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121P/Shoemaker-Holt 2

Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura image of 121P exposed on 1997 January 13
Copyrightę1997 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

This CCD image was taken on 1997 January 13.75, using a 0.60-m f/6 Ritchey-Chretien telescope.


     This comet was discovered by Carolyn S. Shoemaker, Eugene M. Shoemaker, and Henry E. Holt on plates obtained on 1989 March 9.336 with the 0.46-m Schmidt telescope at Palomar Observatory. It was described as diffuse, with a strong central condensation. Its photographic magnitude was estimated as 13 and there was a fan-shaped tail extending 2 arc minutes toward the southwest.

Historical Highlights

  • Daniel W. E. Green (Central Bureau for Astronomical Telegrams) published the first orbit on IAU Circular 4756 (1989 March 13). Although it was parabolic, he added "it seems likely that this is a short-period comet." This suspicion was confirmed by Green two days later when he published the first short-period orbit on IAU Circular 4758 (1989 March 15). This orbit indicated the comet may have passed about 0.60 AU from Jupiter in 1984. Later orbits indicated the comet had passed perihelion on 1988 August 7.47.
  • The comet's maximum observed visual magnitude was about 13.5, reached at about the time of the comet's discovery.
  • J. V. Scotti (Lunar and Planetary Laboratory, Arizona, USA) recovered this comet with the 0.91-meter Spacewatch telescope on 1995 August 29.5. He said the comet's image was stellar and estimated the magnitude as 21.0-21.6. He confirmed the recovery on 1995 August 31.4. The position indicated the predicted orbit needed a correction of -1.2 day.
  • During the 1996-1997 apparition the comet passed perihelion on 1996 August 20 (2.663 AU) and was closest to Earth on 1997 February 10 (1.9245 AU). The maximum total magnitude exceeded 14 during the first few months of 1997.
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