In today’s Universe, most galaxies are held together by orderly rotation. But among the largest, no-longer star-forming systems, many are instead dominated by the chaotic motion of their stars — a class of galaxies astronomers call slow rotators. These galaxies are expected to be rare in the early Universe, and until now, observations have revealed only fast-spinning systems. New observations from the NASA/ESA/CSA James Webb Space Telescope have revealed a slow-rotating massive galaxy, named XMM-VID1-2075, at redshift z = 3.449 (we’re seeing the galaxy as it was about 12 billion years ago).
This Webb/NIRSpec/IFU image shows the slow-rotator galaxy XMM-VID1-2075. Image credit: Forrest et al., doi: 10.1038/s41550-026-02855-0.
According to current theories, as the first galaxies formed, angular momentum from inflowing gas and the influence of gravity set them spinning.
Over many billions of years, some galaxies, especially those within galaxy clusters, merged with each other multiple times and their combined rotations added to or partly canceled each other.
That’s why some galaxies that are closest to Earth can show little overall rotation but a lot of random movement of stars within them.
This process should take an enormously long time, so it’s surprising that the newly-discovered galaxy, XMM-VID1-2075, had achieved this state when the Universe was less than 2 billion years old.
“That’s something only seen in the most massive, mature galaxies that are closer to us in space and time,” said Dr. Ben Forrest, an astronomer at the University of California, Davis.
“This one in particular did not show any evidence of rotation, which was surprising and very interesting.”
Dr. Forrest and his colleagues in the MAGAZ3NE (Massive Ancient Galaxies at z>3 NEar-Infrared) survey had previously observed XMM-VID1-2075 with the W.M. Keck Observatory in Hawaiʻi.
“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,” Dr. Forrest said.
The astronomers used the NASA/ESA/CSA James Webb Space Telescope to measure the relative movement of material inside XMM-VID1-2075 and two other galaxies of similar age.
“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,” Dr. Forrest said.
“Webb is really pushing the frontier for these kinds of studies.”
“Of the three galaxies they sampled, one is clearly rotating, one is kind of messy, and one has no rotation but a lot of random motion.”
“That’s consistent with some of the most massive galaxies in the local Universe, but it was a bit surprising to find it so early on.”
How did this galaxy become a slow rotator in less than 2 billion years?
One possibility is that it is the result not of multiple mergers, but a single collision between two galaxies rotating pretty much in opposite directions. That idea is supported by the team’s observations.
“For this particular galaxy, we see a large excess of light off to the side,” Dr. Forrest said.
“And so that’s suggestive of some other object which has come in and is interacting with the system and potentially changing its dynamics.”
The discovery is reported in a paper in the journal Nature Astronomy.
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B. Forrest et al. A massive and evolved slow-rotating galaxy in the early Universe. Nat Astron, published online May 4, 2026; doi: 10.1038/s41550-026-02855-0
