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37P/Forbes

Past, Present, and Future Orbits by Kazuo Kinoshita

G.
Copyright 1999 by Gerald Rhemann (Austria)

This image was taken by Gerald Rhemann on 1999 July 20.02. He used a 0.25-m Schmidt camera. Exposure time was 10 minutes and the photographic emulsion was hypered TP6415. The comet's magnitude was then estimated as 12.0. The webmaster has cropped the image to save space. (Thanks to Gerald Rhemann for permission to use this image.)

Discovery

     Alexander F. I. Forbes (Rosebank, South Africa) discovered this comet in Microscopium on 1929 August 1. He estimated the magnitude as 11. Forbes informed astronomers at Johannesburg, but no announcement was made until they confirmed the comet on August 3.71.

Historical Highlights

  • Harry Edwin Wood (Union Observatory, South Africa) published the first parabolic orbit on August 21. It indicated a perihelion date of 1929 May 26. Bernhard H. Dawson (La Plata Astronomical Observatory, Argentina) published the first elliptical orbit on September 30. It indicated a perihelion date of June 26 and an orbital period of 6.37 years. Dawson revised his orbit near the end of 1929 and obtained very similar numbers. He added that the comet was last at perihelion during 1923, but had been badly placed. It had passed close to Jupiter prior to that perihelion.
  • Since the comet was already passed its perihelion and closest distance from Earth (0.55 AU on July 15) it faded following it 1929 discovery. It reached magnitude 14 as October began and was near 15 at the beginning of November. George van Biesbroeck (Yerkes Observatory, Wisconsin, USA) was the final observer when he saw the comet at magnitude 16.5 on November 22.
  • Frederick Richard Cripps and Hans Q. Rasmusen independently provided orbits for the 1935. Cripps said the comet would arrive at perihelion on 1935 November 16.18, while Rasmusen gave it as 1935 November 16.00. Unfortunately, the comet was not favorably placed, as the comet would be close to the sun when at its brightest.
  • Apparition of 1942: The comet was recovered at its 1942 apparition. Cripps had provided a prediction that the comet would arrive at perihelion on April 16.90, while N. Makarov (University of Kazan, U.S.S.R.) predicted a perihelion date of April 17.6. Van Biesbroeck recovered this comet on a 20-minute exposure obtained with the 24-inch reflector on 1942 June 15.35. His precise position indicated Cripps' prediction was only in error by one-half day, while Makarov's was off by 1.25 day. Van Biesbroeck said the comet appeared on the two plates as a 15th-magnitude object exhibiting a tail extending about 1 arc minute in PA 270 degrees. The comet apparently reached 12th magnitude during July, and then faded and was last seen by van Biesbroeck at McDonald Observatory on October 5.
  • Apparition of 1948: The comet was again detected on 1948 May 14, and brightened to magnitude 14.5 during September. The comet was last detected on October 2. The 1955 apparition was again not very favorable and no observations were made.
  • Apparition of 1961: The comet's 4th observed apparition came in 1961. Elizabeth Roemer (U. S. Naval Observatory, Flagstaff station, Arizona, USA) recovered the comet on a 120-minute photograph exposed on 1961 January 16.50. The magnitude of the condensed image was determined as 20.2, but as only one photograph was obtained, it was only suspected of being 37P/Forbes. An opportunity for Roemer to confirm the recovery did not come until February 13, when images were found on a pair of plates. The comet reached a maximum magnitude of 10 during July and then faded and was last detected on December 5. The nucleus was then estimated as magnitude 19.8. The 1967 apparition was again unfavorable. Numerous searches were made during the period of March through November, but without success.
  • The comet has been seen at every return since 1974. Prior to the 1999 apparition, the best returns were those of 1974 (magnitude 13) and 1993 (magnitude 14). The comet seemed to be heading for another normal apparition in 1999, when it attained its predicted total magnitude of 13 at the end of May and early in June. Then the comet seemed experienced an outburst around mid-June, when observers began reporting a brightness of magnitude 11, if not slightly brighter. As the comet moved away from both the sun and Earth, it finally faded back to 13 by early September and was near 14 around mid-October.
  • Close approaches to planets: The comet experienced three close approaches to Earth and one close approach to Jupiter during the 20th century. The first half of the 21st century includes four close approaches to Earth and one close approach to Jupiter. (From the orbital work of Kazuo Kinoshita)
    • 0.55 AU from Earth on 1929 July 16
      • contributed to comet's discovery
    • 0.58 AU from Earth on 1961 June 25
    • 0.83 AU from Earth on 1974 August 14
    • 0.37 AU from Jupiter on 1990 August 30
      • decreased perihelion distance from 1.47 AU to 1.45 AU
      • decreased orbital period from 6.26 to 6.13 years
    • 0.56 AU from Jupiter on 2001 October 17
      • increased perihelion distance from 1.45 AU to 1.57 AU
      • increased orbital period from 6.13 to 6.35 years
    • 0.67 AU from Earth on 2005 June 20
    • 0.98 AU from Earth on 2018 August 18
    • 0.95 AU from Earth on 2037 May 30
    • 0.70 AU from Earth on 2050 June 22

    Additional Images

    M.
    Copyright 1999 by Michael Jäger (Austria)

    This image was taken by Michael Jäger on 1999 June 24.02. He used a 0.25-m Schmidt camera. Exposure time was 7 minutes and the photographic emulsion was hypered TP6415. The comet's magnitude was then estimated as 11.5. The webmaster has cropped the image to save space. (Thanks to Gerald Rhemann for permission to use this image.)

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