1. black hole -

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1. black hole -

• region of space where the pull of gravity is so
  great that even light cannot escape.
• Possible end of a very massive star.

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2. event horizon -

• imaginary spherical surface surrounding a
  collapsing star within which no event can be
  detected by an outside observer

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3. gamma-ray burster -

• object that radiates huge amounts of energy in
  the form of gamma rays, believed to be due to the
  accretion of matter onto a neutron star.

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4. gravitational red shift -

• A prediction of Einsteins theory of relativity.
  
• Photons lose energy when they escape the huge
  gravity of a massive object. This energy loss
  decreases the frequency, correspondingly
  increasing the wavelength.

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5. lighthouse model -

• Leading explanation for pulsars. Region near
  magnetic pole of pulsar emits a steady stream of
  radiation which sweeps past Earth each time the
  star rotates.

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6. millisecond pulsar -

• Pulsar with a period indicating that the neutron
  start is rotating nearly 1000 times a second.
• Probably spun up by drawing in matter from a
  companion star.

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7. neutron star -

• Dense ball of neutrons that remains at core of
  star after a supernova explosion has destroyed
  the rest of the star.

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8. photon sphere -

• Imaginary sphere surrounding a black hole at 1.5
  times the Schwarzschild radius where photons move
  in a circular orbit.

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9. Principle of Cosmic Censorship -

• Nature always hide any singularity, such as a
  black hole, inside an event horizon, which
  prevents the universe from seeing inside a
  singularity.

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10. pulsar -

• Object that emits radiation in the form of rapid
  pulses with a characteristic pulse period and
  duration. Charged particles flow along the
  magnetic field lines of a rapidly rotating
  neutron star, producing a beam of radiation.

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11. pulsar glitch -

• Small drop in teh period of a pulsar. Occur when
  teh thin crust on a neutron stars surface cracks
  and settles slightly atop the superfluid interior.

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12. Schwarzschild radius -

• Distance from the center of an object such that,
  if all the mass were compressed within that
  region, the escape velocity would equal the speed
  of light.
• An object smaller than this radius is a black
  hole.

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13. singularity -

• A point in the universe where the density of
  matter and the gravitational field are infinite,
  such as at the center of a black hole.

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14. starquake -

• A cracking and resettling of the crust of a
  neutron star, slightly reducing the radius of the
  star. The spin rate increases, causing a pulsar
  glitch.

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15. superconductor -

• A material that conducts electricity without
  resistance. The interior of a neutron star may
  be a superconductive material.

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16. superfluid -

• A material that flows without friction.
• The interior of a neutron star may be a
  superfluid material.

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17. theory of relativity -

• Einsteins theory, forms the basis of most of
  modern physics.
• Two essential facts
  1) nothing travels faster than light and 2)
  everything is affected by gravity.

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18. time dilation -

• To an outside observer, a clock lowered into a
  strong gravitational field will appear to run
  slow. A prediction of the theory of relativity.

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19. x-ray burster -

• A neutron star accretes matter onto its surface
  until temperatures reach the level needed to
  cause hydrogen fusion. Results in a sudden
  period of rapid nuclear burning.

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1. How does the way in which a neutron star
forms determine some of its basic properties?

• The amount of matter and amount of collapse
  determines the spin rate of the neutron star.
• This determines its pulse rate and pulse period
  if it forms a pulsar.

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2. How can we observe objects as small as
neutron stars?

• By observing pulsars.

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3. Why arent all neutron stars seen as pulsars?

• The beam that is emitted by the neutron star must
  pass over the Earth to be detected as a pulsar.

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4. What are x-ray bursters?

• A neutron binary that accretes material from its
  companion. As the gas builds up, it eventually
  becomes hot enough to fuse hydrogen. At this
  point a sudden period of rapid nuclear burning
  releases a great deal of energy in a brief,
  intense flash of x-rays.

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5. What is the favored explanation for the fast
spin rates of millisecond pulsars?

• That the neutron star has been spun up by
  drawing in matter from a companion star.

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6. How might some neutron stars have come to be
members of binary systems?

• The supernova progenitor must have lost a lot of
  mass before the explosion, or a neutron star may
  displace one member of a preexisting binary
  system.

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7. How might a pulsar acquire planets?

• One possibility is that the binary companion may
  have been destroyed by the energy and gravity of
  the neutron star. The resulting matter may have
  cooled into planets.

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8. Use your knowledge of escape velocity to
explain why black holes are said to be black?

• A black hole is so collapsed that the escape
  velocity has exceeded the speed of light.
  Therefore, nothing, not even light, can escape.

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9. Why is it so difficult to test the
predictions of general relativity?

• Because its effects on the Earth and the solar
  system are so small.

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10. Describe two tests of general relativity.

• Light from a star is deflected as it passes close
  to the Sun.
• Planetary orbits deviate from the perfect
  ellipses of Keplers laws.

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11. What would happen to someone falling into a
black hole? Why?

• The person would be vertically stretched and
  horizontally squeezed. They would be literally
  torn to pieces. The tidal forces are very
  different even over the length of a body.
  Spaghettification.

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12. Explain how a black hole can evaporate?

• I dont want to go into this.
• It was suggested by Stephen Hawking years ago,
  but now even he doesnt believe it occurs

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13. What makes Cygnus X-1 a good black hole
candidate?

• It releases x-rays, probably from an accretion
  disk. The unseen companion exceeds the mass
  normally accepted for neutron stars, which means
  it is probably a black hole.