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22 Cards in this Set

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Giant star
1.core uses up all hydrogen
2.helium accumulates in core, nuclear reactions cease
3.core contracts b/c of gravity and grows hotter..core heats hydrogen shell
4.hydrogen fusion begins in shell around core
5.radiation energy from shell pushes outward, outer layers swell gas expands, it cools
giant star evolution
red giant= large radius, cool (red) temp
as star expands, temp decreases and luminosity increases
helium fusion
as core shrinks, temp increases until hot enough for Helium to fuse.

Tri-Alpha process: 3 Helium nuclei fuse into 1 carbon nucleus
Helium flash
explosive ignition of Helium fusion in core of giant star

core temp expands and increases until fusion becomes stable
degenerate matter
gas so dense that electrons cannot change their energy.
gas resists compression
in stars like sun..
0.4-4 solar mass
temp and pressure in core never high enough for carbon fusion
outer layers are loose/blow away
hot interior releases high speed wind
planetary nebulae
an expanding shell of gas ejected from star during the latter stages of its evolution
white dwarf
after outer layers blown away, if solar mass less than 1.4, no more fusion.

=hot small objects with low luminosity

eventually will radiate away its heat and become black dwarf
sudden brightening of star due to eruptions on white dwarf in a binary system

material from nearby companion star fall toward white dwarf, creating accretion disk.
density and temp increase and violent hydrogen fusion
red dwarfs
less than 0.4 solar mass

hydrogen fusion lasts for long time, never accumulates helium in core

never evolve into giant stars or beyond
massive stars
evolve off main sequence to become giant or supergiant

core hot enough for carbon fusion, higher elements fuse away in onion layer, at core. fusion stops at iron
Type II Supernovae
explosive death of high mass star. spectra rich in hydrogen gases

core/outer layers collapse inward, shock wave of energy moves outward
Type I supernovae
explosive death of white dwarf, which accreated material from a companion star

extra material pushes mass over 1.4, carbon fusion occurs
supernovae remenants
remain for tens of thousands of years. add metals to interstellar medium...later generations of stars have higher metal content
Neutron stars
when massive star goes supernovae, mass is more than 1.4

protons forced to combine w/ electrons to create neutrons. gravity halted
magnetic axis of neutron star inclined to rotational axis. rotation sweeps beam like lighthouse
Earth- detect a pulse but not energy
X ray bursters
sudden brightening star associated with eruptions on neutron star in binary system

higher energy than novae
black hole
if mass more than 2-3, gravity stronger than neutron pressure. star collapses to point singularity

not even light can escape

event horizon= boundary where no radiation can escape
curved space
massive objects curve space around them

more massive=more curvature
falling into black hole
as object nears event horizon, tidal forces rip object apart.
object heats as it falls, radiates x-ray
detection of black holes
matter flows from star into accretion disk around an unseen companion (whos mass is at least 3=black hole)
star cluster
open cluster: 10-1000 stars in region 25 pc in diameter
globular cluster: 10^5-10^6 stars in 10-30 pc region