Astronomers found these two distant galaxies in the same small part of the sky. They estimate that the one on the right is from 300 million years after the Big Bang. Credit: JWST GLASS Survey NASA/CSA/ESA/STScI; Pascal Oesch/University of Geneva NASA built its state-of-the-art James Webb Space Telescope to peer into the distant Universe and back toward the dawn of time — and it’s already doing it spectacularly. In the two weeks since Webb’s first science images and data became available to astronomers, they have reported a flood of preliminary discoveries, including several contenders for what could be the most distant galaxy ever seen. Webb’s images reveal a wealth of galaxies twinkling in the distant universe, appearing as they did just a few hundred million years after the Big Bang 13.8 billion years ago. The telescope’s astonishingly sharp images have shattered astronomers’ preconceptions about the early Universe. “We had an idea in our mind about which galaxies are in them [distances] it would seem like how much detail we could see, but I think the reality is a bit mind-boggling,” says Jeyhan Kartaltepe, an astronomer at the Rochester Institute of Technology in New York. Here are some things astronomers are learning from Webb’s early observations.
There are too many galaxies out there.
Because Webb detects infrared light, and because the expansion of the universe stretches light into redder wavelengths, the telescope is well-suited for detecting galaxies that formed early in the Universe’s history. In his first observing programs, which began in June, Webb discovered many distant galaxies beyond the reach of other observatories, such as the Hubble Space Telescope. “It suggests what many of us have argued, that there are galaxies out there beyond what we saw with Hubble,” says Richard Ellis, an astronomer at University College London. The age of early galaxies began at the “cosmic dawn,” beginning perhaps about 250 million years after the Big Bang, when the first stars formed and lit up the Universe. Later generations of stars clustered into galaxies, which are the faint red blobs that Webb is beginning to discover. Many of Webb’s images are filled with galaxies never before seen in the distant Universe. “There is hardly any empty space that doesn’t have something,” says Kartaltepe. One study combed through data from many of the distant galaxy fields Webb has observed so far to analyze the rate at which stars formed in the early Universe. It found 44 previously unknown galaxies spanning 300 million years since the Big Bang. Combined with 11 previously known galaxies, the findings show that there was a significant population of star-forming galaxies in the early Universe1. The results “reaffirm the enormous potential of the upcoming larger [Webb] programs to transform our understanding of the young Universe,” the team, led by Callum Donnan of the University of Edinburgh, UK, wrote in a paper on the arXiv preprint server.
Many galaxies compete for the “farthest” title.
Perhaps the highest-profile rush is the flurry of research teams racing to spot the most distant galaxy in the Webb data. A number of candidates have been identified that will need to be confirmed through further studies, but all of them would break Hubble’s record for the most distant galaxy, which dates back to about 400 million years after the Big Bang2,3. Maisie’s Galaxy: Astronomer Steven Finkelstein named this distant galaxy after his daughter’s nickname. He estimates that it is from 280 million years after the Big Bang. Credits: Steven Finkelstein (UT Austin), Micaela Bagley (UT Austin), Casey Papovich (Texas A&M) and the CEERS team One candidate appeared in a Webb survey called GLASS that included another, slightly less distant galaxy in the same image4. “The fact that we found these two bright galaxies was really a surprise,” says Marco Castellano, an astronomer at the National Institute of Astrophysics in Rome. He and his colleagues did not expect to find galaxies so far away in this small part of the sky. A second team also independently identified the two galaxies5. Astronomers characterize the distance of galaxies with a measure known as redshift, which quantifies how much a galaxy’s light has shifted to redder wavelengths. The higher the redshift, the more distant the galaxy. The GLASS candidate has a redshift of about 13. But on July 25 and 26, days after astronomers reported the GLASS galaxies, papers claiming even higher redshifts flooded the arXiv preprint server. “This is just the beginning of the beginning,” says Rohan Naidu, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. One candidate, at a shift of 14, appeared in a survey called CEERS, one of Webb’s first and highest-profile projects. CEERS principal investigator Steven Finkelstein at the University of Texas at Austin named the object Maisie’s Galaxy after his daughter6. Another study looked at the first deep-field image from Webb, released by US President Joe Biden on July 11, and found two possible galaxies at a redshift of 16, which would place them just 250 million years after Big Bang7. And other arXiv papers speculate on other candidates, even at redshifts of 208.
Some early galaxies are surprisingly complex.
Webb’s distant galaxies also turn out to have more structure than astronomers expected. A study of Webb’s first deep-field image found a surprisingly large number of distant disc-shaped galaxies9. Using Hubble, astronomers concluded that distant galaxies are more irregular in shape than nearby ones, which, like the Milky Way, often display regular disk-like shapes. The theory was that early galaxies were most often deformed by interactions with neighboring galaxies. But Webb’s observations suggest there are up to 10 times more distant disc-shaped galaxies than previously thought. US President Joe Biden released this image in depth on July 11 — the first scientific insight from Webb to be revealed publicly. Credits: NASA, ESA, CSA and STScI “With the James Webb analysis, we can see that galaxies have discs much earlier than we thought they did,” says Allison Kirkpatrick, an astronomer at the University of Kansas in Lawrence. This is a problem, he says, because it contradicts previous theories of galaxy evolution. “We’ll have to figure it out.” Another preprinted manuscript suggests that massive galaxies formed earlier in the Universe than previously known. A team led by Ivo Labbé of Swinburne University of Technology in Melbourne, Australia, reports that they found seven massive galaxies in the CEERS field, with redshifts between 7 and 1010. in place 500 million years after the Big Bang, and this massive galaxy formation began very early in the history of the Universe,” the scientists wrote. And studies of galactic chemistry also show a rich and complex picture emerging from the Webb data. An analysis of the first deep-field image looked at the light emitted by galaxies at redshift 5 or greater. (Spectral lines appearing at various wavelengths of light correlate with the chemical elements that make up galaxies.) He found a surprising wealth of elements such as oxygen11. Astronomers had thought that the process of chemical enrichment – in which stars fuse hydrogen and helium to form heavier elements – took a while, but finding that it is underway in early galaxies “will make us rethink the speed at which star formation occurs’. , says Kirkpatrick.
The nearest galaxies are smaller than expected.
The surprises from Webb continue even a little later in the evolution of the Universe. One study looked at Webb’s observations of the “cosmic noon,” the period about 3 billion years after the Big Bang. This is when star formation peaked in the Universe and the most light was created. Wren Suess, an astronomer at the University of California, Santa Cruz, compared Hubble images of galaxies at cosmic noon with Webb images of the same galaxies. In the infrared wavelengths detected by Webb, most of the massive galaxies appeared much smaller than in the Hubble images12. “It potentially changes our view of how galaxy sizes evolve over time,” says Suess. Hubble’s studies suggested that galaxies start out small and grow larger over time, but Webb’s findings imply that Hubble didn’t get the whole picture, so the evolution of galaxies may be more complicated than scientists expected. . With Webb just at the beginning of a planned 20-plus year mission, astronomers know they have a lot of changes ahead of them. “Right now I’m up at three in the morning,” says Kirkpatrick, “wondering if everything I’ve ever done is wrong.”
