Nat. Astron. 1, 0029 (2017)

In May 2015 a group of amateur astronomers spotted an unusual star shining brighter every 1.97 minutes in a wide spectrum from ultraviolet to radio wavelengths. AR Scorpii is a binary system made of a cold red dwarf and a fast-spinning white dwarf, orbiting each other every 3.55 hours. But why is it blinking? Using polarization measurements from the South African Astronomical Observatory 1.9-m telescope, David Buckley and colleagues have explained the mechanism behind it.

Pulsars are fast-spinning neutron stars whose strong magnetic field accelerates charged particles that emit synchrotron radiation. The white dwarf in AR Scorpii has a strong magnetic field and rotates rapidly, so a similar thing happens. However, the system is more complex due to the additional magnetic interactions with the other star. The combined effect leads to the pulsed emission. Pulsars were first discovered fifty years ago and a similar behaviour was predicted for white dwarfs, but AR Scorpii is the first one to be spotted.