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Are galaxies losing mass or gaining density or both?

  1. May 15, 2010 #1
    The other day I ran across the idea that galaxies lose mass due to their radiating.

    Before I heard this I assumed that galaxies became more and more dense as their lives wore on. Such that the gasses became gas giants and stars, dust became asteroids, planets, and moons, and the fusion in stars created heavier and heavier elements. All of this an effect of gravity pulling things together. And so, in general, mass has a tendency to become more dense.

    Thus I assumed that the spacetime deformation of a area containing mass becomes more and more deformed as time goes on. (on the galactic scale)

    So when I heard that galaxies loose mass by radiation I was intrigued.

    If this is true then could we assume that at some point in a galaxies life it reaches a maximum distortion of spacetime? Or is the loss of radiation mass not substantial enough to counter the density increases?

    (Also before I simplify my question, I am aware that a the spacetime deformation is the same no matter the size of the star as long as the mass is consistent. So when I say 'increasing' I refer to the exposing of more deformation around the body of mass.)

    Simply put my question is this : Are galactic spacetime deformations increasing or decreasing?
  2. jcsd
  3. May 16, 2010 #2


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    In the sense you posed the question, neither case applies. Spacetime does react to local matter density, but, very little of that is ferried off by photons over any reasonable period of time.
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