Exotic binary identified as a white dwarf pulsar - except those don't exist

An exotic binary star system 380 light-years away has been identified as a white dwarf pulsar – yet those were believed not to exist anywhere in the universe.

Which means we still don't even know what we don't know.

White pulsars were discovered in the 1960s and associated with neutron stars.

Now, the star AR Scorpii (AR Sco) is being called the first white dwarf version of a pulsar, because it contains a rapidly spinning, burnt-out stellar remnant - a white dwarf - which lashes its neighbor – a red dwarf - with powerful beams of electrical particles and radiation, causing the entire system to brighten and fade dramatically twice every two minutes.

 Mark Garlick/University of Warwick

A particle accelerator firing every 2 minutes

The lash of energy from AR Sco is a focused ‘beam’, emitting concentrated radiation in a single direction – much like a particle accelerator – something never before detected. This powerful light house effect accelerates electrons in the atmosphere of the red dwarf to close to the speed of light, which has never been found in similar types of binary stars.

The distance between the two stars is around 1.4 million kilometers, which is three times the distance between the Moon and the Earth. The red dwarf is thus powered by the kinetic energy of its spinning neighbor.

Professor Boris Gänsicke of the University of Warwick says, "AR Sco is like a gigantic dynamo: a magnet, size of the Earth, with a field that is ~10.000 stronger than any field we can produce in a laboratory, and it is rotating every two minutes. This generates an enormous electric current in the companion star, which then produces the variations in the light we detect."

Citation:  D.A.H. Buckley, P.J. Meintjes, S.B. Potter, T. R. Marsh, B.T. Gansicke,  Polarimetric evidence of a white dwarf pulsar in the binary system AR Scorpii, Nature Astronomy