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Stellar Evolution

Stellar Evolution. State Standard: Earth based and space based astronomy reveal the structure, scale, and changes in stars over time. Main Sequence Stage . Longest stage Energy generated H->He 1gram H ->He Fuels 100w bulb for 200 years Size of sun, * lasts 10 billion years

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Stellar Evolution

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  1. Stellar Evolution State Standard: Earth based and space based astronomy reveal the structure, scale, and changes in stars over time.

  2. Main Sequence Stage • Longest stage • Energy generated H->He • 1gram H ->He • Fuels 100w bulb for 200 years • Size of sun, * lasts 10 billion years • Increased size of sun, * lasts 10 million yrs

  3. How old is the universe? • 14-16 b.y. old • Less massive * last longer • Life span increased 100 b.y. • Ex: sun is 5 b.y. old burn 5% of H, when sun is 10 b.y. burn 10% H => fusion stops, Temp. decreases, change in luminocity

  4. Leaving the Main Sequence • Almost all H converted to He • Core contracts from gravity due to pressure decrease • T increase starts fusion once more • Outer shell expands • Giant * created

  5. H-R Diagram

  6. Giant Stars • Shell T decreases as star expands • Gases glow red • Large red star aka giants • Bright due to L. surface area • 10 times larger than the sun

  7. Super giants • Red star • Life span < 1 billion years • More massive than sun • Larger than giants • Swells to 100 X larger than sun • Ex: Betelgeuse, which has cool surface • Easy to find in night sky due to luminosity

  8. Final Stages of Sunlike Star • Evolution cut short He=> C and O • Energy no longer available • Planetary nebulas • Outer gases drift • Form shape around dying star • White Dwarf • Planetary nebulas next stage • Gravity causes matter to collapse in • Hot dense core, dim luminosity • Turns into black dwarf

  9. Supernova • Supergiant * collapse due to gravity • Results in increase T and P • Fusion starts again • C changes into O, Mg, Fe • Collapse of core • Increase of T and P = star explodes • Brighter than original, outshine all other *

  10. Supernova cont. • Can be seen during day • 8 X mass of sun • Explosion produces Cu, Ur, Ag, Pb • Blown into space to mix w/ gas + dust

  11. The Final Stages of Massive Stars • Produce supernova • Core becomes Fe, which needs energy • May be white dwarf • Energy output at peak=400 million suns

  12. Neutron Stars • Mass that may contract after supernova • Tsp.of matter =1 mill. • Larger mass than sun • Small size • Emits 100,000 more energy than sun • Rapid rotation

  13. Pulsars • Neutron emits radio waves • Detect pulse when beam sweeps by • Each pulse = one period • Period: amt. of time needed to complete a 360 cycle • New found w/ supernova remnants • old = no remnant

  14. Black holes • Mass too large to form neutron star • Contraction o center crushes dense core • Gravity lets no light or other material escape • Location determined by affect on near stars • Matter pulled into black hole • Swirls before entering • Gas T rises causing x rays

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