July 5, 2012
Infrared Telescope Finds Impossible Binary Stars
Lee Rannals for redOrbit.com - Your Universe Online
Astronomers have discovered four pairs of stars that orbit each other in less than four hours, according to findings published in the journal Monthly Notices of the Royal Astronomical Society.
It was always thought that if binary stars form too close to each other, they would end up merging into one single, larger star.
Now, for the first time, the team of astronomers have observed binary red dwarf stars, up to ten times smaller than the Sun. No scientists have ever seen stellar binaries that have orbital periods shorter than 5 hours.
"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", Bas Nefs from Leiden Observatory in the Netherlands, lead author of the paper, said in a prepared statement. "It means that we have to rethink how these close-in binaries form and evolve."
The team monitored the brightness of hundreds of stars, including thousands of red dwarfs, for the past five years using UKIRT.
The researchers suggest that the fact these very tight binaries exist means their orbits must also have shrunk since their birth, otherwise the stars would have merged early on.
One theory is that cool stars in binary systems are more active and violent than previously thought.
The team said it is possible the magnetic field lines radiating out from the cool star companions get twisted and deformed as they spiral towards each other, generating the extra activity through stellar wind, explosive flaring and star spots.
Powerful magnetic activity could put a stop to the spinning stars, which would slow them down so they would be able to move closer together.
"Without UKIRT's superb sensitivity, it wouldn't have been possible to find these extraordinary pairs of red dwarfs", David Pinfield said. "The active nature of these stars and their apparently powerful magnetic fields has profound implications for the environments around red dwarfs throughout our Galaxy."