Free Astronomy Magazine November-December 2019

4 EXOPLANETS Discovering water vapor in the atmosphere of an extrasolar planet is not a novelty and it is not even too surprising, but it is an important step. This is especially true if water is discovered on a planet that could have a rocky surface, even if its greater mass and its overall atmosphere make it completely inhospitable. Within a few years, this larger-mass limit of modern instruments will be overcome, and we will finally be able to detect water vapor on Earth-sized planets. K2-18 b and t “streetlamp” NOVEMBER-DECEMBER 2019 by Michele Ferrara revised by Damian G. Allis NASA Solar System Ambassador