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18D/Perrine-Mrkos

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery

     Charles Dillon Perrine (Lick Observatory, California, USA) discovered this comet on 1896 December 9.35. He estimated the magnitude as 8 and said there was a well-defined nucleus, as well as a tail less than 30 arc minutes long. The comet was confirmed by Perrine on December 10.15.
      After being lost following its 1909 apparition, the comet was accidentally found by Antonin Mrkos (Skalnate Pleso Observatory) during a routine search for comets with 25x100 binoculars on 1955 October 19.96. He estimated the magnitude as 9. Almost immediately, Leland E. Cunningham (Leuschner Observatory, University of California, Berkeley) said the comet was probably the lost periodic comet Perrine.

Historical Highlights

  • Following the December full moon, the comet was widely observed during the final days of December. Astronomers then described it as 3 to 4 arc minutes across, with a nucleus of magnitude 10.5 to 11. The comet faded during January and by February it was only being observed at a handful of observatories. R. Schorr (Hamburg) saw the comet on the February 3 and said it appeared small and faint, with a distinct, starlike condensation of magnitude 12.5. Kobold (Strassburg) said the comet was barely seen in an 18-inch refractor on February 24. He described it as "a pale wisp" about 1 arc minute across. Observations continued into March, but only barely. Kobold said the comet was still barely visible in the 18-inch refractor on the 1st and H. C. Wilson (Northfield) obtained the final observation on March 4.1. Wilson was using a 16-inch telescope and noted the comet was "most exceedingly faint, but certainly seen."
  • The first parabolic orbits were published on December 14. The first was computed by W. J. Hussey and Perrine from observations obtained on December 9, 10, and 11. It indicated a perihelion date of 1896 November 26.17. The second was determined by F. Ristenpart (Heidelberg) and indicated a perihelion date of December 1.21. By mid-January, Ristenpart, as well as Hussey and Perrine, had recognised the comet's short-period orbit, as well as a resemblance to the orbit of the lost periodic comet Biela. The orbit of Perrine's comet was indeed similar to that of Biela except for the argument of perihelion, which differed by 60 degrees. Ristenpart computed a revised elliptical orbit which was published on February 4. The perihelion date was November 25.12 and the orbital period was 6.44 years. He examined several hypotheses as to a possible relationship between this comet and the lost periodic comet Biela. Even with the gravitational effects of Jupiter being considered the orbits of the two comets could never be made to match up at any given time between the disappearance of Biela and the discovery of Perrine's comet.
  • F. Ristenpart predicted this comet would arrive at perihelion on 1909 November 4.58. A. Kopff (Astrophysikalisches Institut Königstuhl-Heidelberg, Germany) recovered it on 1909 August 12.93. He estimated the magnitude as 15. The comet was followed until November 21.02 when Wolf photographed it and estimated the magnitude as 14.0. Wolf exposed a photographic plate on the comet's position on 1910 January 8, but no trace could be found.
  • The 1916 apparition was expected to be unfavorable and no searches were made, but that of 1922 was considered much better. Several searches were made, and although the comet's recovery was announced in Japan, this proved not to be the expected comet and no observations were made. The comet was also searched for in 1929, but again no trace was found.
  • After several apparitions went by without predictions or searches, Ichiro Hasegawa published a prediction in 1955 for the 1955 apparition. Searches again proved unsuccessful, but on October 19 Mrkos discovered a comet which later proved to be the lost comet Perrine [see above under Discovery].
  • The comet was again seen during the 1961-2 and 1968-9 apparitions, with the comet reaching magnitude 13 during the latter period. The 1975 return was expected to reach a magnitude of 15, but searches again failed to find the comet. Failures during the next few apparitions also failed and the comet is again lost.
  • The most recent investigation of this comet's orbit was published by S. Nakano on 2001 December 23 in Nakano Note No. 835. He took 17 positions measured during the period of 1961 to 1969, applied perturbations by Mercury to Neptune and five minor planets, and determined the perihelion date as 2002 September 10.39.
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