Astronomers uncover the earliest known signs of galaxy-building in action

Astronomers at Durham University have made a major advance in understanding how galaxies formed and evolved in the early universe. Using powerful new observations, the team discovered the most distant example ever found of a compact, star-forming structure at the heart of a galaxy, dating back more than 9 billion years.

The research reveals clear evidence of a “nuclear disk” (a dense, rotating disk of stars at the very center of a galaxy) forming at a time when the universe was still relatively young.

The work has been published in Monthly Notices of the Royal Astronomical Society.

Nuclear disks are common in nearby, mature galaxies, but until now, they had never been observed so far back in cosmic history. This discovery shows that galaxies were already developing complex internal structures much earlier than scientists had assumed.

The Durham-led team made the discovery using data from the James Webb Space Telescope, whose unprecedented sensitivity and sharp resolution allow astronomers to study distant galaxies in extraordinary detail.

The galaxy they studied is seen as it was just 4.5 billion years after the Big Bang. At its center, the researchers identified a nuclear disk that is actively forming new stars and still growing.

A stellar bar at work

Crucially, the nuclear disk appears to have been built by a long, bar-shaped structure of stars stretching across the galaxy. These bars are a familiar feature of many present-day spiral galaxies and act like cosmic engines, driving gas and stars toward the center and helping new structures form.

While previous studies had shown that bars can form early, there was no direct proof that they were already reshaping galaxies at this stage in the universe’s history. This research provides that missing evidence.

Zoe Le Conte, lead author of the study from Durham University, said, “This is a remarkable and unexpected discovery that will make astronomers revisit the idea of galaxy evolution and the influence of stellar bars in the early universe.

“The extraordinary images and novel results from the James Webb Space Telescope continue to reveal that mature galaxies exist much earlier than we previously thought.”

Despite its great distance, the newly discovered nuclear disk already shares many of the same properties as nuclear disks found in nearby galaxies today.

It is compact, rich in young stars and shows clear signs of organized growth. This suggests that galaxies did not slowly drift into their present-day forms but instead matured rapidly, following similar evolutionary pathways over billions of years.

Clues to black hole growth

The findings challenge long-standing ideas about galaxy evolution and point to a much more active and structured early universe. They also have important implications beyond galaxy formation.

Nuclear disks are thought to act as reservoirs of gas that can eventually feed the supermassive black holes found at the centers of most galaxies, meaning this work could also help scientists better understand how black holes grew during the peak era of cosmic activity.

The research team now plans to follow up on this discovery with further observations to study how stars and gas move within the galaxy. These future studies will help confirm exactly how the nuclear disk formed and how efficiently the bar drives material toward the center.

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Sadie Harley

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Andrew Zinin

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