STANDING on the shore at dusk, you see four planets and an orange sun near the horizon. At night, dazzling ribbons of auroras snake across the sky. You are on Kepler-186f, the smallest exoplanet thought able to support life.
“Of all the planets we’ve seen, this is the one that reminds us most of home,” says Thomas Barclay at NASA’s Ames Research Center in Moffett Field, California. Barclay and his colleagues spotted the planet in data from NASA’s Kepler space telescope (Science, DOI: 10.1126/science.1249403). Only 10 per cent larger than Earth, it is the smallest world outside our solar system that is known to orbit in the habitable zone, the region around a star where liquid water can exist. The host star is a dim red dwarf with four other small planets orbiting it. These worlds are too close to the star to be habitable, but they would shine in the skies of Kepler-186f around dawn or dusk, just as Venus and Mercury do from Earth.
Red dwarf stars produce frequent flares and strong winds of radiation. And as Kepler-186f is slightly larger than Earth, if it has a similar internal structure, it would support a stronger magnetic field. That could spark interactions between any atmosphere and stellar radiation, perhaps creating spectacular auroras.
“It sounds like a great planet to visit, if we could figure out how to travel there,” says Sara Seager of the Massachusetts Institute of Technology.
This article appeared in print under the headline “Stunning auroras may light up life-friendly exoplanet”
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