3
Lines of
constant R in the H-R diagram
•Main sequence not quite constant R
•B stars: R
~10 RSun
•M stars: R
~0.1 RSun
•Betelgeuse:
R~ 1,000 RSun
•Larger than 1 AU
•White dwarfs:
R~ 0.01 RSun
•A few Earth radii
•What causes
the “main sequence”?
•Why
“similar” size, with precise
R related to T?
•Why range of
T?
•Why are a few
stars (giants, white dwarfs)
not on main sequence?
From our text: Horizons, by Seeds