Planetoids
the name given to a great group of minute planets placed together between Mars and Jupiter. Professor Titius, of Wittenberg, having drawn attention in 1772 to the fact that, with the exception of Jupiter, each planet has an orbit just about double that nearest to it on the side of the sun, Professor Bode, of Berlin, drew the natural inference that the one exception to the rule would probably be removed by the discovery of a planet less remote from the sun than Jupiter, and more distant than Mars. On Jan. 1, 1801, a planetary body, afterward called Ceres, was found by Piazzi in the part of the solar system theoretically indicated; it was, however, more diminutive in size than had been expected. Within the next six years three more asteroids (Pallas, Juno, and Vesta) were found in proximity to Ceres. Up to October, 1903, 542 small planets had been discovered, 70 by Americans. All are of minute size, and some angular in place of spherical.