For decades, astronomers have tried to determine how Pluto acquired its unusually large moon Charon, which is about half the size of the dwarf planet. Now, new research suggests that Pluto and Charon briefly came together billions of years ago in a newly discovered “kiss and capture” collision.

The “demoted” dwarf planet Pluto and its largest moon Charon make an unusual pair, and for decades, scientists have been discussing how the binary system—in which each mutually orbits the other—came to be.

Simulations suggest Pluto and its largest moon may have gently stuck together for a few hours before Charon settled into a stable orbit around the dwarf planet