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32P/Comas Solá

Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura image of 32P exposed on 1997 January 18
Copyright © 1997 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

This CCD image was taken on 1997 January 18.87, using a 0.60-m f/6 Ritchey-Chretien telescope. The stars are elongated in this image, while the comet appears just left of center with a diffuse tail projecting upwards and to the right.


Josep Comas Solá (Fabra Observatory, Barcelona) discovered this comet on 1926 November 5.00 in Cetus. This observer was then conducting routine photographic work with a 6-inch telescope as part of his work on asteroids. Comas Solá estimated the magnitude as 12 and noted a slow northwestward movement.

Historical Highlights

  • Eventually astronomers realized this comet was found several months prior to its perihelion passage, which occurred on 1927 March 22. The comet held very close to 12th-magnitude through the remainder of November and throughout December, before a slow fading set in. The reason for this early sustained brightness was a result of the comet's closest approach to Earth on November 27 (1.15 AU) and its approaching perihelion. The comet faded to 12.5 by late January, and reached 13 during March. The final observation on May 31 was obtained by George van Biesbroeck (Yerkes Observatory, Wisconsin, USA). The comet was then estimated as magnitude 14 and was situated at a low altitude, which prevented later observations. Van Biesbroeck's photographic attempts during December 1927, and January-February 1928, revealed nothing brighter than magnitude 16.
  • One of the earliest elliptical orbits was computed and published by Charles H. Smiley and Margaret K. Holbrook (Berkeley Astronomical Department) during early January 1927. They determined the perihelion date as 1927 March 22.20, the perihelion distance as 1.772 AU, and the orbital period as 8.49 years. Later calculations did little to improve on these numbers, although the orbital period was found to be 8.52 years.
  • The comet's past orbital evolution became a point of interest as several astronomers suggested early on that the comet might be a return of the then lost periodic comet Spitaler. This question remained unanswered until the 1935 return. After additional positions had been obtained, P. Ramensky investigated the orbital motion back to 1911 and applied the gravitational effects of Jupiter and Saturn. He noted the comet passed very close to Jupiter (ultimately determined by other astronomers as 0.178 AU) during May of 1912 and that, prior to this approach, the comet had a perihelion distance of 2.15 AU and an orbital period of 9.43 years. The identity with comet Spitaler was disproven.
  • The comet has been recovered at every return since its discovery. Because of the 8.5-year period the returns through 1969 always fell in the spring or autumn months which guaranteed its approaching Earth at distances of between 1.1 and 1.4 AU. This continually brought maximum magnitudes of 12 or 13. A moderately close approach to Jupiter in 1971 (0.73 AU) initially nudged the orbital period up to 8.94 years. This brought another very favorable return in 1978 (maximum magnitude of 13). The orbital period dropped back to 8.8 years for the 1987 and 1996 returns. The comet only brightened to about magnitude 14 during the latter year.
  • Close approaches to planets: The comet experienced four close approaches to Jupiter during the 20th century and makes two more approaches to Jupiter during the 21st century. (From the orbital work of Kazuo Kinoshita)
    • 0.18 AU from Jupiter on 1912 May 19
      • decreased perihelion distance from 2.15 AU to 1.77 AU
      • decreased orbital period from 9.35 to 8.51 years
    • 1.47 AU from Jupiter on 1949 November 25
      • left perihelion distance virtually unchanged at 1.77 AU
      • increased orbital period from 8.50 to 8.54 years
    • 0.73 AU from Jupiter on 1971 September 21
      • increased perihelion distance from 1.77 AU to 1.87 AU
      • increased orbital period from 8.55 to 8.94 years
    • 1.34 AU from Jupiter on 1985 December 30
      • decreased perihelion distance from 1.87 AU to 1.83 AU
      • decreased orbital period from 8.94 to 8.78 years
    • 0.31 AU from Jupiter on 2007 April 5
      • increases perihelion distance from 1.83 AU to 2.00 AU
      • increases orbital period from 8.77 to 9.58 years
    • 1.43 AU from Jupiter on 2021 September 26
      • increases perihelion distance from 2.00 AU to 2.02 AU
      • increases orbital period from 9.58 to 9.71 years