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Chapter 13
chapter 13 cosmic perspective
16
Astronomy
Undergraduate 1
12/17/2013

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Term
What are white dwarfs?
Definition
White dwarf is the corpse of a low-mass star, supported against the crush of gravity by electron degeneracy pressure
Term
what is the mass and size of a white dwarf?
Definition
Mass of the sun, size of the earth
Term
Mass Limit of a white dwarf?
Definition
1.4Msun
Term
What happens to a white dwarf in a binary system?
Definition
gas from a companion star can spill toward a white dwarf, forming a swirling accretion disk around it.
Term
What causes a nova?
Definition
hydrogen fusion on the surface of a white dwarf in a binary star system
Term
white dwarf supernovae
Definition
"carbon bomb" carbon fusion begins and ignites to explode a white dwarf
Term
What happens when a white dwarf exceeds its limit mass?
Definition
it will explode completely in a white dwarf supernova
Term
What is a neutron star?
Definition
the ball of neutrons created by the collapse of the iron core in a massive star supernova.
Term
neutron star, mass, size, temp, density, rotation?
Definition
Mass- 1Msun
Size- few kilometers in radius
temp-
density-extrememly dense
rotation- velocity about half the speed of light
Term
pulsar discovery
Definition
Jocelyn Bell discovered a strange source of radio waves that pulsed at precise intervals
Term
what is a pulsar?
Definition
neutron wars left behind by the supernova explosions
Term
what happens to a neutron star in a binary system?
Definition
the hot accretion disks around neutron stars in close binary stems shine brightly with x rays.
Term
x-ray busters
Definition
helium fuses rapidly to make carbon and heavier elements, generating a burst of energy that flows from the neutron star in the form of x rays.
Term
What are black holes?
Definition
a place where gravity is so strong that nothing, not even light, can escape from within it.
Term
visiting a black hole?
Definition
impossible to visit because it has an escape velocity greater than the speed of light.
Term
event horizon
Definition
boundary between the inside of the black hole and the universe outside
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