205P/Giacobini (0205P)


Type: Periodic Perihelion date: 13 January 2022 Perihelion distance (q): 1.5 Aphelion distance (Q) : 5.6 Period (years): 6.7 Eccentricity (e): 0.57 Inclination (i): 15.3 JPL orbit diagram COBS lightcurve Michel Giacobini (Nice Observatory, France) discovered this comet in Serpens on 4 September 1896. He described it as a faint, circular object about 1' across. F. Sy (Algiers Observatory) was the first to confirm the comet. On 5 September, he described it as faint, about 30" across, and with a central condensation. W. A. Villiger (Germany) independently confirmed the comet on 5 September. He observed with a 27-cm refractor and determined the total magnitude as 11.3. He added that the coma was 1' across and contained a sharp nucleus. Beginning on 26 September, the first of a series of observations were made indicating the comet had split. On that date, Perrotin detected an extremely faint companion very near the main nucleus while using the 76-cm refractor. Perrotin observed the secondary nucleus the next two nights, but these remain the only direct observations of a secondary nucleus. There were, however, some additional observations by others which certainly suggest something did happen to the comet. The first such observations were rather cautious reports of a second condensation within the coma by Perrine and Hussey of Lick Observatory on 30 September and 1 October. They were using the 91-cm refractor. Sy reported the nucleus appeared elongated when he observed the comet on 10 October with a 32-cm refractor. Interestingly, the position angle given by Sy significantly differed from Perrotin's and many past researchers have ignored it; however, in 1978, Z. Sekanina examined the comet's motion and its earth-sun orientation and concluded that the "position angle of the companion should have changed rapidly with time." Based on the available information Sekanina concluded the comet's nucleus had split on 24 April 1896 . The first parabolic orbit was calculated by H. C. F. Kreutz using positions spanning the period of 5 to 7 September. The perihelion date was 8 October 1896 . Additional calculations by Giacobini, Kreutz, and Perrotin during the next few weeks established the perihelion date as 17 October. The first elliptical orbit was calculated by Perrotin and Giacobini using positions spanning the period of 4 to 27 September. They determined the perihelion date as 28 October and the period as 6.55 years. Additional calculations by W. J. Hussey, Perrotin, and C. W. L. M. Ebell (1903) eventually established the perihelion date as 28 October and the period as 6.65 years. This comet was not seen again for over a century, but was finally rediscovered by Koichi Itagaki (Yamagata, Japan) on 10 September 2008, in the course of his routine supernova search program. The images were obtained with his 60-cm reflector and CCD camera and revealed the magnitude as 13.5. About five hours after the object had been posted on the Near-Earth Object Comfirmation page of the Harvard-Smithsonian Center for Astrophysics, Maik Meyer (Germany) made the suggestion that this new object was identical to D/1896 R2 (Giacobini), which had been lost since its discovery apparition. One of the people he directly informed was Syuichi Nakano (Japan), who quickly confirmed the link. New companions were announced by D. T. Durig and K. N. Hatchett (Cordell-Lorenz Observatory, Sewanee, Tennessee, USA). They found two faint companions moving in the same direction as the main comet and as the same speed on 22 September. A recheck of their images revealed the companion nearest the main comet had also been photographed on 17 September. The main comet is now formally known as fragment "A", the closest fragment is now fragment "B", while the more distant object is fragment "C". Fragment "B" is about four magnitudes fainter than "A", while "C" is five magnitudes fainter than "A". Observations (VEMag = visual equivalent magnitude) Date 10x10 mag Error VEmag Coma ' 09-Sep-15 16.09 0.01 15.7 0.2 16-Sep-15 14.67 0.06 13.9 0.5 23-Sep-15 15.73 0.03 13.9 0.3 13-Oct-15 17.12 0.06 13.7 0.2 20-Oct-15 17.45 0.03 14.4 0.3 04-Nov-15 17.86 0.04 14.7 0.2