Galaxy EGS8p7: 13.2 Billion Years Old and Revolutionary

A discovery of galactic proportions is causing scientists to rethink their theories of the early evolution of the universe.

The finding is grand in scope: It is what is perhaps the most distant galaxy ever discovered. The galaxy, called EGS8p7, is over 13.2 billion years old, compared with the 13.8 billion years of age of the universe. Previously, it had not been thought that a galaxy of this type could exist so early in the universe's formation.

The find was made by a group of California Institute of Technology (CalTech) researchers and is described in Astrophysical Journal Letters by Adi Zitrin and Richard Ellis.

The first clue as to the importance of EGS8p7, however, came earlier this year, when scientists used data from NASA's Hubble Space Telescope and Spitzer Space Telescope to name it a candidate for further investigation. Delving further, researchers used the multi-object spectrometer for infrared exploration (MOSFIRE) at the W. M. Keck Observatory in Hawaii to determine the galaxy's redshift.

The peculiar nature of EGS8p7 rests in its amount of radiation. At its particular stage in the universe's formation, EGS8p7's radiation should have been absorbed to some extent by clouds of neutral hydrogen atoms. This includes the so-called Lyman-alpha line, which is often used to indicate star formation in galaxies. Radiation absorption should have made it impossible to view a Lyman-alpha line from the galaxy.

"If you look at the galaxies in the early universe, there is a lot of neutral hydrogen that is not transparent to this emission," Zitrin said in a release. "We expect that most of the radiation from this galaxy would be absorbed by the hydrogen in the intervening space. Yet we still see Lyman-alpha from this galaxy."

A proposed reason for the galaxy's visibility rests in the theory that hydrogen reionization did not occur uniformly during the universe's formation.

"The galaxy we have observed, EGS8p7, which is unusually luminous, may be powered by a population of unusually hot stars, and it may have special properties that enabled it to create a large bubble of ionized hydrogen much earlier than is possible for more typical galaxies at these times," Sirio Belli, a graduate student who worked on the project, said in the release.

"We are currently calculating more thoroughly the exact chances of finding this galaxy and seeing this emission from it, and to understand whether we need to revise the timeline of the reionization, which is one of the major key questions to answer in our understanding of the evolution of the universe," Zitrin noted in the release.