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200P/Larsen

Past, Present, and Future Orbits by Kazuo Kinoshita

Spacewatch photo of 200P exposed on 1997 November 3
Copyright © 1997 by The Spacewatch Project

This is one of the discovery images obtained by Jeff Larsen on 1997 November 3.27 UT, using a the 0.9-m Spacewatch telescope and a CCD camera. The total exposure time was about 2.5 minutes. The comet was then magnitude 16.6. (The webmaster reversed the image to better illustrate the comet's true appearance. I also wish to thank James Scotti for permission to use this image.)

Discovery

Jeff Larson (Lunar and Planetary Laboratory) discovered this comet on CCD images obtained with the 0.91-m Spacewatch telescope on 1997 November 3.23. Additional CCD images obtained by him during the period of November 3.25 to 3.38 indicated a total magnitude of 16.6-16.7. The coma was 14 arcsec across and contained a nuclear condensation of magnitude 19.2-19.7. There was a tail extending 0.89 arcmin toward PA 258°. The first confirmation came from M. Tichy and Z. Moravec (Klet Observatory) when they detected the comet with the 0.57-m f/5.2 reflector and a CCD on November 3.96 to 3.97. They estimated the magnitude as 16.0. They said the coma was 11 arcsec across, but less-than-perfect seeing prevented detection of the tail.

Historical Highlights

  • Daniel W. E. Green (Central Bureau for Astronomical Telegrams) computed a parabolic orbit that was first published on IAU Circular 6770 (1997 November 5). Based on 35 positions obtained during the period of November 3-5, the orbit indicated a perihelion date of 1997 February 1 and a perihelion distance of 1.92 AU. The low inclination of about 14° prompted Green to suggest the comet was possibly moving in a short-period orbit. The Central Bureau issued MPEC 1997-V23 on November 12, showing that Brian G. Marsden had confirmed Green's suggestion. Based on 113 positions obtained during the period of November 3 to 9, Marsden determined a short-period orbit with a perihelion date of 1997 August 16.27, a perihelion distance of 3.286 AU, and an orbital period of 10.8 years.
  • During the days immediately following discovery, most observers were determining the total magnitude as between 16.2 and 16.4. When detected, the tail was extending about 15-20 arcsec toward the west. The orbit indicated the comet was moving away from both the sun and Earth and was therefore fading. Because of the large perihelion distance, the fading was slow. The comet was last detected because of a decreasing solar elongation on 1998 February 19 by observers at the Astronomical and Geophysical Observatory (Modra). The determined the magnitude as 16.9.
  • Following the final observations of this comet, Patrick Rocher and Kenji Muraoka independently determined the orbit of this comet. Rocher used 264 positions obtained between 1997 November 3 and 1998 February 19 and determined the perihelion date as 1997 September 15.071, the perihelion distance as 3.293 AU, and the orbital period as 10.958 years. He estimated the period's uncertainty as ±0.2238 day. Muraoka used 258 positions measured during the same period of time and determined the perihelion date as 1997 September 15.084, the perihelion distance as 3.293 AU, and the orbital period as 10.955 years. He gave the uncertainty as ±0.30 day.
  • Following the comet's recovery in 2008, K. Kinoshita integrated the comet's motion backwards and noted it was diverted into its present orbit just two years prior to its discovery because of a close approach to Jupiter. The approach occurred on 1995 February 9, when it passed 0.35 AU from the giant planet. The result was a decrease in the period from 13.56 to 10.95 years and a decrease in the perihelion distance from 3.95 AU to 3.29 AU.
  • Additional Images

    A. Nakamura photo of 200P exposed on 1997 November 5
    Copyright © 1997 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

    This CCD image was taken on 1997 November 5.48 UT, using a 0.60-m f/6 Ritchey-Chretien telescope.

    cometography.com