2PEncke

2P/Encke, commonly written 2P Encke, is a short-period comet in the inner solar system. It is classified as a Jupiter-family comet and completes an orbit around the Sun in about 3.3 years. The comet is notable for its frequent returns and relatively small orbital distance from the Sun.

Discovery and naming

2P/Encke was discovered in October 1786 by the French astronomer Pierre Méchain. Its periodic nature was established by Johann Franz Encke, who calculated a precise orbit and predicted its returns. In recognition of Encke’s work, the comet bears his name and the designation 2P, indicating it was the second periodic comet to be identified.

Orbit and physical characteristics

The orbit has a semi-major axis of roughly 2.2 astronomical units and an eccentricity near 0.85, bringing the perihelion to about 0.33 AU and the aphelion to around 4 AU. Its inclination is approximately 11 degrees relative to the ecliptic. The nucleus is small, estimated to be a few kilometers in diameter, and is irregular in shape. As it approaches perihelion, 2P/Encke becomes active, developing a coma and, on some apparitions, a short tail due to the sublimation of volatile ices.

Observational and scientific significance

Because of its short period and well-determined orbit, 2P/Encke has been the subject of extensive observational campaigns. Its activity provides data on non-gravitational forces acting on comets, and its repeated apparitions help scientists study the evolution and fragmentation processes of Jupiter-family comets.