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Star Formation

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Star Formation

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    1. Star Formation Gravitational collapse of molecular cloud Evolution of protostars onto main sequence Gravitational contraction Luminosity versus temperature and radius

    3. Star formation Watch for: Collapse of cloud Rotation of cloud Formation of disk near protostar Show animation

    4. Gravitational collapse

    5. Potential energy due to gravity

    6. Gravitational collapse

    7. Potential energy due to gravity

    8. Gravitational collapse How much energy is released when 1 M? of material collapses from a radius of 10 R ? to 1 R ??

    9. Evolution of stars Stars change over their lifetimes (from formation to death). We can track these changes via motion of the star in the HR diagram.

    10. Protostars on HR diagram

    11. Gravitational collapse About 2?1041 J of energy is released when 1 M? of material collapses from a radius of 10 R ? to 1 R ?. This collapse takes about 10-20 million years. The luminosity is:

    12. Protostars evolve into main-sequence stars

    13. Cloud collapse to main-sequence star: evolutionary track on HR diagram

    14. Protostars on the HR diagram

    15. Luminosity versus radius and temperature

    16. Luminosity versus radius and temperature

    17. Luminosity of a Black Body Radiator

    18. Protostars evolve into main-sequence stars

    19. Note that luminosity remains constant. To produce constant luminosity as radius decreases, need increase in temperature Why does temperature increase as star contracts?

    20. More massive stars form faster

    21. As gas is pulled in towards a protostar which does not occur the gas starts to rotate more rapidly some of the gas is ejected in jets some of the gas forms a disk around the protostar some of the gas undergoes nuclear fusion

    22. Which clouds will collapse? Gravitational force causes objects to collapse. What keeps objects from collapsing? In the solar system, the motion of the planets keeps them from falling in to the Sun. In a gas, the random motions of the gas atoms can support the gas against gravity.

    23. Temperature Temperature is proportional to the average kinetic energy per molecule

    24. Energy of gas cloud

    25. Energy of gas cloud

    26. Critical size of gas cloud

    27. Critical size of gas cloud

    28. Star cluster

    30. Critical size of gas cloud

    31. Review Questions What is a protostars source of energy? How does a protostars radius and luminosity change as it contracts? What is the relation between luminosity, radius, and temperature. How does a protostars mass influence its speed of formation? What is the Jeans mass?

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