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8 Cards in this Set

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  • Back
stellar radii
luminosity=area x intensity
L=r^2 T^4

stars with radii greater than 10 s.radii= giant stars
stars with radii less than 10 s.radii= dwarf stars

sun is 1 solar radii
selection effects
most common stars are high luminosity O and B main-sequence, as well as giants and supergiants

most common are very faint stars: lower main-sequence red dwarfs; white dwarfs
spectral line broadening
smaller stars have denser atmospheres

luminosity class

bigger the star, the thinner the spectral line/the more the gases are spread out
binary pairs
2 stars which revolve around common center of mass
the heavier mass is closer to the center of mass

Ma+Mb=a^3/ P^2
spectroscopic binary systems
orbital pd (P):how long it takes to go thru one complete cycle
orbital velocities (v):doppler shifts->radial velocity of each star
radii of orbits(a):pd times velocity gives circumfrence of orbit

doppler shifts only measure radial motion
eclipsing binary systems
when small star crosses in front of large, we decrease in brightness

when small star is eclipsed behind star, brightness drops
mass-luminosity relation
hotter stars are more massive than coller stars


a star twice as massive is MORE than twice as luminous
main-sequence lifetimes
stars spend 90% of lives on the main-sequence