Planetoids

Collier's New Encyclopedia (1921)

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. The term asteroid, applied to these small bodies, is now becoming obsolete, the appellation minor planets taking its place. They are sometimes also called extra-zodiacal planets, from their orbits stretching outside the zodiac, which is not the case with those of the normal type. Authorities differ respecting some minute points in the list of asteroids. Melete, when discovered on Sept. 9, 1857, was mistaken for Daphne, an error not detected till January, 1859. Herschel, Proctor, etc., number it 56, and place the date 1857, where it offends the eye, in 1859; others, with Mr. G. F. Chambers, transfer it to 1857, which alters the numbering of all the minor planets from 47 to 56. There are other minute differences between lists of asteroids by leading authorities.