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20D/Westphal

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery

     J. G. Westphal (Göttingen, Germany) discovered this comet on 1852 July 24.97 in the constellation of Cetus. He noted that a comet-seeker showed it as a bright nebulosity several arc minutes across. Westphal confirmed his discovery on July 26.05. C. H. F. Peters (Constantinople) independently discovered this comet on August 9.

Historical Highlights

  • Apparition of 1852 (discovery): Moonlight was initially a problem for observers, but the comet finally came under widespread observation after August 10. The comet brightened throughout August, although no magnitude estimates were made. A probable taillike extension was noted around mid-month, with H. L. d'Arrest and E. Hartwig (Leipzig, Germany) noting it pointed toward PA 55° on the 17th. For the period of August 16 to 22, observers noted the comet was between 2.5 arc minutes and 5 arc minutes across. The comet continued to brighten during September, but where Eduard Schoenfeld (Bonn, Germany) reported it was possibly visible to the naked eye on the 5th, no other naked-eye observations were reported until A. Reslhuber (Kremsmünster, Austria) found it easily visible on October 4. Reslhuber described the comet as not easy to see on September 10, but bright in strong moonlight on the 23rd. C. Fearnley (Christiania, now Oslo, Norway) said the tail extended 30' toward PA 225° on the 2nd. The comet was moving away from Earth, but still heading toward the sun as October began. It was also visible throughout the night for most observers, and passed within two degrees of the north celestial pole on October 5. Schoenfeld reported the final naked-eye observation on the 19th, with the moon interfering thereafter. The longest tail length was reported on October 5, when J. R. Hind noted it was 40' long. Fearnley said the tail was extending toward PA 25° on the 14th. The comet's most interesting day during the 1852 apparition was October 11. Hind described the comet as rather curious and then elaborated, "The nebulosity was extended in the usual direction of the tail and a small glimmering point was visible in the more condensed part situated near the boundary of the nebulosity toward the sun. From this point a ray of light shot out into the cometic matter forming a short tail: at moments this was very distinct and reminded me of some of the drawings of Halley's Comet with its luminous sector." Interestingly, Fearnley also reported a jet emanating from the nucleus and extending about 1 arc minute toward the tail. The comet was moving away from both the sun and Earth as November began. All descriptions of it during the month indicated it was very faint, especially after moonlight began interfering from the 17th onward. Aside from the brightness, little else was reported about this comet other than positions, although Fearnley did note on the 12th that the coma was 3 arc minutes across and exhibited a tail extending toward PA 30°. The comet continued to fade during December and observations were obtained until the moon began interfering around mid-month. Reslhuber said the comet was seen with great difficulty on December 5 and was seen as a weak trace on the 10th. Other observers, such as C. A. F. Peters (Königsberg, now Kaliningrad, Russia), typically reported the comet as very faint and diffuse. Fearnley said the coma was 8 arc minutes across on December 3, while the tail extended toward PA 0°. As January began, only a handful of observers were continuing to follow the comet. Peters described the comet as very faint and diffuse on the 3rd and 7th, while N. R. Pogson (Radcliffe Observatory, Oxford) gave the same description on the 6th. Schoenfeld measured the position for the final time on January 11.75. Following the period of moonlit evening skies, Schoenfeld looked for and found the comet on January 27, but the moon rose and prevented a measure of its position. Many days of bad weather followed and Schoenfeld found the comet again in the evening sky on February 9. Its large and very faint appearance prevented a measure of the position and no further observations were made.
  • The first orbit was calculated by A. Sonntag. He used three positions obtained during the period of July 26 to 30, and determined a parabolic orbit with a perihelion date of 1852 October 14.58. Additional orbits by Sonntag, G. Rümker, and B. Valz during the next few weeks revealed a notable departure from parabolic motion. The first elliptical orbit was calculated by A. Marth using positions covering the period of July 28 to September 18. The resulting perihelion date was October 13.13 and the period was 67.8 years. Orbits during the next few weeks and years by Sonntag, A. Möller, and Westphal indicated the orbital period was between 60.0 and 60.7 years.
  • Apparition of 1913: Although predictions were made for the next return, searches proved fruitless until the comet was accidentally found by Pablo T. Delavan (La Plata Observatory) on 1913 September 27.0. He was conducting a routine search of the sky with a 20-cm comet-seeker when he found the comet near Omicron Aquarii and described it as "nearly round with a strong central condensation, but having no truly stellar nucleus. No tail was visible with the instruments used. Its total magnitude was then nearly equal to that of a seventh-magnitude star." Although Delavan had been sure that no one else had seen this comet, he was unaware that ephemerides had been published for the expected return of the comet Westphal. His colleague, W. J. Hussey suggested a possible link in the first telegrams announcing the comet's discovery. Orbital computations thereafter revealed the perihelion date for the 1852 apparition had actually been October 13.22, while the period was 61.20 years. Although astronomers quickly began observing the comet during the last days of September, there were unusual changes during October. The comet was expected to brighten throughout October and most of November. E. E. Barnard (Yerkes Observatory, Wisconsin, USA) observed the comet on September 28 and estimated the coma was about magnitude 9, while the nucleus was near magnitude 8. That same evening, R. G. Aitken (Lick Observatory, California, USA) reported a "small, disk-like nucleus" of magnitude 11. Barnard and Kiyofusa Sotome (Tokyo Astronomical Observatory, Japan) both reported a star-like nucleus during the first days of October, but Barnard could no longer see the nucleus on the 6th. During the next few days he reported the central condensation became more diffuse. Following interference from moonlight, Barnard found the comet on October 22 and described it as "very much elongated as if it had a more or less pointed head." By the 26th, Barnard said the comet was very diffuse, with no definite condensation. Barnard's final observations were made with the 40-inch refractor on November 5. At 1:10 UT he wrote, "there is a feeble glow about the small star which I think must be it." At 3:37 UT, Barnard said "there is absolutely no form to the comet nor any condensation. It seems to be somewhat elongated. All you can say is that there is something large there."
  • Predictions were made for the comet's return in 1976. Although some searches were conducted, no trace of the comet was found.
  • Close approaches to planets: Using an orbit calculated by L. M. Belous in 1975, the webmaster has meticulously integrated the orbit of this comet, both forward and backward. For the 19th, 20th, and 21st centuries, there were no close approaches to any planet that would result in alterations of the orbit. There were, however, two close approaches to Earth.
    • 0.61 AU from Earth on 1852 September 13 (contributed to comet's discovery)
    • 0.59 AU from Earth on 1913 September 30

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