Copyright © 2001 by Near Earth Asteroid Tracking (NEAT)
PREDISCOVERY IMAGE: The faint smudge of this comet can be seen in the middle of this image, which is a combination of three images obtained by the Near Earth Asteroid Tracking (NEAT) program using the 48-inch Oschin telescope and a CCD camera. The images were exposed on 2001 October 30.36, October 30.38, and October 30.39. Each image was exposed for about 20 seconds.
Ernst Wilhelm Liebrecht Tempel (Marseilles, France) discovered this comet on 1869 November 27 in Pegasus. Shortly thereafter, observers were describing it as diffuse and circular, with a coma about 5 arc minutes across. The comet was only observed for 39 days and although recognised as a short-period comet, astronomers were uncertain as to the exact period. An attempt to find the comet in 1875 was unsuccessful.
Lewis Swift (Warner Observatory, New York) discovered a diffuse, circular comet in Pegasus on 1880 October 11. By mid-November, astronomers realized Swift's comet was a return of Tempel's 1869 comet.
Perturbations by Jupiter caused the comet to become unobservable after 1908 and the comet was listed as lost. On 2001 December 7.08, astronomers at MIT's Lincoln Laboratory in New Mexico found an object on images obtained in the course of the Lincoln Near Earth Asteroid Research (LINEAR) program. They were using a 1.0-m reflector and a CCD camera. Prediscovery images were subsequently found on additional LINEAR images from September 10 and October 17. LINEAR images on December 17 revealed the object was diffuse, and this was confirmed on December 19 by G. Hug (Eskridge, Kansas). An orbit by B. G. Marsden (Central Bureau for Astronomical Telegrams) then revealed this was a short-period comet with a period of 6.37 years. C. Hergenrother (Lunar and Planetary Laboratory) and K. Muraoka (Kochi, Japan) independently suggested to Marsden that the LINEAR comet might be a return of comet Tempel-Swift. The link was almost immediately confirmed by Marsden and S. Nakano (Sumoto, Japan).
An independent discovery was actually made in 1880, following Swift's initial discovery announcement. Although observations were made in the United States within a few days of Swift's discovery, an error in the telegram sent to Europe prevented the comet from being observed. Subsequently, J. G. Lohse (Dun Echt Observatory) found a comet in Lacerta on November 8. After a few more days of observations an orbit was computed. About the same time correct positions and an orbit arrived from the United States and Lohse's comet turned out to be identical to Swift's.
The final observation of the 1880-1 apparition came on January 26. Shortly thereafter it was determined that the comet's orbital period was 5.5 years, making every other return favorable and the others unfavorable.
The 1891 apparition was predicted to be favorable and E. E. Barnard (Lick Observatory) recovered the comet on September 28, about 4 degrees from the prediction. W. F. Denning (Bristol, England) made an independent recovery on September 30. During October the comet was frequently described as a large shapeless nebula, with a faint condensation. The comet was last detected on 1892 January 21.
The comet was again unfavorably situated during the 1897 return and an approach to within 1.16 AU from Jupiter during 1899 May increased the orbital period to 5.68 years. This led to the 1903 apparition being unfavorable as well and the comet was not recovered.
The comet was next recovered on 1908 September 30, when Javelle (Nice Observatory) found it about two degrees from the predicted position. The comet was fainter during this apparition, because the 1899 Jupiter approach had altered the observing conditions, and the comet was last seen on December 30.
An approach to within 0.61 AU of Jupiter in 1911 increased the orbital period again and made the comet's next approach unfavorable. The comet then passed 0.50 AU from Jupiter during 1923. These two encounters altered the orbital period to almost exactly 6 years and were expected to make the comet almost impossible to see as it would reach perihelion on the opposite side of the sun from Earth. Predictions were still provided for the 1925 and 1932 returns, with A. C. D. Crommelin noting in the latter year, "The conditions at this return are still unfavourable, but not quite hopeless." Nevertheless, the comet was not found. Another close approach to Jupiter in 1935 (0.53 AU) increased the perihelion distance from 1.33 to 1.49 AU and bumped the orbital period up to nearly 6.2 years. The change in perihelion distance would cause the comet to appear much fainter at future returns. No further predictions were provided during the next few years.
Kanda supplied the next prediction in 1949, indicating a rather favorable return during 1950. Unfortunately, this prediction later proved to be in error by almost 6 weeks. B. G. Marsden provided the next prediction on IAU Circular 1838 (1963 Aug. 3). Using positions from the 1891 and 1908 apparitions, he applied perturbations by Venus to Saturn and predicted a very favorable return in 1963, with the perihelion date occurring on August 29. Searches failed to reveal the comet. Marsden worked to determine the nongravitational effects upon the comet's orbit and published details on IAU Circular 2164 (1969 August 28). He found it likely that the 1963 apparition was in error by three or four weeks because of these effects and predicted the comet would next return to perihelion on 1969 December 29. Again searches failed to reveal the comet. Marsden teamed up with Z. Sekanina in 1971 and published a paper in the Astronomical Journal that attempted to more precisely determine the nongravitational forces for this comet. Although they predicted returns for 1976 May 25 and 1982 October 22, they admitted "the unknown character of the nongravitational effects since 1908 obviously introduces some uncertainty into current predictions." Further predictions were published by Nakano in 1989, 1995, and 1996, but to no avail.
Predictions for the 2001 return were published by several astronomers. K. Kinoshita published a prediction on his web site on 1998 April 29 that gave a perihelion date of December 21.2. Nakano predicted a perihelion date of December 27.3 on Nakano Note 686 (1998 May 2). K. Muraoka (Kochi, Japan) published a prediction on his web site on 1998 June 26 that gave a perihelion date of December 12.1. Following the comet's accidental rediscovery on 2001 December 7, Marsden and Nakano independently determined that the comet would pass perihelion on December 30.
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