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151P/Helin

Past, Present, and Future Orbits by Kazuo Kinoshita

DSS2 image of 151P exposed on 1987 August 26
Copyright © 1993-2000 by the California Institute of Technology

This is one of the two discovery photographs of this comet. In the course of the Second Palomar Observatory Sky Survey, the 48-inch Oschin Schmidt Telescope at Palomar Observatory (California, USA) accidently photographed this comet on 1987 August 26.46. The comet trailed during the exposure of the Kodak IIIaF (red) plate, while a trace of tail extends toward the right. This image was obtained through SkyMorph at the Goddard Space Flight Center.

Discovery

     During September 1987, E. F. Helin discovered this comet on plates exposed on 1987 August 24.43 and August 26.42 in the course of the Second Palomar Observatory Sky Survey (Palomar Observatory, California, USA). The plates were originally exposed by J. Mueller using the 48-inch Oschin Schmidt Telescope. Helin described the comet as magnitude 16.5 and condensed, with a faint diffuseness toward PA 235°. A. Maury (Palomar Observatory) subsequently reported that faint images were found on exposures by Mueller and J. Phinney on September 17 and 18.

Historical Highlights

  • The first orbit was calculated by B. G. Marsden using positions spanning the period of August 24 to September 18. It revealed the comet was moving in a short-period orbit with a perihelion date of 1987 August 16.49, a perihelion distance of 2.58 AU, and a period of 14.2 years. This orbit was very close to what later calculations would reveal once further positions became available, with the actual perihelion date being August 12.20.
  • The comet was followed into 1988 and was last seen on February 13.14 by observers at Spacewatch (Steward Observatory, Kitt Peak, Arizona, USA).
  • The comet was recovered by M. Busch, A. Seib, F. Hormuth, R. Stoss, A. Gnadig, and A. Doppler on 2001 June 20.14, while using the Estaci¬ón de Observaci¬ón de Calar Alto (EOCA) 1.52-m reflector (Calar Alto, Almería, Spain). The magnitude was estimated as 20. The prediction by B. G. Marsden was only 1.0 day late, so that the actual perihelion date was 2001 September 23.72. The comet was last detected on 2001 December 17.17, when it was detected by the Lowell Observatory Near-Earth Object Search program.
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