A new orbit for comet C/1861 J1 (Great comet of 1861)

Abstract

A new orbit is calculated for Comet C/1861 J1 (Great comet of 1861) to replace Kreutz?s orbit of 1880. The orbit is based upon 2,362 observations, 1,198 in right ascension and 1,164 in declination, made between May of 1861 and March of 1862. The comet?s period of 364.96 ± 0.51 yr differs significantly from Kreutz?s period of 409 yr. This orbit is linked with one calculated from 5 observations made in the Far East in 1500, possibly of the Great comet, by imposing boundary conditions on the differential equations of motion. The linked orbit indicates a period of 361.3 yr. This increases the probability that the Great comet is indeed the comet observed in 1500. Although the residuals are relatively random (16.0% probability of randomness), post-perihelion residuals are less random indicating possible deviations from Keplerian motion such as systematics error or nongravitational forces.