The star system AR Scorpii, or AR Sco for short, lies in the constellation of Scorpius, 380 light-years from Earth. It comprises a rapidly spinning white dwarf, the same size as Earth but containing 200,000 times more mass, and a cool red dwarf companion one third the mass of the Sun. They are orbiting one another every 3.6 hours in a cosmic dance as regular as clockwork.