How the James Webb telescope’s glances back in time are reshaping cosmology
Galaxies might have formed earlier and faster than previously thought

BALTIMORE — The James Webb Space Telescope is living up to its promise as a wayback machine. The spectacularly sensitive observatory is finding and confirming galaxies more distant, and therefore existing earlier in the universe’s history, than any seen before.
The telescope, also known as JWST, has confirmed extreme distances to four galaxies, one of which sets a record for cosmic remoteness by shining about 13.475 billion years ago, astronomers reported December 12 at the conference. Dozens of other galaxies may have been spotted as they were just 550 million years or less after the Big Bang, meaning the light from those galaxies traveled at least 13.1 billion years before reaching the telescope.Science News headlines, in your inbox
Headlines and summaries of the latest Science News articles, delivered to your email inbox every Thursday.That new era is thanks in part to JWST’s ability to see very faint infrared light (SN: 10/6/21). For the most distant objects, like the first stars and galaxies, their visible light is stretched by the relentless expansion of the universe into longer infrared wavelengths that are invisible to human eyes and some previous space telescopes. But now, measurements that were recently impossible are suddenly easy with JWST, researchers say.
“JWST is the most powerful infrared telescope that has ever been built,” astrophysicist Jane Rigby said at the conference. Rigby, of NASA’s Goddard Space Flight Center in Greenbelt, Md., is the JWST operations project scientist. “Almost across the board, the science performance is better than expected.”Even in the very first image, released in July, astronomers spotted galaxies whose light originated 13 billion years ago or more (SN: 7/11/22). But those distances were estimates. To measure the distances precisely, astronomers need spectra, measurements of how much light the galaxies emit across many wavelengths. Those measurements are slower and more difficult to make than pictures.
“Thanks to this glorious telescope, we’re now getting spectra … for hundreds of galaxies at once,” said astronomer Emma Curtis-Lake of the University of Hertfordshire in England.Among those are , some of which existed less than 400 million years after the Big Bang, Curtis-Lake and colleagues reported at the meeting and in a paper submitted December 8 to arXiv.org. The team spotted these record holders in a patch of sky that the Hubble Space Telescope once scoured for ultra-remote galaxies (SN: 1/3/10).
The previous distance record holder existed between 13.3 billion and 13.4 billion years ago, or about 400 million years after the Big Bang (SN: 1/28/20). JWST confirmed the distance to that galaxy and came back with three more whose light comes from as early as 325 million years after the Big Bang.
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Get great science journalism, from the most trusted source, delivered to your doorstep.The first of these to be discovered, after Finkelstein’s daughter, appears to be just 380 million years after the Big Bang, the researchers reported December 1 in the Astrophysical Journal Letters. The most distant galaxy in the team’s survey might lie as much as 130 million years earlier than Maisie. Those galaxies’ distances still need to be confirmed with spectra, but the team expect to get those data in the next few weeks.

All these new galaxies are exciting because they could be responsible for making the universe transparent to visible light, a process astronomers call reionization (SN: 12/2/22). Before the first stars ignited, the universe was filled with a hot dense soup of particles. The first stars and galaxies bathed the universe in ultraviolet light, splitting electrons off hydrogen atoms and allowing light to zip through until it reached JWST.
The new data, Roberts-Borsani said, “give us constraints on when this process started, ended, and which galaxies were the culprits for this process.”