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Seven exoplanets and a star

An observation campaign involving earth-based telescopes around the world as well as space telescopes such as NASA’s Hubble and Spitzer, has confirmed the presence of seven exoplanets in the orbit of the TRAPPIST-1 star 40 light-years from Earth, in the constellation Aquarius. The initiative, led by Michael Gillon, an astronomer from the University of Liege, Belgium, is the first to observe that number of extrasolar planets around a single star, all of which have a mass and size similar to those of Earth (Nature, February 22, 2017). The exoplanets have been named only with letters, arranged in alphabetical order according to their distance from the star: b, c, d, e, f, g and h. After observing variations in the brightness of TRAPPIST-1, the researchers were able to determine each planet’s distance from the star and their orbital periods around it. They also estimated the size and mass of each one, except for exoplanet h. The new worlds are closer to their star than the distance between Mercury and the Sun. Since the small TRAPPIST-1 is about a thousand times dimmer than the Sun, there is some possibility that the exoplanets have liquid water on their rocky surfaces, especially planets c, d and e. The astronomers hope that the James Webb Space Telescope, set for launching by NASA in 2018, will be able to detect the light from the atmosphere of these exoplanets and infer their chemical makeup.