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72P/Denning-Fujikawa

Past, Present, and Future Orbits by Kazuo Kinoshita

T. Seki image of 72P exposed on 1978 October 12
Copyright © 1978 by T. Seki (Japan)

This image was obtained by T. Seki on 1978 October 12. Using his 40-cm reflector, this is a 7-minute exposure on a Fuji FLO-II photographic plate.

Discovery

     W. F. Denning (Bristol, England) discovered this comet in the morning sky on 1881 October 4.13. It was then in the constellation Leo and had a daily motion of 30' eastward. Denning described the comet as "a small bright nebula, round, and much brighter in the middle." An independent discovery was made by W. R. Brooks (Phelps, New York) with a 13-cm reflector. The 1882 March issue of the Siderial Messenger said that Brooks made the observation on October 4.33 "but that clouds obscured it before a position could be obtained."

     Shigehisa Fujikawa (Onohara, Kagawa, Japan) discovered a "cometlike object" on 1978 October 9.81. He estimated the magnitude as 11, and said the comet was diffuse, without a condensation. E. Everhart (Chamberlin Observatory, Colorado, USA) confirmed the discovery on October 10.47. He estimated the magnitude as 11, and described the comet as diffuse, with a slight condensation. H. L. Giclas (Lowell Observatory, Arizona, USA) independently confirmed the comet on October 10.51. He estimated the magnitude as 9, and described it as diffuse, with a condensation.

Historical Highlights

  • 1881 Apparition: The comet had already passed closest to the sun and Earth when discovered. During the remainder of October, observers generally described the comet as fairly bright, with a central condensation. F. A. T. Winnecke (Strasbourg, France) observed with a 46-cm refractor on the 19th and said the comet exhibited a distinct, eccentric condensation. J. F. J. Schmidt (Athens, Greece) could not find the comet in the morning sky with the 17-cm Reinfelder refractor on October 20 and 21; however, he did locate it with the same telescope on the 28th and described it as an extremely faint nebulosity. On the 29th, Winnecke said the comet was faintly seen during poor seeing, but appeared oblong during moments of good seeing, with a major axis of about 2'. Also on October 29, E. Hartwig (Strasbourg, France) saw the comet very easily in the finder of the 15-cm refractor. During November, the only physical descriptions came from E. J. M. Stephan (Marseille, France) and Schmidt. Stephan said the comet was very faint with slight condensation in an 80-cm telescope on November 3. Schmidt said the comet appeared as an extremely faint nebulosity in the 17-cm refractor on November 4. The comet was last seen on November 25.13 by Winnecke.
  • The first orbit was calculated by H. Oppenheim. Using positions from October 6, 10, and 12, he provided a parabolic orbit with a perihelion date of 1881 September 12.96. A few days later, L. Schulhof took positions spanning the period of October 6 to 19 and determined the perihelion date as September 13.89, while J. Palisa took a similar set of positions and found a perihelion date of September 13.13. Schulhof noted that this orbit left generally large errors between the observed and calculated positions. He then found that an elliptical orbit with a perihelion date of September 13.54 and a period of 7.74 years fit the positions much better. In the following weeks the period was determined as 8.34 years by S. C. Chandler, Jr., 8.45 years by Schulhof, 8.41 years by E. Hartwig and L. Wutschichowsky, 9.11 years by E. E. Block, and 8.83 years by Hartwig. Block suggested this comet was a return of D/1819 W1. Interestingly, it was not until 1889 that an astronomer calculated an orbit using positions spanning the entire period of visibility. B. Matthiessen took those positions, applied perturbations by Mercury to Saturn, and determined the perihelion date as September 13.81 and the period as 8.69 years. Following the comet's rediscovery in 1978, orbits using positions from both 1881 and 1978 revealed that the 1881 orbit had a perihelion date of September 13.83-13.85, while the period was 8.71 years.
  • Matthiessen provided a prediction for the 1890 apparition. He took his orbit for the 1881 appearance and applied perturbations by Mercury to Saturn. The result was a perihelion date of 1890 May 19.33. The comet was not found and actually remained lost until accidentally found by Fujikawa in 1978. Interestingly, following the 1978 appearance, astronomers found that Matthiessen's prediction for the 1890 apparition was only about a day late.
  • 1978 Apparition: The comet was well observed during this apparition, with observers generally giving the magnitude as 10-11 during the days following discovery; however, since it was moving away from both the sun and Earth, it faded fairly rapidly. On October 16, T. Seki (Kochi Observatory, Geisei station, Japan) gave the magnitude as 13 in moonlight and noted the comet's image was weak and faint, but appeared diffuse and uncondensed. Seki then estimated the magnitude as 15 on October 29 and 31, 15.5 on November 2, 17.5 on November 8, and 18 on November 9. C.-Y. Shao (Harvard College Observatory, Agassiz Station) obtained several photographs of the comet using the 155-cm reflector. He noted the comet was very diffuse on October 28 and November 1. Shao also noted a tail on November 2 and 3, which extended 1.0-1.5 arc minutes in PA 300°. The comet was last detected on December 29.39, when it was photographed by astronomers at Harvard College Observatory's Agassiz station.
  • The first orbital calculations for the 1978 rediscovery were made by B. G. Marsden. He used five available positions and calculated three orbits. The first orbit was parabolic and gave the perihelion date as 1978 September 30.71. The second orbit was elliptical and gave the perihelion date as October 2.26 and the period as 4.37 years. The third orbit was "derived on the assumption that the comet is identical with P/Denning 1 (1881 V) and that 11 revolutions have been made since the original discovery...." Marsden included approximate perturbations by the five outer planets, and noted a fit about as good as that obtained by the parabola. The perihelion date was determined as October 2.04 and the period was 9.01 years. On November 6, Marsden approximately linked the apparitions of 1881 and 1978. For this apparition, he determined the perihelion date as October 2.04 and the orbital period as 9.01 years. Perturbations by Jupiter to Pluto were included. Marsden suggested, "The comet would have been favorably placed for observation near its perihelion dates of 1916 Oct. 8, 1960 Sept. 14 and 1969 Sept. 23." Ultimately, the orbit proved to have a perihelion date of October 2.14 and a period of 9.01 years.
  • Several predictions were provided for the 1987 apparition. The perihelion date was given as August 3.91 by S. Nakano, using 17 positions from the 1978 apparition. Karen Meech (Cerro Tololo Inter-American Observatory) used the Schmidt telescope to obtain 80-minute exposures on 1988 March 18, 19, 20, and 21, but the comet was not found. Seki said that he "meticulously searched using the 60cm reflector, but failed to find it."
  • Several predictions were provided for the 1996 apparition. The perihelion date was given as May 31.26 by P. Rocher, using 26 positions from the 1978 apparition. The perihelion date was given as May 29.78 by K. Muraoka, using 28 positions from the 1881 and 1978 apparitions.
  • Several predictions were provided for the 2005 apparition. The perihelion date was given as June 19.96 by S. Nakano, using 34 positions from the 1881 and 1978 apparitions. The perihelion date was given as June 20.04 by K. Kinoshita, using 20 positions from the 1881 and 1978 apparitions.
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