Disintegration of Long-Period Comet C/2021 A1 (Leonard)

Abstract

We present imaging observations of the disintegrating long-period comet C/2021 A1 (Leonard). High resolution observations with Hubble Space Telescope show no evidence for surviving fragments, and place a 3 sigma upper limit to their possible radius about 60 m (albedo 0.1 assumed). In contrast, wide field observations from the Swan Hill Observatory, Australia, show an extensive debris cloud, the cross-section and estimated mass of which are consistent with complete disintegration of the nucleus near mid- December 2021 (at about 0.8 au). Two methods give the pre-disruption nucleus radius, r = 0.6+/-0.2 km. Tidal, collisional, sublimation and pressure-confined explosion models provide implausible explanations of the disintegration. However, rotational instability driven by outgassing torques has a very short timescale (of order 0.1 year) given the orbit and size of the C/2021 A1 nucleus, and offers the most plausible mechanism for the disruption. Initial rotational breakup is accelerated by the exposure and strong sublimation of previously buried volatiles, leading to catastrophic destruction of the nucleus.

35 pages, 7 figures

References in corpus (5)

• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• Destruction of Long-Period Comets
• Systematics and Consequences of Comet Nucleus Outgassing Torques
• Disappearance of Comet C/2010 X1 (Elenin): Gone with a Whimper, not a Bang
• Preview of Comet C/2021 A1 (Leonard) and Its Encounter with Venus

Cited by in corpus (2)

• Chemical composition of comets C/2021 A1 (Leonard) and C/2022 E3 (ZTF) from radio spectroscopy and the abundance of HCOOH and HNCO in comets
• Great comet C/2023 A3 (Tsuchinshan-ATLAS): dust loss before perihelion