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JWST Reveals Previously Hidden “Undiscovered Country” Of Early Galaxies

The objects challenge the currently accepted ideas about galaxy evolution.


Dr. Alfredo Carpineti


Dr. Alfredo Carpineti

Senior Staff Writer & Space Correspondent

Alfredo (he/him) has a PhD in Astrophysics on galaxy evolution and a Master's in Quantum Fields and Fundamental Forces.

Senior Staff Writer & Space Correspondent

Two fields full of galaxies and zoomed in are the two galaxies in questions. very little details are clear in the single galaxy images.
Two of the furthest galaxies ever seen snapped by JWST. Image credit: NASA, ESA, CSA, Tommaso Treu (UCLA). Image processing: Zolt G. Levay (STScI)

Among its many scientific objectives, JWST is set up to see further into the universe than ever before. This means that, thanks to the finite nature of the speed of light, the space telescope is looking into the past further than ever before. Incredible insights were expected, but astronomers were not prepared for the speed at which the telescope might find spectacular sights. Two new galaxies, remarkably bright, have now been discovered in the early universe. And, they challenge what we know about the cosmos.

After the Big Bang, the universe experienced the Cosmic Dark Ages, when no visible light was shining. It took stars and galaxies coming together a long time later to bring brightness to the universe again. Galaxies are expected to slowly grow over the first several hundred million years, slowly getting bigger and brighter in chaotic environments.


But new JWST observations suggest that the picture is more complex than that. Two exceptionally bright galaxies in the Grism Lens-Amplified Survey from Space-JWST images have been analyzed by two research groups. These galaxies existed approximately 450 and 350 million years after the Big Bang.

"We've nailed something that is incredibly fascinating. 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," Garth Illingworth of the University of California at Santa Cruz, a member of the one of the research teams, said in a statement. "The primal universe would have been just one hundredth its current age. It's a sliver of time in the 13.8 billion-year-old evolving cosmos."

The galaxies were found remarkably quickly, with just four days of analysis, suggesting that these incredibly bright and distant objects might not be needles in a haystack.

"Based on all the predictions, we thought we had to search a much bigger volume of space to find such galaxies," leader of the other team Marco Castellano, of the National Institute for Astrophysics in Rome, explained.


"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," added Paola Santini, part of Castellano's team.

The galaxies' incredible light output is a puzzling thing. They are either filled with many small stars, making them extremely massive; or, they have fewer, but much larger stars. These more massive stars could be the fabled Population III stars, the first stars that ever shone in the universe, which we are yet to see and that JWST is going to look for.

"Indeed, the farthest source is very compact, and its colors seem to indicate that its stellar population is particularly devoid of heavy elements and could even contain some Population III stars," added Adriano Fontana, also part of Castellano’s team.

The confirmation of the distance and composition will come from the spectroscopic analysis from JWST. The light spectrum is like a fingerprint that will allow scientists to answer these and other questions about these incredible galaxies.


The papers are published in The Astrophysical Journal Letters, here and here.  


spaceSpace and PhysicsspaceAstronomy
  • tag
  • galaxy,

  • stars,

  • early universe,

  • JWST,

  • Astronomy,

  • galaxy evolution