PROBLEMS OF MODERN SCIENCE 



be two groups of M stars differing so greatly in 

 brightness, the only possible answer is that the 



B A 



White 



4 



~2 



44 



46 



48 



410- 





Red 



V\?!l!''- S 



T-f 



Fig. 8. ABSOLUTE MAGNITUDE AND SPECTRAL TYPE 



stars in the brighter group are very much larger 

 than those in the other. The spectrum and 

 surface temperature being the same, the amount 

 66 



