Free Astronomy Magazine September-October 2015

PLANETOLOGY be significantly older, 6 billion years, even if this estimate is highly dependent upon the models used to derive it, with a degree of un- certainty of ± 2 billion years. The aspect that most interests us here is nonetheless that related to the stellar diameter (and conse- quently that of the brightness per unit area), since in being greater than previous- ly estimated, it resul- tantly increases the one of Kepler-452b up to 1.63 times that of Earth (about 20,800 ± 2,500 km). Also the ra- diation flux reaching the planet is greater, but given that it is about 7 million km far- ther from its star than the average Earth-Sun distance, the heat it receives is only 10% greater. Once established that KIC 8311864 is not exactly identical to the Sun, but that it is prob- ably a more evolved version, what now re- mains to be seen is if and how Kepler-452b resembles Earth. In or- der to provide an an- swer to these questions we must add to the overall picture a key parameter, the planet’s mass. Unfortu- nately, its value is unknown, and in fact, no spectroscopic observation of the star has shown lines displacements in response to whichever planetary pull. Even when transiting on the disk (and behind it), and thus being in the best position for moving the star towards the observer (and in the opposite direction), Kepler-452b is too small and far from KIC 8311864 to produce in the star’s dim light any effect detectable with the instruments currently available to astronomers. The absence of any variation in the star's radial velocity could also mean the non- existence of the planet, since a periodic sig- E arth and Ke- pler-452b face to face. The artist who depicted large continents on the new plan- et did not consid- er that according to more recent and