Page:Popular Science Monthly Volume 47.djvu/210

200. Sometimes it attains nearly the fourth magnitude, although usually at maximum it is below the fifth, while at minimum it is occasionally of the sixth and at other times of the seventh or eighth magnitude. Its period is irregular.

Turning back to Sagittarius, we resume our search for interesting objects there, and the first that we discover is another star cluster, for the stars are wonderfully gregarious in this quarter of the heavens. The number our cluster bears on the map is 4424, corresponding with M 22 in Messier's catalogue. It is very bright, containing many stars of the tenth and eleventh magnitudes, as well as a swarm of smaller ones. Sir John Herschel regarded the larger stars in this cluster as possessing a reddish tint. Possibly there was some peculiarity in his eye that gave him this impression, for he has described a cluster in the constellation Toucan in the southern hemisphere as containing a globular mass of rose-colored stars inclosed in a spherical shell of white stars. Later observers have confirmed his description of the shape and richness of this cluster in Toucan, but have been unable to perceive the red hue of the interior stars.

The eastern expanse of Sagittarius is a poor region compared with the western end of the constellation, where the wide stream of the Milky Way like a great river enriches its surroundings. The variables T and R are of little interest to us, for they never become bright enough to be seen without the aid of a telescope. In 54 we find, however, an interesting double, which with larger telescopes than any of ours appears as a triple. The two stars that we see are of magnitudes six and seven and a half; distance 45″, p. 42°, colors yellow and blue. The third star, perhaps of thirteenth magnitude, is distant 36″, p. 245°.

Retaining map No. 13 as our guide, we examine the western part of the constellation Capricornus. Its leader α is a naked-eye double, the two stars being a little more than 6′ apart. Their magnitudes are three and four, and both have a yellowish hue. The western star is α1, and is the fainter of the two. The other is designated as α2. Both are double. The components of α1 are of magnitudes four and eight and a half; distance 44″, p. 220°. With the Washington twenty-six-inch telescope a third star of magnitude fourteen has been found at a distance of 40″, p. 182°. In α2 the magnitudes of the components are three and ten and a half; distance 7·4″, p. 150°. The smaller star has a companion of the twelfth or thirteenth magnitude; distance 1·2″, p. 240°. This, of course, is hopelessly beyond our reach. Yet another star of magnitude nine, distance 154″, p. 150°, we may see easily.

Dropping down to β, we find it to be a most beautiful and easy double, possessing finely contrasted colors, gold and blue. The larger star is of magnitude three, and the smaller, the