1889.] of the various Species of Heavenly Bodies. 



257 



VI. Binary Stars, Class 3. Equal or Nearly Equal Magnitudes, one 

 Star being Blue. 



There is a considerable number of binary stars in which the magni- 

 tudes of the components do not differ very much, but where one star 

 is blue. If we take these blue stars as belonging to Group 1 

 we shall have an average case represented by fig. 23, both curves 

 starting at the same point. From this point of view the companion 

 which has the smaller magnitude has the greater mass, and the 

 system is young. 



FIG-. 23. Light curves of the components of a binary star of Class 3, in which both 

 components have equal or nearly equal magnitudes, one being blue. 



If these curves are a fair representation of binary stars of this 

 class, it is clear that we ought to find the primaries in every case, 

 white with a tendency to yellow. This is a severe test, bat yet on 

 referring to the following table, which is a list of such binary stars, 

 it will be seen that there is not a single case in which the primary 

 is not white or yellow : 



Table III. Binary Stars, Class 3. 



