Radio signals could 'tag' distant planets

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LEICESTER, England, April 19 (UPI) -- British astronomers say the search for exoplanets outside our solar system could seek out radio "auroras" like ones detected on Jupiter and Saturn.

Most exoplanets discovered to date orbit very close to their stars and are detected by the dimming of the star's light as the planet transits in front of it or by the wobble in the star's motion as it is tugged on by the planet's gravity.

But detecting planets that orbit their stars at large distance, comparable to Jupiter and Saturn in our solar system, would be difficult with these techniques, a release by the Royal Astronomical Society said Tuesday.

"Jupiter and Saturn take 12 and 30 years respectively to orbit the sun, so you would have to be incredibly lucky or look for a very long time to spot them by a transit or a wobble," Jonathan Nichols at the University of Leicester said.

Instead, he said, astronomers could look for radio auroras of the kind that have been detected at Jupiter and Saturn.

"At both planets, we see radio waves associated with auroras generated by interactions with ionized gas escaping from the volcanic moons Io and Enceladus," Nichols said.

Such radio emissions could be detectable from systems 150 light years away from Earth, he said.

"In our Solar System, we have a stable system with outer gas giants and inner terrestrial planets, like Earth, where life has been able to evolve," Nichols said. "Being able to detect Jupiter-like planets may help us find planetary systems like our own, with other planets that are capable of supporting life."