156P/Russell-LINEAR

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery      The story of this comet officially began in September of 1986. K. S. Russell (Siding Spring Observatory, Australia) was examining a 90-min exposure taken by F. G. Watson on September 3.64 with the U.K. Schmidt Telescope. The comet appeared as a diffuse trail, since it moved during the exposure, and the magnitude was estimated as 17. M. Hartley obtained a 30-minute exposure with the same telescope on September 25.63, but independent examination by Russell and, later, R. H. McNaught revealed no trace of the comet. No formal announcement was ever made by the Central Bureau for Astronomical Telegrams.      The story continued in 1993, when C. S. Shoemaker (Palomar Observatory, California, USA) discovered a minor planet on plates exposed with the 46-cm Palomar Schmidt telescope and gave positions for November 19.40, November 19.44, and November 20.44. It received the designation "1993 WU", but it was not followed further.      The object was found a third time in 2000. The LINEAR survey obtained five images of a minor planet during the period of August 31.42 to August 31.47. It received the designation 2000 QD181. LINEAR obtained three more positions during the period of September 5.44 to September 5.46. Another minor planet was found by LINEAR on November 6.41, which was designated 2000 XV43. Three additional images were obtained on November 6, and additional images were obtained on December 5 and 7.      T. B. Spahr announced on 2001 January 20 (MPEC 2001-B13) that minor planet 2000 QD181 was identical to minor planet 2000 XV43 and, also, minor planet 1993 WU. Historical Highlights The first orbit was calculated by T. B. Spahr after successfully linking the minor planets 1993 WU, 2000 QD181, and 2000 XV43 in January of 2001. He gave the perihelion date as 2000 August 17 and the period as 6.84 years. Following Spahr's announcement in April 2003 that this minor planet was identical to the comet found by Russell on 1986 September 3, D. W. E. Green calculated orbits for the 1986, 1993, and 2000 apparitions. He gave the respective perihelion dates as 1986 December 4.81, 1993 October 11.54, and 2000 August 17.62. The orbital period at the time of the 2000 apparition was 6.85 years. Close approaches to planets: During the period spanning 1945 to 2033, this comet makes three close approaches to Earth and two close approaches to Jupiter. (From the orbital work of Kazuo Kinoshita) 0.70 AU from Jupiter on 1970 November 20 decreased perihelion distance from 1.73 AU to 1.56 AU decreased orbital period from ?? to ?? years 0.78 AU from Earth on 1986 October 15 0.66 AU from Earth on 1993 November 6 0.36 AU from Jupiter on 2018 March 1 decreased perihelion distance from 1.58 AU to 1.33 AU decreased orbital period from ?? to ?? years 0.48 AU from Earth on 2020 October 24 cometography.com