A Dormant Captured Oort Cloud Comet Awakens: (18916) 2000 OG44

TL;DR

This paper reports the discovery of cometary activity in the asteroid (18916) 2000 OG44, likely caused by volatile sublimation, supported by observations and dynamical and thermodynamical modeling indicating its origin in the Oort cloud.

Contribution

First detection of activity in (18916) 2000 OG44, combining observational data with dynamical and thermodynamical models to understand its origin and activity mechanism.

Findings

2000 OG44 exhibits a tail aligned with anti-solar and anti-motion directions.

Dynamical simulations suggest origin in the Oort cloud within the last 4 million years.

Thermodynamical modeling indicates activity is likely due to volatile sublimation.

Abstract

We report the discovery of activity emanating from (18916) 2000 OG44 (alternately designated 1977 SD), a minor planet previously reported to be both an extinct comet or an asteroid on a cometary orbit. We observed 2000 OG44 with a thin tail oriented towards the coincident anti-solar and anti-motion vectors (as projected on the sky) in images we acquired on UT 2023 July 24 and 26 with the Apache Point Observatory 3.5-meter Astrophysical Research Consortium telescope (New Mexico, USA). We also include observations made in Arizona with the Vatican Advanced Technology Telescope at the Mount Graham International Observatory and the Lowell Observatory Lowell Discovery Telescope near Happy Jack. We performed dynamical simulations that reveal 2000 OG44 most likely originated in the Oort cloud, arriving within the last 4 Myr. We find 2000 OG44, which crosses the orbits of both Jupiter and Mars, is at present on an orbit consistent with a Jupiter-family comet (JFC). We carried out thermodynamical modeling that informed our broader diagnosis that the observed activity is most likely due to volatile sublimation.