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Past, Present, and Future Orbits by Kazuo Kinoshita

H. Mikuz image of 67P exposed on 1995 November 20
Copyright © 1995 by Herman Mikuz (Crni Vhr Observatory, Slovenia)

This V-filter image was obtained by H. Mikuz on 1995 November 20 with the 36-cm, f/6.8 S-C telescope and CCD. Exposure time was 300s, starting at 18:36:49 UT.


Periodic comet 67P/Churyumov-Gerasimenko has a nucleus measuring about 5 by 3 kilometers across that rotates once every 12.7 hours. It belongs to the Jupiter family of comets (comets with periods less than 20 years). The comet was discovered in 1969. Although it then had an orbital period of 6.55 years, an analysis of its orbit reveals the period had been longer in the recent past. During the early years of the 20th century, the orbital period had been about 9.3 years. A close approach to Jupiter in February 1959 (0.22 AU) reduced the period to 6.5 years. The comet has been seen at every return since its discovery.


     During mid-1969, several astronomers from Kiev visited the Alma-Ata Astrophysical Institute to conduct a survey of comets. On September 20, while still at Alma-Ata, Klim Ivanovic Churyumov examined a photograph exposed for periodic comet Comas Solá by Svetlana Ivanovna Gerasimenko on September 11.92, and found a cometary object near the edge of the plate which he assumed was the expected periodic comet. Upon returning to Kiev, the plates went under intense scrutiny. Precise positions were determined for all of the observed comets, as well as estimates of the coma diameter, and photographic magnitude estimates of the comet and nucleus. On October 22, it was realized that the position determined for P/Comas Solá was 1.8° from the expected position based on observations from other observatories. Further examination revealed P/Comas Solá in the proper position, near the limit of the photographic plate, which meant a new comet had been found. They estimated the magnitude of the new comet as 13, and said it had a faint coma 0.6 arc minute across, with a central condensation about 0.3 arc minute across. There was also a faint tail extending 1 arc minute toward PA 280 degrees.

[Perihelion Date=1969 September 11.04; Period=6.55 years]
  • In addition to the discovery observations noted above, additional images were found on a plate exposed by Gerasimenko on September 9.91 and on a plate exposed by Churyumov on September 21.93. The magnitude was estimated as 13 on the first date and 12 on the second.
    [Perihelion Date=1976 April 7.23; Period=6.59 years]
    [Perihelion Date=1982 November 12.10; Period=6.61 years]
  • The comet was very favorably placed for observations during 1982, with the closest distance from the Sun occurring on November 12 (1.3062 AU) and the closest distance from the Earth occurring on November 27 (0.39 AU). Interestingly, the comet continued to brighten throughout December as it headed away from both the Sun and Earth, with amateur astronomers finding total magnitudes of 9 to 9.5. Around Christmas, Alan Hale (California) was even able to detect the comet with 10x50 binoculars.
    [Perihelion Date=1989 June 18.39; Period=6.59 years]
  • The comet's 1989 appearance was its longest observed apparition. Recovered on 1988 July 6, it was last seen on 1991 May 16, at which time it was situated 4.02 AU from Earth and 4.98 AU from the sun.
    [Perihelion Date=1996 January 17.66; Period=6.59 years]
  • The 1996 appearance was another rather favorable one, although the comet never came closer than 0.9040 AU from Earth (1995 October 7). The comet had become brighter than magnitude 13 at the end of 1995 and continued to brighten. It passed perihelion on 1996 January 17, and with the distances from the Earth and sun increasing thereafter, it continued to brighten for another month. After reaching a maximum brightness of nearly 10.5 in February the comet faded and had dropped below magnitude 13 my mid-April. The coma diameter never exceeded two arc minutes during this apparition.
  • Tim Puckett image of 67P exposed on 1995 November 13
    Copyright © 1995 by Tim Puckett

    This image was taken by Tim Puckett (Villa Rica, Georgia, USA) on 1995 November 13.06, using a 0.30-m f/7 Meade LX-200 and an SBIG ST-6 CCD camera. It is a 300-second exposure.

    [Perihelion Date=2002 August 18.31; Period=6.57 years]
  • The European Space Agency announced on 2003 May 28 that the Rosetta comet-chasing space probe will have a new target: periodic comet Churyumov-Gerasimenko. The spacecraft will be launched during February of 2004 and should rendezvous with the comet during November of 2014. To learn more about Rosetta go to the following web site: http://sci.esa.int/rosetta/.
  • 3-D model of the nucleus of 67P based on Hubble Space Telescope observations from March 2003
    Copyright © 2003 by NASA, European Space Agency and Philippe Lamy (Laboratoire d'Astronomie Spatiale, France)

    The Hubble Space Telescope acquired several images of comet 67P during March 2003 using the WFPC2 camera. This mathematical model indicates the possible shape of the nucleus, which probably measures 5 by 3 kilometers.

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