ASTRONOMY 



example, a standard star of magnitude 2 is about 

 2 J times as bright as a standard star of magnitude 3. 

 Returning now to the Franklin-Adams plates, 

 it was, of course, clearly impossible to count all 

 the stars which they showed, and therefore typical 

 areas were selected and the stars of different mag- 

 nitudes counted. The result of the counts thus 

 made by Chapman and Melotte are shown in the 

 accompanying table : 



Magnitude 



The Numbers of Stars of Different Magnitudes 



Number 

 . II 



27 



73 

 189 



650 



2,200 



1 

 1-2 



2-3 

 3-4 

 4-S 

 5-6 



6-7 

 7-8 



8-9 

 9-10 



10-1 1 



1 1-12 



12-13 



13-H 

 14-15 



15-16 



16-17 



6,600 



22,550 



65,000 



174,000 



426,000 



961,000 



2,020,000 



3,960,000 



7,820,000 



1 4,040., 000 



25,400,000 



Although the faintest stars shown on the plates 

 are of the seventeenth magnitude, there must be 



49 



