

Simple but Challenging: The Universe According to Planck - kdavis
http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51551

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cristianpascu
Could someone, please, clue me on something that has been on my mind for a
while now: The thermal radiation coming from distant stars has been red-
shifted by the Universe expansion, together with the light in the visible
spectrum. I suppose. Is it now in the same spectral area as the background
radiation? Or is it the same thing?

Also, if we see the stars, do we also see the thermal radiation coming from
them?

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shardling
Starlight (and sunlight) chiefly _is_ thermal radiation. The CMB is something
distinct, originating from before there were any stars at all!

Re:contamination, luckily stars in general are fairly sparsely distributed, so
we can simply remove those areas. Apparently the plane of our own galaxy does
have to be mostly cut out, though.

[http://en.wikipedia.org/wiki/Cosmic_microwave_background_rad...](http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation#Data_reduction_and_analysis)

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XaspR8d
> Starlight (and sunlight) chiefly is thermal radiation.

I just wanted to clarify for others that while we are used to learning that
stellar radiation "originates" from nuclear fusion, most of the emission from
fusion is absorbed by the outer layers of the star and then re-emitted. Hence
why it is all thermal, and why starlight replicates blackbody radiation so
well.

Just something I had been confused about for a while. Feel free to correct me
if I am still confused. ;)

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xk_id
Wow. Looks like time for a revolution in physics.

