Stunning auroras may light up life-friendly exoplanet

摘要

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.