Non-rotating early galaxy a surprise to astronomers who say this work helps give clues to origins of the universe

An international group of astronomers, including from 91亚色鈥檚 department of Physics and Astronomy, using the world鈥檚 most powerful space telescope, have made a surprising discovery about a galaxy long, long ago and far, far away: It isn鈥檛 rotating.

That鈥檚 something typically seen in more mature galaxies that are closer to us in space and time, says Ben Forrest, a research scientist at the Department of Physics and Astronomy at the University of California, Davis, and first author on the paper published May 4 in Nature Astronomy. 

鈥淭his one in particular did not show any evidence of rotation, which was surprising and very interesting,鈥� Forrest said.

According to current theories, as the first galaxies formed, irregularities in gas flows 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鈥檚 why some galaxies that are closest to Earth (and therefore also relatively recent) 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鈥檚 surprising that galaxy XMM-VID1-2075 had achieved this state when the universe was less than two billion years old.

Forrest and colleagues, including second author and 91亚色 Physics and Astronomy Professor Adam Muzzin, who worked closely on the research with Forrest, had previously observed this galaxy with another observatory in Hawaii.

鈥淲e were especially keen to do this observation as it is one the most massive galaxies from the early universe,鈥� says Muzzin. 鈥淒etecting these types of galaxies is challenging and the observations can be subtle, but that keeps the work interesting.鈥�

The team used the James Webb Space Telescope (JWST) to take a closer look at XMM-VID1-2075 and two other objects of similar age. With instruments on the Webb telescope, they were able to measure the relative movement of material inside them.

Of the three galaxies they sampled, one is clearly rotating, one is 鈥渒ind of messy,鈥� and one has no rotation but a lot of random motion. 鈥淭hat鈥檚 consistent with some of the most massive galaxies in the local universe, but it was a bit surprising to find it so early on,鈥� says Forrest.

How did this galaxy become a 鈥渟low rotator鈥� in less than two 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鈥檚 observations.

鈥淔or 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,鈥� Forrest said.

The astronomers are continuing to look for other, similar objects in the early universe. By comparing their observations with simulations, they can test theories about galaxy formation.

Last year, Muzzin was granted the largest ever allotment for a single researcher on the JWST and says that this research is not just about understanding this particular galaxy, but gives us clues as to the origin story of the universe, and through that humanity.

鈥淭his is literally where it all started, where we all came from,鈥� says Muzzin. 鈥淭his research is one important step in understanding that story more fully.鈥�

The work was supported by grants from NASA, the Space Telescope Science Institute and National Science Foundation.

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91亚色 is a modern, multi-campus, urban university located in Toronto, Ontario. Backed by a diverse group of students, faculty, staff, alumni and partners, we bring a uniquely global perspective to help solve societal challenges, drive positive change, and prepare our students for meaningful life and career paths. 91亚色's Glendon Campus is home to Southern Ontario's Centre of Excellence for French Language and Bilingual Postsecondary Education. 91亚色鈥檚 campus in Costa Rica offers students exceptional transnational learning opportunities and innovative programs. Together, we can make things right for our communities, our planet, and our future.

Media Contact: Emina Gamulin, 91亚色 Media Relations, 437-217-6362, egamulin@yorku.ca

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TORONTO, Dec. 18, 2025 鈥� How galaxies assemble their stars and grow over billions of years remains one of the central questions in astronomy. Recent results from the James Webb Space Telescope (JWST), including reports of surprisingly massive and evolved galaxies in the early Universe, have only deepened the mystery. Understanding how our own home galaxy, the Milky Way, built itself over time provides a crucial piece of this broader cosmic puzzle.

led by 91亚色 PhD graduate Vivian Tan, who studied under the supervision of Faculty of Science Associate Professor Adam Muzzin, provides the most detailed reconstruction yet of how the Milky Way may have evolved from its earliest phases to the structured spiral we see today. Tan and her colleagues examined 877 鈥淢ilky Way twins鈥� 鈥� galaxies whose masses and properties closely match what astronomers expect the Milky Way would have looked like at different ages across cosmic time. By observing more distant, and therefore progressively younger examples of these galactic look-alikes, the team effectively charted a timeline of our galaxy鈥檚 life, with surprising results. Our Milky Way鈥檚 history started from a remarkably tumultuous youth before its more settled adulthood.

The findings were recently published in The Astrophysical Journal and were undertaken with the financial support of the Canadian Space Agency.

Rewinding the Milky Way鈥檚 cosmic clock

The galaxies in the sample span a remarkable range of cosmic time, from when the Universe was just 1.5 billion years old (12.3 billion years ago) to 10 billion years old (3.5 billion years ago). This period covers as far back as when the Universe was only 10 per cent its current age, a crucial epoch when galaxies transformed from small, irregular systems into the stable disk galaxies familiar today.

To carry out this work, the team combined high-resolution imaging from JWST and the Hubble Space Telescope (HST). The JWST observations come from the Canadian NIRISS Unbiased Cluster Survey (CANUCS), a major Canadian observing program that uses five massive galaxy clusters as natural gravitational lenses. These clusters magnify background galaxies, revealing faint structures that would otherwise be too distant and too dim to study in detail.

