G A R Y   W.   K R O N K ' S   C O M E T O G R A P H Y

122P/de Vico

Past, Present, and Future Orbits by Kazuo Kinoshita

H. Mikuz image of 122P exposed on 1995 October 1
Copyright © 1995 by Herman Mikuz (Crni Vhr Observatory, Slovenia)

An excellent mosaic of two 180s exposures was taken by H. Mikuz on 1995 October 1 with the 20-cm, f/2 Baker-Schmidt camera, ST-6 CCD and V filter.


     Francesco de Vico (Collegio Romano Observatory, Rome, Italy) discovered this comet in Cetus on 1846 February 20. He described it as fairly bright, with a substantial condensation and a tail. It was moving rapidly northward. An independent discovery was made by William C. Bond (Harvard Observatory, Massachusetts) on February 26. The comet reached a maximum magnitude of about 5 by mid-March and then faded. It was last seen on May 20. Several astronomers computed orbits during the years that followed. Ultimately the calculations revealed orbital periods ranging from 69.7 to 75.7 years.
     Three Japanese astronomers found this comet within minutes of each other around 1995 September 17.8. They were Yuji Nakamura (Suzuka, Mie), Masaaki Tanaka (Iwaki, Fukushima), and Shougo Utsunomiya (Minamioguni, Kumamoto). The comet was about five arc minutes across with a central condensation. Tanaka obtained a 2-minute exposure with a 0.20-m Schmidt camera which revealed an ion tail 25 arc minutes long in PA 260° and a dust tail five arc minutes long in PA320°. Independent discoveries were also made by T. Seki (Geisei, Japan) on September 17.82 and Don E. Machholz (Colfax, California, USA) on September 18.5. Seki estimated the magnitude as 5, while Machholz gave it as 6.
     After enough observations had come in it was realized this comet was the same as de Vico's periodic comet of 1846. These observations indicated the comet had apparently returned to perihelion during April 1922.

Historical Highlights

  • In 1887, von Hepperger predicted the comet would next arrive at perihelion during the latter half of 1921. Because of the uncertainty in the orbital period, he said perihelion could actually occur anytime between 1919 and 1925. Searches revealed nothing. Buckley reinvestigated this comet's orbit in 1976 and concluded the orbital period was 76.30 years, indicating a perihelion passage in early 1922. But he said the uncertainly was still about 2 years.
  • Following the recovery around mid-September of 1995, the comet came under widespread observation by amateur astronomers around the world. Charles S. Morris (California, USA) saw the comet on September 18. He estimated the magnitude as 6.5 and saw a strongly condensed coma about four arc minutes across, as well as two faint tails: one 70 arc minutes long in PA 295°, the other 45 arc minutes long in PA 5°. By the end of the month, observers were generally estimating the magnitude as slightly brighter than 6, while the coma was about five arc minutes across. The tail was narrow in appearance and was over 2° long.
  • The comet reached its peak brightness during the early half of October. Observers were then consistently estimating a brightness of 5.5. The coma diameter was given as between 6 and 7 arc minutes across and there was a central condensation nearly one arc minute across. Nearly 2° of tail was easily visible to observers, while photography indicated the length was over 8°. The comet steadily faded during the latter half of the month, with magnitude estimates near 6.5 by the end of the month. Coma diameter estimates continued to increase, with several observers reporting a size of 7 to 8 arc minutes by the end of the month. About one-half degree of tail was still easily visible with a pair of binoculars. The comet was last detected on 1996 June 25.28, when Hergenrother detected it with a 120-cm telescope. He determined the magnitude as 22.4.
  • Additional Images

    Yuichi Chimura image of 122P exposed on 1995 September 24
    Copyright © 1998 by Yuichi Chimura

    This image was taken by Yuichi Chimura (Japan) on 1995 September 24.

    Kazuyuki Ito image of 122P exposed on 1995 October 6
    Copyright © 1995 by Kazuyuki Ito (Sengamine Observatory, Japan)

    This image was obtained by Kazuyuki Ito on 1995 October 6 with the 20-cm, f/6.0 reflector and an ST-6 CCD.