13 January 2022
Perihelion Distance (q)
Aphelion Distance (Q)
Click for NASA orbit diagram
Hills Observatory: 1 January 2013 to 15 September 2019
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 on24 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".
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