Outburst and Splitting of Interstellar Comet 2I/Borisov

Abstract

We present Hubble Space Telescope observations of a photometric outburst and splitting event in interstellar comet 2I/Borisov. The outburst, first reported with the comet outbound at 2.8 AU (Drahus et al.~2020), was caused by the expulsion of solid particles having a combined cross-section about 100 sq. km and a mass in 0.1 mm sized particles about 2e7 kg. The latter corresponds to 1e-4 of the mass of the nucleus, taken as a sphere of radius 500 m. A transient ``double nucleus'' was observed on UT 2020 March 30 (about three weeks after the outburst), having a cross-section about 0.6 sq. km and corresponding dust mass 1e5 kg. The secondary was absent in images taken on and before March 28, and in images taken on and after April 03. The unexpectedly delayed appearance and rapid disappearance of the secondary are consistent with an origin through rotational bursting of one or more large (meter-sized) boulders under the action of outgassing torques, following their ejection from the main nucleus. Overall, our observations reveal that the outburst and splitting of the nucleus are minor events involving a negligible fraction of the total mass: 2I/Borisov will survive its passage through the planetary region largely unscathed.

21 pages, 5 figures, 1 appendix

References in corpus (21)

• Initial characterization of interstellar comet 2I/Borisov
• Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov)
• The carbon monoxide-rich interstellar comet 2I/Borisov
• Unusually High CO Abundance of the First Active Interstellar Comet
• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• Detection of CN gas in Interstellar Object 2I/Borisov
• Rotation of Cometary Nuclei: New Lightcurves and an Update of the Ensemble Properties of Jupiter-Family Comets
• Constraints on the Physical Properties of Main Belt Comet P/2013 R3 from its Breakup Event
• The Nucleus of Interstellar Comet 2I/Borisov
• Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 3
• Acceleration of Individual, Decimetre-sized Aggregates in the Lower Coma of Comet 67P/Churyumov-Gerasimenko
• Pre-discovery Activity of New Interstellar Comet 2I/Borisov Beyond 5 AU
• Detection of a Water Tracer in Interstellar Comet 2I/Borisov
• Could 1I/'Oumuamua be an icy fractal aggregate?
• Coma Anisotropy and the Rotation Pole of Interstellar Comet 2I/Borisov
• Fragmentation Kinematics in Comet 332P/Ikeya-Murakami
• The interstellar object 'Oumuamua as a fractal dust aggregate
• Outbursting Comet P/2010 V1 (Ikeya-Murakami): A Miniature Comet Holmes
• Hyperbolic Orbits in the Solar System: Interstellar Origin or Perturbed Oort Cloud Comets?
• Interstellar Comet 2I/Borisov exhibits a structure similar to native Solar System comets
• Searching for water ice in the coma of interstellar object 2I/Borisov

Cited by in corpus (8)

• Cometary Activity Begins at Kuiper Belt Distances: Evidence from C/2017 K2
• Destruction of Long-Period Comets
• Activity of the first interstellar comet 2I/Borisov around perihelion: Results from Indian observatories
• Varying water activity and momentum transfer on comet 67P/Churyumov-Gerasimenko from its non-gravitational forces and torques
• Perihelion Asymmetry in the Water Production Rate of the Interstellar Object 3I/ATLAS
• Fitting the Light Curve of 1I/`Oumuamua with a Nonprincipal Axis Rotational Model and Outgassing Torques
• On The Spin Dynamics of Elongated Minor Bodies with Applications to a Possible Solar System Analogue Composition for `Oumuamua
• Dynamically New Comet C/2025 D1 (Groeller) with Record Perihelion Distance