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


Past, Present, and Future Orbits by Kazuo Kinoshita

A. Nakamura image of 97P exposed on 2000 November 22
Copyright © 2000 by Akimasa Nakamura (Kuma Kogen Astronomical Observatory, Japan)

This CCD image was taken on 2000 November 22.54 UT, using a 0.60-m f/6 Ritchey-Chretien telescope.


     The Reverend Joel Hastings Metcalf (Taunton, Massachusetts, USA) discovered this comet in Eridanus on a photograph exposed on 1906 November 15.11. He estimated the magnitude as 12, and described the comet as about 2 arc minutes across, with a distinct central condensation. The comet was extensively observed, but only until 1907 January 16. There was subsequently an uncertainty of several weeks in the orbital period and the comet was lost.
     Howard J. Brewington (near Cloudcroft, New Mexico, USA) was comet hunting on the night of 1991 January 7, when he found a diffuse object on January 7.18. He determined the total magnitude as 9.8 and said the object was strongly condensed. An independent discovery was made by William A. Bradfield on January 7.53, but it was reported too late to rename the comet. On January 9 the Central Bureau for Astronomical Telegrams announced that Brewington's comet was identical to the lost periodic comet Metcalf.

Historical Highlights

  • The first orbit was computed by Carl Wilhelm Ludwig Martin Ebell and was first published on 1906 November 28. It was a parabolic orbit with a perihelion date of 1906 September 15.83 and a perihelion distance of 1.993 AU. During early December Crawford computed the first elliptical orbit. The perihelion date was given as 1906 October 16.95 and the perihelion distance was given as 1.630 AU. The orbital period was 6.89 years. After the final observation, the orbit was revised and the orbital period was given as 7.77 years.
  • Computations revealed the comet would likely return to perihelion during 1915 June. Searches were made and Leavitt reported she recovered this comet on 1915 February 10.22; however, a few days later, Edward Charles Pickering said the object found by Leavitt turned out to be a minor planet. The comet was not recovered, and in 1922 Gerald Merton revealed the comet had passed 0.86 AU from Jupiter on 1911 September 15, which slightly altered the orbit.
  • For the 1922 apparition, searches were made using orbits supplied by A. C. D. Crommelin and Merton. The former astronomer suggested a perihelion date of 1921 December, while the second gave it as 1922 March 3. The comet was again not found.
  • Searches were again attempted in 1929, using Merton's orbit which indicated a perihelion date of 1929 November 23. This was not considered a favorable apparition and the comet was not located.
  • The comet was assumed lost and was generally ignored during the next 4 decades, but a new analysis of the 1906-1907 apparition was made by V. V. Emel'yanenko, N. Yu. Goryajnova, and N. A. Belyaev during 1975. They confirmed the close approach to Jupiter during 1911 September, but added that additional close approaches occurred during 1935 August (1.17 AU) and 1969 August (1.05 AU). They predicted the comet would next arrive at perihelion during 1975 June 20.92, but searches revealed nothing.
  • Another prediction was made for the comet's anticipated 1983 appearance. During early January Jeff Johnston and Michael Candy (Perth Observatory, Australia) were conducting a photographic search for the lost periodic comet when they found a 15th-magnitude diffuse object on a plate exposed on January 5. Additional images were found on plates exposed on January 7 and 9. The images obviously did not represent the motion expected for comet Metcalf and the object was announced as a new comet. No further images were obtained and no reasonable orbit could be determined. Re-examination of the three plates revealed the "observations" were nothing more than plate defects.
  • Brewington found the comet just two days after its January 5 perihelion passage during 1991. The comet had actually passed closest to Earth on 1990 September 16 (1.0425 AU). After passing perihelion, the comet brightened to about magnitude 9 by mid-January, and then began fading.
  • As the comet left the sun's vicinity during 1991 it passed close to Jupiter on 1993 March 28 (0.11 AU). The result was the orbital period increasing to about 10.5 years and the perihelion distance increasing to about 2.61 AU.
  • In the course of the routine search for near-Earth asteroids, LINEAR found an asteroid-like object on 2000 September 1.26. The magnitude was given as 19.0. G. V. Williams (Minor Planet Center) identified the "asteroid" as comet 97P. It was then 1.1° from the prediction, which indicated a correction to the predicted perihelion date of about +3.5 days.
  • cometography.com