Life Cycles of Stars

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Life Cycles of Stars
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The Hertzsprung-Russell Diagram
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How Stars Form

• Collapsing gas and dust cloud
• Protostar - mostly infrared

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Main Sequence Stars

• Brown Dwarf
• Red Dwarf
• Normal Star

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All Objects Exist Because of a Balance Between
Gravity and Some Other Force

• People, Planets-Interatomic Forces
• Normal Stars-Radiation
• White Dwarfs-Electron Repulsion
• Neutron Stars-Nuclear Forces
• Black Holes-No Known Force

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How Stars Die

• Main Sequence Stars Brighten With Age
• The More Massive a Star, the Faster it Uses Fuel
• Giant Phase
• White Dwarf
• Supernova
• Neutron Star - Pulsar
• Black Hole

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Historical Supernovae

• 1006 - Chinese
• 1054 - Chinese, European, Anasazi?
• 1572 - Tychos Star
• 1604 - Keplers Star
• 1987 - Small Magellanic Cloud (170,000 l.y.)

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Life (Briefly!) Near a Supernova

• Suns Energy Output 77 billion megatons/second
• Lets relate that to human scales. What would
  that be at one kilometer distance?
• 77 x 1015 tons/(150 x 106km)2 3 tons
• Picture a truckload of explosives a km away
  giving off a one-second burst of heat and light
  to rival the Sun

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Now Assume the Sun Goes Supernova

• Brightens by 100 billion times
• Our 3 tons of explosive becomes 300,000 megatons
• Equivalent to entire Earths nuclear arsenal
  going off one km away - every second
• This energy output would last for days

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Planetary Systems

• Protoplanetary Disks
• Accretion of Planets
• Expulsion and Migration of Planets
• About 30 extrasolar planets known
• Our Solar System may be unusual?

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Protoplanetary Disks in Orion