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Steller Evolution

Steller Evolution. How stars are born, evolve, and finally die. Hydrostatic Equilibrium. S tellar evolution is a struggle between two opposing forces; gravity continually tries to make a star shrink while the star’s internal pressure tends to make the star expand. Interstellar Medium.

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Steller Evolution

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  1. Steller Evolution How stars are born, evolve, and finally die.

  2. Hydrostatic Equilibrium Stellar evolution is a struggle between two opposing forces; gravity continually tries to make a star shrink while the star’s internal pressure tends to make the star expand.

  3. Interstellar Medium • Nebulae are an interstellar cloud of dust, hydrogen, helium and other ionized gases. • Contracting cloud gives birth to a clump called a protostar.

  4. Protostar • cool blob of gas larger than our solar system • pressure inside is too low to support the gas so it contracts • as it contracts, gravitational energy is converted to thermal energy • this makes the gasses heat up and start glowing • no thermonuclear reactions occur yet. • http://upload.wikimedia.org/wikipedia/commons/thumb/d/d6/A_Young_Star_Flaunts_its_X-ray_Spots.ogv/A_Young_Star_Flaunts_its_X-ray_Spots.ogv.360p.webm

  5. Main-Sequence Stars • Form when the protostar contracts and heats up enough to start thermonuclear reactions to convert hydrogen into helium. • At this point there is enough heat and internal pressure being created to stop the star's gravitational contraction.

  6. Red Giant After the core hydrogen has been used up the star expands. Star’s core contracts as fewer particles are available. Outer layer expands and cool.

  7. slide; Suns chemical composition

  8. Red Giant • The resulting helium core then undergoes thermonuclear reactions producing heavier nuclei. • Two helium fuse to produce Beryllium

  9. Star Death Two kinds depending on star mass.

  10. Low Mass Star Deaths • Our sun is considered a relatively low mass star. Eventually, after low mass red giants expel their outer layers, leaving a glowing planetary nebula. • The remaining burned-out core is called a white dwarf.

  11. High Mass Star Death • The core of a high mass red giant collapses suddenly. This causes an explosion called a supernova. • The resulting collapsed core can form either a neutron star or black hole. A Supernova from 1006 AD was ¼ as bright as the moon

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