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Stellar Evolution

This overview of stellar evolution explores the life cycle of stars, detailing both earth-based and space-based astronomical observations. We delve into the main sequence stage, where stars like our sun convert hydrogen to helium over billions of years. The transition into later stages, including red giants and supernovae, is examined, alongside the formation of white dwarfs, neutron stars, and black holes. This fascinating process showcases the dynamic nature of the universe and the transformations stars undergo over vast timescales.

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Stellar Evolution

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Presentation Transcript

  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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