Page:Popular Science Monthly Volume 47.djvu/813

Rh four, seven, and eight, distances 2″, p. 256°, and 7·5″, p. 112°. Cassiopeia contains many star clusters, three of which are indicated in the map. Of these 392 is perhaps the most interesting, as it contains stars of many magnitudes, including a red one of the eighth magnitude, and a ninth-magnitude double whose components are 8″ apart. Not far from the star κ, we find the spot where the most brilliant temporary star on record made its appearance on November 11, 1572. Tycho Brahe studied this phenomenon during the entire period of its visibility, which lasted until March, 1574. It burst out suddenly with overpowering splendor, far outshining every fixed star, and even equaling Venus at her brightest. In a very short time it began to fade, regularly diminishing in brightness, and at the same time undergoing changes of color, ending in red, until it disappeared. It has never been seen since, and the suspicion once entertained that it was a variable with a period considerably exceeding three hundred years has not been justified. There is a tenth-magnitude star near the place given by Tycho as that occupied by the stranger. Many other faint stars are scattered about, however, and Tycho's measures were not sufficiently exact to enable us to identify the precise position of his star. If the phenomenon was due to a collision, no reappearance of the star is to be expected.

Camelopardalus is a very inconspicuous constellation, yet it furnishes considerable occupation for the telescope. Σ 390, of magnitude five, has a companion of magnitude nine and a half, distance 15″, 160°. Σ 385, also of the fifth magnitude, has a ninth-magnitude companion, distance only 2·4″, p. 160°. According to some observers, the larger star is yellow and the smaller white. The star I is a very pretty double, magnitudes both six, distance 10·4″. Its neighbor 2 of magnitude six has an eighth-magnitude companion, distance 1·7″, p. 278°. The star 7 of magnitude five is also double, the companion of magnitude eight being distant only 1·2″. A glance at star cluster 940, which shows a slight central condensation, completes our work in Camelopardalus, and we turn to Ursa Major, represented in map No. 26. Here there are many interesting doubles and triples. Beginning with ι we find at once occupation for our largest glass. The magnitudes are three and ten, distance 10″, p. 357°. In the double star 23 the magnitudes are four and nine, distance 23″ p. 272°. A more pleasing object is σ2, a greenish fifth-magnitude star which has an eighth-magnitude companion, distance 2·6″, p. 245°. A good double for our four-inch glass is ξ, whose magnitudes are four and five, distance 1·87″, p. 183°. This is a binary with a period of revolution of about sixty years, and is interesting as the first binary star whose orbit was determined. Savary calculated it in 1828. Near by is ν, a difficult double, magnitudes four and ten and