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Neutron Stars and Black Holes

Neutron Stars and Black Holes. Neutron Stars: Formation. Remnant of a Type II supernova explosion Iron core collapses until neutrons are squeezed tightly together During the explosion core remains intact, outer layers explode outward. Neutron Stars: Formation. Neutron Stars: Size.

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Neutron Stars and Black Holes

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  1. Neutron Stars and Black Holes

  2. Neutron Stars: Formation • Remnant of a Type II supernova explosion • Iron core collapses until neutrons are squeezed tightly together • During the explosion core remains intact, outer layers explode outward

  3. Neutron Stars: Formation

  4. Neutron Stars: Size • 10 - 20 km across • Mass > sun’s mass • Density: 1 tsp would weigh 100 million tons

  5. Neutron Stars: Properties • Solid surface • Immense gravity • A 70 kg person on Earth would weigh 100 billion kg • However you would be crushed by the gravity

  6. Neutron Stars: Structure

  7. Neutron Stars

  8. Pulsars • First discovered in 1967 • A pulsating radio source; many discovered since • Explained by a lighthouse model • The pulses are usually radio waves, but may include other EM radiations

  9. Pulsars

  10. Pulsars

  11. Pulsars Not all pulsars can be detected: • Improper orientation • So old that the rate of rotation can not be detected (they slowed down!)

  12. Neutron Star Binaries • Occurs when a star and a neutron star orbit each other • Matter from the giant is drawn off the star and spirals toward the neutron star • Two types: X-ray bursters and gamma ray bursters

  13. Neutron Star Binaries

  14. Black Holes • If the remaining core of a supernova explosion is > 3 solar masses, even neutrons can not stop the collapse • All the material collapses to a point called singularity • Stellar black holes range from 3 - 20 solar masses

  15. Black Holes • Gravity near a black hole is so large that even light can not escape • All objects (including Earth) have an escape speed • The greater the mass, (and the smaller the radius) the greater the escape speed

  16. Black Holes: The Event Horizon • The distance from singularity at which the escape speed = light speed is called the Schwarzchild Radius (Rs) • An imaginary sphere at a distance equal to Rs is called the event horizon

  17. Black Holes: The Event Horizon • Rs is proportional to mass • Rs for some common objects: • Earth = 1 cm • Jupiter = 3 m • Sun = 3 km

  18. Black Holes: Detection

  19. Black Holes:

  20. Black Holes What happens to someone falling into a black hole? • Tidal forces would stretch you out and squeeze you at the same time • Light emitted red-shifts • Time dilates

  21. Non-stellar Black Holes: • Located at the centers of galaxies and other large objects (globular clusters, quasars) • Different formation process • Many times more massive! May be millions of solar masses

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