New JWST images of abnormally well-developed galaxy cluster open up the “cosmic noon” frontier | EurekAlert!
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image: This image shows a distant galaxy cluster as it has been observed by NASA’s James Webb Space Telescope (JWST). At over 10 billion light-years away, the cluster XLSSC 122 is the most distant known example of a cluster found to act as a strong gravitational lens, magnifying and distorting images of yet more distant galaxies behind it.
The brightest clump of orange-red fuzzy objects at the very center of the image are the central galaxies of the cluster. The gravitationally lensed background galaxies can be seen as a series of blue-gray arcs that extend around the fuzzy bounds of the central galaxies, particularly to the lower right.
The existence of the strong gravitational lensing effect around such an early, distant cluster challenges conventional cosmological models that suggest such massive structures should take longer to form and mature.
This image uses data from four different JWST filters. Light at wavelengths of 0.9, 2.0, and 3.56 microns have been assigned to the colors blue, green, and red, respectively. Data from the 2.77 micron filter were used to assign the overall brightness of the image.
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Credit: Credit: NASA, ESA, CSA; Kyle Finner (Caltech/IPAC)<br>Image processing: Robert Hurt (Caltech/IPAC-SELab)
A stunningly concentrated and hefty galaxy cluster, from a time in the universe’s history when such massive structures aren’t expected to have fully formed yet, is challenging cosmic evolution theories. Across a series of three recent papers, a team led by researchers from IPAC—a science and data center for astrophysics and planetary science at Caltech—have revealed that the cluster is the most distant example of strong gravitational lensing with a galaxy cluster. The new results, based on observations from NASA’s James Webb Space Telescope (JWST), were presented in a press conference on June 17, 2026 at the 248th meeting of the American Astronomical Society.
When astronomers first laid eyes on this galaxy cluster dubbed XLSSC 122, they knew they had found something special. The cluster appeared highly evolved—meaning big and organized like a galaxy cluster in the nearby, modern universe—despite being more than 10 billion light-years away, back in an era when other galaxy groupings had only just started to come together.
Now thanks to the unmatched resolving and light-gathering power of JWST, researchers have discovered that XLSSC 122 is luckily aligned with one or more even more distant galaxies. This chance alignment is causing the giant cluster’s gravity to warp the far-off galaxy’s light—an ultra-rare phenomenon called strong gravitational lensing—in a way that enables newly precise mass measurements of XLSSC 122.
“When we got those first images back from JWST, we said, ‘wow, look at this, there's strong lensing coming from this cluster!’” said Kyle Finner, a staff scientist at IPAC and lead author of the first paper studying the cluster. “XLSSC 122 has now set the record for the most distant galaxy cluster displaying strong lensing, which is a valuable tool for astronomers.”
The serendipitous lensing has provided the most detailed look yet at mass distribution in an early galaxy cluster from the period known as “cosmic noon,” around 10 billion years ago. In this critically formative era, galaxy clusters began to form in bulk as the universe hit its peak in star formation, cranking out stars at a torrid place as much as 100 times faster than the present-day cosmos.
In keeping with XLSSC 122’s iconoclastic reputation, its mass turned out to be extremely concentrated toward the cluster’s center. Such a feature at so early a time in cosmic history challenges conventional cosmological models that chronicle a far slower buildup of massive structure.
“XLSSC 122 is one of the first clusters we know of that formed in the universe, and it has a mass concentration that doesn't agree with our cosmological model predictions,” said Finner.
Following up their strong lensing discovery, Finner and colleagues have recently published two more papers, first authored by Zachary Scofield and Hyungjin Joo at Yonsei University, examining other aspects of XLSSC 122 with JWST. Their slew of new results have positioned XLSSC 122 as a trailblazer of galaxy clusters at cosmic noon.
Seeing in the dark
XLSSC 122 first literally came to light in 2014 during an x-ray survey conducted by the European Space Agency’s XMM-Newton spacecraft. Subsequent observations by the Hubble Space Telescope helped firm up the cluster’s distance, about 10.4 billion light-years away, and its unexpectedly mature features.
Hubble data, however, showed no definitive signs of strong lensing, which appears as arcs of light around the cluster center in JWST images. Capturing these arcs with...