Page:Popular Science Monthly Volume 46.djvu/494

478 beautiful contrast. We should make a sad mistake if we regarded this wonderful distribution of color among the double stars as accidental. It is manifestly expressive of their physical condition, although we can not yet decipher its exact meaning.

The binary 42 Comæ Berenicis is too close for ordinary telescopes, but it is highly interesting as an intermediate between those pairs which the telescope is able to separate and those—like β, Aurigæ—which no magnifying power can divide, but which reveal the fact that they are double by the periodical splitting of their spectral lines. The orbit in 42 Comæ Berenicis is a very small one, so that even when the components are at their greatest distance apart they can not be separated by a five or six inch glass. Burnham, using the Lick telescope, in 1890 made the distance 0·7″; Hall, using the Washington telescope, in 1891 made it a trifle more than 0·5″. He had measured it in 1880 as only 0·27″. The period of revolution is believed to be about twenty-five years.

In Coma Berenices there is an outlying field of the wonderful nebulous region of Virgo, which we may explore on some future evening. But the nebulæ in Coma are very faint, and, for an amateur, hardly worth the trouble required to pick them up. The two clusters included in the map, 2752 and 3453, are bright enough to repay inspection with our largest aperture.

Although Hydra is the largest constellation in the heavens, extending about seven hours, or 105°, in right ascension, it contains comparatively few objects of interest, and most of these are in the head or western end of the constellation, which we examined during our first night at the telescope. In the central portion of Hydra, represented on map No. 7, we find its leading star α, sometimes called Alphard, or Cor Hydræ, a bright second-magnitude star that has been suspected of variability. It has a decided orange tint, and is accompanied, at a distance of 281″, p. 153°, by a greenish tenth-magnitude star. Bu. 339 is a fine double, magnitudes eight and nine and a half, distance 1·3″, p. 216°. The planetary nebula 2102 is about 1′ in diameter, pale blue in color, and worth looking at, because it is brighter than most objects of its class. Tempel and Secchi have given wonderful descriptions of it, both finding multitudes of stars intermingled with nebulous matter.

For a last glimpse at celestial splendors for the night, let us turn to the rich cluster 1630, in Argo, just above the place where the stream of the Milky Way—here bright in mid-channel and shallowing toward the shores—separates into two or three currents before disappearing behind the horizon. It is by no means as brilliant as some of the star clusters we have seen, but it gains in beauty and impressiveness from the presence of one bright star that seems to captain a host of inferior luminaries.