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Past, Present, and Future Orbits by Kazuo Kinoshita

J. Ticha and M.Tichy obtained this image on 2001 December 9
Copyright © 2001 by J. Ticha and M.Tichy (Klet' Observatory, Czech Republic)

The image of two nuclei (A and D) of comet 51P/Harrington was taken on 2001 Dec. 9.87 UT with 0.57-m f/5.2 reflector and an SBIG ST-8 CCD camera. of Klet' Observatory. It is a 60-second exposure. The comet is arrowed and nucleus A is on the left, while D on the right. The field of view is 16 to 10 arc minutes with north to the top and west to the right. A faint tail can be seen streaming off toward the right.


     Robert G. Harrington discovered this comet on a plate taken on 1953 August 14.41 with the 122-cm Schmidt camera during the National Geographic Society-Palomar Sky Survey. The comet was located in Aquarius. He estimated the magnitude as 15, and described the comet as diffuse, with a central condensation, and a tail less than 1° long.

Historical Highlights

  • This was a very favorable apparition for this comet, with its perihelion and closest approach to Earth coming within 10 days of one another during 1953 September. The comet's brightness held near 15 throughout September and then began fading. The magnitude had dropped to 18 during the final days of October, and was determined as 18.8 when last seen on December 10.
  • During 1967, Grzegorz Sitarski (Institute of Astronomy, Polish Academy of Sciences, Warsaw, Poland) computed corrected orbital elements for the 1953 apparition. He then advanced the comet backwards to check on its recent orbital evolution. Sitarski noted the comet's orbital period was 6.65 years when it passed perihelion in 1918. It then passed 0.8 AU from Jupiter on 1920 November 19 and the orbital period was changed to 6.99 years. The result of this nearly 7-year orbital period was that the apparitions of 1925, 1932, 1939, 1946, and 1953 were all nearly identical, having passed perihelion within a few days of September 25 each time. These favorable conditions ended because of a close approach to Jupiter on 1956 October 26 (0.50 AU). Sitarski noted that the 1953 apparition "was the last opportunity to discover this faint comet on the sky."
  • B. G. Marsden investigated the orbit of this comet and predicted it would next arrive at perihelion on 1960 June 28.35. Elizabeth Roemer (U. S. Naval Observatory, Flagstaff station, Arizona, USA) recovered this comet on 1960 August 3.45. The magnitude was estimated as 19, and the comet was described as diffuse, with a condensation, and a tail less than 1° long. The comet changed little in brightness from its recovery until it was last seen on October 26 when Roemer determined the magnitude as 19.8. This was primarily because the comet was steadily approaching Earth, the closest distance being 1.13 AU on November 4.
  • The comet was not observed during its returns in 1967 and 1974 since perihelion occurred when the comet was in conjunction with the sun.
  • The comet was next recovered on 1980 September 4 when P. Jekabsons photographed it at magnitude 18.5. This was still not a favorable apparition and the comet was not seen after October 6. It was also seen during its returns in 1987 and 1994. The latter was very favorable, allowing amateur astronomers to make observations as it reached magnitude 13.5.
  • This comet surprised astronomers during its 1994 return. IAU Circular 6089, reported that Jim Scotti (Lunar and Planetary Laboratory, Arizona, USA) discovered two companions on 1994 October 5. The magnitude of the primary was 12.8, while the two fragments shown at 21.3 and 20.2.
  • The comet next passed perihelion on 2001 June 5. Following that apparition it will approach to within 0.37 AU from Jupiter on 2003 October 23. This close approach will rotate the orbit's ascending node by over 30 degrees and increase the perihelion distance from 1.568 AU to 1.688 AU. The orbital period will change from 6.77 to 7.13 years. Overall this will make the comet an even fainter object at each perihelion passage. The next close approach will not occur until 2039 (0.41 AU).
  • Additional Images

    Pepe Manteca of Spain obtained this image on 2001 December 5, which shows the comet's motion
    Copyright © 2001 by P. Manteca (Observatorio de Begues, Spain)

    This animated image was obtained by Pepe Manteca (Observatorio de Begues, Spain) on 2001 December 5. It shows the movement of nucleus "A" and "D". Note the fan-shaped tail extending toward the left.

    Pepe Manteca of Spain obtained this image on 2001 December 6
    Copyright © 2001 by P. Manteca (Observatorio de Begues, Spain)

    This image was obtained by Pepe Manteca (Observatorio de Begues, Spain) on 2001 December 6. It shows nucleus "A" and "D".

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