A Youngstown State University professor is helping uncover how some of the universe’s densest star clusters are formed, in research just published in “Nature”, one of the world’s top science journals.

Patrick Durrell, Distinguished Professor of Physics and Astronomy at YSU, is part of an international team of astronomers that used the Hubble Space Telescope to capture rare images showing star clusters in dwarf galaxies merging together, something Durrell says scientists have long believed happens, but had never clearly seen until now.

“These are some of the clearest images ever captured of this process actually taking place,” Durrell said. “We’ve known this could happen, but now we have direct visual evidence.”

The study, “Evidence of star cluster migration and merger in dwarf galaxies,” shows that smaller star clusters can gradually move toward the center of a galaxy and combine into what’s called a nuclear star cluster or a dense group of stars packed into the galaxy’s core.

Durrell helped lead the planning and setup of the Hubble observations that made the discovery possible. The research was part of a special Hubble program that uses short observing ‘snapshots’ to collect data between other, larger scientific programs. Originally, the team set out to simply catalog star clusters in dozens of smaller galaxies.

“But when we started looking closely at the images, we saw something unexpected,” Durrell said. “Some of these galaxies had strange-looking structures in their centers, what looked like the leftovers from two star clusters smashing into each other.”

To confirm the theory, the team ran computer simulations showing what such a collision would look like and the results matched the Hubble images. “It’s like a cosmic demolition derby,” Durrell said. “When two clusters collide and merge, you expect to see a bit of a mess. And that’s exactly what we saw.”

This finding supports a long-standing theory in astronomy: that nuclear star clusters can form not just from new stars being born at the galaxy’s center, but also from older clusters slowly migrating inward and merging over time. Until now, scientists had little direct proof of that second scenario.

Durrell has worked with this research group for more than a decade, contributing to multiple space-based and ground-based astronomy projects. For this study, he coordinated the technical planning for more than 70 Hubble galaxy observations.

“This kind of discovery shows how astronomers at universities like YSU are contributing to big, international science,” he said. “It’s exciting to see something we’ve theorized for years actually show up so clearly in images.”

The discovery also highlights the important work happening at YSU’s Department of Physics, Astronomy, Geology, and Environmental Science, where faculty are involved in real-time scientific discoveries that reach far beyond the classroom.

To read more about the research team’s findings, visit Nature’s website.