nature of Sun
radius of Sun
- from angular diameter (0.5o), distance (1 AU) and Small Angle Formula
- ~ 2 l.s., ~ 100 Earth radii
- surface area 104 times the earth’s
- volume 106 times the earth’s
- but mass only 3 x 105 earth’s => lower density
mass of Sun -- 4 x 1030 kg
- From Newton’s version of Kepler’s IIIrd law
- (GM/4?2)P2 = a3
- Enough H to power the sun for ~ 10 billion years