A study has suggested it might be possible to detect aurorae on Proxima b, the closest exoplanet to Earth, which might tell us about the planet’s potential habitability.
Published in The Astrophysical Journal, the research suggests that if Proxima b has an atmosphere that’s rich in oxygen and nitrogen, like Earth, we might be able to see a noticeable green glow – a “Pale Green Dot”, if you will. The findings were led by Rodrigo Luger from the University of Washington in Seattle.
"The northern and southern lights [on Proxima b] would be at least 100 times brighter than on Earth," Luger told Space.com. "Proxima Centauri b is optimal for auroral detection.”
In our Solar System, two of our terrestrial planets have magnetic fields – Earth and Mercury. It’s an open question as to whether Proxima b does, though, or whether it even has an atmosphere.
At the moment we know it is about 1.3 times the mass of Earth, and orbits its red dwarf star Proxima Centauri – which is considerably dimmer than our Sun – in just 11.3 days, in the star’s habitable zone.
This relative proximity means it is subjected to many more solar particles than we are on Earth. These drive aurorae, but they may also have ripped the atmosphere of Proxima b away. We don’t know the answer to that yet.
But if the planet passed all these tests, then it would be possible to see its aurora. With oxygen and nitrogen, it would shine green – telling us the planet has similar characteristics to our own world.
“Proxima Cen b's intrinsic planetary properties may favor production of aurorae from oxygen atoms,” the team wrote in their paper.
Unfortunately, we don’t have a telescope yet that could detect Proxima b’s aurora. Our best bet in the future is the Thirty Meter Telescope (TMT) in Hawaii, which was recently approved for construction. It is expected to be switched on in the 2020s.
The researchers note that a green aurora due to oxygen is not guaranteed. The planet’s atmosphere, if it exists, could be rich in other gases like carbon dioxide. If that’s the case, we might still be able to notice the glow of the planet’s night side – known as airglow.
Other exoplanets, too, might be prime targets for finding aurorae. One mentioned is GJ 1132b, an Earth-sized world 39 light-years away that we already know to have an atmosphere.
As we continue to find worlds outside the Solar System, all avenues of study are going to be explored. And just maybe, one of these will tell us about potentially habitable worlds elsewhere.