. Astronomy for high schools and colleges . n considerable distances fromeach other. Asteroids, now more generally known as S7nall orminor planets, are celestial bodies which move about thesun in orbits, either of little or of considerable eccen-tricity, the planes of which orbits may be inclined to theecliptic in any angle whatsoever. They may or may nothave considerable atmospheres. Comets are celestial bodies, generally of a very smallmass, though how far this may be limited is yet un-known. They move in very eccentric ellipses or in parabolicarcs about the sun. The planes of their motion a
. Astronomy for high schools and colleges . n considerable distances fromeach other. Asteroids, now more generally known as S7nall orminor planets, are celestial bodies which move about thesun in orbits, either of little or of considerable eccen-tricity, the planes of which orbits may be inclined to theecliptic in any angle whatsoever. They may or may nothave considerable atmospheres. Comets are celestial bodies, generally of a very smallmass, though how far this may be limited is yet un-known. They move in very eccentric ellipses or in parabolicarcs about the sun. The planes of their motion admit of the greatest varietyin their situation. The direction of their motion is also totally undeter-mined. They have atmospheres of very great extent, whichshow themselves in various forms as tails, coma, haziness,etc. MAGNITUDES OF THE PLANETS. 269 Relative Sizes of the Planets.—The comparative sizes ofthe major planets, as they would appear to an observersituated at an equal distance from all of them, is given inthe following • • Pig. 74.—relative sizes op the planets. The relative apparent magnitudes of the sun, as seenfrom the various planets, is shown in the next figure. Flora and Mnemosyne are two of the asteroids. A curious relation between the distances of the planets,known as Bodes law, deserves mention. If to the nimi-bers, 0, 3, 6, 12, 24, 48, 96, 192, 384, 270 ASTRONOMY, each of whicli (the second excepted) is twice the preced-ing, we add 4, we obtain the series, 4, Y, 10, 16, 28, 52, 100, 196, 388. These last numbers represent approximately the dis-
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