Speaker: Olivia Logan
Affiliation: UCLA, EPSS
Date: Wednesday, May 20, 2026
Time: 12:00 PM
Abstract
The Main Belt is a region lying between Jupiter and Mars that contains a vast number of small bodies ranging in both size and shape. Until the 1990s, it was believed that the Main Belt consisted primarily of asteroids. However, the observation of 7968 Elst–Pizarro (133P/Elst–Pizarro) in 1996 by Eric Elst and Guido Pizarro, along with the work of Jewitt and Hsieh in the early 2000s, led to a new classification of small bodies: Main Belt Comets (MBCs). These comets – later deemed a subset of Active Asteroids – exhibit circular, asteroid-like orbits with semi-major axes 𝑎 < 𝑎_J, but maintain comet-like characteristics such as a coma, tail, or 𝐽𝑢𝑝𝑖𝑡𝑒𝑟 visible mass loss. Since their initial discovery, MBCs have been inadvertently observed throughout the Main Belt, and many have attempted to put constraints on their number density. A 2013 study by Waszczak and others placed upper limits of 33 and 22 active MBCs per million main-belt asteroids down to∼1-km diameter (Waszczak et al, 2013). A more recent study in 2022, by Ferellec and others, deduced a MBC-to-asteroid ratio of <1:500 (Ferellec et al. 2022). For this
study, we plan to utilize the data from the WISE/NEOWISE survey to search for MBCs. WISE/NEOWISE is a space-based wide-field infrared telescope that surveyed MB small bodies over the past ten years. The mission’s objective was to identify near-earth objects (NEOs) and MBAs; thus, it has not been analyzed for MBCs. A thorough search of this data set should yield a number of MBCs which can then be used to place constraints on their number density in the Main Belt.