Astrophysicists using a telescope in Hawaii report they've found and dated the most distant galaxy ever detected, seen from Earth as it would have looked only around 600 million years after the creation of the universe in the Big Bang.
Given the identifier EGSY8p7, the galaxy is 13.2 light years from Earth, allowing astronomers to peer deep into the universe's past.
Using an infrared spectrograph instrument at the W.M. Keck Observatory, the scientists were able to detect and date the galaxy from an emission signal known at the Lyman-alpha line, a distinctive signature created by the heating of hydrogen gas by strong emissions of ultraviolet lights from the galaxy's newborn stars.
The researchers say they were pleased to be able to detect the signal, since it is often absorbed by hydrogen present between galaxies, which was especially prevalent in the universe's dawning age.
"We frequently see the Lyman-alpha emission line of hydrogen in nearby objects as it is one of most reliable tracers of star-formation," stated Adi Zitrin, and astronomer as the California Institute of Technology and first author of a study set to appear in Astrophysical Journal Letters.
"However, as we penetrate deeper into the universe, and hence back to earlier times, the space between galaxies contains an increasing number of dark clouds of hydrogen which absorb this signal."
That pervasive hydrogen probably made the universe completely opaque to Lyman-alpha emission for the first 400 million years of its existence, scientists suggest, until radiation from the stars forming in the universe's first galaxies "burned off" much of it by splitting hydrogen atoms into protons and neutrons in a process known as "cosmic reionization."
Detection the emission from EGSY8p7 suggests some regions of the universe were cleared of their hydrogen much earlier than others, the researchers say.
EGSY8p7, which exhibits unusual brilliance, has unique attributes that may have allowed it to produce a large "bubble" of hydrogen that had been ionized even before typical galaxies were able to, explains study participant and Caltech graduate student Sirio Belli.
Zitrin calls the era of reionization a final missing puzzle piece vital to a complete understanding of how the universe evolved.
EGSY8p7 will provide some hints as to how the universe evolved from when it was only 600 years old.
