At 13.2bn light years lies a galaxy really, really far away

7 Sep 2015

A team of astronomers is believed to have found the most distant galaxy known to mankind – EGS8p7 – located 13.2bn light years away from Earth, which makes it one of the oldest, too.

The distant galaxy was discovered by a team of Caltech astronomers who made the historic finding using NASA’s Hubble Space Telescope and Spitzer Space Telescope.

Dubbed EGS8p7, the galaxy had been marked by the researchers for future investigation and now, with the help of the multi-object spectrometer for infrared exploration (MOSFIRE) at the WM Keck Observatory in Hawaii, they have been able to reveal more about its make-up.

By looking at the drops in colour seen in the light wavelengths emitted from the galaxy – known as redshifts – the astronomers were able to determine not only its distance from Earth, but also that it is about 13.8bn years old.

This discovery of redshift in the furthest reaches of the universe presents an interesting challenge to astronomy, as it was believed that, at these distances, we shouldn’t be able to see light emitted from galaxies.

Distant galaxy

Galaxy EGS8p7, as seen from the Hubble Space Telescope (wide and top right) and Spitzer Space Telescope (inset, bottom right), taken in infrared. Image via I. Labbé (Leiden University), NASA/ESA/JPL-Caltech

After the Big Bang, the universe was awash with electrons and protons, and not until 380,000 years after the event could the universe have cooled enough to re-ionise the two particles to create visible light.

With this theory, light beyond the so-called Lyman-alpha line shouldn’t be visible. And, yet, EGS8p7 appears.

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

With the previous theory thrown into doubt, Caltech researchers involved with the discovery believe it could suggest that the Lyman-alpha line might have been more porous than once thought.

“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,” said Sirio Belli, a Caltech graduate student who worked on the project.

Galaxy illustration via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic