Solar System Bodies: Asteroids. An orbit, approximately midway between those of Mars and Jupiter,
occupied by a large number of planetoids or minor planets: variously explained as fragments of a major planet
broken up in some prehistoric catastrophe; or particles drawn out of the Sun which failed to coalesce into a
single planet. In all there are estimated to be some 50,000 of these Asteroids, of which 1380 had been identified
in 1937. As many as 5000 are estimated to have been seen, and again lost. Many of them are more readily
visible than Pluto, and may have some astrological significance not as yet identified. Their average diameter is
less than 100 miles.
The Astronomischer Rechen-Institut at Dahlem, near Berlin, was world headquarters for Asteroid research, and
up to World War 11 published a yearly ephemeris of the larger Asteroids for the periods when they are best
observed.
Statistics of the five principal Asteroids are as follows:
............Diameter..................Albedo
...Name......(miles)...Magnitude...(rel. to Sun)...Discovered
...Ceres.......480........7.4..........0.06...........1801
...Pallas......304........8.0..........0.07...........1802
...Juno........120........8.7..........0.12...........1804
...Vesta.......240........6.5..........0.26...........18O7
...Astraea................9.9.........................1845
The next five, in the order of their discovery, are Hebe (1847), Iris (1847), Flora (1847), Metis (1848), Hygeia
(1849).
The orbit of 944 Hidalgo has an eccentricity of 0.65 - more elongated than some comets. At its aphelion
distance (9.6 units) it extends into Saturn's orbit.
That of 1177 Gounessia, has an eccentricity of 0.006399, more circular than that of Venus, the most circular
among the major planets.
That of 846 Lipperta, is almost parallel with that of the Earth, with an inclination of 0°.244 - more nearly
parallel than that of Uranus 0°.77.
That of 2 Pallas has an inclination of 34°.726 - double that of Pluto's 17°.1.
Three Asteroids come closer to the Earth than do any of the major planets. They are Amor, Apollo, and Adonis.