pages, 1 table, 4 figures, To be published on ApJL

References in corpus (2)

• That's the way the comet crumbles: Splitting Jupiter-family comets
• Outbursting Comet P/2010 V1 (Ikeya-Murakami): A Miniature Comet Holmes

Cited by in corpus (8)

• Origin and Evolution of Short-Period Comets
• Outburst and Splitting of Interstellar Comet 2I/Borisov
• Split Active Asteroid P/2016 J1 (PANSTARRS)
• Dynamically correlated minor bodies in the outer Solar system
• Rotational Mass Shedding from Asteroid (6478) Gault
• New observational evidence of active asteroid P/2010 A2: Slow rotation of the largest fragment
• Rising from Ashes or Dying Flash? Mega Outburst of Small Comet 289P/Blanpain in 2013
• Constraints on Comet 332P/Ikeya-Murakami