|Past, Present, and Future Orbits by Kazuo Kinoshita|
Discovery Apparition of 1960-1961
During September and October 1960, T. Gehrels (Palomar Observatory, California, USA) utilized the 122-cm Schmidt telescope for a survey of faint minor planets. During the next few years, the plates were painstakingly examined by C. J. van Houten and I. van Houten-Groeneveld (Leiden, Netherlands) and thousands of asteroids were measured for precise positions. During the blinking of the plates in March 1966, "a moving object was found which was conspicuous by its hazy appearance." This comet first appeared on a plate exposed on 1960 September 24.41. The magnitude was determined as 17.0. The discoverers also found images on plates exposed on September 26 (magnitude 16.9), September 27, September 28 (magnitude 17.1), October 17 (magnitude 17.5), October 22 (magnitude 17.4), and October 25. The last photographic plate to show the comet was obtained on October 26.36, when the magnitude was given as 17.0. Two very similar short-period orbits were calculated from the available positions. P. Herget (1966) took three precise positions and determined the perihelion date as 1961 April 29.60 and the period as 15.75 years. G. Sitarski (1976) used all eight positions, included perturbations by all nine planets, and determined the perihelion date as April 26.84 and the period as 15.62 years.
Several predictions were published for the 1976-1977 apparition. The perihelion date was given as 1976 December 21 by S. Nakano and Y. Banno, December 29 by Sitarski, and 1977 January 1 by Marsden. Nakano and Banno also took the orbit calculated by Herget for the 1961 apparition and integrated it forward, with the resulting perihelion date being 1977 February 19. Photographic plates were exposed by Charles Kowal at Palomar Observatory on 1975 September 30 and October 1, but the comet was not found. Marsden also noted that searches in 1976 were also unsuccessful. Following the comet's accidental discovery in 2012, it was shown that the comet had actually passed perihelion on 1977 March 14. The comet then passed 0.63 AU from Jupiter on 1979 March 10, which increased the perihelion distance from 3.96 to 4.22 AU and increased the period from 16.20 to 18.10 years. No searches were apparently conducted at the next return in 1995.
Rediscovery Apparition of 2013
In the course of the Mount Lemmon Survey (Arizona, USA), this comet was accidentally rediscovered by S. M. Larson on images acquired using the 152-cm reflector on 2012 October 5. It was initially reported as a minor planet of magnitude 19.9-20.2, which resulted in it receiving the minor planet designation 2012 TB36. Prediscovery images were subsequently found on Mount Lemmon Survey images from September 17, when the magnitude was 20.3-20.9. M. Micheli and R. Wainscoat (Haleakala, Hawaii, USA) obtained images with the 178-cm Pan-STARRS1 reflector on October 9, which revealed the coma was slightly larger than the surrounding stars and that a faint tail was detected that extended 4 arc seconds in about position angle 225°. The cometary nature was confirmed by G. Elliot (Mauna Kea, Hawaii, USA) on October 17, when the 2.2-m reflector revealed a faint tail extending 4 arc seconds in about position angle 240°. Following the announcement of its cometary nature, M. Meyer (Limburg, Germany) reported that this appeared to be the lost comet van Houten and G. V. Williams (Central Bureau for Astronomical Telegrams, Massachusetts, USA) confirmed the identity. This rediscovery proved the orbital period was slightly longer than had been determined for the 1961 apparition, which placed the actual perihelion date 1-2 months later than had been predicted for the 1977 return. Nakano said the comet passed 0.63 AU from Jupiter on 1979 March 10.8, which increased the perihelion distance by about 0.2 AU and increased by orbit period by about 2 years.
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