65P/Gunn

Lore & Background

65P/Gunn was discovered on 11 October 1970 by James E. Gunn of Princeton University using the 122-cm Schmidt telescope at Palomar Observatory, with a low brightness of magnitude 16. In 1972, Elizabeth Roemer observed the comet close to aphelion. In 1980, a 19th magnitude comet found on plates from Palomar Observatory taken on 8 August 1954 was identified as a previous apparition of 65P/Gunn; the link was confirmed by Toshiro Nomura and Brian G. Marsden. During the very favorable apparition of 1996, the comet reached magnitude 12.

As of June 2026, the comet's orbit is inclined about 9.2 degrees from the ecliptic, taking it between 2.93 AU and 4.852 AU from the Sun. Between 1910 and 2135, the comet made several close approaches to Jupiter, including four closer than 1.0 AU. On 4 February 1970, it passed 0.015 AU from Ceres.

Infrared observations from the IRAS satellite in 1983 detected a dust trail around 65P/Gunn, indicating a mass loss rate of 27±9 kg/s. Additional observations from the Infrared Space Observatory in 1996 revealed a strongly asymmetric dust trail with a higher mass loss rate of 100–300 kg/s by November 1996. CCD photometry between 1993 and 1996 gave a nucleus diameter of less than 11 km, later revised to 10.8 km; because the comet was very active when observed, this size estimate likely represents an upper limit.

Reader's Guide

65P/Gunn is significant as a Jupiter-family comet that remains entirely within the main asteroid belt, a relatively rare orbital configuration. Its discovery by James E. Gunn in 1970 and the subsequent identification of a pre-discovery observation from 1954 illustrate the importance of archival plate searches in cometary astronomy. The comet's dust trail, detected by IRAS in 1983 and further studied by the Infrared Space Observatory in 1996, provides key data on mass loss rates and dust production in short-period comets. The strongly asymmetric dust trail observed in 1996, with mass loss rates reaching 100–300 kg/s, indicates variable activity. The nucleus size estimate of less than 11 km, later revised to 10.8 km, is considered an upper limit due to the comet's high activity during observation. Close approaches to Jupiter and a notable passage near Ceres in 1970 add to its dynamical interest. The comet's legacy lies in its contribution to understanding the physical properties and evolution of Jupiter-family comets, particularly through infrared and photometric studies.

Did You Know?

• A pre-discovery observation from 8 August 1954 was linked to 65P/Gunn in 1980, confirmed by Toshiro Nomura and Brian G. Marsden.
• On 4 February 1970, the comet passed 0.015 AU (2.2 million km) from Ceres.