Breakthrough from Webb telescope: confirmation of galaxies in the very early Universe

9 December 2022

An international team of astronomers, including scientists at the Universities of Hertfordshire, Cambridge, Oxford and Liverpool John Moores, has today reported the discovery of the earliest galaxies ever confirmed in our Universe.

Thanks to data from the James Webb Space Telescope, scientists have confirmed observations of galaxies dating back to the earliest days of the Universe, less than 400 million years after the Big Bang – when the Universe was just 2% of its current age.

Images from Webb had previously suggested possible candidates for such early galaxies. Now, their age has been confirmed using long spectroscopic observations, which measure light to determine the speed and composition of objects in space.

These observations have revealed distinctive patterns in the tiny amount of light coming from these incredibly faint galaxies, allowing scientists to ascertain that the light they are emitting has taken 13.4 billion years to reach us, and corroborating their status as some of the earliest galaxies ever observed.

Scientists can also now confirm that two of these galaxies are further away than any observations made by the Hubble telescope – underlining Webb’s incredible power and ability to detect never-before-seen parts of the earliest Universe.

Dr Emma Curtis-Lake, Webb Fellow at the University of Hertfordshire and lead author on one of the two scientific papers on the findings, explained the breakthrough:

“It was crucial to prove that these galaxies do indeed inhabit the early Universe, as it’s very possible for closer galaxies to masquerade as very distant galaxies. Seeing the spectrum revealed as we hoped, confirming these galaxies as being at the true edge of our view, some further away than Hubble could see – it is a tremendously exciting achievement for the mission!”

The findings have been achieved by an international collaboration of more than 80 astronomers from ten countries via the JWST Advanced Deep Extragalactic Survey (JADES) programme. The team were allocated just over a month of observation on the telescope, using the two on-board instruments: the Near-Infrared Spectrograph (NIRSpec) and the Near-Infrared Camera (NIRCam). These instruments were developed with the primary purpose of investigating the earliest and faintest galaxies, and the team have spoken of their huge excitement at taking a step closer to understanding them:

“Our observations suggest that the formation of the first stars and galaxies started very early in the history of the Universe”, explains Prof. Andrew Bunker, Professor of Astrophysics at the University of Oxford.

Across 10 days of their observation time, the JADES team of astronomers focused on a small patch of sky in and around Hubble Space Telescope’s Ultra Deep Field, which for over 20 years has been a favourite of astronomers and has been analysed at the limit of nearly every large telescope to have existed. However, with Webb, the team were able to observe in nine different infrared wavelength ranges, providing an exquisitely sharp and sensitive picture of the field. The image reveals nearly 100,000 galaxies, each billions of light years away, in a pinprick of the sky equivalent to looking at a mobile phone screen across a football field.

The very earliest galaxies were identifiable by their distinctive banded colours, visible in infra-red light but invisible in other wavelengths. In one rare continuous 28-hour observation window, the Near-Infrared Spectrograph was used to spread out the light emitting from each galaxy into a rainbow spectrum. This allowed astronomers to measure the amount of light received at each wavelength and study the unique light patterns created by the properties of the gas and stars within each galaxy.

Crucially, four of the galaxies were revealed to originate earlier in the Universe than any previous observations. “This confirms we are in new frontier of our investigations into the birth of galaxies”, said Dr Curtis-Lake.

Assistant Professor Sandro Tacchella from the Cavendish Laboratory, University of Cambridge – co-lead author of the other paper – explained why it’s important to understand the origins of these galaxies:

“It is hard to understand galaxies without understanding the initial periods of their development. Much as with humans, so much of what happens later depends on the impact of these early generations of stars. So many questions about galaxies have been waiting for the transformative opportunity of Webb, and we're thrilled to be able to play a part in revealing this story."

Astronomers in the JADES team now plan to focus on another area of the sky to conduct further spectroscopy and imaging, hoping to reveal more about the earliest origins of our Universe and how these first galaxies evolve with cosmic time.

“This is still just the early phase of JWST’s mission” said Dr Alex Cameron, astronomer at the University of Oxford. “It’s one thing to find these galaxies, but as the mission progresses we’ll also continue to develop our understanding of the properties of these early galaxies. This is an exciting early step in a much longer process.”

More information about the findings can be found on NASA's blog. Pre-prints of the team’s two papers are now available here (Discovery and properties of the earliest galaxies with confirmed distances) and here (Spectroscopy of four metal-poor galaxies beyond redshift ten).

Image credit: NASA, ESA, CSA, M. Zamani (ESA/Webb)


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