i6o 



THE EVOLUTION OF 



would appear from the Earth in fig. n. It will be 

 noticed from fig. n, that at the central eclipse the com- 

 panion is just, and only just, projected upon the disk of 

 the star l . 



Pickering's investigation had left little doubt of the 

 truth of the eclipse theory of Algol's variation, but 

 evidence of a still more definite nature was soon to be 



FIG. 10. Algol and relative orbit of companion. 



forthcoming. If Algol is accompanied by a revolving 

 companion, it must, as we have seen, be itself in revolu- 

 tion, star and companion describing similar orbits round 

 their common centre of mass. In fig. 10, the relative 

 orbit of the companion is represented, and Pickering had 



1 The reader will scarcely need to be reminded that it would be 

 impossible to recognize the disk of the companion upon that of the 

 star by the telescope. The distances of the stars are so great that all of 

 them appear as mere specks of light through the finest telescopes. 



