Dust On, Dust Off: HST Observations of the Newly Dormant Jupiter Co-orbital Comet P/2023 V6 (PANSTARRS)

Abstract

As the Centaurs of the Outer Solar System have become better studied, their relationship with the Jupiter Family Comets and their connection to the primordial protoplanetary disk has come under deeper scrutiny: which properties of the comets observed closer to the Sun are original, and which were modified significantly en route during their Centaur phase? The active Jupiter co-orbital comet P/2019 LD2 (ATLAS) attracted significant attention after its discovery when it was realized that the object would transition between a Centaur and JFC orbit in 2063, the first time this change can be observed and monitored in real time. In this study, we present new ground-based and Hubble Space Telescope imaging of the single other Jupiter co-orbital comet, P/2023 V6 (PANSTARRS), throughout late 2024 and early 2025. V6 was not detected in ground-based imaging after early October, and deep imaging with HST taken in early December is consistent with a $m_V = 28.06 \pm 0.03$ point source at its expected location. This both implies that the object ceased activity sometime in late 2024, and is thus in a different thermal state than LD2 despite both having large active fractions, and that V6's diameter is approximately $D\sim340$ meters. This is likely the smallest object directly observed by HST beyond the Main Belt, and certainly the smallest Centaur yet discovered, highlighting the ability to detect active sub-km objects beyond Jupiter with current surveys and potentially probing smaller sizes with LSST.