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Faint, distant galaxies may have driven early universe makeover

Hubble telescope finds clues to cause of cosmic reionization, study claims

7:00am, February 6, 2017
Abell 2744

LIGHTEN UP  Some of the faintest, most distant galaxies detected to date (arcs) appear in this Hubble Space Telescope image of the massive galaxy cluster Abell 2744. The cluster acts as a gravitational lens, magnifying light from galaxies much farther away.

Two cosmic magnifying glasses are giving astronomers a glimpse of some extremely faint galaxies that existed as far back as 600 million years after the Big Bang (13.8 billion years ago). Such views suggest that tiny galaxies in the early universe played a crucial role in cosmic reionization — when ultraviolet radiation stripped electrons from hydrogen atoms in the cosmos.

“That we detected galaxies as faint as we did supports the idea that a lot of little galaxies reionized the early universe and that these galaxies may have played a bigger role in reionization than we thought,” says Rachael Livermore, an astronomer at the University of Texas at Austin. She and colleagues report the results in the Feb. 1 Astrophysical Journal.

The team identified the dim galaxies in images taken with the Hubble Space Telescope while it was pointed at two closer clusters of galaxies. Those clusters act as a gravitational lens, brightening and magnifying the

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