Copyright � 2000 by Akimasa Nakamura
This image was obtained on 2000 August 04.65 UT, using a 60cm F6 reflector and a CCD camera. The comet was then about three and a half months from perihelion and was stellar in appearance.
Max Wolf (Heidelberg, Germany) discovered this comet on 1884 September 17. It was then moving slowly through Cygnus and was described as between magnitude 9 and 10, with a coma diameter of about 2.5 arc minutes. Beginning on September 21, observers were reporting the brightness as close to magnitude 7, indicating Wolf's initial estimate represented the comet's central condensation.
Ralph Copeland (Dun Echt Observatory, Aberdeen, Scotland) independently discovered this comet on September 23.00 UT, while he was in the course of sweeping the sky for "remarkable spectra." Using a 6.06-inch Simms refractor, with an object-glass prism, he was mainly looking in the Milky Way and had found some nebula and interesting stars, when comet Wolf's interesting spectra showed up. Another 12 hours would pass before news of Wolf's discovery would reach Dun Echt Observatory.
The comet was discovered when only a few days from its closest approach to Earth (0.80 AU on 1884 October 2), but still two months from perihelion. The result was that the comet faded very slowly during October and into November as it steadily moved away from Earth. The coma diameter was reported as 2 arc minutes across in October and 4 arc minutes across in November. Following its November 18 perihelion, fading became more rapid. It was described as much fainter as January began, and was last seen on 1885 April 7.
The comet was soon recognized as a short-period comet. The orbital period was determined as 6.77 years and the perihelion distance was 1.57 AU. A prediction by Thraen enabled R. Spitaler (Vienna, Austria) to recover the comet at its next return in 1891.
Modern calculations reveal the comet was moved into its discovery orbit following an approach to within 0.116 AU from Jupiter on 1875 June 9. Prior to this encounter the comet was moving in an orbit with a perihelion distance of 2.74 AU and an orbital period of 8.84 years.
The comet's brightest apparition was that of 1884, when it reached magnitude 7. That of 1891 was next, when the magnitude reached 8. The comet was more poorly situated in 1898 and was missed entirely in 1905. The maximum magnitude reached 12.0 at the 1912 return and 10.5 at the 1918 return. Then on 1922 September 27, the comet passed 0.125 AU from Jupiter, which resulted in an increase of the perihelion distance to 2.43 AU and the orbital period to 8.28 years. Although the comet reached magnitude 14.5 during the 1925 apparition, it has never become brighter than 17 since.
The comet returns to perihelion on 2000 November 21. It is not expected to become brighter than magnitude 18. Apparitions in the future will be more difficult to observe because the comet will approach Jupiter to within 0.541 AU on 2005 August 13. The new orbit will be similar to the comet's orbit prior to the Jupiter encounter of 1875, with a perihelion distance of 2.72 AU and an orbital period of 8.74 years. The comet will remain in this orbit during the apparitions of 2009, 2017, 2026, and 2035. Another close approach to Jupiter on 2041 March 10 (0.601 AU) will change the orbit back to parameters that existed during the period of 1925 to 2000.
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