NASA’s James Webb Space Telescope has begun to provide new insights into the history of the universe, revealing the formation and assembly of galaxies that were previously beyond our reach. The telescope has confirmed the existence of a protocluster of seven galaxies at a distance of redshift 7.9, or a mere 650 million years after the big bang. Based on the data collected, astronomers have predicted that the cluster will grow in size and mass to resemble the Coma Cluster, a monster of the modern universe.
Takahiro Morishita of IPAC-California Institute of Technology, the lead author of the study published in the Astrophysical Journal Letters, said, “This site of accelerated galaxy evolution is very special and unique, and Webb gave us the unprecedented ability to measure the velocities of these seven galaxies and confidently confirm that they are bound together in a protocluster.”
The precise measurements captured by Webb’s Near-Infrared Spectrograph (NIRSpec) were key to confirming the galaxies’ collective distance and the high velocities at which they are moving within a halo of dark matter – more than two million miles per hour (about one thousand kilometers per second). The spectral data allowed astronomers to model and map the future development of the gathering group, all the way to our time in the modern universe. The prediction that the protocluster will eventually resemble the Coma Cluster means that it could eventually be among the densest known galaxy collections, with thousands of members.
“We can see these far-off galaxies like small drops of water in different rivers, and we can see that eventually they will all become part of one big, powerful river,” said Benedetta Vulcani of the National Institute of Astrophysics in Italy, another member of the research team.
Galaxy clusters are the largest concentrations of mass in the known universe, which can greatly bend the fabric of spacetime itself. This bending, called gravitational lensing, can magnify objects beyond the cluster, allowing astronomers to see through the cluster like a giant magnifying glass. The research team used this effect by looking through Pandora’s Cluster to observe the protocluster. Even Webb’s powerful instruments require assistance from nature to observe so far.
Studying how large clusters like Pandora and Coma were formed has been challenging due to the expansion of the universe stretching light beyond visible wavelengths into the infrared, where astronomers lacked high-resolution data before Webb. Webb’s infrared instruments were developed to fill in these gaps at the beginning of the universe’s story.
Webb confirmed the existence of seven galaxies that were first identified by the Hubble Space Telescope’s Frontier Fields program. The Hubble program used gravitational lensing to observe distant galaxies, but its capabilities were limited by its inability to detect light beyond near-infrared. Webb’s investigation focused on the galaxies scouted by Hubble and gathered detailed imagery and spectroscopic data.
The research team expects that Webb’s collaboration with NASA’s Nancy Grace Roman Space Telescope will yield more results on early galaxy clusters. Roman has a high-resolution, wide-field survey mission that will identify more protocluster galaxy candidates, which Webb can confirm with its spectroscopic instruments. The Roman mission is expected to launch by May 2027.
“The science we can now dream of doing with Webb is amazing,” said Tommaso Treu of the University of California, Los Angeles, a member of the protocluster research team. “With this small protocluster of seven galaxies, at this great distance, we had a 100% spectroscopic confirmation rate, demonstrating the future potential for mapping dark matter and filling in the timeline of the universe’s early development.”
The James Webb Space Telescope, an international program led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency, is the world’s premier space science observatory. Webb will solve mysteries in our solar system, look beyond to distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it.
