Page:Popular Science Monthly Volume 46.djvu/485

Rh also a double star; unfortunately the companion, being of only the tenth magnitude and distant less than 1″ from its third-magnitude primary, is beyond the reach of our telescopes. But η points the way to one of the finest star clusters in the sky, marked 1360 on the map. The naked eye perceives that there is something remarkable in that spot, the opera glass faintly reveals its distant splendors, but the telescope fairly carries us into its presence. Its stars are innumerable, varying from the ninth magnitude downward to the last limit of visibility, and presenting a wonderful array of curves which are highly interesting from the point of view of the nebular origin of such clusters. Looking backward in time, with that theory to guide us, we can see spiral lines of nebulous mist occupying the space that now glitters with interlacing rows of stars. It is certainly difficult to understand how such lines of nebula could become knotted with the nuclei of future stars, and then gradually be absorbed into those stars; and yet, if such a process does not occur, what is the meaning of that narrow nebulous streak in the Pleiades along which five or six stars are strung like beads on a string? The surroundings of this cluster, 1360, as one sweeps over them with the telescope gradually drawing toward the nucleus, have often reminded me of the approaches to such a city as London. Thicker and closer the twinkling points become, until at last, as the observer's eye follows the gorgeous lines of stars trending inward, he seems to be entering the streets of a brilliantly lighted metropolis.

Other objects in Gemini that we can ill miss are: μ, double, magnitudes three and eleven, distance 73″, p. 76°, colors yellow and blue; 15, double, magnitudes six and eight, distance 33″, p. 205°; γ, remarkable for array of small stars near it; 38, double, magnitudes six and eight, distance 6·5″, p. 162°, colors yellow and blue (very pretty); λ, double, magnitudes four and eleven, distance 10″, p. 30°, color of larger star blue—try with the five-inch; ε, double, magnitudes three and nine, distance 110″, p. 94°.

From Gemini we pass to Cancer. This constellation has no large stars, but its great cluster Præsepe (1681 on map No. 4) is easily seen as a starry cloud with the naked eye. With the telescope it presents the most brilliant appearance with a very low power. It was one of the first objects that Galileo turned to when he had completed his telescope, and he wonderingly counted its stars, of which he enumerated thirty-six, and made a diagram showing their positions.

The most interesting star in Cancer is ζ, a celebrated triple. The magnitudes of its components are six, seven, and seven and a half; distances 1″, p. 35°, and 5·5″, p. 122°. We must use our five-inch glass in order satisfactorily to separate the two nearest stars. The gravitational relationship of the three stars is very peculiar.