Discovery and Characteristics of the Rapidly Rotating Active Asteroid (62412) 2000 SY178 in the Main Belt

TL;DR

This paper reports the discovery of a new active asteroid in the main belt, characterized by rapid rotation, activity linked to its spin, and its association with the Hygiea family, providing insights into asteroid activity mechanisms.

Contribution

It is the first active asteroid identified in the Hygiea family, with detailed analysis of its rotation, activity, and physical properties, highlighting the link between rapid spin and activity.

Findings

62412 exhibits a tail and activity persists over a year after perihelion.

It has the fastest rotation period among Hygiea family asteroids.

Its activity is likely caused by rapid rotation near the break-up threshold.

Abstract

We report a new active asteroid in the main belt of asteroids between Mars and Jupiter. Object (62412) 2000 SY178 exhibited a tail in images collected during our survey for objects beyond the Kuiper Belt using the Dark Energy Camera (DECam) on the CTIO 4 meter telescope. We obtained broad-band colors of 62412 at the Magellan telescope, which along with 62412's low albedo suggest it is a C-type asteroid. 62412's orbital dynamics and color strongly correlate with the Hygiea family in the outer main belt, making it the first active asteroid known in this heavily populated family. We also find 62412 to have a very short rotation period of 3.33+-0.01 hours from a double-peaked light curve with a maximum peak-to-peak amplitude of 0.45+-0.01 magnitudes. We identify 62412 as the fastest known rotator of the Hygiea family and the nearby Themis family of similar composition, which contains several known main belt comets. The activity on 62412 was seen over 1 year after perihelion passage in its 5.6 year orbit. 62412 has the highest perihelion and one of the most circular orbits known for any active asteroid. The observed activity is probably linked to 62412's rapid rotation, which is near the critical period for break-up. The fast spin rate may also change the shape and shift material around 62412's surface, possibly exposing buried ice. Assuming 62412 is a strengthless rubble pile, we find the density of 62412 to be around 1500 kg/m3.