Solving the mystery

The question remains: why is Ophion behaving so unusually?

The scientists discuss several options. The star family resides around 650 light-years away near to some other massive gatherings of young stars; energetic events within and interactions between these colossal neighbours may have influenced Ophion through the years.

There are also signs that stars have exploded here in the past. These supernova bursts could have swept material away from Ophion and caused its stars to move far more rapidly and erratically than before.

“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,” says co-author Marina Kounkel of the University of North Florida, USA.

“Excitingly, it changes how we think about star groups, and how to find them. Previous methods identified families by clustering similarly moving stars together, but Ophion would have slipped through this net. Without the huge, high-quality datasets from Gaia, and the new models we can now use to dig into these, we may have been missing a big piece of the stellar puzzle.”

After more than a decade spent mapping our skies, Gaia stopped observing in March. This marks the end of the spacecraft’s operations – but it’s just the beginning of the science. Many more discoveries are anticipated in the coming years, along with Gaia’s biggest data releases yet. (Data Release 4 is planned towards the end of 2026, and the Gaia legacy data release is planned for publication not before the end of 2030).