From images captured by NASA’s James Webb Space Telescope (JWST), researchers found two exceptionally bright galaxies that existed when the universe was practically in its infancy, approximately 450 million and 350 million years after the Big Bang, which occurred 13.8 billion years go. The JWST, with its super infrared imaging capability, was launched in December 2021 and began its science operations in July 2022.
The recent findings—one led by Marco Castellano of the National Institute for Astrophysics in Rome and the other by Rohan Naidu of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts—have been published in The Astrophysical Journal Letters.
According to a NASA release, these initial findings are from a broader Webb research initiative involving two Early Release Science programmes: the Grism Lens-Amplified Survey from Space (GLASS) and the Cosmic Evolution Early Release Science Survey (CEERS). The two earliest galaxies seen were spotted in the GLASS-JWST images. These first distance estimates will, however, need to be independently confirmed by future spectroscopic measurements with Webb.
“Everything we see is new. Webb is showing us that there’s a very rich universe beyond what we imagined,” the release quoted Tommaso Treu of the University of California at Los Angeles, principal investigator of GLASS. “These early galaxies are very unusual in many ways.”
“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 Naidu of the more distant GLASS galaxy, referred to as GLASS-z12. The previous record holder is galaxy GN-z11, which existed 400 million years after the Big Bang and which the Hubble telescope and the Keck Observatory identified in 2016 in deep-sky programmes.
“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,” added Paola Santini, a co-author of the Castellano et al. paper.
“Their extreme brightness is a real puzzle, challenging our understanding of galaxy formation,” noted Pascal Oesch at the University of Geneva in Switzerland, second author of the Naidu et al. paper. “These galaxies would have had to have started coming together maybe just 100 million years after the Big Bang. Nobody expected that the dark ages would have ended so early,” said Garth Illingworth of the University of California at Santa Cruz, a member of the Naidu team.
Erica Nelson of the University of Colorado, another member of the Naidu team, noted: “Our team was struck by being able to measure the shapes of these first galaxies; their calm, orderly disks question our understanding of how the first galaxies formed in the crowded, chaotic early universe.” This remarkable discovery of compact disks at such early times was only possible because of Webb’s much sharper images in infrared light.
“These galaxies are very different than the Milky Way or other big galaxies we see around us today,” said Treu. According to Illingworth, they would be the first stars ever born, blazing at blistering temperatures and made up only of primordial hydrogen and helium, before their nuclear fusion furnaces could make heavier elements. No such extremely hot, primordial stars are seen in the local universe.
