_Dimensions and Brightness._—Vesta is the largest and brightest of the group, while Ceres and Pallas rank as second and third in the same respect. Vesta is about 214 miles in diameter; but the more insignificant members of this family are probably not more than about 15 or 20 miles in diameter. Pallas has the most inclined orbit of all, the inclination amounting to 30° 44′; so that its position is by no means confined to the planet-zone of the ecliptic. Vesta is sometimes brighter than a 6th mag. star; while Ceres, Pallas, and Juno vary between about the 7th and 8th magnitudes, according to their distances from the Earth. A real variation of light has been assumed to occur, but this is not fully proved.
In March 1887 Mr. Backhouse, of Sunderland, saw an apparently new, yellowish-white star near 103 Piscium, and it was just visible to the naked eye. This proved to be Vesta, though the identity of the object was not known at first, and it formed the subject of two Dun Echt circulars.
Formerly, hazy indefinite outlines were attributed to some of the planetoids; but the appearance probably arose from instrumental defects.
The search for these bodies is not a work likely to engage amateurs. Professional observers are best able to grapple with the difficulties attending this kind of observation, where large telescopes, means of exact measurement, and ample data, such as star-charts and ephemerides of the planetoids previously discovered, are requisite. The ‘Nautical Almanack’ annually contains ephemerides of Ceres, Pallas, Juno, and Vesta; and observers wishing to pick up any one of them may readily ascertain positions by reference to this work.
_Occultation of Vesta._—An occultation of Vesta occurred on Dec. 30, 1871, and it was observed by Mr. C. G. Talmage at Leyton with a 10-inch refractor, power 80. He says the planet was exceedingly bright right up to the Moon’s limb.
An interesting Object.—Brightness and Position.—Period &c.—Belts and Spots on the Planet.—Observations of Hooke, Cassini, and others.—The “Ellipse” of 1869-70.—The Red Spot, its appearance, dimensions, and rotation-period.—Bright equatoreal Spots.—Dark Spots in N. hemisphere.—Rotation-period.—Nature of the Red Spot and of the bright and dark equatoreal Spots.—New Belts.—Changes on Jupiter.—Further Observations required.—Occultations of Jupiter.—The four Satellites, and their phenomena.—Occultation of a star by Jupiter.
