James Webb Telescope observes two of the most distant galaxies ever found

The James Webb Space Telescope observed one of the first galaxies formed after the Big Bang, about 350 million years after the beginning of the universe.

This one, called GLASS-z12, and another galaxy formed about 450 million years after the Big Bang, were found during the summer, just after the powerful space telescope began its infrared observations of the cosmos.

Webb’s ability to look deeper into the universe than other telescopes is revealing previously hidden aspects of the universe, including incredibly distant galaxies like these two discoveries.

The discovery could change the way astronomers understand the galaxy and star formation in the early days of the universe.

“With Webb, we were stunned to find the most distant starlight anyone had ever seen, just days after Webb released its first data,” said astronomer Rohan Naidu, a researcher at the Massachusetts Institute of Technology (MIT), in an announcement. Naidu was the lead author of a study published in November in The Astrophysical Journal Letters.

Previously, the first observed galaxy was GN-z11, which was born 400 million years after the big bang and was detected by the Hubble Space Telescope in 2016.

“Once we started collecting data, we found that there are many more distant galaxies than we expected,” said Tommaso Treu, principal investigator of the GLASS-JWST Early Release Science Program and professor at the University of California, Los Angeles.

“Somehow the universe managed to form galaxies faster and sooner than we thought. Just a few hundred million years after the Big Bang, there were already many galaxies. Webb has opened up a new frontier, bringing us closer to understanding how it all began. And we’ve only just begun to explore it,” said Treu, co-author of an October study in The Astrophysical Journal Letters.

The two 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.

Change in the timeline of galaxy formation

The first galaxies discovered in this new cosmic frontier are surprising and unusual for astronomers in many ways, Treu said.

Both galaxies have spherical or disk shapes, and are only a small percentage of the size of the Milky Way. The two galaxies are incredibly distant, but they are also extremely bright and formed stars very quickly.

The research results suggest that galaxies may have started to appear in the universe just 100 million years after the Big Bang, which occurred 13.8 billion years ago. This timeline challenges astronomers’ theories 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 orderly, said Erica Nelson, an assistant professor of astrophysics at the University of Colorado 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, which is similar to the types of galaxies that formed later in the universe.

Or it might suggest the opposite: smaller galaxies with fewer stars but extremely bright. These luminous objects, called Population III stars, have long been theorized to be the first stars to be born in the cosmos.

The first stars in the universe would be glowing with heat and would be made only of hydrogen and helium. Later stars contain heavier elements that were created when the first stars exploded. So far, no Population III stars have been seen in our local universe.

But telescopes that can peer into the distant universe, effectively looking back in time, might be able to see the first Population III stars one day. The older of the two galaxies, GLASS-z12, may even contain Population III stars, said Adriano Fontana, a member of the GLASS-JWST team and co-author of the October study.

Detection of light invisible to the human eye

The new discoveries about the two galaxies could mean that there are other bright galaxies waiting to be found in the distant universe.

Distance estimates for galaxies are based on Webb’s infrared detection. Spectroscopic observations can confirm how long its light traveled through the universe, as well as the rate of star formation in each galaxy and the elements those stars contained.

Webb will capture the data that can lead to these conclusions.

“These remarks just make your head explode. This is a whole new chapter in astronomy. It’s like an archeological 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 Rome Astronomical Observatory of the National Institute of Astrophysics, who co-authored the October study.

The Webb telescope has entered its fifth month of science operations and has proven to be more powerful and capture 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 within the confines of what Hubble could do. They were there waiting for us. We just had to get a little redder and go deeper than Hubble could.”