ASTRONOMY 



example, a standard star of magnitude 2 is about 

 2 1 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 show r n in the 

 accompanying table : 



THE NUMBERS OF STARS OF DIFFERENT MAGNITUDES 



Magnitude Number 



i . ;J -V >^ . :. iii 



1-2 . , . * , . ,. 27 



2-3 ..' . . - * . . 73 



3-4 I8 9 



4-5 650 



5-6 . . . :';:* V . 2,2oo 



6-7 . ,. ; , . , 6,600 



7-8 . ^ . . 22,550 



8-9 , .* if . . 65,000 



9-10 > . , . . 174,000 



IO-II .:/> Vv - ... 426,OOO 



I I-I2 . . . . 961,000 



12-13 ; ^ A . . . 2,020,000 



13-14 . . . 3,960,000 



14-15 p| : ... 7,820,000 



15-16 . 14,040^000 



16-17 .... 25,400,000 



Although the faintest stars shown on the plates 

 are of the seventeenth magnitude, there must be 



49 



