Free Astronomy Magazine September-October 2015

18 PLANETOLOGY Discovering a planet very similar to ours, at just the right distance from a star identical to the Sun, would be an important step for- ward in the search for extra- terrestrial life. The rush to reach this goal could, how- ever, make us overly opti- mistic and lead us to define the same as Earth a planet that in reality has very little in common with ours. Kepler-452b new Earth D uring the last ten days of July, the mass media have emphasized – per- haps excessively – the discovery of an exoplanet, indicated by NASA as possible Earth’s “older cousin”. In the fantasy mind of many generalist journalists, this had turn- ed into the discovery of a habitable planet like ours, or even inhabited. Evidently there is need of some clarification, and to this end we can briefly go back to the spring of 2014, when in the May-June issue of the magazine (to which the reader can refer for further details) we featured the discovery of Kepler-186f, the exoplanet until then considered the least dissimilar to Earth. Al- most identical in size and probably also in the mass, likely rocky and almost certainly with an atmosphere, Kepler-186f orbits in the habitable zone of a red dwarf, which is basically the only great difference with the SEPTEMBER-OCTOBER 2015 I n the back- ground, artist's interpretation of how Kepler-452b, the planet too hastily defined by the mass media as “Earth's twin”, may ap- pear. [NASA Ames/JPL-Cal- tech/T. Pyle] by Michele Ferrara