Astronomers have detected oxygen in JADES-GS-z14-0, the most distant known galaxy.
The galaxy is 13.4 billion lightyears away, which means astronomers are observing it as it existed when the Universe was just 300 million years old.
As well as being an incredible discovery itself, the oxygen detection shows that this early galaxy is more chemically mature than expected.
Detecting the oxygen
Two different teams of astronomers detected oxygen in JADES-GS-z14-0 in two separate studies.
JADES-GS-z14-0 is the most distant galaxy ever found.
It's so far away, it takes light from the galaxy 13.4 billion years to reach us.
And because the Universe is 13.8 billion years old, this means we're seeing the galaxy as it existed when the Universe was about 2% if its current age.
The detection was made using the the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile's Atacama Desert.
What it means
The oxygen detection suggests astronomers need to rethink what they know about how quickly galaxies formed in the early Universe.
"It is like finding an adolescent where you would only expect babies," says Sander Schouws, a PhD candidate at Leiden Observatory, the Netherlands, and first author of the Dutch-led study, accepted for publication in The Astrophysical Journal.
"The results show the galaxy has formed very rapidly and is also maturing rapidly, adding to a growing body of evidence that the formation of galaxies happens much faster than was expected."
Galaxies begin their lives full of young stars made up of 'light' elements like hydrogen and helium.
Over time, those stars evolve and produce 'heavier' elements like oxygen.
These heavier elements are distributed throughout the host galaxy when the stars die.
Researchers thought that, when it was as young as 300 million years old, the Universe was too young to have galaxies ripe with heavy elements.
But these two separate studies using ALMA show JADES-GS-z14-0 has 10 times more heavy elements than expected.
"I was astonished by the unexpected results because they opened a new view on the first phases of galaxy evolution," says Stefano Carniani of the Scuola Normale Superiore of Pisa, Italy, lead author on the paper now accepted for publication in Astronomy & Astrophysics.
"The evidence that a galaxy is already mature in the infant Universe raises questions about when and how galaxies formed."
Cosmic measuring stick
The oxygen detection has had another happy benefit for the astronomers: fine-tuning measurements of just how far away JADES-GS-z14-0 is.
Astronomers measure far-away objects like galaxies by using something called redshift.
If an object is millions – even billions – of lightyears away, its light takes millions or billions of years to reach Earth.
As that light travels through space, it is affected by the expansion of the Universe and is shifted more towards the red end of the spectrum.
The further away galaxies are, the more red they look.
So, astronomers can observe how redshifted a galaxy's light is and work out how far away that galaxy is.
The astronomers say previous measurements showed JADES-GS-z-14-0 was at a redshift between about 14.12 and 14.4.
With their oxygen detections, both teams have narrowed this down to a redshift around 14.18.
"The ALMA detection offers an extraordinarily precise measurement of the galaxy’s distance down to an uncertainty of just 0.005%," says Eleonora Parlanti, PhD student at the Scuola Normale Superiore of Pisa and author on the Astronomy & Astrophysics study.
"This level of precision — analogous to being accurate within 5cm over a distance of 1km — helps refine our understanding of distant galaxy properties."
"While the galaxy was originally discovered with the James Webb Space Telescope, it took ALMA to confirm and precisely determine its enormous distance," says Associate Professor Rychard Bouwens, a member of the team at Leiden Observatory.
"This shows the amazing synergy between ALMA and JWST to reveal the formation and evolution of the first galaxies."
