A study led by British planetary scientists has provided evidence that auroras occur on a number of very low mass stars and brown dwarfs, collectively termed ultracool dwarfs.
This artist’s conception illustrates a brown dwarf (NASA / JPL-Caltech)
Auroras occur on Earth and some other planets within our Solar System, and the brightest – on Jupiter – are 100 times brighter than those on Earth. This phenomenon occurs when charged particles in an object’s magnetosphere collide with atoms in its upper atmosphere, causing them to glow. However, before hitting the atmosphere, these particles also emit radio waves into space.
No auroras have yet been observed beyond Neptune.
The new study, published in the Astrophysical Journal (arXiv.org version), suggests that processes strikingly similar to those which power Jupiter’s auroras could be responsible for radio emissions detected from a number of objects outside our Solar System.
The findings suggest the radio emissions from a number of ultracool dwarfs may be caused in a very similar, but significantly more powerful, way to Jupiter’s auroras.
“We have recently shown that beefed-up versions of the auroral processes on Jupiter are able to account for the radio emissions observed from certain ‘ultracool dwarfs’ – bodies which comprise the very lowest mass stars – and ‘brown dwarfs’ – failed stars which lie in between planets and stars in terms of mass,” said lead author Dr Jonathan Nichols of the University of Leicester’s Department of Physics and Astronomy.
“These results strongly suggest that auroras do occur on bodies outside our Solar System, and the auroral radio emissions are powerful enough – one hundred thousand times brighter than Jupiter’s – to be detectable across interstellar distances.”
The study could have major implications for the detection of planets and objects outside our Solar System which could not be discovered with other methods.
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Bibliographic information: J. D. Nichols et al. 2012. Origin of Electron Cyclotron Maser Induced Radio Emissions at Ultracool Dwarfs: Magnetosphere-Ionosphere Coupling Currents. ApJ 760, 59; doi: 10.1088/0004-637X/760/1/59
