Lives of Stars

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Lives of Stars

• Section 21.3

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• Stephen Hawking - The Birth of Stars - YouTube

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Life Cycle of Stars

• Nebula large cloud of gas and dust spread out
  in an immense volume

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Life Cycle of Stars

• Gravity pulls gas and dust together in the
  densest part of the nebula
• When there
• is enough mass
• for a star to form
• it is called a

Protostar
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Life Cycle of Stars

• When the contracting gas and dust from a nebula
  becomes so dense and hot that nuclear fusion
  starts, a star is born.
• Dust Cloud Theory

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Life Cycle of Stars

• How long a star lives depends on its mass
• -Stars with less mass live longer
• - Stars with more mass live shorter
• Small mass stars use up their fuel more slowly
  than larger mass stars

Small stars 200 billion years Medium stars 10
billion years Larger stars 10 millions years
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Life Cycle of Stars

• When a star begins to run out of fuel, its core
  shrinks and its outer portion expands
• Depending on its size, the star becomes a red
  giant or a supergiant
• After the fuel runs out it becomes a white dwarf,
  a neutron star, or a black hole

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Life Cycle of Stars
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Life Cycle of Stars
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Death of Stars

• When the fuel begins to run out of medium and
  low mass stars, their outer layers expand to
  become a red giant.
• The outer layer then expands out in to space
  (planetary nebula) and the blue-white core cools
  (White Dwarf)

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Death of Stars

• The core is very dense. A spoonful of material
  would weigh as much as a truck
• It would cool to become a black dwarf

Black Dwarf
White dwarf
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Death of Stars

• Supernovas
• High mass stars evolve quickly into supergiants
• The supergiant can explode suddenly when it runs
  out of fuel

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Death of Stars

• The outer portion can form partly recycled stars
• We are made of recycled stars
• The inner portion can
• become other kinds
• of stars

Supernova
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Death of Stars

• Neutron star
• The remains of a high mass star, smaller and
  denser than white dwarfs
• Spinning neutron stars (pulsars) give off pulses
  of radio waves

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Death of Stars

• Black Hole
• Form from the most massive stars when they die
• Gravity is so strong, light (or any kind of
  radiation) can not escape

Black hole
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Videos

• Black Holes, Neutron Stars, White Dwarfs, Space
  and Time

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Star Systems and Galaxies

• Binary stars

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Star Systems and Galaxies

• Eclipsing Stars

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Star Systems and Galaxies

• Open Cluster

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Star Systems and Galaxies

• Globular Cluster

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Star Systems and Galaxies

• Galaxy

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Star Systems and Galaxies

• Spiral Galaxy

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Star Systems and Galaxies

• Elliptical Galaxy

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Star Systems and Galaxies

• Irregular Galaxy

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Star Systems and Galaxies

• Quasar an enormous, distant,bright

galaxy with a black hole at its center
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Star Systems and Galaxies

• Milky Way (our galaxy)

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Star Systems and Galaxies
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Star Systems and Galaxies
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Star Systems and Galaxies
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Star Systems and Galaxies