AR Scorpii, about 380 light years away in Scorpius, brightens and fades every couple of minutes and puzzled astronomers for over 40 years. It is not one star but two: a white dwarf the size of Earth but 200,000 times more massive, and a cool red dwarf a third the size of the Sun.
Observations with ESO's Very Large Telescope, Hubble and others show the white dwarf spins very fast, accelerating electrons to almost the speed of light. These particles lash the companion and release a pulse of radiation every 1.97 minutes. Pulsing like this was known from neutron stars but had never been seen from a white dwarf. The study was published in Nature.
via The Terrifying Reason This Star Flickers Every 2 Minutes | Gizmodo