Regarding matter that has the highest redshifts, do we see such matter in every general direction we look (relative to Earth: up down left right front back)?

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    $\begingroup$ Yes we do, and it looks like this. $\endgroup$ – pela Apr 19 '16 at 13:22
  • $\begingroup$ That's CMB levels. I want redshifts. $\endgroup$ – Paul Apr 19 '16 at 13:25
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    $\begingroup$ The CMB is all at the same redshift (~1100), to a relative precision within $10^{-5}$, no matter if you look up, down, left, or right. We haven't observed anything with higher redshifts. $\endgroup$ – pela Apr 19 '16 at 14:23
  • $\begingroup$ So if the measured CMB peak wavelength is ~2mm, then the originating CMB was ~2mm/1100 (~2um)? $\endgroup$ – Paul Apr 19 '16 at 15:21
  • $\begingroup$ More or less, yes. The answer depends a bit on whether you express intensity as a function of wavelength or frequency. I think 1 $\mu$m is considered the peak wavelength $\endgroup$ – pela Apr 20 '16 at 9:07

It's not possible to see photons from "beyond" the cosmic microwave background (CMB), because (assuming our cosmology is generally correct) the CMB is the result of recombination of electrons with protons in the early universe. Photons from before that era were absorbed in the plasma.

Essentially then, the earliest matter we can see (in photonic terms) is this glowing hot hydrogen, but massively red-shifted so it looks like hydrogen at 3K.

We see the CMB in every direction.


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