James Webb Space Telescope enables discovery of earliest confirmed galaxies, 350 million years after the Big Bang
The discovery of the earliest galaxies yet found in our Universe has been confirmed, thanks to data from the James Webb Space Telescope (JWTST), which has peered back in time to less than 350 million years after the Big Bang.
Images from the telescope had previously suggested possible candidate to examine, and their age has now been confirmed by an international team using long spectroscopic observations, which measure light to determine the speed and composition of objects in space.
Distinctive patterns in the tiny amount of light from these incredibly faint galaxies were enough for scientists to prove the light they are emitting has taken 13.4 billion years to reach us - making them some of the earliest ever observed.
Two are further away than any observations made by the Hubble telescope, in a discovery that underlines the stunning power of JWST to detect never-before-seen parts of the earliest Universe.
“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,” said Dr Emma Curtis-Lake, from the University of Hertfordshire, lead author on one of two papers on the findings. “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!”
More than 80 astronomers from 10 countries - including researchers at the University of Cambridge - worked on the JWST Advanced Deep Extragalactic Survey (JADES) programme after being allocated just over a month of observation on the telescope using its its two on-board instruments - the Near-Infrared Spectrograph (NIRSpec) and the Near-Infrared Camera (NIRCam). These were developed primarily to probe the earliest galaxies.
“It is hard to understand galaxies without understanding the initial periods of their development,” said Dr Sandro Tacchella, from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, and co-lead author on the second paper. “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.”
The team focused for 10 days on a small patch of sky in and around Hubble Space Telescope’s Ultra Deep Field. For more than 20 years, this has been analysed at the limit of nearly every large telescope.
With JWST, they observed it in nine different infrared wavelength ranges, to provide an exquisitely sharp and sensitive picture of the field.
The image reveals nearly 100,000 galaxies, each of which is billions of light years away.
They occupy a pinprick of the sky - equivalent to looking at a mobile phone screen across a football field.
Distinctive banded colours, visible in infrared light but invisible in other wavelengths, revealed the earliest galaxies.
A rare continuous 28-hour observation window enabled the Near-Infrared Spectrograph to spread out the light emitting from each galaxy into a rainbow spectrum.
Measuring the amount of light received at each wavelength enabled the team to study the unique light patterns created by the properties of the gas and stars within each galaxy.
Four of the galaxies were shown to originate earlier in the Universe than any previous observations.
“Our observations suggest that the formation of the first stars and galaxies started very early in the history of the Universe,” said Prof Andrew Bunker, from the University of Oxford.
Prof Roberto Maiolino, from Cambridge’s Cavendish Laboratory and Kavli Institute for Cosmology, and co-author on one of the two papers, added: “This is a major leap forward in our understanding of how the first galaxies formed.
“We have been able to dissect the light coming from these galaxies in the very early universe and, for the first time, characterise in detail their properties. It’s really fascinating and intriguing to discover how young these systems were and that stellar processes hadn’t yet managed to pollute these galaxies with chemical elements heavier than helium.”
The JADES team plans 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 the evolution of these first galaxies.
Pre-prints of the work, not yet peer-reviewed, are available online,
