Lecture02

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Unformatted text preview: ensity near the Sun •  Local mass density of stars is about 0.05 M¤༊ pc- 3; total local mass density is 0.076 ± 0.015 M¤༊ pc- 3 (Robin et al. 2003, A&A, 409, 523) •  Local number density of stars is 0.085 pc- 3 (most of these are M dwarfs). •  Average mass per star is: __________ •  Homework - compute surface densi8es of +∞ stars: Σ( R) = ρ( R, z) dz ∫ 4/4/13 −∞ UW, ASTR 323, SP13, Eric Agol ©2013 18 Stellar collisions •  For two stars like Sun, geometric cross sec8on is σgeom=π(2R)2=4πR2. •  However, gravity focuses stars and enhances cross sec8on to (homework): 2 $ v esc ' σ = σ geom &...
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This document was uploaded on 04/05/2014.

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