Hubble, and a host of amateur astronomers in Europe have discovered strange behavior from a white dwarf star in the AR Scorpii system. See video below.

In May 2015, a group of amateur astronomers from Germany, Belgium and the UK came across a star system that was exhibiting behavior unlike anything they had ever encountered before. Follow-up observations led by the University of Warwick and using a multitude of telescopes on the ground and in space, including the NASA/ESA Hubble Space Telescope, have now revealed the true nature of this previously misidentified system.

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.

 

In a unique twist, this binary star system is exhibiting some brutal behaviour. Highly magnetic and spinning rapidly, AR Sco's white dwarf accelerates electrons up to almost the speed of light. As these high energy particles whip through space, they release radiation in a lighthouse-like beam which lashes across the face of the cool red dwarf star, causing the entire system to brighten and fade dramatically every 1.97 minutes. These powerful pulses include radiation at radio frequencies, which has never been detected before from a white dwarf system.

Lead researcher Tom Marsh of the University of Warwick's Astrophysics Group commented: "AR Scorpii was discovered over 40 years ago, but its true nature was not suspected until we started observing it in June 2015. We realised we were seeing something extraordinary the more we progressed with our observations."

The observed properties of AR Sco are unique. And they are also mysterious. The radiation across a broad range of frequencies is indicative of emission from electrons accelerated in magnetic fields, which can be explained by AR Sco's spinning white dwarf. The source of the electrons themselves, however, is a major mystery – it is not clear whether it is associated with the white dwarf, or its cooler companion.

Read more: Hubble/European Space Agency