A look at outbursts of Comet C/2014 UN 271 (Bernardinelli–Bernstein) near 20 au

Abstract: Cometary activity may be driven by ices with very low sublimation temperatures, such as carbon monoxide ice, which can sublimate at distances well beyond 20 au. This point is emphasized by the discovery of the Oort cloud comet C/2014 UN271 (Bernardinelli–Bernstein) and its observed activity out to ∼26 au. Through observations of this comet’s optical brightness and behavior, we can potentially discern the drivers of activity in the outer solar system. We present a study of the activity of comet Bernardinelli–Bernstein with broad-band optical photometry taken at 19–20 au from the Sun (2021 June to 2022 February) as part of the LCO Outbursting Objects Key (LOOK) Project. Our analysis shows that the comet’s optical brightness during this period was initially dominated by cometary outbursts, stochastic events that ejected ∼107 to ∼108 kg of material on short (