Annie Jump Cannon Antonia Maury

Letter&Number

B0 hotter than B9

O - F5 = “Early” Type

F5 - T = “Late” Type

Evolution

Early-type Late-type

Ejnar Hertzsprung Henry Norris Russell

L = 4πR2σT4

William W. Morgan Philip Keenan Edith Kellman

?

L class Description

Ia-0 Hypergiant

Ia Bright supergiant

Iab Normal supergiant

Ib Subluminous supergiant

II Bright giants

III Normal giants

IV Subgiant

V Main-sequence (dwarf) star

Roman Numeral

Sun: G2V

V

III

I