Most extreme white dwarf binary system found with orbit of just 5 minutes

www2.warwick.ac.uk...

Quote from source:
An international team of astronomers, including Professor Tom Marsh and Dr Danny Steeghs from the University of Warwick, have shown that the two stars in the binary HM Cancri definitely revolve around each other in a mere 5.4 minutes. This makes HM Cancri the binary star with by far the shortest known orbital period. It is also the smallest known binary. The binary system is no larger than 8 times the diameter of the Earth which is the equivalent of no more than a quarter of the distance from the Earth to the Moon.

The binary system consists of two white dwarfs. These are the burnt- out cinders of stars such as our Sun, and contain a highly condensed form of helium, carbon and oxygen. The two white dwarfs in HM Cancri are so close together that mass is flowing from one star to the other. HM Cancri was first noticed as an X-ray source in 1999 showing a 5.4 minutes periodicity but for a long time it has remained unclear whether this period also indicated the actual orbital period of the system. It was so short that astronomers were reluctant to accept the possibility without solid proof.

The team of astronomers, led by Dr Gijs Roelofs of the Harvard-Smithsonian Center of Astrophysics, and including Professor Tom Marsh and Dr Danny Steeghs at the University of Warwick in the UK, have now used the world's largest telescope, the Keck telescope on Hawaii, to prove that the 5.4 minute period is indeed the binary period of the system. This has been done by detecting the velocity variations in the spectral lines in the light of HM Cancri. These velocity variations are induced by the Doppler effect, caused by the orbital motion of the two stars revolving around each other. The Doppler effect causes the lines to periodically shift from blue to red and back.

The observations of HM Cancri were an ultimate challenge due to the extremely short period that needed to be resolved and the faintness of the binary system. At a distance of close to 16,000 light years from Earth, the binary shines at a brightness no more than one millionth of the faintest stars visible to the naked eye.

Professor Tom Marsh from the University of Warwick said; "This is an intriguing system in a number of ways: it has an extremely short period; mass flows from one star and crashes down onto the equator of the other in a region comparable in size to the English Midlands where it liberates more than the Sun's entire power in X-rays. It could also be a strong emitter of gravitational waves which may one day be detected from this type of star system."

Wow, this is amazing, two white dwarfs. We need pictures, get Hubble on this, if he can't see it lets get something up there that can!!

I wish we could fly a rover in between these two stars and measure the gravity in there.

Any thoughts?

Pred...

Wow. It's mind-boggling to think about how fast these two stars are moving. Imagine of the moon orbited the Earth every 5 minutes. Think how fast it would appear to be going from our perspective. Now imagine this as two stars, which are undoubtedly MUCH larger than either the earth or the moon.

Incredible. Nice find.

Imagine the gravitational and inertia forces at work there, two massively dense objects rotating around each other in an orgasmic frenzy.

Wait a minute...does this say the two stars are super tiny? I thought stars had to be super humongous?

reply to post by ExPostFacto


It says the entire system (meaning both stars together) is no more than 8 times the diameter of Earth. So as stars go, these ones are tiny. Not sure how big each of them are individually though. Obviously their average diameter could not be more than 4 times the diameter of earth, otherwise they would be touching each other.

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