Typically, stellar families form in clusters, with stars born in close proximity and moving in concert over extended periods. Many such groups, particularly larger ones, maintain coordinated movement patterns for billions of years. Gaia has identified countless such families, helping astronomers understand stellar formation and the evolution of our galaxy.
Ophion defies this trend. The stars in this massive grouping are already showing signs of scattering randomly and quickly, despite being just under 20 million years old. "Ophion is filled with stars that are set to rush out across the galaxy in a totally haphazard, uncoordinated way, which is far from what we'd expect for a family so big," said Dylan Huson of Western Washington University, lead author of the discovery study. "What's more, this will happen in a fraction of the time it'd usually take for such a large family to scatter."
To identify the Ophion family, Huson and his team created a new analysis framework called Gaia Net, designed to analyze Gaia's extensive spectroscopic dataset. By narrowing the data to young, nearby, low-mass stars, the researchers isolated the unique characteristics of the Ophion group. This marked the first successful application of such a model to large populations of young stars.
"This is the first time that it's been possible to use a model like this for young stars, due to the immense volume and high quality of spectroscopic observations needed to make it work," noted ESA Gaia Project Scientist Johannes Sahlmann. He added that the project showcased the power of Gaia's open data policy, enabling interdisciplinary contributions from student researchers in computer science.
Why Ophion is behaving so unusually remains an open question. Its location, roughly 650 light-years from Earth, places it near other dense clusters of young stars, suggesting possible gravitational or dynamical interactions. Additionally, historical supernovae in the region may have triggered the current chaotic behavior by disrupting the cluster's gravitational cohesion.
"We don't know exactly what happened to this star family to make it behave this way, as we haven't found anything quite like it before. It's a mystery," said Marina Kounkel of the University of North Florida, a co-author of the study. "Excitingly, it changes how we think about star groups, and how to find them."
Although Gaia ceased scientific observations in March 2025, the mission's legacy is far from complete. Further major data releases are expected, including Data Release 4 in 2026 and a comprehensive legacy dataset anticipated after 2030.
Research Report:Gaia Net: Towards robust spectroscopic parameters of stars of all evolutionary stages
Related Links
Gaia's data release 3
Understanding Time and Space
| Subscribe Free To Our Daily Newsletters |
| Subscribe Free To Our Daily Newsletters |
