Are we looking at dead stars?

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Lee Yott

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Are we looking at dead stars?
« on: 14/12/2010 12:30:03 »
Lee Yott  asked the Naked Scientists:
Hello Chris,

I was hoping you could shine some light on a question I have.

Light from stars takes a long time to reach us, and at the same time galaxies are moving away from us at break-neck speeds. With these two factors in mind, is it possible that a percentage of light that makes up the starry sky as we know it is from stars that are now far beyond our visual horizon, or from stars that have burned out long ago? If so, what is that percentage, and does it mean that we are floating around in a much darker and more isolated universe than we suspect?

What do you think?
« Last Edit: 14/12/2010 12:30:03 by _system »


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Are we looking at dead stars?
« Reply #1 on: 14/12/2010 12:44:58 »
Yes particularly for the brightest stars we see even in relatively nearby galaxies like the Virgo cluster.  A bright star will only last for a few million years before exploding as a supernova so for galaxies more than a few million light years away the whole life story of that star may be still on its way to us.

There is one other point we can see in the past that the universe was a good deal brighter when the many quasars were shining brightly and there are good reasons to believe that star formation has passed its peak in the overall universe.
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