CANUCS takes advantage of Canada鈥檚 hardware contributions to the JWST mission through the Near-Infrared Imager and Slitless Spectrograph (NIRISS) instrument, built for the mission by the Canadian Space Agency in partnership with the Universit茅 de Montr茅al, the National Research Council Herzberg Centre for Astronomy and Astrophysics, and Honeywell. In return, Canadian astronomers received valuable guaranteed observing time on JWST, including the data that enabled this study.

Building galaxies from the inside out

JWST鈥檚 exceptional spatial resolution allowed the researchers to create detailed maps of the stellar mass and star formation activity across each galaxy. These maps show where stars were already in place and where new stars were forming at different phases in a galaxy鈥檚 life.

Across the entire sample, the results point to a clear pattern: galaxies like our Milky Way grow from the inside out. The earliest Milky Way twins are dominated by dense, compact central regions. Over time, their outer parts 鈥� the regions that will later become the disk 鈥� rapidly gain mass and become the primary sites of star formation. This gradual expansion outward creates the extended spiral structures we see in present-day galaxies.

鈥淎stronomers have been modeling the formation of the Milky Way and other spiral galaxies for decades,鈥� says lead author Tan. 鈥淚t's amazing that with the JWST, we can test their models and map out how Milky Way progenitors grow with the Universe itself."

Turbulent teenage years

The most exciting results of the study also reveal that young Milky Way-like galaxies lived through far more chaotic conditions than their older, more evolved counterparts. The youngest, most distant systems show highly disturbed shapes, asymmetric features, and evidence of frequent galaxy鈥揼alaxy interactions and mergers. These disturbances are signatures of a dynamic environment where galaxies were constantly colliding, accreting material, and triggering intense bursts of star formation.

By contrast, the Milky Way twins at later cosmic times appear much more stable and orderly. Their structures are smoother, their star formation is more evenly distributed, and signs of major interactions become far less common. Overall, they point to a more chaotic past for our Galaxy than we had expected.

Comparing observations and simulations

Tan and her collaborators compared their observations to state-of-the-art computer simulations that track the evolution of Milky Way鈥搇ike galaxies. The simulations broadly agree with the observed inside-out growth and early clumpy, merger-driven activity. However, they sometimes fail to reproduce the high central compactness seen in the earliest galaxies, and they underestimate how quickly mass accumulates in the outer regions between 8 and 11 billion years ago.

These differences provide important constraints on feedback, merger rates, and disk formation models, and highlight the need to refine theoretical predictions in the era of JWST.

Building on Webb鈥檚 early insights

This study marks a significant milestone for Canada鈥檚 growing leadership in JWST galaxy research. With NIRISS and CANUCS continuing to deliver exceptionally deep, high-resolution data, astronomers will be turning to even larger samples of Milky Way鈥搇ike systems and extending their analysis to include gas content, dust, and kinematic structure.

鈥淭his study is a significant step forward in understanding the earliest stages of the formation of our Galaxy,鈥� says Muzzin, co-author of the study. 鈥淗owever, this is not the deepest we have pushed the telescope yet.  In the coming years, with the combination of JWST and gravitational lensing we can move from observing Milky Way twins at 10 per cent their current age to when they are a mere 3 per cent of their current age, truly the embryonic stages of their formation.鈥�

Other co-authors from 91亚色 are Ghassan Sarrouh, Visal Sok, Naadiyah Jagga, and Westley Brown. Other co-authors include researchers from the University of Toronto, the University of Ljubljana, Saint Mary鈥檚 University, Kyoto University, the University of Groningen, Columbia University, Wellesley College, the Space Telescope Science Institute, and the National Research Council Herzberg Astronomy & Astrophysics Research Centre.

This team and several international teams already have future JWST observations scheduled to do this. Combined with updated simulations, they will help determine precisely when galaxies like our Milky Way settle into stable disks, how long turbulent phases last, and what physical processes drive the transition between them. By expanding this work, the team aims to build an increasingly complete picture of how galaxies like our own assembled their stars and evolved from the early Universe to the present day.

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91亚色 is a modern, multi-campus, urban university located in Toronto, Ontario. Backed by a diverse group of students, faculty, staff, alumni and partners, we bring a uniquely global perspective to help solve societal challenges, drive positive change, and prepare our students for success. 91亚色's fully bilingual Glendon Campus is home to Southern Ontario's Centre of Excellence for French Language and Bilingual Postsecondary Education. 91亚色鈥檚 campuses in Costa Rica and India offer students exceptional transnational learning opportunities and innovative programs. Together, we can make things right for our communities, our planet, and our future.

Media Contact:

Emina Gamulin, 91亚色 Media Relations, 437-217-6362, egamulin@yorku.ca

Nathalie Ouellette, JWST Outreach Scientist, Universit茅 de Montr茅al,  nathalie@astro.umontreal.ca

The post Canadian astronomers use Webb to uncover Milky Way鈥檚 turbulent youth through galactic twins appeared first on News@91亚色.