How many things can you name that travel at a million miles an hour? Probably not that many. However, some citizen scientists know at least one. The group recently discovered an object moving so fast that it will escape the Milky Way’s gravity and shoot into intergalactic space. This hypervelocity object is the first such object found with the mass of a small star.

Fast and furious

Unlike the stars that calmly orbit the center of our galaxy, this newfound body — possibly a brown dwarf — 408 light years from Earth labeled CWISE J124909.08+362116.0 (CWISE J1249) is on a trajectory that will see it leave the Milky Way entirely.

The discovery was made by volunteers involved in NASA’s Backyard Worlds: Planet 9 project. The project uses data from the recently retired WISE telescope (Wide Field Infrared Explorer), which surveyed the sky in infrared light. It’s not the first time citizen scientists have made an important discovery. Because there’s so much data to analyze, NASA often appeals to citizen science groups to help in the preliminary stages of data analysis.

The object was first noticed by Martin Kabatnik from Nuremberg, Germany, along with fellow citizen scientists Thomas P. Bickle and Dan Caselden. As they scanned the WISE images, the rapid motion of this faint object caught their attention.

“I can’t describe the level of excitement,” Kabatnik said. “When I first saw how fast it was moving, I was convinced it must have been reported already.” Yet, it wasn’t.

What makes CWISE J1249 particularly intriguing is its speed — around one million miles per hour — and its low mass, which makes it difficult to categorize. It might be a small star, or possibly a brown dwarf, an object that straddles the line between a planet and a star.

Brown dwarfs aren’t uncommon. Backyard Worlds volunteers have discovered more than 4,000 of them. However, none of those objects are on a path to escape the galaxy.

The composition of CWISE J1249, revealed through observations from the W. M. Keck Observatory in Hawaii, shows it contains much less iron and other metals than typical stars or brown dwarfs. This suggests it could be from one of the oldest generations of stars in our galaxy.

But why is it moving so fast? One theory suggests that CWISE J1249 was part of a binary system with a white dwarf. When the white dwarf triggered a supernova, it might have ejected CWISE J1249. Another possibility is that it originated in a dense globular cluster, and an encounter with a pair of black holes sent it hurtling out of the cluster.

“When a star encounters a black hole binary, the complex dynamics of this three-body interaction can toss that star right out of the globular cluster,” says Kyle Kremer, incoming assistant professor in UC San Diego’s Department of Astronomy and Astrophysics.

The discovery highlighted not only an insanely fast and mysterious object but also the importance everyday citizens can play in planetary science.