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70P/Kojima

Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura image of 70P exposed on 2000 Nov. 28
Copyright © 2000 by Akimasa Nakamura (Austria)

This image of periodic comet Kojima was obtained by Akimasa Nakamura on 2000 November 28.84 UT. He was using a 60cm f/6 reflector.

Discovery

     Nobuhisa Kojima (Ishiki, Aichi) discovered this comet in Virgo on 1970 December 27.79. He confirmed the find on December 29.84. On both occasions the comet's brightness was estimated as magnitude 14. Kojima also described the comet as diffuse, with a condensation.

Historical Highlights

  • The first parabolic orbit was computed by K. Hurukawa and was first published on January 6. It indicated the perihelion date was 1970 November 1. Following the accumulation of more precise positions, B. G. Marsden computed the first elliptical orbit which was published on February 3. It indicated the perihelion date was 1970 October 6 and the orbital period was 6.09 years. Orbits computed after the comet had been observed at other apparitions indicated the perihelion date was October 7.05 and the period was 6.16 years.
  • Observations following the comet's discovery indicated it brightened to about 13 during early January 1970 and then began fading. It was last detected on June 27, at which time Elizabeth Roemer determined the nuclear magnitude as 19.0.
  • CLOSE ENCOUNTER WITH JUPITER: 1973
         The comet approached Jupiter following the 1970 apparition. The two bodies passed 0.158 AU from one another on 1973 April 10. This ultimately acted to increase the comet's perihelion distance from 1.63 AU to 2.40 AU and increase the orbital period from 6.16 years to 7.85 years.

    APPARITION OF 1978
    [Perihelion Date=1978 May 24.58; Period=7.85 years]
         A prediction for the comet's 1978 apparition was published in the 1977 British Astronomical Association Handbook. It was considered uncertain by perhaps 2 days. H. Kosai and Hurukawa (Kiso Station) recovered this comet with the 105-cm Schmidt telescope on 1977 December 9.79. They estimated the magnitude as 18, and described the comet as diffuse, without condensation. Observers at Harvard College Observatory's Agassiz station confirmed the recovery on December 10.29. Interestingly, the precise positions indicated the predicted perihelion date required a correction of only -0.18 day. C. Kowal (Hale Observatories) subsequently found images of this comet on plates exposed with the Palomar Schmidt on December 8.41 and December 9.42. For the first night, Kowal estimated the magnitude as 19, and described the comet as a "somewhat diffuse" image. Towards the end of December, Tsutomu Seki (Kochi Observatory, Geisei Station) found prerecovery images on a plate exposed on December 5.59. About the middle of 1978, observers at Harvard College Observatory's Agassiz Station found prediscovery images on plates exposed on November 12.34 and November 15.35. The comet never became brighter than magnitude 18 and was last detected on 1978 March 13.

  • The comet was next seen in 1985/1986 and 1992/1994. It was recovered by Spacewatch at both apparitions and the recovery magnitude was 20 in 1985 and 22.1 in 1992. The comet did not become bright enough to become visible in amateur telescopes at either apparition.
  • CLOSE ENCOUNTER WITH JUPITER: 1996
         The comet approached Jupiter following the 1994 apparition. The two bodies passed 0.147 AU from one another on 1996 December 22. This ultimately acted to decrease the comet's perihelion distance from 2.40 AU to 1.97 AU and decrease the orbital period from 7.85 years to 6.99 years.

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