331P/Gibbs

331P/Gibbs (P/2012 F5)
Discovery
Discovered by	A. R. Gibbs; (Mount Lemmon Survey)
Discovery date	March 22, 2012
Orbital characteristics
Epoch	4 February 2012 (JD 2455961.5)
Observation arc	11.3 years
Number of; observations	148
Aphelion	3.130 AU
Perihelion	2.877 AU
Semi-major axis	3.004 AU
Eccentricity	0.042
Orbital period	5.21 years (1902 days)
Inclination	9.740°
Longitude of; ascending node	216.86°
Argument of; periapsis	177.40°
Last perihelion	29 September 2020; 16 June 2015
Next perihelion	2025-Dec-25
TJupiter	3.229
Earth MOID	1.88 AU
Jupiter MOID	2.08 AU
Physical characteristics
Dimensions	~2-5 km
Comet total; magnitude (M1)	12.3
Comet nuclear; magnitude (M2)	15.4

331P/Gibbs (P/2012 F5) is a small periodic Encke-type and rare main-belt comet, discovered by American amateur astronomer Alex Gibbs.^[2]

Description

It is a rare type of comet called a main-belt comet. Although most comets come from the Oort cloud or the Kuiper belt, main-belt comets are instead members of the asteroid belt that have a coma and tail. As of 2016, it is one of only 15 known main-belt comets.^[3]

Precovery observations of 331P/Gibbs in Sloan Digital Sky Survey data were found dating to August 2004, in which the object was visible as a regular asteroid. Further observations in 2014 by the Keck Observatory showed that the comet was fractured into 5 pieces and rotating rapidly, with a rotation period of only 3.2 hours. Due to the YORP effect, P/2012 F5 had begun to spin so quickly that, being a likely rubble pile, parts began to be thrown off, leaving a very long dust trail.^[4] This is very similar to 311P/PANSTARRS, being the best-established cause for main-belt comets along with impacts between small asteroids (such as with 596 Scheila and P/2010 A2 (LINEAR)).