Free Astronomy Magazine March-April 2018

8 MARCH-APRIL 2018 EXOPLANETS T his artist's concept appeared on the Feb. 23, 2017, cover of the journal Nature announcing that the nearby star TRAPPIST-1, an ultra-cool dwarf, has seven Earth-sized planets orbiting it. Now, astronomers have used NASA's Hubble Space Telescope to conduct the first spectroscopic survey of the Earth-sized planets (d, e, f, and g) within TRAPPIST-1's habitable zone. [Artist's Concept: NASA and JPL/Caltech. Science: NASA, ESA, J. de Wit (MIT), H. Wake- ford (University of Exeter/STScI), and N. Lewis (STScI)]