
Space & PhysicsJune 1, 1961
Subdwarf Stars
Certain stars seem dimmer than normal stars having the same temperature. It now appears that they are not less luminous but are bluer because they are poorer in the heavier elements

Subdwarf Stars
Certain stars seem dimmer than normal stars having the same temperature. It now appears that they are not less luminous but are bluer because they are poorer in the heavier elements

Stellar Populations
Fifteen years ago Walter Baade observed that stars are divided into two populations. His concept opened up a broad field of study, and now astronomers classify stars into five populations instead of two