156P/Russell–LINEAR

156P/Russell–LINEAR is a Jupiter family periodic comet with an orbital period of 6.4 years. It was discovered by Kenneth S. Russell in September 1986.

Observational history
The comet was found by Australian astronomer Kenneth S. Russell in September 1986 on a plate exposed on 3 September 1986 using the U.K. Schmidt Telescope of Siding Spring Observatory, Australia. The comet had an apparent magnitude of 17. Follow up observations on 25 September failed to recover the comet. The comet was spotted again in a plate exposed using the 0.46-m Schmidt telescope of Palomar Observatory by Carolyn S. Shoemaker on 19 November 1993. The comet had asteroidal appearance and was given the provisional designation 1993 WU.

The comet was observed again during the 2000 perihelion. The comet was noted as an asteroidal object by Lincoln Near-Earth Asteroid Research on 31 August and 5 November and was given the provisional designation, and was observed again in November 2000-January 2001 and named. Timothy B. Spahr noted that these objects were the same as the 1986 comet. It was then given the number 156.

The comet had passed 0.70 AU from Jupiter in November 1970 and its perihelion distance decreased from 1.73 AU to 1.56 AU. The comet approached again to Jupiter in March 2018 at a distance of 0.36 AU and its perihelion distance decreased to 1.33 AU, while the orbital period decreased from 6.85 years to 6.44 years.

During the 2020 perihelion, the comet approached to 0.48 AU from Earth on 24 October 2020. It brightened to an apparent magnitude of 9.7 in mid November 2020. The cyanide and diatomic carbon production rate was estimated to be $2.85$ mol/s and $3.44$ mol/s respectively on 14 October 2020, when the comet was located at an heliocentrical distance of 1.40 AU. The production rates are comparable to that of other Jupiter-family comets. Two strong jets were observed during perihelion and persisted until December, indicating increased activity after perihelion.