CrazyNeutrino said:
Astronomers find baby blue galaxy close to dawn of time
A team of astronomers peering deep into the heavens have discovered the earliest, most distant galaxy yet, just 670 million years after the Big Bang.
The findings, described in Astrophysical Journal Letters, reveal a surprisingly active, bright galaxy near the very dawn of the cosmos that could shed light on what the universe, now 13.8 billion years old, was really like in its young, formative years.
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Hang on – because of red-shift the most distant galaxies always appear very red, never blue. The further away the redder. (Read more from article).
> One of the many challenges with looking for such faint galaxies is that it’s hard to tell if they’re bright and far, or dim and near. Astronomers can usually figure out which it is by measuring how much that distant starlight gets stretched, “redshifted”. EGS-zs8-1 seemed to be too bright to be coming from the vast distances that the Hubble data suggested.
Ah, so it did appear to be extremely red.
> To narrow in, they used the MOSFIRE infrared spectrograph at the Keck I telescope in Hawaii to search for a particularly reliable fingerprint of hydrogen in the starlight known as the Lyman-alpha line. This fingerprint lies in the ultraviolet part of the light spectrum, but has been shifted to redder, longer wavelengths over the vast distance between the galaxy and Earth. It’s a dependable line on which to base redshift (and distance) estimates, Illingworth said – and with that settled, the team could put constraints on the star mass, star formation rate and formation epoch of this galaxy.
They can use a spectrograph on this!? The most distant galaxies are only visible as extremely faint dots on Hubble’s deepest images, far to faint to take a spectrum of with Keck. I’m starting to understand. EGS-zs8-1 has a redshift of 7.73 which is huge, but not as far as the most distant galaxies found. The most distant galaxy found has redshift 10.8, with a possible at redshift 11.9.
Getting a recognisable spectrum of a galaxy with redshift 7.73 is a stunningly remarkable achievement.