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66P/du Toit

Past, Present, and Future Orbits by Kazuo Kinoshita

NEAT image of 66P exposed on 2003 May 16
Copyright © 2003 by Near Earth Asteroid Tracking (NEAT)

This image is a combination of three images obtained by the Near Earth Asteroid Tracking (NEAT) program on 2003 May 16.25, May 16.26, and May 16.27. Each image was exposed for about one minute.

Discovery

     D. du Toit (Harvard College Observatory, Boyden station, Bloemfontein, South Africa) discovered this comet on a photograph obtained on 1944 May 17.04. He estimated the magnitude as 10. Confirmation came from H. van Gent (Union Observatory, Johannesburg, South Africa) on May 23.03. He estimated the magnitude as 11. Van Gent also found a prediscovery image on a plate exposed on April 22.95 and estimated the magnitude as 12.5.

Historical Highlights

  • J. Jackson made the first attempt at calculating an orbit for this comet; however, he said even though the observation arc spanned over a month (1944 April 22 to May 28), his calculations did not reveal a parabola. He suggested an error might have existed with one of the positions he used. His various attempts revealed a perihelion date "in late June or July." J. Bobone became very interested in this comet and his observatory obtained more positions than any other observatory. His first parabolic orbit was calculated in early June and revealed a perihelion date of 1944 June 10.57. At the end of June, Bobone calculated an elliptical orbit with a perihelion date of June 17.52 and a period of 14.02 years. Ultimately, the orbit proved to have a perihelion date of June 17.49 and a period of 14.78 years.
  • The comet was not widely observed in 1944, but it did remain visible well into November. J. Bobone and C. G. Torres (National Astronomical Observatory, Cordoba, Argentina) obtained a fine series of photographs spanning the period of May 29 to September 21. Physical descriptions were not plentiful. Van Gent gave the magnitude as 11 on May 28. When the comet finally became visible in the Northern Hemisphere, G. van Biesbroeck (Yerkes Observatory, Wisconsin, USA) photographed it on September 26 and gave the magnitude as 17.5. Van Biesbroeck traveled to McDonald Observatory (Texas, USA) and made observations during October and November. He gave the magnitude as 18 in late October and about 19.5 on November 14 and 20. The last date was the final time the comet was observed during this apparition.
  • During 1957, Bobone redetermined the comet's 1944 orbit and published a prediction for the 1959 return. He gave the perihelion date as 1959 April 10.22. E. Roemer (U. S. Naval Observatory, Flagstaff station, Arizona, USA) obtained search plates on two nights during 1958 December and 1959 January using the 40-inch reflector. The comet was not found. Search plates were also obtained by Roemer on 1959 February 6, but again nothing was found. She wrote, "The awkward position of P/du Toit very low in the southeastern sky at dawn has made it impossible to cover properly the line of variation." Later calculations revealed Bobone's orbit was only two days late.
  • Although the prospects were not much better for the 1974 return, two predictions were published. The first was by N. A. Belyaev, V. V. Emelyanenko, and N. Yu. Goryajnova, and gave the perihelion date as 1974 April 4.88. The second was by G. Sitarski and gave the perihelion date as April 6.35. C. T. Kowal (Palomar Observatory, California, USA) used the 122-cm Schmidt to photograph the comet's predicted position on 1974 January 26 and 27. He found no trace of a comet of magnitude 19 or brighter. A photographic search was conducted using the 0.7-m Maksutov astrograph at Cerro El Roble (Chile) during March and April, but the comet was not initially seen. A somewhat limited search was conducted at Steward Observatory during June 15-17. Interestingly, during 1975 January, C. Torres (Department of Astronomy, University of Chile) found that two plates exposed at Cerro El Roble did contained images of the comet. The plates had been exposed on 1974 March 22.40 and April 22.41. Torres said the comet was near the edge of the first plate and about magnitude 19. On the second plate, the comet was magnitude 18-19, with a centrally condensed coma one arc minute across. The positions indicated the actual perihelion date came on April 1.50.
  • The comet was missed at its 1989 apparition, but it was very well observed during its 2003 apparition. It was recovered on 2003 March 10.51, when J. V. Scotti (Spacewatch, Kitt Peak Observatory, Arizona, USA) photographed it using the 1.8-m reflector and a CCD camera. He gave the total magnitude as 20.5. He gave the magnitude as 20.3-20.4 on March 11. Northern Hemisphere observers saw the comet brighten to magnitude 16 and slightly brighter during May and June, while the coma was typically around 2 arc minutes across. Observers in the Southern Hemisphere began observing the comet during the latter half of July and gave the magnitude as about 13. The comet was at its brightest during the latter half of August, when observers in Australia and South Africa gave the magnitude as around 12. The coma was then about 2 arc minutes across and diffuse. David Higgins measured a precise position for this comet on September 8.40 and gave the "nuclear" magnitude as 16.1-16.7. D. A. J. Seargent (Cowra, New South Wales, Australia) observed using a 25.4-cm reflector on September 19.45. He gave the magnitude as 12.7. M. Mattiazzo (Wallaroo, SA, Australia) observed with a 28.0-cm telescope on September 21.43 and gave the magnitude as 12.9. He also noted a diffuse coma one arc minute across. Mattiazzo was not able to find the comet on October 13.45 and noted it was then in the Milky Way.
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