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13P/Olbers

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery

     Heinrich Wilhelm Matthäus Olbers (Bremen, Germany) discovered this comet on 1815 March 6.89 UT. He simply described it as a small comet. It was then in the constellation Camelopardalis. He confirmed the discovery and motion on March 7.80 UT and commented, "The comet goes thus slowly to the north and the east to the body of Perseus. It is small, has a badly defined nucleus, and a very pale transparent coma, and was visible in the cometseeker."

Historical Highlights

  • The comet attained a maximum magnitude of about 5 during the 1815 apparition, and the tail reached a maximum length of about one degree.
  • The comet's first orbit was computed by Gauss on 1815 March 31. It was parabolic and indicated a perihelion date of 1815 April 25.17 UT. During mid-July of 1815, F. W. Bessel noted that observations acquired during the period of March 11 to May 20, could not be well represented by a parabolic orbit, so he determined the first elliptical one. His first result, using the same observational arc revealed a perihelion date of April 26.50 and an orbital period of 73.00 years. He then added an observation obtained during late June of 1815 and revised the orbital period to 73.90 years. Calculations by other astronomers during the following years typically revealed periods of 72 to 77 years.
  • A definitive orbit was later computed by Bessel which gave the period as 74.10 years and predicted the comet would return to perihelion on 1887 February 9. Ginzel reexamined the orbit and gave the perihelion date as 1886 December 17, with a probable error of +/- 1.6 years! Searches were largely unsuccessful, until the comet was accidentally found by William R. Brooks (Phelps, New York) on 1887 August 25. A revised orbit revealed the comet had passed perihelion on 1887 October 8.
  • The comet was last detected in 1956. It reached a maximum magnitude of 6.5, while the tail reached a maximum length of one degree. The calculated perihelion date was only 5.5 days off.
  • The orbit of this comet seems to be relatively stable, with no orbit-altering close approaches to Jupiter during the period of 1668 to 2165. The comet will make its closest approach to Earth on 2094 January 10, with the distance then being 0.756 AU.
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