"Impossible" binary red dwarf star system discovered

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“Impossible” binary red dwarf star system discovered

There are plenty of binary star systems out there, but it’s often been thought that there’s an absolute minimum distance two starts can orbit each other before they just slam into each other and form a single star. But several pairs of new red dwarf stars are challenging that minimum distance.

“To our complete surprise, we found several red dwarf binaries with orbital periods significantly shorter than the 5 hour cut-off found for Sun-like stars, something previously thought to be impossible,” said Bas Nefs from Leiden Observatory in the Netherlands, lead author of the paper which was published in journal Monthly Notices of the Royal Astronomical Society. “It means that we have to rethink how these close-in binaries form and evolve.”

Since stars shrink in size early in their lifetime, the fact that these very tight binaries exist means that their orbits must also have shrunk as well since their birth, otherwise the stars would have been in contact early on and have merged. However, it is not at all clear how these orbits could have shrunk by so much. One possible scenario is that cool stars in binary systems are much more active and violent than previously thought.

The astronomers said it is possible that the magnetic field lines radiating out from the cool star companions get twisted and deformed as they spiral in towards each other, generating the extra activity through stellar wind, explosive flaring and star spots. Powerful magnetic activity could apply the brakes to these spinning stars, slowing them down so that they move closer together.

“The active nature of these stars and their apparently powerful magnetic fields has profound implications for the environments around red dwarfs throughout our Galaxy, ” said team member said David Pinfield from the University of Hertfordshire.

Via