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The James Webb Space Telescope has spied one of the earliest galaxies 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 over the summer, shortly after the powerful space observatory began its infrared observations of the cosmos.
Webb’s capability to look deeper into the universe than other telescopes is revealing previously hidden aspects of the universe, including astonishingly distant galaxies such as these two finds.
The discovery could change the way astronomers understand galaxy and star formation in the early days of the universe.
“With Webb, we were amazed to find the most distant starlight that anyone had ever seen, just days after Webb released its first data,” said astronomer Rohan Naidu, research fellow at the Massachusetts Institute of Technology, in a statement. Naidu was the lead author of a November study published in The Astrophysical Journal Letters.
Previously, the earliest galaxy observed 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 discovered that there are many more distant galaxies than we were expecting,” said Tommaso Treu, principal investigator for the GLASS-JWST Early Release Science Program and professor at the University of California at 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, there were already lots of galaxies. JWST has opened up a new frontier, bringing us closer to understanding how it all began. And we’ve just started to explore it,” said Treu, who was a coauthor of an October study in The Astrophysical Journal Letters.
The two journal studies have 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.
Timeline shift for early galaxy formation
The early galaxies discovered in this new cosmic frontier are surprising and unusual to astronomers in many ways, Treu said.
Both galaxies have sphere or disklike shapes, and they’re just a tiny percentage of the size of the Milky Way galaxy. The two galaxies are incredibly distant, but they’re also extremely bright and formed stars very rapidly.
The research findings have suggested that galaxies may have began appearing in the universe just 100 million years after the big bang, which occurred 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 appear calm and orderly, said Erica Nelson, assistant professor of astrophysics at the University of Colorado, Boulder, who was a coauthor of the November study.
The amount of brightness in the two galaxies has puzzled scientists. One possibility is that the galaxies were massive and contained a lot of low-mass stars, which is similar to the types of galaxies that formed later on in the universe.
Or it could suggest the opposite: smaller galaxies with fewer but extremely bright stars. These luminous objects, called Population III stars, have long been theorized as the first stars ever born in the cosmos.
The first stars in the universe would have been blazing with heat and only made of hydrogen and helium. Later stars contain heavier elements that were created when the first stars exploded. So far, no Population III stars have ever been seen within our local universe.
But telescopes that can peer back into the distant universe, effectively looking back in time, may be able to see the first Population III stars one day. The older of the two galaxies, GLASS-z12, might even contain Population III stars, said Adriano Fontana, a member of the GLASS-JWST team and a coauthor of the October study.
Detection of light invisible to the human eye
The new findings about the two galaxies might mean there are other bright galaxies waiting to be found in the distant universe.
The distance estimates of the galaxies are based on Webb’s infrared detection. Follow-up 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 contained.
Webb’s Near-Infrared Spectrograph will capture the 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 just staggering,” said Paola Santini, researcher at the National Institute for Astrophysics’ Astronomical Observatory of Rome, who was a coauthor of the October study.
The Webb telescope has entered its fifth month of science operations and has proven to be more powerful and capturing sharper images than prelaunch expectations, said Dr. Jane Rigby, Webb operations project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
“These galaxies we’re talking about are bright,” Rigby said. “They were hiding just under the limits of what Hubble could do. They were right there waiting for us. We just had to go a little redder and go deeper than what Hubble could do.”