The history of the asteroids really starts before they were discovered. Their existence was first suspected as a result of the discovery of ""Bede's Law"" as it was called: a relation between the mean distances of the planets from the Sun.
During the last thirty-three years a considerable amount of work on the observation of Miner Planets has been carried out at the Union Observatory in Johannesburg. This was the result of the gift to the Observatory in 1909 of the Franklin-Adams Star Camera with its powerful photographic triplet lens of 10"" diameter and focal length, i.e. an aperture of f/4.5.
The computation of the orbits of the Minor Planets is a problem ,of some difficulty. This difficulty is principally due to the fact that- these bodies may approach of Jupiter, the most massive of the major planets, more closely than do the other major planets.
The Trojan Group constitutes perhaps one of the most interesting sets of the minor planets. In order that the interest attaching to this set or group might be fully appreciated, it is necessary that we understand the mathematical background which anticipated their discovery.
A Trojan asteroid forms an equilateral triangle with Jupiter and the Sun. The orbits of all three are roughly circular, and the mass of the asteroid is negligable in comparison with that of the Sun or Jupiter.