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105P/Singer Brewster

Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura photo of 105P exposed on 1999 June 8
Copyright © 1999 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

The CCD image was taken on 1999 June 8.70, using a 0.60-m f/6 Ritchey-Chretien telescope.


     Stephen Singer-Brewster discovered this comet on two plates exposed by D. Schneeberger, E. Burr and himself on 1986 May 3.34 with the 0.46-m Schmidt telescope at Palomar Observatory. The images were obtained in the course of the International Near-Earth Asteroid Survey under the direction of E. F. Helin. The magnitude was estimated as 15 and the comet was described as "diffuse and only slightly condensed." Another image of the comet was found on plates exposed with the same telescope the next evening by Carolyn S. and Eugene M. Shoemaker. The Shoemaker images revealed a possible faint tail to the northeast.

Historical Highlights

  • B. G. Marsden (Central Bureau for Astronomical Telegrams) computed the first orbit, or rather, orbits, for this comet. After receiving observations through May 6, Marsden computed both a parabolic and an elliptical orbit. For the parabolic he gave the perihelion date as 1985 December 16 and the perihelion distance as 1.97 AU. For the elliptical orbit he gave the perihelion date as 1986 June 27, the perihelion distance as 1.76 AU, and the orbital period as 5.2 years. Marsden said the elliptical orbit was more preferable, but added that the eccentricity (and therefore the orbital period) was "very uncertain." By May 13 Marsden had enough observations to confirm the elliptical orbit. He said the perihelion date was probably closer to 1986 May 28.7, the perihelion distance was probably near 1.95 AU, and the orbital period was probably near 6.1 years. A close approach to Jupiter in 1976 was indicated. Ultimately, a June 8 perihelion date was revealed, while the period was 6.30 years.
  • The comet slowly faded after its discovery and was steadily moving away from both the sun and Earth after June 8. It was last detected on September 6.
  • James V. Scotti (Lunar and Planetary Laboratory) recovered this comet on 1992 April 1.35, while using the Spacewatch telescope at Kitt Peak. The precise position indicated the prediction required a correction of -0.84 day. Scotti described the comet as magnitude 20.4. He added that it was slightly diffuse, with a coma 8 arc seconds across.
  • The comet was next expected to arrive at perihelion on 1999 April 6.46. It was recovered on 1999 February 13.51 by S. M. Larson and C. W. Hergenrother (University of Arizona, Catalina Station, USA), using the 1.5-m reflector and a CCD camera.
  • Kazuo Kinoshita has examined the orbital history of this comet. As indicated back in 1986 by Marsden, the comet did pass close to Jupiter in 1976. The actual details are that it passed 0.3765 AU from Jupiter on 1976 August 5, which made fairly significant alterations in the orbit. Most notable was a change in the perihelion distance from 2.27 AU to 1.95 AU and a change in the orbital period from 6.70 years to 6.29 years. The comet will undergo only very minor changes in its orbit until 2059 August 6, when a passage of 0.4072 AU from Jupiter will again change the orbit to some degree.
  • cometography.com