A research team led by Daniel Ivanov, a graduate student in physics and astronomy at the University of Pittsburgh’s Kenneth P. Dietrich School of Arts and Sciences, has identified one of the earliest known spiral galaxies with a stellar bar. The galaxy, named COSMOS-74706, dates back approximately 11.5 billion years.
Ivanov explained that the discovery sheds light on when such bars may have first appeared in the universe. “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 were presented at the 247th meeting of the American Astronomical Society on January 8.
Stellar bars are dense regions of stars and gas forming a linear feature at a galaxy’s center. These structures can appear as bright lines dividing a galaxy in images taken from above or below its plane. The Milky Way also contains a stellar bar.
Ivanov noted that these features are not permanent but rather waves of denser material resulting from instabilities within galaxies. “Stellar bars are expected to emerge, over certain timescales, on their own,” he said, adding that they may form and dissipate multiple times throughout a galaxy’s history.
External forces can also influence their formation. “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 stated.
Stellar bars play an important role in galactic evolution by channeling gas toward central regions and feeding supermassive black holes located there. This supports models suggesting galaxies evolve from inside out: star formation begins near galactic centers before spreading outward as interstellar gas accumulates.
“There’s a large burst of star formation near the center of the galaxy, early in its history,” Ivanov said. He added that this process results in older cores compared to outer disks where less early star formation occurs.
The research team discovered COSMOS-74706 while cataloging barred and non-barred galaxies within a specific region of space. High redshift values flagged some galaxies for further study; redshift measures how long light has traveled through space since emission.
While other researchers have reported earlier barred spiral galaxies, Ivanov pointed out limitations in those studies due to less definitive analysis methods or distortions caused by gravitational lensing—when light passes near massive objects en route to Earth. In contrast, spectroscopy confirmed COSMOS-74706’s status without such distortion.
“It’s the highest redshift, spectroscopically confirmed, unlensed barred spiral galaxy,” Ivanov said.
Although simulations suggest bars could form even earlier—at about 12.5 billion years ago—Ivanov noted that finding such objects from this epoch is rare and helps refine timelines for bar formation within galaxies.
