NEW, VARIABLE, AND COMPOUND STARS. 



175 



1719 



1779 



1802 



Position of the two stars of Castor. 



Position of the two stars of -y Virginis. 



the conclusion that casual situations will not account for these multiplied phenomena ; 



that consequently their 

 existence must be owing 

 to some general law of 

 nature ; and as the mutual 

 gravitation of bodies toward 

 each other is quite sufficient 

 to account for the union 

 of two stars, he felt autho 

 rised to ascribe such com 

 binations to that principle. 

 This reasoning has been emphatically confirmed by physical facts. The conclusion has 

 1833 i&sj, 485? 1836 been established beyond all 



doubt, that the multiple 

 stars are made up of bodies 

 in real association phy 

 sically connected. The 

 constituents of a double 

 star, closely watched through a series of years, are found to change their relative position, 

 and to repeat the same cycle of change, indicating their systematic union under control 



of the law of gravitation. 

 The diagram exhibits the 

 observed positions of the 

 two stars of Castor, of y 

 Virginis, and of Ursae 

 Majoris, at the respective 

 times named. Here we 

 have unquestionable signs 

 of orbital motion, real 



JB2SA &&& 1836"* binai> y S ^ StemS f SUnS 



revolving around suns, 



the smaller around the 

 greater, or both about a 



Position of the two stars off Ursae Majoris. Common Centre of gravity. 



One has accomplished a complete revolution, 77 Corona?, since observation was first 

 directed to it ; and, from the progress already made by others, their times of revolution 

 have been estimated as follows : 



1781 



1809 



Star's Name. 

 f Herculis 

 7? Coronas 

 f Cancri 

 | Ursae Majoris 

 co Leonis 

 | Bobtis 

 5 Cygni 

 7 Virginis 

 Castor 

 ff Coronae 



Period in Years. 



31 



43 



58 



58 



82 

 117 

 178 

 182 



- 252 



- 608 



By whom computed. 

 Madler. 

 Ditto. 

 Ditto. 

 Savary. 

 Madler. 



Sir J. Herschel. 

 Hind. 



Sir J. Herschel. 

 Ditto. 

 Madler. 



In consequence of revolution, the apparent distance between the constituents of a double 

 star varies remarkably. Thus the two stars of y Virginis have apparently approached 



