Fastest (and Most Compact) Stellar Spinner Confirmed

gregg writes "HM Cancri has been confirmed as a binary system of two white dwarfs orbiting each other so closely that they complete one orbit every 5.4 minutes; they are separated by a mere 8 Earth diameters. '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. '"

Re:Tidal bulges

[mrtommyb]

Actually the less massive donor star is really quite non-spherical. The shape will will what is known as a Roche Lobe, this is a 3D teardrop shape. The donor will also be several time larger than the more massive primary star.

Re:Mass flow is common.

[FatdogHaiku]

Does this mean that at some point one of them could lose so much mass that there will no longer be a stable pair? I have this vision of one of them suddenly shooting off at a tangent at a horrendous velocity like some cosmic bowling ball.