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79P/du Toit-Hartley

Past, Present, and Future Orbits by Kazuo Kinoshita

Discovery

     D. du Toit (Harvard College Observatory, Boyden station, Bloemfontein, South Africa) discovered this comet on 1945 April 9.71 and estimated the magnitude as 10. The comet was confirmed by H. van Gent (Union Observatory, Johannesburg, South Africa) on April 12.90, when he photographed it using the Franklin-Adams Star Camera.

     Malcolm Hartley (U. K. Schmidt Telescope Unit, Siding Spring, Australia) discovered two comets on plates exposed with the 1.2-m Schmidt on 1982 February 5.73 and February 6.75. The northwestern-most comet was magnitude 14, while the other comet was magnitude 17. Both comets showed evidence of a short tail. K. S. Russell (U. K. Schmidt Telescope Unit) noted, "the remarkable similarity of the motions of the two objects and suggests that they may be genetically related." [Note: The original discovery announcement on IAU Circular 3663 gives the discover's name as "Marc Hartley". According to Robert McNaught (Siding Spring Observatory), Malcolm Hartley is commonly called "Malc" and the "Marc" may have came about from a misunderstanding.]

Historical Highlights

APPARITION OF 1945: DISCOVERY
[Perihelion Date=1945 April 18.72; Period=5.28 years]
     The comet was followed by astronomers at Union Observatory (Johannesburg, South Africa) until May 31 and by astronomers as Harvard College Observatory, Boyden station (Bloemfontein, South Africa) until June 4. Aside from the discovery information, no further physical descriptions were provided.
     The first orbit was calculated by J. Jackson, using positions from April 12, May 1, and May 17. The result was a perihelion date of 1945 April 16.93. L. E. Cunningham calculated an elliptical orbit using positions spanning a period of 58 days. Because of du Toit's discovery of another periodic comet in 1944, this comet became known as "du Toit 2".

APPARITION OF 1950: MISSED
     T. A. Goodchild (1948) took Cunningham's 1945 orbit, applied perturbations by Jupiter and Saturn, and predicted the comet would next arrive at perihelion on 1949 November 10.6. K. Hurukawa (1952) calculated a definitive orbit for the 1945 apparition. After applying approximate perturbations by Jupiter, he said the next perihelion date probably occurred on 1950 July 26.

APPARITION OF 1955: MISSED
     K. Hurukawa took the orbit he computed for the 1945 apparition and applied perturbations by Jupiter up to the expected 1955 apparition. The perihelion date was given as 1955 November 17.88 and the period was 5.32 years.

APPARITION OF 1966: MISSED
     Using an orbit computed by M. P. Candy in 1961, B. G. Marsden (Smithsonian Astrophysical Observatory, Massachusetts) applied perturbations by Cowell's method and integrated the orbit up to 1966. He predicted the date of perihelion would be 1966 July 10.0146. Marsden said the conditions for recovery "are not quite so favorable as in 1961, but it is hoped that more extensive searches will be made." A. R. Klemola (Yale-Columbia Southern Station) was unable to locate the comet during 1966 January, while H. Hirose (Tokyo, Japan) could not detect it during several searches during the period of January to April. The comet had passed only 0.34 AU from Jupiter during 1963.

APPARITION OF 1982: REDISCOVERY
[Perihelion Date=1982 March 30.45; Period=5.21 years]
     The first orbits were calculated by B. G. Marsden. The first orbit was parabolic with a perihelion date of 1982 March 26.62. The second orbit was elliptical with an assumed eccentricity of 0.59. The resulting perihelion date was 1982 April 2.26. Marsden commented, "The orbital eccentricity is very uncertain, but it seems likely that the comet is a short-period one." Marsden noted that an orbit calculated for the fainter comet was "very similar" to that of the brighter comet. It was reported on February 19 that S. Nakano made the suggestion that the two comets were identical to the lost periodic comet "du Toit 2". Marsden then published an "approximate linkage" which resulted in a perihelion date of March 30.47 for the main comet and March 30.84 for the smaller comet. Marsden added, "The comet passed 0.34 AU from Jupiter in 1963 Dec."

     Russell photographed both comets with the 1.2-m Schmidt on February 7 and noted that both exhibited a short tail. On February 11, Z. Sekanina remarked that the original comet probably split in late 1976. He noted that the most massive component "must in fact be the currently fainter comet" and said the brighter comet would ultimately become fainter. Interestingly, on February 17, T. Seki (Geisei, Japan) found that the brighter comet had rapidly faded to magnitude 17.5, while the once fainter comet had remained at magnitude 17.0. The comet was last detected by A. C. Gilmore and P. M. Kilmartin (Mount John Observatory, Lake Tekapo, New Zealand) on June 23.49. They gave the magnitude as 17.5.

APPARITION OF 2003
[Perihelion Date=2003 February 15.38; Period=5.28 years]
     The comet was recovered by astronomers at Los Molinos Observatory (Uruguay) on 2003 March 4.29, while using a 46-cm reflector and a CCD camera. Several additional images on that night and on March 5, confirmed that this was comet 79P. The magnitude was given as 17.4 on March 5.

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