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The History of Comet Halley
by Donald K. Yeomans,
Jurgen Rahe, and
Ruth S. Freitag
October 17 1985
Royal Astronomy Society of Canada
NASA Astrophysics Data System
In an attempt to account for this 4-day discrepancy between the actual period of Comet Halley and that computed from perturbations by the known planets, some unorthodox solutions have been proposed. Brady (1972) suggested the influence of a massive trans-Plutonian planet, and Rasmusen (1967) adjusted the sun:Jupiter mass ratio from the accepted value of 1047 to 1051. Both of these proposed solutions must be rejected because they would produce efects on the motion of the known planets that are not supported by observation. Rasmusen (1981) derived a 1986 perihelion date of February 5.46 from a fit to the observations in 1835 and 1910 and then added +3.96 days to yield a 1986 perihelion passage time prediction of February 9.42. Brady and Carpenter (1967) first suggested a 1986 perihelion passage time of February 5.37 based upon a "trial and error" fit to the observations during the 1835 and 1910 returns. Brady and Carpenter (1971) then introduced an empirical secular term in the radial component of the comet's equations of motion... By stepping backward in time at roughly 76-77 year intervals and analyzing European and Chinese observations, Hind (1850) attempted to identify Comet Halley apparitions from 11 B.C. to 1301... Although many of Hind's identifications were correct, he was seriously in error for his suggested perihelion passage times in A.D., 1223, 912, 837, 608, 373, and 11 B.C... It is fortunate that this apparition, during which Comet Halley made its closest approach to the earth, is covered by the most detailed set of observations preserved in Far-Eastern records. On the night of March 22, a broom star appeared in the east with a 11 deg tail pointing west. On the night of April 6, the 15 deg tail pointed slightly south while on the evening of April 11, the 76 deg tail pointed north. Two nights later the tail reached its maximum length of 93 deg and pointed east. Thus, in a few weeks' time, the Chinese reported the tail pointing in all four directions.

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