How are L, T, and R related?
L = area T4 = 4 R2 T4
Stars can be intrinsically bright because of either large R or large T
Use ratio equations to simplify above equation
(Note book’s symbol for Sun is circle with dot inside)
Example:  Assume T is different but size is same
A star is ~ 2 as hot as sun, expect L is 24 = 16 times as bright
M star is ~1/2 as hot as sun, expect L is 2-4 = 1/16 as bright
B star is ~  4 as hot as sun, expect L is 44 = 256 times as bright
Example:  Assume T same but size is different
If a G star 4 as large as sun, expect L would be 42=16 times as bright