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Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura image of 74P exposed on 2000 January 4
Copyright © 2000 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

This CCD image was taken on 2000 January 4.61, using a 0.60-m f/6 Ritchey-Chretien telescope.


     During late March 1975, Tamara Mikhajlovna Smirnova (Institute for Theoretical Astronomy, Leningrad, USSR) was examining 60-minute exposures obtained at the Crimean Astrophysical Observatory, when an object was found on plates exposed on 1975 March 4.78 and March 16.84. It was then near the Leo-Cancer border. The object's appearance was virtually unchanged between the two photographic plates, with the magnitude estimated as 15-15.5 on the former date, and 15 on the latter, but it was not certain whether this was a comet or an asteroid. On March 30.81, Nikolaj Stepanovich Chernykh photographed the region where the object was expected to lie, based on its extrapolated position and confirmed it was a comet. The magnitude was still 15 and the comet was described as diffuse, with a condensation.
     Interestingly, during the early 1980s, S. Nakano revealed that this comet had actually been photographed during 1967 and was identified as an asteroid. The first photograph of the comet had been obtained on March 9, while the last was on April 4.

Historical Highlights

  • The comet continued to be estimated as 14.5 to 15 during the next month or so, before a gradual fading set in. The coma was typically estimated as about 30 arc seconds across, with only slight condensation. Photographs by Elizabeth Roemer showed only the inner-most portion of the coma and revealed a strong condensation and a nucleus of about magnitude 18.
  • The first orbit was published on April 15. It was computed by Brian G. Marsden. Although it was parabolic, Marsden suggested, "There is a possibility that the comet is yet another new short-period one." This suspicion was confirmed shortly thereafter when G. R. Kastel' (Institute for Theoretical Astronomy) determined the orbital period as 8.49 years and said the comet would pass perihelion on 1975 August 6. This orbit indicated the comet was probably diverted into its discovery orbit by a close approach to Jupiter in 1963. The orbit also indicated the comet was probably observable throughout its orbit.
  • The comet attained a maximum magnitude of 15.5 in 1976. The comet was only slightly fainter during observations in 1977 and 1978. In the latter year, Marsden published a revised orbit indicating an orbital period of 8.53 years. It was photographed near aphelion by observers at Oak Ridge Observatory on 1979 September 17.15, at which time its total magnitude was given as 19.
  • The comet next passed through perihelion in 1984 and 1992. It was again photographed near aphelion on 1996 October 16.54 by Akimasa Nakamura at Kuma Kogen Astronomical Observatory. The total magnitude was then determined as 18.1.
  • Additional Images

    A. Nakamura image of 74P exposed on 1996 October 5
    Copyright © 1996 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

    This CCD image was taken on 1996 October 5, using a 0.60-m f/6 Ritchey-Chretien telescope. The comet was then near aphelion.

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