Far, far away is the faintest galaxy astronomy has ever seen

24 May 2016

ASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. Image via ESA/Hubble & NASA

Our telescopes are getting more and more powerful with each passing decade, and now, a team of astronomers has detected the faintest early-universe galaxy ever seen, revealing what our universe looked like 13bn years ago.

The international team of astronomers were able to catch a glimpse of the galaxy from the W M Keck Observatory on the summit on Mauna Kea in Hawaii using an effect known as gravitational lensing, which is comparable to an image behind a glass lens appearing distorted because of how the lens bends light.

Gravitational lensing was first predicted by Albert Einstein almost a century ago as part of his General Theory of Relativity and is somewhat related to the major discovery of gravitational waves announced earlier this year.

Publishing a research paper on the team’s discovery in the journal Astrophysical Letters, this distant galaxy cluster has been dubbed MACS2129.4-0741 and, according to UCLA, which contributed researchers to the project, it is massive enough to create three different images of the galaxy.

Distant galaxies

Composite image of the galaxy cluster from three different filters on the Hubble Space Telescope. Image via BRADAC/HST/W M Keck Observatory

Importance of gravitational lensing

Speaking of the three different images of this galaxy, co-author of the paper Tommaso Treu said that, by peering at the universe 13bn years ago, we are analysing the Big Bang theory, which suggests that the universe cooled as it expanded.

This, in turn, would have led to protons capturing electrons forming into hydrogen atoms, which on a cosmic scale would make the universe completely opaque to radiation, entering a cosmic dark age.

However, following a process called cosmic reionisation 13bn years ago, the universe once again sprung to life, however, it hasn’t been known whether this was the result of a considerable number of stars, or an event like gas falling onto supermassive black holes.

“Currently, the most likely suspect is stars within faint galaxies that are too faint to see with our telescopes without gravitational lensing magnification,” said Treu.

“This study exploits gravitational lensing to demonstrate that such galaxies exist, and is thus an important step toward solving this mystery.”

Colm Gorey was a senior journalist with Silicon Republic