The James Webb Space Telescope, a NASA space telescope, is scheduled to launch in December 2021. It is intended to be the Hubble Space Telescope’s replacement, and it will be used to study the early universe, galaxy formation and evolution, and the formation of stars and planetary systems.
Every giant was once a baby, though you may have never seen them at that age. NASA’s James Webb Space Telescope has begun to shed light on formative years in the history of the universe that have previously been out of reach: the formation and assembly of galaxies. A protocluster of seven galaxies has been confirmed for the first time at a distance known as redshift 7.9, or only 650 million years after the big bang. Based on the data collected, astronomers predicted the nascent cluster’s future evolution, concluding that it will likely grow in size and mass to resemble the Coma Cluster, a modern-day monster.
“This is a very special, unique site of accelerated galaxy evolution, 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,” said Takahiro Morishita of IPAC-California Institute of Technology, the lead author of the study published in the Astrophysical Journal Letters.
This is a very special, unique site of accelerated galaxy evolution, 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.
Takahiro Morishita
The precise measurements taken by Webb’s Near-Infrared Spectrograph (NIRSpec) were critical in 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 gathering group’s future evolution all the way to our time in the modern universe. The prediction that the protocluster will eventually resemble the Coma Cluster implies that it may become one of the densest known galaxy collections, with thousands of members.
“We can see these distant galaxies like small drops of water in different rivers, and we can see that eventually they will all become part of one big, mighty river,” said Benedetta Vulcani of Italy’s National Institute of Astrophysics, another member of the research team.
Galaxy clusters are the greatest concentrations of mass in the known universe, which can dramatically warp the fabric of spacetime itself. This warping, called gravitational lensing, can have a magnifying effect for objects beyond the cluster, allowing astronomers to look through the cluster like a giant magnifying glass. The research team was able to utilize this effect, looking through Pandora’s Cluster to view the protocluster; even Webb’s powerful instruments need an assist from nature to see so far.
Exploring how large clusters like Pandora and Coma first formed has been difficult due to the universe’s expansion stretching light beyond visible wavelengths into the infrared, where astronomers lacked high-resolution data prior to Webb. Webb’s infrared instruments were specifically designed to fill in these gaps at the start of the universe’s story.
The seven galaxies confirmed by Webb were first identified as candidates for observation using Hubble Space Telescope data from the Frontier Fields program. The program dedicated Hubble time to detailed observations of very distant galaxies using gravitational lensing. However, because Hubble cannot detect light beyond the near-infrared, it can only see so much detail. Webb picked up the investigation, focusing on the galaxies scouted by Hubble and gathering detailed spectroscopic data in addition to imagery.
The research team believes that future collaboration between Webb and NASA’s Nancy Grace Roman Space Telescope, a high-resolution, wide-field survey mission, will yield even more information on early galaxy clusters. With a field of view 200 times that of Hubble’s infrared, Roman will be able to identify more protocluster galaxy candidates, which Webb will be able to confirm with its spectroscopic instruments. The Roman mission is scheduled to launch in May 2027.
“It’s amazing the science we can now dream of doing now that we have Webb,” said Tommaso Treu, a member of the protocluster research team at the University of California, Los Angeles. “With this small protocluster of seven galaxies, at this great distance, we had a one hundred percent spectroscopic confirmation rate, demonstrating the future potential for mapping dark matter and filling in the timeline of the universe’s early development.”
