MIRACLES OF SCIENCE 



A notable example of a star accompanied by dark 

 companions is the pole star itself. Professor Camp- 

 bell has shown that this star has two dark associates 

 circling about it. One of these is so near that it 

 makes the circuit in about four days; the other so 

 distant that its period of revolution is several years. 



There are numerous double stars that may readily 

 be located by the amateur. One of the most inter- 

 esting is Mizar, already referred to. It is readily 

 located, as it is the second star from the end of the 

 handle of the big dipper. A sharp eye may see that 

 this star has a small companion. A three-inch tele- 

 scope will show that one of these two stars is white 

 and the other emerald in color. The two are in 

 reality so far apart that to an observer on the small 

 one the large one would look only as a bright star 

 looks from the earth. Yet the spectroscope shows 

 that this larger companion is itself composed of two 

 suns, separated by a distance of about 36,000,000 

 miles, something more than the distance of our 

 planet Mercury from the sun. They are more than 

 100 light years from our system, and no telescope 

 separates the two components. Yet the shift of their 

 spectroscopic lines enables astronomers to compute 

 that Mizar has twenty times the bulk of our sun, 

 and is coming toward us at the rate of twenty miles 

 an hour. 



Another interesting double is the small star lying 

 rather inconspicuously in one of the middle arms of 

 the big W-shaped cluster in the constellation Cassio- 

 peia. A small telescope separates the two compo- 

 nents, which in reality lie so far apart that they re- 



