Exogalactic starsystems

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Cyperium, Apr 22, 2009.

  1. Xylene Valued Senior Member

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    You're always going to have that--stars which have been flung too far away to ever be recovered, unless they accidently stray too close to another cluster of stars and are dragged in.
     
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  3. Cyperium I'm always me Valued Senior Member

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    All clusters move away from eachother...could it be that the perceived acceleration is actually just that the stars that had a greater velocity has moved further away?

    If the velocities of the early stars that once formed the galaxies weren't uniform then we would perceive what we perceive right? It would seem like it was the galaxies that moved at that speed, but it is actually the uniformity of velocities on the individual stars that enabled them to gather to form a galaxy, as such it is only natural that the galaxies that have been for the longest time is farther away, and it would seem like they are moving at an accelerating rate.

    I have two questions for you:
    1: Have they measured that the clusters are moving apart from eachother at an accelerating rate (not just measuring the velocity, but actually measuring that the velocity is greater and greater at that particular supernova)?
    2: Or could it be that it only seems that way because of the distance they are from each other the older they are?

    Cause if 1 is false, that they have only measured the current velocity and age and not the actual acceleration, then there might not be any acceleration, cause the velocities might not have been uniform at the start and it would only seem like space is expanding, while it in reality is that it is the stars with the same relative velocities that made up the galaxies.

    Also, if the stars didn't have a uniform velocity at the beginning, then they don't all have to gather at the same point, the universe would still look the same if they just went randomly into any direction with any speed (from any starting point).
     
    Last edited: May 25, 2009
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  5. Xylene Valued Senior Member

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    There''s a couple of colliding galaxies that are called The Mice because they look exactly like the two in the 5.7 MB simulation.
     
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  7. Xylene Valued Senior Member

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    I heard a couple of years ago that they had come up with a definitive answer to that question at long last--they've decided that the Universe is open-ended, so to speak; ie it will go on expanding forever, and never come back into a Big Crunch. So ultimately the stars and galaxies will get further and further away from each other, the strength of gravity will continue to decline, and stars will go on being formed until the Universe runs out of hydrogen (or until the force of gravity becomes so weak because of increasing distances that stars can no longer form, no matter how much hydrogen is present). So it seems that in the very deep future, our remotest descendents going to be looking at a sky almost devoid of stars.
     
  8. Cyperium I'm always me Valued Senior Member

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    Yes, but I don't think that it is for them to decide. There are still many voids in regard to this. I mean, we don't even know what dark matter is or if it even is. If the universe isn't actually expanding (exponentially), but the stars (and thus galaxies) make it seem that way because of their "random" distribution and velocities, then perhaps we have no need for dark matter. Sure the observable universe would still be expanding, but it's only the stars (and thus galaxies) that are fastest that make it seem that way.
     
  9. Xylene Valued Senior Member

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    I agree--it's always the stars and galaxies that are farthest away which seem to have the greatest red-shift, ie be moving away from us fastest--that's always made me wonder whether they've got the right idea with red-shift, or if there's another reason for it...

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  10. kaneda Actual Cynic Registered Senior Member

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    Of course there is another reason for it. There are a number of possible reason of which expansion is just one of them. However, as expansion relies on a number of impossibilities and nonsense, it is probably not the correct one.
     
  11. Starthane Xyzth returns occasionally... Valued Senior Member

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    Are you suggesting that the Gravitational Constant itself is changing as the Universe expands? Paul Dirac once published that theory.

    If not - and I certainly hope not! - galaxy clusters and their descendent supergalaxies will remain gravitationally bound and continue forming stars, however isolated they are from other clusters. Intergalactic-medium hydrogen, however, will certainly become ever more thinly spread, and most likely never form into anything coherent.
     

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