A second planetesimal collision in the Fomalhaut system

The nearby star Fomalhaut is orbited by a compact source, Fomalhaut b, which has previously been interpreted as either a dust-enshrouded exoplanet or a dust cloud generated by the collision of two planetesimals. Such collisions are rarely observed, but their debris can appear in direct imaging. We report Hubble Space Telescope observations that show the appearance in 2023 of a second point source around Fomalhaut, resembling the appearance of Fomalhaut b 20 years earlier. We interpret this additional source as a dust cloud produced by a recent impact between two planetesimals. The positions and motion of two impact-generated dust clouds over 20 years provide constraints on the collisional dynamics in the debris belt.