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Way Way Bigger than Canis Majoris?

  1. Feb 1, 2012 #1
    Is it possible that there are stars in our universe so large that light cannot escape their gravity similar to a black hole?
  2. jcsd
  3. Feb 1, 2012 #2


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    No, anything that massive becomes a black hole. Also note the difference between size and mass, whilst VY Canis Majoris is 3 billion km in diameter 2000x bigger than the sun it is only ~40x as massive. Contrast this to a Neutron star which can be 2x as massive as the sun and ~100,000x smaller.
  4. Feb 1, 2012 #3
    I wanna say the escape velocity of neutron star is something like 100,000 km/s.
  5. Feb 1, 2012 #4


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    There is a limit to how massive a star can be. As a star grows in size, it becomes hotter and radiates more intensely. After a certain point, it will just blow away its outer layers.

    The largest known star is ~300 times as massive as the Sun. A black hole this massive would only be ~900 km in radius, much smaller than our Sun. A really massive star would extend past where its event horizon would need to be.
  6. Feb 1, 2012 #5
    If there were such a star, then it would be difficult to observe its light. It would be difficult, if not impossible, to say that such a star exist.

    One way of looking at black holes is that they form island universes, separated in space-time from our universe. Another way of asking your question: Is it possible to have a star that is so massive that it can form an island universe, something like a black hole?

    Unlikely, the way gravity seems to work.
  7. Feb 2, 2012 #6
    Another way to think about this is to say that the amount of gravitational "slope" in spacetime required to capture all light emitted is also too steep for the repulsive forces between matter that keep them separate. So these repulsive forces give out and matter collapses in on itself.
  8. Feb 8, 2012 #7
    A star by definition is a self-luminous body. So if the hypothetical object in in question doesn't produce its own light-then it would automatically disqualify itself as a star. In short, according to definition, it can’t be a star and not shine.

    That’s why astronomers plot stars' by color, temperature, luminosity, and spectral type.

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