Azerbaijan National Academy of Science

An international team of astronomers funded in part by NASA has found the farthest galaxy group identified to date. Called EGS77, the trio of galaxies dates to a time when the universe was only 680 million years old, or less than 5% of its current age of 13.8 billion years.

More significantly, observations show the galaxies are participants in a sweeping cosmic makeover called reionization. The era began when light from the first stars changed the nature of hydrogen throughout the universe in a manner akin to a frozen lake melting in the spring. This transformed the dark, light-quenching early cosmos into the one we see around us today.

"The young universe was filled with hydrogen atoms, which so attenuate ultraviolet light that they block our view of early galaxies," said James Rhoads at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who presented the findings on Jan. 5 at the 235th meeting of the American Astronomical Society in Honolulu. "EGS77 is the first galaxy group caught in the act of clearing out this cosmic fog."

While more distant individual galaxies have been observed, EGS77 is the farthest galaxy group to date showing the specific wavelengths of far-ultraviolet light revealed by reionization. This emission, called Lyman alpha light, is prominent in all members of EGS77.

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