Chapter 14: Stellar Remnants

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Chapter 14 Stellar Remnants

• Dr. Michelle Arnold
• November 13, 2009

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What Remains After a Star Dies

• Low mass stars, after a planetary nebula
• White dwarf
• Initial star 0.1-10 M
• White dwarf lt1.4 M
• High mass stars, after a supernova explosion
• Neutron star
• Initial star 10-25 M
• White dwarf 1-3 M
• Black hole
• Initial star 25-30 M
• White dwarf gt3 M

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White Dwarfs

• About the mass of Sun
• About the size of the Earth
• Mostly degenerate carbon, may have a small amount
  of helium and hydrogen on the surface
• High temperatures remain from previous fusion and
  gravitational collapse
• Small size means they are very dim
• Continue to cool

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Neutron Star

• Degenerate neutrons
• Very small
• About 10 km across
• MUCH smaller than white dwarfs
• Neutrons squish together tighter than carbon
  atoms
• Spin about 1000 times per second!
• Some are pulsars
• Axis of rotation is different from magnetic axis
• Appear as light house lights blinking on and
  off in the radio wave frequency

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Gravity

• Newton described gravity in an equation
• He did not explain the why or how
• Einstein proposed that any mass will distort or
  bend the space around it
• 2D world, it bends into the third dimension
• 3D world, it bends into the fourth dimension!
• If another mass approaches this dip in space,
  it can fall in, setup a stable orbit or escape
  and fly off (depending on how fast it is going)

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Distorted 2D Space
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Evidence that SupportsEinsteins Theory of
Gravity

• Circumference of Earths orbit 2?r
• Measured distance (radius) from Earth to Sun is
  bigger!
• Gravity can effect light which has no mass!

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Black Hole

• Large mass (singularity) causes a large
  distortion in space
• They are not little vacuum cleaners!
• Event horizon distance from the singularity at
  which the escape velocity equals the speed of
  light
• Nothing can escape after it passes closer than
  the event horizon
• Black holes appear black
• Left on its own a black hole would evaporate!
  (Hawking radiation)

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• http//www.dailymotion.com/video/x2enyl_homer-3d_s
  hortfilms

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Adding Mass to a Star Remnant(Type 1 Supernova
anddetecting a black hole)