NEW, VARIABLE, AND COMPOUND STARS. 



175 



1719 



1779 



1802, 



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 

 1853 1836 1836 18Z6 been established beyond all 



2?J%/. 20? May 6* June 



Position of two stars of Castor. 



1781 



Position of two stars in Virgo. 



1802 



1809 



doubt, that the multiple 

 stars are made up of bodies 

 in real association T- 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 

 binary systems of suns 

 revolving around suns, 

 the smaller around the 

 greater, or both about a 



Position of the Pointers in Ursa Major. Common Centre of gravity. 



One has accomplished a complete revolution r\ Coronae, since observation was first 

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

 have been estimated as follows : 



Herculis 

 7 Coronae 

 77 Coronae 

 Cancri - 

 Ursae Majoris 

 77 Ophiuchi 

 w Leonis - 

 T Ophiuchi 

 A Ophiuchi 

 51 Librae 

 Bobtis - 



Years. 



35 



40 



44 



60 



65 



80 



82 



83 



86 

 1OO 

 120 



Years. 



7 Virginis - - - 150 

 o Geminorum (Castor) - 240 

 127 Virginis - - 240 



36 Andromeda - - 250 



4 Aquarii 

 Arietis 

 fj? Bob'tis 

 37 Pegasi 

 61 Cygni 

 a Coronae 

 t Leonis 



- 300 



- 400 



- 460 



- 500 



- 514 



- 560 



- 580 



fjL Draconis 

 49 Serpentis 

 12 Lyncis 

 77 Cassiopeiae 

 Aquarii 

 e Bob'tis 

 7 Leonis 

 5 Lyra? - 

 e Lyrae - 

 5 Herculis 

 65 Piscium 



Years. 



- 600 



- 610 



- 680 



- 700 



- 750 



- 980 



- 1000 



- 1000 



- 2000 



- 2046 



- 3077 



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

 star varies remarkably. Thus the two stars of 7 Virginis have apparently approached 



