LETTER V - Triple Stars—More Complex Relationships—Existence of Large Groups—Conjectures respecting Firmamental Systems

Summary

2. Guided by the Genius, whose prophetic eye pierced the obscurity, which, until then, had concealed the arrangements we have just unfolded—we advance cautiously, but without dread, to take cognizance of still higher schemes.—The arguments which induced Herschel to pronounce on the connexion and motion of the constituents of binary systems, penetrate much farther, and intimate as a general law, that every cluster or unusual aggregation of orbs must be systematic, and probably united by common motion. If it is unlikely that the principles of random scattering would produce numbers of double stars, it is plainly as unlikely that anytriple or quadruple bodies should be found in the whole sky ; and this holds even where the stars are more separated, as in the case of the six principal constituents of the Pleiades, against whose fortuitous aggregation within that space—as Michell long ago calculated—there is a balance of probabilities of 500,000 to 1. The presence of a great law thus lays it on astronomers as a command that they watch these higher systems, take their measurements with every minuteness, and transmit them to posterity. The results must be brilliant, and they are already foreshadowed. In a triple star in Cancer (ζ), we are certain of a common motion, in which three suns seem to revolve around a common central point; and in another—ψ CassiopeiÆ — one sun probably revolves around a second, while the two in union—a sun and an associated sun, circulate around the third.