The seven Earth-sized exoplanets orbiting the star TRAPPIST-1 generated a lot of excitement when their discovery was announced last month. This is the largest collection of Earth-sized worlds in one planetary system found so far, and some of them are well within the star’s “habitable zone” where temperatures could allow liquid water to exist on their surfaces. Little else is known about the actual conditions on these planets so far, but NASA’s Kepler Space Telescope has also been observing TRAPPIST-1 in recent weeks.
Read MoreNASA’s Kepler Space Telescope continues observations of TRAPPIST-1 planetary system