Lecture 12 Flashcards
(33 cards)
luminosity is the measure of what?
what is the unit?
E output
J/s = W
stefan boltzmann law is for what variables?
intrinsic luminosity (depending on radius and temp)
what does the hertzsprung russell diagram show?
luminosity of stars vs temperature
shows the main sequence, and other groups of stars (white dwarfs, giants, supergiants)
what does the main sequence represent?
all stars which have their primary E source as nuclear fusion of H
stars off the main sequence have a different primary E source
what is fusion of H also called?
H burning
describe the two components of hydrostatic equilibrium
forces pointing inward: pressure b/c of gravity
forces pointing outward: radiation pressure
what determines where a H burning star will sit on the main sequence?
mass
massive stars use nuclear fuel _____ than lighter stars
faster/slower?
faster
the lifetime of a star depends on what two factors?
mass of star (how much fuel it has)
luminosity of star (how fast it uses up fuel)
____ (high/low) mass stars stay on the main sequence for a ____ (long/short) time
high mass stars –> short time on MS
low mass stars –> stay on MS for long time
when does a star leave the main sequence?
what happens when this occurs?
when it runs out of H to fuse
star will move to red giant branch of HR diagram; the primary E source is still nuclear fusion, but the internal structure changes
a high turn off point means that the cluster is _____
a low turn off point means that the cluster is ___
young (at higher luminosity and temp)
old (at lower luminosity and temp)
what is used to measure masses of stars?
what is it?
binary star systems (when 2 stars are gravitationally bound and orbits around a common centre of mass)
with the doppler shift, is the frequency higher in front or behind the car?
higher frequency in front
in a blue shift, how is the wavelength affected?
shorter wavelength
in a red shift, how is the wavelength affected?
longer wavelength
motion AWAY from observer causes which type of shift?
red
motion TOWARD observer causes what type of shift?
blue
stars with higher velocity have ____ (lower/higher) mass
lower
how can you determine mass ratio of stars?
double line binary
how can you determine orbital inclination angle
single line binary
which binary gives all information about orbit and masses?
binary must be visual/eclipsing AND double-line
cooler stars are ____ massive than hotter stars
less
what are 4 phases of stellar evolution?
1) formulation and pre main sequence
2) main sequence
3) post main sequence
4) death
