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X/1106 C1

Discovery

The earliest published account of this comet also contains the comet's discovery observation. The Belgian historian Sigebertus Gemblacensis completed Chronica in 1111. He wrote that on 1106 February 2 a star appeared during the daytime, between the third and ninth hours, about a cubit from the sun. The probable universal time of this observation was February 2.3. A cubit is roughly equal to one degree, so that the comet was in Aquarius. The comet was also discovered in the evening sky during the period of February 7 to 10 by observers in other European countries, as well as in Japan, Korea, and China.

Historical Highlights

  • This comet's initial appearance in the evening sky was impressive. In general it was situated in the southwest in the vicinity of Pisces on February 7 and Cetus by the 9th. An anonymous treatise entitled De Significatione Cometarum said the comet was seen in Palestine on February 7. The comet was said to have been situated at the beginning of Pisces and exhibited a tail extending toward the beginning of Gemini. The indicated length was about 100°. The Japanese text Dainihonshi (1715) said the comet "appeared in the southwest" on February 9 "with its rays pointing eastward...." The comet was described as white and about 100° long. The Chinese texts Wen hsien t'ung k'ao (1308), Sung shih (1345), and Hsü Thung Chien Kang Mu (1476) said the comet was seen in the west on February 10 and measured about 60° long and 3° wide. The tail was pointing obliquely towards the northeast. By February 11 the Japanese reported the comet had "gradually diminished" and they gave the tail length as 10°. They also pointed out the comet was moving eastward.
  • The duration of the comet is certainly a matter of debate. European texts claim total durations of 15 to 70 days, although the majority gave it as 25 days. Since most of these texts gave the discovery date as February 16, this indicated a final observation date of March 12. The text of Historia Hierosolymitana said the comet was discovered on February 5 and was seen for 40 days, which placed the final observation on March 17. The Japanese and Koreans discovered the comet on February 9 and said it remained visible for over 30 days, which indicated it was still seen after March 10.
  • This comet has always caught the interest of astronomers. During the last two centuries ideas have been put forth that this comet was a previous appearance of the Great Comet of 1680 or a member of the sungrazing family of comets. E. Halley was the first to suggest that the Great Comet of 1680 had been previously seen in 1106, but he did not strive to prove this fact; instead, the first person to examine this possibility was R. Dunthorne (1751). He said the positions available for the comet of 1106 were too few and rough for an orbital calculation; however, based on Halley's earlier suggestion, he used an assumed perihelion date of February 4 and the orbit of the comet of 1680, and determined the positions this comet should have moved during the period of February 7 to March 24. He said, that significant alterations were required for the orbit of the comet of 1680 to make it move in the direction observed for the comet of 1106. The possibility that the comet of 1106 was a member of the sungrazing family of comets was first suggested by H. C. F. Kreutz in 1891, as he wrote his famous paper suggesting the existence of such a family of comets. Although an orbit could not be computed for the 1106 comet, Kreutz discussed whether or not the Great September Comet of 1882 could have been seen in 1106. His own orbit for the comet of 1882 indicated a perihelion date of 1138 April and he said the daytime and nighttime observations probably referred to two different objects; however, he believed the daytime object was possibly the 1882 comet. This comet's relationship to the sungrazing family was again brought up in 1967 when B. G. Marsden reexamined many of the observations given above. He said there were many contradictions in the observations, especially between those of Europe and the Far East, but he still indicated a belief that this was a sungrazer. In addition, Marsden integrated the orbit of the sungrazer Ikeya-Seki of 1965 back to its previous perihelion passage and found it could have occurred sometime within the period of 1114 to 1116. He said unknown forces acting upon the comet could easily push the perihelion date back even further, so that the comet of 1106 is "by far the most promising candidate for the previous appearance of comet 1965 VIII." He also commented that it is not out of the question that comets 1965 VIII and 1882 II "separated from each other at their previous perihelion passage."
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