Thursday, January 31, 2013

Faint Radio Signals Reveal Secrets of Failed Stars

An artist's impression of auroras at the magnetic pole of a brown dwarf. Astronomers believe this phenomenon may account for the bright "radio flares" given off by dwarfs such as J1047+21.
CREDIT: Hallinan et al., NRAO/AUI/NSF
Failed stars can emit detectable radio waves at much cooler temperatures than previously expected, according to new research.

The discovery could help astronomers understand how these so-called "brown dwarfs" generate a magnetic field. Some scientists think a faster rotation makes the magnetic field stronger.
"We don’t really understand what [the magnetic fields] are shaped like, or whether they're steady, or come and go," said Peter Williams, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and the lead author of a paper announcing the find submitted to Astrophysical Journal Letters.
The new research is based on only two hours of observations of one brown dwarf star. However, Williams said much of the groundwork came from another science team that did a survey of brown dwarfs this summer. It was from this work that Williams' team selected its target: 2MASS J10475385+2124234, a brown dwarf more than 33 light-years away in the constellation Leo.
The dwarf, which is too tiny to fuse atoms togetheras a star does, has a surface temperature of just 1,160 Fahrenheit (900 Kelvin). This is more than six times cooler than the surface of Earth's sun.

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