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Distant Metals Reveal the Universe’s Evolution

30 Mar 2020, 16:00 UTC
Distant Metals Reveal the Universe’s Evolution
(200 words excerpt, click title or image to see full post)

When did the first sources of light bombard the universe’s gas, tearing electrons from atoms in a period known as reionization? A new study uses the metal-filled gas surrounding galaxies to learn more about this important transition.
Drama in the Early Universe
In the schematic timeline of the universe, the epoch of reionization is when the first galaxies and quasars began to form and evolve. [NASA]After the universe’s birth in the hot Big Bang, expansion and cooling allowed the soup of electrons and protons that pervaded space to recombine into neutral hydrogen atoms. But sometime within the first billion years after the Big Bang, these atoms were again ionized by high-energy radiation from the first sources of light in the universe.
How and when, exactly, did this period of reionization occur? One way we can seek to answer these questions is by studying the gas that lies both between and immediately around galaxies.
Clues from Distant Gas
While the broadly dispersed intergalactic medium (IGM) consists largely of hydrogen gas, the circumgalactic medium (CGM) immediately around galaxies is a little more complicated: it’s enriched with elements heavier than helium — “metals” — that have been produced by the galaxy’s stars and ...

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