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The Life Cycle of a Star

The Life Cycle of a Star. Upper Fifth Physics. In The Beginning…. Lots of gas and dust All this stuff gravitationally attracted Click picture for full news story. War between gravity and pressure.

brianna-sampson
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The Life Cycle of a Star

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  1. The Life Cycle of a Star Upper Fifth Physics

  2. In The Beginning… • Lots of gas and dust • All this stuff gravitationally attracted • Click picture for full news story

  3. War between gravity and pressure • If the mass of gas is large enough, then the gravitational attraction of the particles will overcome the pressure and the cloud will contract

  4. Ignition! • As the cloud contracts, GPE is converted into KE. • Temperature of cloud is related to the average KE of the molecules. • Increase in KE ‘means’ an increase in temperature. • If temperature exceeds 15 million K, hydrogen fuses into helium and we have ignition!

  5. Just keep glowing… • Star continues to glow as long as there is sufficient hydrogen. • Battle between forces due to gravity and pressure continues but is stable. • Each second, the Sun converts 1 million kg of hydrogen in helium

  6. Running low on gas • Helium production continues until hydrogen runs out. • Helium fuses into other nuclei, but the process isn’t as efficient. • What happens next depends on the original mass of the star (click on a button) Great Links Little Star Big Star

  7. Little Star • Hydrogen cloud around hot central core drifts off • As last of hydrogen drifts off, big wind comes from surface of core • Wind distorts hydrogen cloud. • We have a ‘planetary nebula’ surrounding a white dwarf • White dwarf cools and fades away Return to ‘Running Low on Gas’

  8. Big Star • Star burns helium to other elements, which in turn can be fuses into heavier elements still.

  9. Large pop! • Iron doesn’t burn so eventually the fusion stops! • There is nothing to stop the gravitational pull of the nuclei on each other. • Iron core collapses in a second. • Resulting explosion is a supernova, visible between galaxies. • During this explosion, heavier elements are made (all elements in universe heavier than iron originally came from supernovae – including those inside you!

  10. What’s left? • If the star’s core was ‘small’ then a small spinning lump of neutrons called a neutron star is left. • If the star’s core was ‘large’ then a black hole is left. Back to ‘Running out of Gas’

  11. Great Links • NASA – for a more in depth description • More pretty pictures of • Stellar births • Stellar deaths • The science of black holes (odd stuff happens there)

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