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The James Webb Space Telescope has discovered one of the earliest galaxies that formed after the big bang, about 350 million years after the universe began.
The galaxy, called GLASS-z12, and another galaxy formed about 450 million years after the Big Bang, were found in summer, shortly after the powerful space observatory began its infrared observations of the cosmos.
Webb’s ability to peer deeper into the universe than other telescopes reveals previously hidden aspects of the universe, including stunningly distant galaxies like these two finds.
The discovery could change the way astronomers understand galaxy and star formation in the early days of the universe.
“Webb and I were stunned to find the most distant starlight anyone had ever seen, just days after Webb published the first data,” astronomer Rohan Naidu, a research associate at the Massachusetts Institute of Technology, said in a statement. Naidu was lead author of the November study published in The Astrophysical Journal Letters.
Previously, the earliest observed galaxy was GN-z11, which existed 400 million years after the big bang, and was spotted by the Hubble Space Telescope in 2016.
“As soon as we started taking data, we found that there are many more distant galaxies than we expected,” said Tommaso Treu, principal investigator of the GLASS-JVST Early Publication Science Program and professor at the University of California, Los Angeles.
“Somehow, the universe managed to form galaxies faster and earlier than we thought.” Just a few hundred million years after the big bang, many galaxies already existed. JVST has opened a new frontier, bringing us closer to understanding how it all began. And we’ve only just begun to explore that,” said Treu, who co-authored the October study in The Astrophysical Journal Letters.
Two journal studies highlighted these discoveries made during the Grism Lens-Amplified Survey from Space, also known as GLASS, and the Cosmic Evolution Early Release Science Survey, or CEERS.
The early galaxies discovered in this new cosmic frontier are surprising and unusual for astronomers in many ways, Treu said.
Both galaxies are spherical or disc-shaped, and are only a small percentage of the size of the Milky Way galaxy. The two galaxies are incredibly far away, but they are also extremely bright and form stars very quickly.
The research results suggest that galaxies may have started to appear in the universe only 100 million years after the big bang, which happened 13.8 billion years ago. This timeline challenges theories astronomers have held about how and when the first galaxies formed.
The early universe was chaotic and crowded, but the structure of the two galaxies appears calm and ordered, said Erika Nelson, an assistant professor of astrophysics at the University of Colorado at Boulder, who co-authored the November study.
The amount of brightness in the two galaxies has puzzled scientists. One possibility is that the galaxies were massive and contained many low-mass stars, similar to the types of galaxies that formed later in the universe.
Or it could suggest the opposite: smaller galaxies with fewer but extremely bright stars. These luminous objects, called Population III stars, were long thought to be the first stars ever born in the cosmos.
The first stars in the universe would have been burning with heat and made of only hydrogen and helium. Later stars contain heavier elements that were formed when the first stars exploded. So far, no Population III stars have ever been seen in our local universe.
But telescopes that can peer back into the distant universe, effectively looking backwards, may one day be able to see the first stars of Population III. The older of the two galaxies, GLASS-z12, may even contain Population III stars, said Adriano Fontana, a GLASS-JVST team member and co-author of the October study.
The new discoveries about the two galaxies could mean that there are other bright galaxies waiting to be found in the distant universe.
Galaxy distance estimates are based on Webb’s infrared detections. Accompanying spectroscopic observations can confirm how long their light has been stretched across the universe, as well as the rate of star formation in each galaxy and the elements these stars contain.
Webb’s Near-Infrared Spectrograph will capture data that could lead to these insights.
“These observations just make your head explode.” This is a whole new chapter in astronomy. It’s like an archaeological dig, and suddenly you find a lost city or something you didn’t know about. It’s simply stunning,” said Paola Santini, a researcher at the Astronomical Observatory of the National Institute of Astrophysics in Rome, who co-authored the October study.
The Webb Telescope has entered its fifth month of science operations and is proving more powerful and capturing sharper images than expected before launch, said Dr. Jane Rigby, Webb Project Scientist for Operations at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“These galaxies we’re talking about are bright,” Rigby said. “They were hiding just below the limits of what Hubble could do.” They were waiting for us there. We just had to go a little redder and go deeper than Hubble could do.”