Free Astronomy Magazine September-October 2016

certainly have a rocky surface. Two of them have an energy input similar to that of our planet and may therefore be both habit- able. The orbital periods of the four planets are approximately 5.5, 8, 15 and 24 days, thus inevitably brief, due to the short dis- tance from the red dwarf. If they were to orbit around the Sun, these planets would be blazing-hot, but K2-72 has a diameter that is 40% that of the Sun, which means a proportionally reduced mass, surface tem- perature and irradiation level. Given that the K2 mission has increased 20- fold the number of monitored red dwarfs, we may expect the discovery of numerous systems similar to that of K2-72. The brief revolution periods and the favourable ratio between the diameters of the Earth-sized planets and those of the red dwarfs, make it easier to detect the former while they transit on the disks of the latter. Crossfield and colleagues predict that in the 4 years scheduled for the K2 mission, the Kepler space telescope will discover between 500 and 1,000 new exoplanets, if adequate re- sources will be available for performing the verification observations from the ground. These are absolutely essential as there are several natural phenomena that can mimic the transit of a planet in front of a star. It is only through an accurate spectral analysis of the starlight and equally accurate photomet- ric measurements, combined with in-depth high-resolution imaging, that it will be pos- sible to characterize the guest-stars and, to some extent, the planets orbiting them. S ince Kepler’s current targets are arranged along the ecliptic, verification ob- servations for exoplanets candi- dates can now also be made with the large telescopes of the southern hemi- sphere, such as the Gemini South telescope (pic- tured), located on Cerro Pachón, Chile. [Gemini Ob- servatory/AURA] n