January 21, 2013
Auroras Exist Elsewhere Besides Earth, Say Planetary Scientists
John P. Millis, Ph.D. for redOrbit.com — Your Universe Online
Every year, eager sky watchers travel to the northern reaches of the Earth to catch a glimpse of the northern lights. This spectacle of color in the atmosphere — the Aurora Borealis and its companion to the south, the Aurora Australis — arises as the solar wind interacts with our atmosphere.
When charged particles from our Sun hit our atmosphere, oxygen and nitrogen atoms become excited. As the atoms relax, they emit light that appears to us as green, or occasionally red. This happens all over the Earth, but the number of particles hitting any particular place on the atmosphere is low, so it is usually not visible to the naked eye, even in dark skies.
But near the magnetic poles, the effect can be dramatic. This is because the Earth´s magnetic field funnels particles from the solar wind — and from within the Earth´s magnetosphere itself - directing them to the North and South poles.
Additionally, strong radio waves are beamed out into space as the charged particles are accelerated around the magnetic field lines. This effect is quite prominent in other aurora systems, like those on Jupiter — which are about 100 times brighter than the auroras on Earth.
Finding Auroras Beyond Our Solar System
It is expected that auroras are commonplace on objects across our galaxy. But the planets we have found so far are too distant to possibly see the optical auroras. But it could be possible to see the radio emission “signature” of these events if they are strong enough.
A recent study, led by Dr Jonathan Nichols, a lecturer and research fellow in the University of Leicester´s Department of Physics and Astronomy, noted, “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.”
With strong magnetic fields and dense solar atmospheres, these sources could produce radio signals by a mechanism similar to those produced on Jupiter. Only they would be a hundred thousand times stronger, making them detectible from Earth.
In addition to reconciling the radio profiles of previously detected low mass stars, this discovery suggests a new way to detect new objects — even certain types of planets — outside of our solar system.
Particularly exciting is the prospect such radio data from extrasolar planets could help inform researchers about the planet´s properties, such as its rotation dynamics, magnetic field strength, and even if it has any moons.