Team Including Current and Alumni CNS Astronomers Finds One of the Oldest Barred-Spiral Galaxies in the Universe
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Research led by Daniel Ivanov, who earned his undergraduate degree at UMass Amherst studying under Professor of Astronomy Mauro Giavalisco and is now a physics and astronomy graduate student at the University of Pittsburgh, has uncovered a contender for one of the earliest observed spiral galaxies containing a stellar bar—a sometimes-striking visual feature that can play an important role in the evolution of a galaxy.
Giavalisco, as well as Yingjie Cheng, who received her doctorate in astronomy from UMass Amherst, and John Weaver, who completed a postdoc in UMass Amherst’s astronomy department, are all co-authors of the new research, which helps constrain the timeframe in which bars could have first emerged in the universe. Analysis of light from the galaxy, called COSMOS-74706, places it on the cosmic timeline at about 11.5 billion years ago.
“This galaxy was developing bars 2 billion years after the birth of the universe," Ivanov said. “Two billion years after the Big Bang.”
The findings are scheduled to be presented at the 247th meeting of the American Astronomical Society on Thursday, January 8, 2026.
The defining feature of these galaxies is right in the name: “A stellar bar is a linear feature at the center of the galaxy,” Ivanov said. The bar isn’t an object itself, but a dense collection of stars and gas that is aligned in such a way that in images taken perpendicular to a galactic plane, there appears to be a bright line bisecting the galaxy.
“Bars are very important because they reflect key features of the gravitational potential and of the dynamics of disk galaxies,” says Giavalisco. “Their conceptual importance in our understanding of gravitational systems is highlighted by the fact that they are very common in the present-day universe among disk galaxies—and yet we do not fully understand the conditions for bar formation.”
Despite appearing like a permanent feature, stellar bars are density waves that form as the result of some kind of instability in the galaxy. In the absence of an external event, a settled disc will naturally develop a global instability. “Stellar bars are expected to emerge, over certain timescales, on their own,” Ivanov said.
They likely appear and disappear multiple times.
But they can also be the result of “tidal perturbations,” gravitational forces caused by something outside of the galaxy. “If you have a close interaction with a nearby galaxy, that can actually trigger the global instability that leads to the formation of a stellar bar,” Ivanov said.
Stellar bars can play a role shaping their galaxy’s evolution by funneling gas inward from the outer reaches of a galaxy, feeding the supermassive black hole in the center.
This process supports the model of inside-out evolution, which posits that the inside of a galaxy forms and begins creating stars first, followed by stellar creation in the outer parts of the galaxy, which is driven by the accretion of interstellar gas. “There’s a large burst of star formation near the center of the galaxy, early in its history,” Ivanov said, but not much star formation farther out. “So, you end up with a much older core of the galaxy than in the outer disk.”
The team made their discovery as they were developing a catalog of barred and non-barred galaxies in a particular region of space. It was during this work that a couple of galaxies were flagged for their unusually high spectroscopically confirmed redshifts, an indication of how long the light had been traveling and, therefore, how long ago it was emitted.
“Charting the presence of bars across the cosmic times provides a powerful diagnostics of the assembly and evolution of disk galaxies,” Giavalisco concludes.
This story was originally published by the UMass News Office.