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7P/Pons-Winnecke

Past, Present, and Future Orbits by Kazuo Kinoshita

NEAT image of 7P exposed on 2002 May 27
Copyright © 2002 by Near Earth Asteroid Tracking (NEAT)

This image is a combination of three images obtained by the Near Earth Asteroid Tracking (NEAT) program using the 48-inch Oschin telescope and a CCD camera on 2002 May 27.54, May 27.55, and May 27.56. Each image was exposed for 20 seconds.

Discovery

     Jean Louis Pons (Observatory of Marseille, France) discovered this comet on 1819 June 12. The comet was then in Leo and was described as small, with a central condensation.
     Friedrich August Theodor Winnecke (Bonn, Germany) accidentally rediscovered this comet on 1858 March 9.06. It was then located in Ophiuchus and was described it as a pale and diffuse nebulosity, about 3 arcmin across.

Historical Highlights

  • The comet was particularly well placed during its discovery apparition, but its most significant event, a close approach to Earth on 1819 August 21 (0.1318 AU) was missed. Following its discovery on June 12 the comet was followed until lost in evening twilight after July 22. The comet took on a southwestern motion thereafter, and was in southern skies by the time it emerged from the sun's glare. On August 31 it reached its most southerly declination of -43.6°.
  • Using only three positions obtained during the period of 1858 March 9 to 13, Krüger computed a parabolic orbit that he immediately recognized as so similar to Pons' comet of 1819 that he suggested they were identical. Shortly thereafter, Winnecke applied the orbit of the 1819 comet to the available positions and found an almost perfect agreement by assuming a perihelion date of 1858 May 2.47, and slightly increasing the inclination.
  • Predictions were made for the 1863 return, but they revealed the comet was very poorly placed for recovery and the comet was subsequently missed. Predictions for the 1869 return showed the comet would be much more favorably placed. The comet was subsequently recovered on 1869 April 10 by Winnecke. It was very close to the predicted positions. The comet passed 0.25 AU from Earth on July 8 and observers saw a coma 10 arcmin across which contained a nucleus of magnitude 8. A short tail was also seen.
  • Since the 1869 appearance, the comet has only been missed on three occasions (1880, 1904, and 1957).
  • Perturbations by Jupiter have steadily increased the comet's orbital period and perihelion distance since its first successfully predicted recovery in 1869. Close approaches occurred in 1882 November (0.44 AU), 1894 November (0.45 AU), 1906 December (0.42 AU), 1918 November (0.36 AU), and 1930 July (0.47 AU). In 1869 the period was 5.59 years and perihelion distance was 0.78 AU, while in 1996 they were 6.37 years and 1.26 AU.
  • The 1927 appearance was the best since the comet's discovery. It passed only 0.0404 AU from Earth on 1927 June 26 and attained a maximum brightness of magnitude 3.5.
  • For a few years the perturbations by Jupiter enabled strong displays of meteors to be seen around June 28 of the years the comet arrived at perihelion. The meteor stream became known as the June Boötids, but was occasionally also known as the Pons-Winneckids. Very strong displays were noticed in 1916, 1921, and 1927, which also marked three consecutive perihelion returns for the comet. In the latter year, rates reached 500 per hour at one point. Continued perturbations by Jupiter have moved the comet and its meteor stream into slightly different orbits and the June Boötids have been hardly noticeable in recent years.
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