The Hubble Space Telescope has observed the farthest galaxy ever seen in the Universe, revealing the object to astronomers as it existed 13.4 billion years in the past, 400 million years after the big bang. Young galaxy GN-z11 is located in the direction of Ursa Major.

Observations with Hubble’s Wide Field Camera 3 have revealed it is 25 times smaller than the Milky Way and contains just one per cent of our Galaxy’s stellar mass.

But GN-z11 is forming stars at a rate 20 times greater than the Milky Way today, meaning it was bright enough for the astronomers to spot it.

"We've taken a major step back in time, beyond what we'd ever expected to be able to do with Hubble.

We see GN-z11 at a time when the universe was only three per cent of its current age," says Pascal Oesch of Yale University, principal investigator of the study.

A timeline of the Universe, showing how close GN-z11 is to the point in the Universe at which the first stars began to form. Credit: NASA, ESA, P. Oesch (Yale University), G. Brammer (STScI), P. van Dokkum (Yale University), and G. Illingworth (University of California, Santa Cruz)

The team had previously estimated the galaxy’s distance by determining its colour using Hubble and NASA’s Spitzer Space Telescope, but Hubble’s Wide Field Camera 3 enabled the astronomers to split light from the galaxy and determine its distance by analysing the component colours.

This technique is known as spectroscopy and is done by determining the ‘redshift’ of the galaxy.

Because the Universe is expanding, distant objects appear to be receding as their light is stretched to longer wavelengths during its journey to Earth.

Measuring how much the light is stretched enables astronomers to determine the distance it has travelled.

The previous most distant galaxy had a redshift of 8.68, meaning astronomers were observing it as it appeared 13.2 billion years in the past.

But this latest galaxy has a redshift of 11.1, bringing its age nearly 200 million years closer to the Big Bang.

"This is an extraordinary accomplishment for Hubble.

It managed to beat all the previous distance records held for years by much larger ground-based telescopes," says investigator Pieter van Dokkum of Yale University.

As well as detecting the record-breaking galaxy, the observations also reveal new information about the early Universe after the Big Bang.

"It's amazing that a galaxy so massive existed only 200 million to 300 million years after the very first stars started to form,” says investigator Garth Illingworth of the University of California, Santa Cruz.

“It takes really fast growth, producing stars at a huge rate, to have formed a galaxy that is a billion solar masses so soon.”


Iain Todd BBC Sky at Night Magazine
Iain ToddScience journalist

Iain Todd is BBC Sky at Night Magazine's Content Editor. He fell in love with the night sky when he caught his first glimpse of Orion, aged 10.