The two newfound galaxies, dubbed GLASS-z12 and GLASS-z10, existed approximately 350 and 450 million years after the Big Bang.
GLASS-z12 (redshift of 12.5) and GLASS-z10 (redshift of 10.5) are captured in these Webb images of the outer regions of the galaxy cluster Abell 2744. Image credit: NASA / ESA / CSA / T. Treu, UCLA.
GLASS-z12 and GLASS-z10 were spotted in the flanking field of the Hubble Frontier Fields cluster Abell 2744, a group of roughly 500 galaxies — also known as ACO 2744 and the Pandora’s Box — located approximately 4 billion light-years from Earth.
The detections were made by the NASA/ESA/CSA James Webb Space Telescope as part the GLASS-JWST Early Release Science Program and the Cosmic Evolution Early Release Science Survey (CEERS).
“Everything we see is new. Webb is showing us that there’s a very rich Universe beyond what we imagined,” said Dr. Tommaso Treu, an astronomer at the University of California at Los Angeles.
“Once again the Universe has surprised us. These early galaxies are very unusual in many ways.”
GLASS-z12 and GLASS-z10 existed 350 and 450 million years after the Big Bang (with redshifts of approximately 12.5 and 10.5, respectively), which future spectroscopic measurements with Webb will help confirm.
The previous record holder is a galaxy called GN-z11, which existed 400 million years after the Big Bang and was discovered in 2016 by the NASA/ESA Hubble Space Telescope and Keck Observatory.
“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 Dr. Rohan Naidu, an astronomer at the Harvard & Smithsonian’s Center for Astrophysics and MIT.
“While the distances of these early sources still need to be confirmed with spectroscopy, their extreme brightnesses are a real puzzle, challenging our understanding of galaxy formation,” added Dr. Pascal Oesch, an astronomer at the University of Geneva.
The new Webb observations nudge astronomers toward a consensus that an unusual number of galaxies in the early Universe were much brighter than expected.
“We’ve nailed something that is incredibly fascinating,” said Dr. Garth Illingworth, an astronomer at the University of California at Santa Cruz.
“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.”
“The primal Universe would have been just one hundredth of its current age. It’s a sliver of time in the 13.8-billion-year-old evolving cosmos.”
“GLASS-z12 and GLASS-z10 have a lot of light,” the astronomer added.
“One option is that they could have been very massive, with lots of low-mass stars, like later galaxies.”
“Alternatively, they could be much less massive, consisting of far fewer extraordinarily bright stars, known as Population III stars.”
“They would be the first stars ever born, blazing at blistering temperatures and made up of only primordial hydrogen and helium; only later would stars cook up heavier elements in their nuclear fusion furnaces. No such extremely hot, primordial stars are seen in the local Universe.”
“Indeed, the most distant 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. Only Webb spectra will tell,” said Dr. Adriano Fontana, an astronomer at Italy’s National Institute for Astrophysics.
“Present Webb distance estimates to these two galaxies are based on measuring their infrared colors.”
“Eventually, follow-up spectroscopy measurements showing how light has been stretched in the expanding Universe will provide independent verification of these cosmic yardstick measurements.”
The results appear in two papers in the Astrophysical Journal Letters.
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Rohan P. Naidu et al. 2022. Two Remarkably Luminous Galaxy Candidates at z ≈ 10–12 Revealed by JWST. ApJL 940, L14; doi: 10.3847/2041-8213/ac9b22
Marco Castellano et al. 2022. Early Results from GLASS-JWST. III. Galaxy Candidates at z~9–15. ApJL 938, L15; doi: 10.3847/2041-8213/ac94d0
