313P/Gibbs (P/2014 S4) is an Encke-type comet and active asteroid, discovered by American astronomer Alex Gibbs. It is the third main-belt comet after 133P/Elst–Pizzaro and 238P/Read observed to show mass loss in different orbits.
Observational history Alex R. Gibbs reported the discovery of this comet as a nearly stellar object with a narrow tail from CCD images taken by the Catalina Sky Survey in 24 September 2014. Shuichi Nakano later identified precovery images of the comet taken as early as September 2003 from the LONEOS and SDSS surveys. It was recovered ahead of its 2020 apparition in August 2019, exhibiting significant non-perihelion activity compared to 2014. The comet was given an official numerical designation in 2017.
Orbit 313P/Gibbs currently orbits at a distance between from the Sun, within the outer portion of the main asteroid belt. Computations of its orbit reveal that 313P is intrinsically chaotic, with a Lyapunov time of only years and being located near two three-body mean-motion resonances with Jupiter and Saturn, yet appears stable over 50 million years. Astrometric data analysis shows that 313P is experiencing some transverse non-gravitational acceleration caused by recoil forces due to anisotropic mass loss. It is a member of the Lixiaohua asteroid family, a group of more than 700 asteroids estimated to be around 155 million years old.
Physical characteristics Nucleus size Archival imagery from the Subaru Telescope taken in 2004 indicated an upper-limit size of the comet's nucleus to be around in radius, assuming a geometric albedo of 0.05. Data obtained from the Hubble Space Telescope resulted in a lower-limit of around 0.5–0.7 km in radius. Further observations from the Gemini Observatory in 2017 revised the size estimate to be around in radius.
Cometary activity From its three known appearances since 2003, 313P/Gibbs has consistently shown signs of activity, suggesting that it is likely to be generated from the sublimation of volatile material (ice) from its nucleus. In both the 2003 and 2014 apparitions, dust emissions lasted for at least 3–4 months. Impact driven activity was ruled out, as the mass-loss rate is consistent at . The persistent sublimation activity on 313P, along with other active asteroids (133P/Elst–Pizzaro, 238P/Read, and 358P/PanSTARRS), suggests an abundance of ice within the outer asteroid belt. Its water-ice sublimation is non-uniform around perihelion, which is likely related to the seasonal modulation driven by the orientation of its rotational axis.
References
External links
at the Minor Planet Center database 313P/Gibbs at Gideon van Buitenen's website 313P/Gibbs at Seiichi Yoshida's website