GALACTIC ASTRONOMY FINAL

STUDY
PLAY
Blackbody Radiation
Light emitted from a blackbody in which the shape of the spectrum only depends on the object's temperature
Blackbody
An object that absorbs all incident radiation upon it.
Wien's Displacement Law
measures PEAK ; constant / temp
TELLS US THAT the curve peaks at shorter wavelengths for higher temperature
Stefan-Boltzmann Law
measures FLUX (apparent distance) ; constant x temp
TELLS US why the curves don't overlap
Parallax
determine distance to the star
Wein's Law
determine the star's temperature
Combining the Stefan- Boltzmann law and inverse square law gives us an expression to determine ____.
the radius
Luminosity depends on _____ and _____ ...
temperature and radius of a star
OBAFGKM
high to low temperature (only boys at frats get kegs made)
stars A and B have SAME LUMINOSITY but star A is COOLER...
star A is LARGER than star B.
stars A and B have the SAME TEMPERATURE but star B is more luminous.
star B has LARGER surface area than B.
Stars spend ____ in the main sequence.
90% of their lives
STEPS TO BECOME A STAR
1. collapse
2. fusion
3. hydrostatic equilibrium
stars that BURN BRIGHT
DIE YOUNG
LOW MASS STARS (i.e. sun)
slow reaction, 'proton-proton train'
HIGH MASS STARS
fast reaction, "CNO cycle" ; greater pressure in core
star cycle for LOW MASS
cloud - MS * - red giant - planetary nebula - white dwarf

LEAVES BEHIND WHITE DWARF
star cycle for HIGH MASS
cloud - big MS - red giant - type 2 supernova - - neutron OR black hole

NO HELIUM FLASH
RED GIANTS become
1) SMALL MASS: Planetary Nebula -- WD
2) LARGE MASS: Type II Supernova -- N* or BH
ISOLATED white dwarfs
cool down to become BLACK DWARVES
MAIN SEQUENCE binary white dwarfs
result in NOVA explosions / SUPERNOVA explosions
to detect a BLACK HOLE
look for x-rays given off by material as it falls toward BH
not all ___ are ___ but all ___ are ___.
not all NEUTRON STARS are PULSARS, but all PULSARS are NEUTRON STARS.
we can find BH MASS if we know
1) Orbital period
2) Semi-Major Axis
'NO HAIR' theorem: three basic prop's of BH
1) Mass
2) Spin
3) Electrical Charge
MASS CLASSES
1) Stellar (5-10)
2) Intermediate (100-10^5)
3) Supermassive (>10^5)
SIZE of BH is defined by
event horizon (region in which light cannot escape BH)
supermassive BH = size of
SUN
thin disk
young stars
thick disk
old stars
bulge
older stars
halo
oldest stars
elliptical galaxy (major)
formed by merger of 2 ROUGHLY SAME SIZED galaxies
spiral disk preserved (minor)
2 merging galaxies are VERY DIFF in SIZE
SPIRALS
late-type galaxies
ELLIPTICALS
early-type galaxies
IRREGULARS
peculiar galaxies
Lenticular galaxies
no spiral arms

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