Astronomers Find Red Dwarfs With Remarkably Close Orbits
Posted on July 8, 2012
Astronomers using the United Kingdom Infrared Telescope (UKIRT) in Hawaii have discovered four pairs of Red Dwarf stars that orbit each other in less than four hours. Until now it was thought that such close-in binary stars could not exist. The new discoveries come from the telescope's Wide Field Camera (WFCAM) Transit Survey, and appear in the journal Monthly Notices of the Royal Astronomical Society.
The astronomers say that until this discovery it thought that if binary stars form too close to each other, they would merge into one single, bigger star. For the last five years, UKIRT has been monitoring the brightness of hundreds of thousands of stars, including thousands of red dwarfs, in near-infrared light, using its Wide-Field Camera (WFC).
Bas Nefs from Leiden Observatory in the Netherlands, lead author of the paper, says, "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. 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. The astronomers say it is not clear how these orbits could have shrunk by so much. They say one possible explanation is that cool stars in binary systems are much more active and violent than previously thought.
The astronomers say, "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."
You can find the research paper online here.