Stars circling at record rate

UK astronomers have discovered a pair of stars twirling around each other at record-breaking speed. The mini-suns, both of a type called white dwarfs, are circling at an astonishing rate of once every five and a half MINUTES.

If the Earth spun around the Sun in the same way, our months would each last less than 30 seconds.

The fast movers are a double star in the constellation of Cancer called HM Cancri. Their orbtiing time of 5.4 minutes is the shortest known in the galaxy. The pairing is the smallest known too, at around eight times the diameter of the Earth, meaning both could fit easily in a quarter the gap between us and the Moon.

Astronomers including Professor Tom Marsh and Dr Danny Steeghs from the University of Warwick confirmed the stars’ record using the world’s largest optical telescope at the Keck Observatory on Hawaii.

They also found that material from one of the stars – burnt-out stellar cinders – is pouring down onto the other where it erupts with more X-ray power than is put out by our own Sun.

The team speculate that HM Cancri could also be strongly emiting gravitational waves – a phenomenon that is a holy grail being sought by astronomers as a test for Einstein’s theory of general relativity.

Colleague Dr Gijs Nelemans of the Radboud University in the Netherlands said: “HM Cancri is a real challenge for our understanding of stellar evolution. We know the system must have come from two normal stars that somehow spiralled together, but the physics of this process is very poorly known.”

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