Event #9: Broom star; Comet Halley

This marks the first proven observation of 1P/Halley. The only ancient document to report the comet is the Chinese text Shih chi (-90), but the scant details indicate a movement and time period which certainly fit that expected of 1P/Halley in -239.

The text reports a “broom star” was first seen “in the east and then was seen in the north.” It adds that the comet was also seen during the month of -239 May 24 to June 23 in the west. Further details are also given by the Shih chi, but their exact translation is open to some debate. After reporting that General Meng Ao died, Burton Watson (SC1993 #2) has said the text states, “The comet appeared in the west once more. On the sixteenth day of the month Queen Dowager Xia died.” On the other hand, a translation by William H. Nienhauser, Jr (SC1994) gives the text as, “The comet appeared again in the west for sixteen days. The Queen Dowager Hsia died.” Either way the comet obviously reappeared in the west.

The first identification of 1P/Halley with the comet of -239 was mad by P.H. Cowell and A.C.D. Crommelin in 1908. Without the aid of the very well-observed apparition of 1910, Cowell and Crommelin determined a perihelion date of -239 May 15, which was only 10 days off from the likely true date. Additional orbital investigations conducted by astronomers during the 1970s and 1980s have confirmed the link.

The orbit calculated by D.K. Yeomans and T. Kiang (1981) is given below and indicates the following highlights for this apparition. The comet reached a minimum solar elongation of about 1 degree on March 31 and a maximum solar elongation of 36 degrees on May 18. It then attained its most northerly declination of +43 degrees (apparent) on June 4. The comet reached a minimum solar elongation of 21 degrees on June 2 and a maximum solar elongation of 50 degrees on June 23. This orbit also indicates the comet was probably not detected prior to the first week of May, as the solar elongation was steadily increasing from about 1 degree on April 1, and did not reach 30 degrees until May 5.

The Author concludes, using the Yeomans-Kiang orbit as a guide, that the comet could not have been seen in China in the western sky until June 3.5 UT. It was probably last seen 16 days later (June 19.5 UT) confirming the translation of Nienhauser. From these two observations, it seems likely the comet was first detected in the eastern sky around mid-May.

Comet Halley was described as a broom star and it first appeared in the east, then at the north. During the month May 24 to June 23, it was seen in the west. Ho, (19), p. 265