Unformatted text preview: A modern value is
1 AU = 149; 597; 870 1 km : 1.2.3 Newton's Law of Gravitation gives mass of Sun
Given the AU, we can use Newton's Law of Gravitation to get the mass of
the Sun. This is probably the rst example of true astrophysics:
F Sun So: GM m
R2 = F = m!2R
\gravity = centripetal acceleration" M 2 2 3
!2R3 = 1yr 3:161yr 7 s (1:50 1013 cm)
6:67 10 8 cm3 g 1 s 2
= 2:00 1033 g (a modern value is 1:989 1033 g). 1.2.4 Compare Sun to candle to get its \candlepower"
What is the \solar luminosity" L (power or energy per time emitted by )?
Use inverse square law for radiant ux, a form of conservation energy:
2 3 1 Candle How to compare to a candle? Not easy before electrical measurements!
In modern units, solar illuminance is 127000 lux.
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This document was uploaded on 11/02/2011 for the course AST 345 at SUNY Stony Brook.
- Fall '08