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How are stars formed?

  1. Jul 28, 2006 #1
    Someone told me stars are formed by black hole, yet, I didn't believe him, are they really?
     
  2. jcsd
  3. Jul 28, 2006 #2
    no

    look up star birth

    its from dust + hydrogen in Nebulae + gravity makes lumps which get bigger and bigger causeing the dust to heat up

    when they heat up enought they start fission of hydrogen
     
  4. Jul 28, 2006 #3

    robphy

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  5. Jul 28, 2006 #4
  6. Jul 29, 2006 #5

    chroot

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    You mean... fusion.

    - Warren
     
  7. Jul 29, 2006 #6
    Yep I do Warren, thanks for pointing this out.
    I also knew that it was Fusion, but I didnt proof read the post, Sorry!
     
  8. Jul 30, 2006 #7
  9. Jul 31, 2006 #8
    thats intresting, i fully understand where hees coming from. looks like he was kinda right after all
     
  10. Jul 31, 2006 #9

    selfAdjoint

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    Well that isn't the role of a black hole everybody assumed your original post was referring to. Here's a quaote from the site.

    So the star formation process currently supposed - condensation from a cloud - isn't being challenged. Rather it's proposed that a jet from a black hole triggers that process, at least in some cases.
     
  11. Jul 31, 2006 #10
    But since everytime stars die, they turn into black hole and black hole gives off the stuff needed to make the stars, doesn't it make most of the stars?
     
  12. Jul 31, 2006 #11

    Labguy

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    Please start at this site for a decent answer to your questions so far. After reviewing that, you might have some more specific questions.(?) That website has nice pictures too...
     
  13. Jul 31, 2006 #12
    Not all stars evolve into blackholes. And blackholes don't give off anything but radiation in the form of x-rays...
     
  14. Jul 31, 2006 #13

    chroot

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    Only very massive stars (more than twenty-five times the mass of the Sun) have the potential to become black holes when they die. Most stars do not become black holes, becoming instead only white dwaf stars or being ripped to shreds in a supernova explosion.

    - Warren
     
  15. Jul 31, 2006 #14

    SpaceTiger

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    Well, not entirely ripped to shreds. We expect intermediate mass stars (3 solar masses) to leave behind neutron stars when they die.
     
  16. Aug 1, 2006 #15
    Wait a sec., supermassive stars become normal black hole then what kind of stars make up supermassive blackhole. I thought that whenever a star dies, it becomes a black hole and the bigger a star is, the bigger the balck hole is.
     
  17. Aug 1, 2006 #16
    'supermassive black holes' 'exist' in he center of Galaxies, where a collosal mass must have existed to pull together the stars in a galaxy.
     
  18. Aug 1, 2006 #17
    But normal black holes are formed by normal stars right? And supermassive black hole are formed by supermassive stars.
     
  19. Aug 1, 2006 #18
    normal blackholes are formed by masive stars

    supermassive blackholes are formed at the creation of a Galaxy, or maybe a colision of multiple massive stars
     
  20. Aug 1, 2006 #19

    chroot

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    Supermassive black holes may be of primordial origin, born long before the universe cooled enough to to allow stars to form. On the other hand, they could be simply normal black holes that have absorbed a large amount of matter after formation. The supermassive black holes suspected to exist at the centers of galaxies are almost certainly of primordial origin, and served as the "attractors" that pulled galaxies together in the early universe.

    Perhaps one of our resident astronomers can expand more on the topic?

    - Warren
     
  21. Aug 1, 2006 #20

    No, only stars with a enough mass so that gravity overcomes the neutron degeneracy pressure will become black holes. We're not entirely sure what that limit is though, because accurately determining the neutron degeneracy pressure is much harder than say determining the electron degeneracy pressure (which is what keeps white dwarfs from collapsing). Its likely that you can't have a neutron star much larger than 3 solar masses (the star that formed the neutron star would of course be much larger). Supermassive blackholes would be formed by matter falling into an existing blackhole, cause into to grow. You can't have stars much over 100 solar masses as they slimply blast matter off with radiation driven stellar winds when they get to be that big.
     
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