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Life Cycle of Stars


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Life Cycle of Stars

  1. 1. 26.2 3/27/07 Star Stuff
  2. 2. Forming a Star <ul><li>Nebula </li></ul>cloud of dust and gas protostar (takes 10 million years) Contracts and rotates to form a ________
  3. 3. A Star is Born! <ul><li>A star when ______ starts </li></ul>fusion 10 <ul><li>Hydrogen atoms combine </li></ul><ul><li>to form Helium, other atoms </li></ul><ul><li>Takes ___ billion years </li></ul><ul><li>to form </li></ul>
  4. 4. Adult Stars <ul><li>Called “main sequence” stars </li></ul><ul><li>Longest period in life cycle </li></ul><ul><li>How long depends on star mass </li></ul>
  5. 5. A Balancing Act <ul><li>Two forces act on stars </li></ul><ul><ul><li>Outward force from energy released by nuclear fusion </li></ul></ul><ul><ul><li>Inward force from gravity </li></ul></ul>
  6. 6. Old Age <ul><li>Hydrogen fusion slows </li></ul><ul><li>Gravity contracts core </li></ul><ul><li>Core temperature rises </li></ul><ul><li>Helium fusion starts, releasing even more energy </li></ul>
  7. 7. Small Stars <ul><li>Mass of our sun </li></ul><ul><li>Fusion forms Helium, some Lithium, Carbon and Oxygen </li></ul><ul><li>Last up to ___ billion years </li></ul>10
  8. 8. Small Star Old Age Red Giant <ul><li>Core temperature rises with Helium fusion </li></ul><ul><li>Outer layers expand </li></ul><ul><li>Fusion in core produces heavier atoms – carbon & oxygen </li></ul><ul><li>Lasts ____ million years </li></ul>100
  9. 9. Small Star Death <ul><li>Hydrogen & Helium used up </li></ul>white dwarf planetary nebula <ul><li>Outer layers expand to form a ________ _______ </li></ul><ul><li>Star core cools and contracts to form a dim _____ _____ </li></ul>
  10. 11. Large Stars <ul><li>6 x mass of our sun, or more </li></ul><ul><li>Fusion forms Helium, some Lithium, Carbon, Oxygen and Iron </li></ul><ul><li>Last up to ___ million years </li></ul>10
  11. 12. Old Massive Star SUPERGIANT! <ul><li>Can be 100 x larger than our sun </li></ul><ul><li>Hydrogen used up </li></ul><ul><li>Fusion in core produces heavier atoms </li></ul><ul><li>Finally, core made of Iron </li></ul>
  12. 13. Dying Large Stars <ul><li>Hydrogen gone - fusion stops </li></ul><ul><li>Core collapses, then rebounds with explosion </li></ul><ul><li>SUPERNOVA! </li></ul><ul><li>Lasts few seconds </li></ul>
  13. 14. After Supernova… <ul><li>If mass 3 or more times the sun, final stage is _______ ____ </li></ul>neutron star pulsar dense <ul><li>Protons and electrons collapse together to form ________ </li></ul>neutrons <ul><li>Very ______ </li></ul><ul><li>Called ______ if rotating </li></ul>
  14. 15. After Supernova 2… <ul><li>For the most massive stars, final stage is _____ ____ </li></ul>black hole gravity dense <ul><li>Extreme ______ </li></ul><ul><li>Very ______ </li></ul><ul><li>No light escapes from it </li></ul>