Encke's Comet

1895

A Little Visitor That Travels by a Curiously Regular Time Table.

Encke's comet is one of the best known of the Jupiter group of comets. This group, so far as known, consists of 19 objects, all of which are members of our solar system and are revolving about our sun in orbits of from three and a half years to double that time. The group is so called because there is every reason to believe that these wanderers were intercepted in their path through space by the giant planet Jupiter and perturbed into orbits about the sun, the distant end of which lies in the neighborhood of the orbit of this planet.

Encke's comet is the most noted of this group, having been known to astronomers for upward of a century and having been sufficiently well observed to conform very closely to its computated path. It was first seen by Mechain of Paris on Jan. 17, 1786, and was again discovered by Miss Caroline Herschel in November, 1795, and after a few days by other astronomers. It was again observed in 1805, but none of the astronomers at the time knew of the identity of the objects which they saw. In the winter of 1818-9 it was visible for some seven weeks, and Encke busied himself with the computation of its orbit. In a remarkably short time he had his computations finished and was able to show that it was moving in an orbit of three and a half years period; that the comets above enumerated were identical with it, and that it had approached the sun 18 times in the intervals unobserved.

Encke next computed the time of its return, announcing this date as May 24, 1822, having been delayed on the way some nine days by the attraction of Jupiter, and according to this time table the object was again observed on its return. This computation of Encke's was a most remarkable one, involving as it did some of the most intricate and laborious problems known by the astronomers of the time. — Boston Transcript.