Free Astronomy Magazine November-December 2018

40 NOVEMBER-DECEMBER 2018 ASTROBIOLOGY Existing moons in ex- trasolar systems may have born through different processes, and those moons could have sizes far larger than those of the terrestrial plan- ets we know and could orbit around gaseous giants even bigger than Jupiter. For some years, this possibility intrigued astronomers, who have started specific programs aimed at discovering the so- called “exomoons” (hereafter simply moons, and the “exo- planets” simply planets). One of those pro- grams is the Hunt for Exomoons with Kepler T he two au- thors of the study that high- lighted evidence of a possible ex- omoon in orbit around Kepler- 1625b, Alex Teachey (above), and David Kip- ping. [Columbia University] (HEK) that sifts through data produced by the Kepler Space Telescope during its mon- itoring of over 150 thousand stars not very different from the Sun. In the first four years of the mission, Kepler has gathered many photo- metric measurements of planetary transits. By further scrutinizing this material, it is possible to highlight anomalies in the light curves of tran- sits that could be due to the pres- ence of moons. This is what two researchers at Columbia University did − the astronomer David Kipping (founder of HEK) and graduate stu- dent Alex Teachey − by analyzing data of 284 planets discovered by Kepler by their planetary transits across the discs of their stars. The sample to be analyzed was ob- viously chosen on the basis of some requirements necessary to exclude a priori all those planets that for vari- ous reasons should not host moons. For example, the two researchers preferred to consider only worlds in orbits with a period longer than 30 days, since previous research had es- tablished that the existence of large moons in planet-moon systems to close to the star (between 0.1 and 1