A Small Centaur with a Coma and Tail and Another with a Coma

Abstract

We report discovery and initial investigation of extended optical emission from two known Centaurs, 2020 XV1 and 2021 RK133. These objects are classified as Centaurs using the Jet Propulsion Laboratory HORIZONS Centaur criteria, but not the Minor Planet Center criteria, as both have q < 5.2 au. We derive limits on the fraction of light coming from the nuclei and from the extended emission regions and derive magnitude limits for the nuclei. Using these nuclear magnitudes and an assumed albedo of 7% we estimate that these two Centaurs are rather small, with diameters of no more than 2.4 and 1.7 km.