Observations by NASA’s James Webb Space Telescope (JWST) have led to the surprising discovery that an ancient, distant galaxy is not rotating as expected, adding to our knowledge of the diverse conditions of the early universe.
The recent JWST finding was especially unusual because similar behavior has been observed only in nearby, mature, massive galaxies whose star formation slowed gradually over billions of years.
A team of researchers estimates that the galaxy XMM-VID1-2075 is not even 2 billion years old, based on the JWST observations, compared to the Milky Way’s 13.6 billion years, making its behavior highly unusual, according to their recent paper published in Nature Astronomy.
“This one in particular did not show any evidence of rotation, which was surprising and very interesting,” said lead author Ben Forrest, a research scientist in the Department of Physics and Astronomy at the University of California, Davis.
As gas flowed into early galaxies, most astronomers believe that angular momentum, combined with gravity, caused them to spin. However, over long periods of time, galaxies can lose their initial spin through mergers rather than spins canceling one another out.
Because of this, we would expect to see this lack of spin primarily in galaxies close to Earth, as the distance light has traveled would be shorter, and therefore the light would come from older, more mature galaxies that have had the opportunity to experience such mergers. Finding a galaxy so distant, and therefore so young based on the speed of the light, is most unexpected.
The research was part of the MAGAZ3NE (Massive Ancient Galaxies at z>3 NEar-Infrared) survey on the JWST by researchers who had used Hawaii’s W.M. Keck observatory to observe XMM-VID1-2075 previously.
“Previous MAGAZ3NE observations had confirmed this was one of the most massive galaxies in the early universe, with already several times as many stars as our Milky Way, and also confirmed that it was no longer forming new stars, making it a compelling target for follow-up observations,” Forrest said.
Using the JWST’s advanced capabilities, the researchers compared XMM-VID1-2075 with two galaxies of similar age to measure their relative motion.
“This type of work has been done a lot with nearby galaxies because they’re closer and larger and so you can do these kinds of studies from the ground, but it’s very difficult to do with high redshift galaxies because they appear a lot smaller in the sky,” Forrest said. “(JWST) is really pushing the frontier for these kinds of studies.”
The JWST data on the three galaxies yield a strange combination of results: one rotates as expected, another is described as “messy,” and the last does not rotate but exhibits significant random movement. While this behavior is expected of massive galaxies in our local neighborhood, the researchers were stunned to find it occurring so close to the beginning of the universe.
The team leans toward one possibility that may offer an explanation, suggesting that a kind of equilibrium was achieved when two galaxies with almost perfectly opposite rotations collided in a single event.
“For this particular galaxy, we see a large excess of light off to the side. And so that’s suggestive of some other object which has come in and is interacting with the system and potentially changing its dynamics,” Forrest said.
Continuing their work, the team will seek other early galaxies lacking spin and explore galaxy-formation simulations that could explain this behavior.
“There are some simulations that predict that there will be a very small number of these non-rotating galaxies very early in the universe, but they expect them to be quite rare,” Forrest concluded. “And so this is one way in which we can test these simulations and really figure out how common they are, and that can then give us information about whether our theories of this evolution are correct.”
The paper, “A Massive and Evolved Slow-Rotating Galaxy in the Early Universe,” appeared in Nature Astronomy on May 04, 2026.
Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.
The universe is around 14 billion years old, but scientists theorize that no stars formed for the first several hundred million years, during an era known as the cosmic dark ages. They refer to the first billion years or so after this, when stars formed, as the cosmic dawn. At that time, the very oldest galaxies first assembled from collections of gas and plasma.
As these galaxies assembled and more material became available, the number of stars formed each year increased. Around 2 to 3 billion years after the Big Bang, galaxies grew faster than they ever would, producing stars at the highest rate in the universe’s history. This era is called cosmic noon.
Researchers from the Netherlands recently investigated 3 distant galaxies whose light began its journey to Earth during cosmic noon. They selected targets from a set of ancient star-forming galaxies identified in the ALMA – Archival Large Program to Advance Kinematic Analysis or ALMA-ALPAKA project. Of these, they chose to study 3 galaxies labeled ID1, ID3, and ID13.
They combined 2 different types of data to produce a detailed description of these galaxies. First, they collected data from an enormous telescope comprising 66 antennas in Chile, known as the Atacama Large Millimeter/submillimeter Array or ALMA. They used ALMA to detect radio-wave emissions from carbon monoxide and elemental carbon in these galaxies. The researchers stated that studying these chemicals in distant galaxies could reveal how their free-floating gas clouds move. They also used publicly available data from JWST’s Near Infrared Camera, or NIRCam, to determine how much light the galaxies’ stars emitted. By analyzing cosmic noon galaxies in multiple different ways, the team aimed to measure their masses and the relative contributions of regular matter and dark matter.
They used a computer program developed by other astronomers to interpret the JWST data as a series of maps showing the distribution of stars across each galaxy. They used this light-emission data to estimate the total mass of all the stars in these galaxies. Then they developed an original computer program to map the distribution of gas through each galaxy using the ALMA data. The team used these maps to create plots, known as rotation curves, which show how fast particles orbit each galaxy’s center as a function of their distance from it.
The astronomers used these rotation curves to estimate the amount of dark matter in each galaxy. They explained that this method works because dark matter is totally invisible, but it still exerts a gravitational pull. Its gravitational pull causes visible material like stars and gas closer to the edges of these galaxies to move faster than they would in galaxies without dark matter.
The team found that these galaxies had between 39 and 80 billion times the mass of our sun, or solar masses, in stars. They had between 4 billion and nearly 16 billion solar masses worth of free-floating gas. And they had from 1 trillion to 31 trillion solar masses of dark matter.
However, when the team compared the light-emission data with the rotation curves, they found a discrepancy. Typically, dark matter resides in a shell or halo surrounding a galaxy, meaning it should mostly affect material near the galaxy’s outer edge. Since astronomers don’t usually have to account for dark matter near a galaxy’s center, they can calculate the total mass of center material based on the amount of gas and stars they see there. But near the centers of these galaxies, the team found that the masses they derived from the light emissions were less than what they calculated from the rotation curves.
They proposed multiple potential explanations for this discrepancy. First, they suggested that the halo shape might not be a good model for the dark matter distribution in all galaxies, meaning that cosmic noon galaxies could contain dark matter near their centers. Second, they suggested that stars could be packed tightly in the center of these galaxies, blocking each other’s light emissions. Third, they suggested that galaxy ID1 could have a supermassive black hole as big as 1.5% its total stellar mass at its center.
The team concluded that they now have a detailed picture of the mass distribution in these cosmic noon galaxies, but the reason for their center mass discrepancies remains elusive. They suggested that a complex relationship exists between the dark matter halos and the rest of the material within these galaxies. They indicated that future astronomers could adapt their methods to study the distribution of material in other distant galaxies studied by ALMA-ALPAKA and forthcoming galactic surveys.
The post Characterizing galaxies at “cosmic noon” appeared first on Sciworthy.
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