Free Astronomy Magazine July-August 2014

EXOPLANETS final size of planets is the distance from their stars, especially in those planetary sys- tems characterized by small orbits and hence short periods. According to a recent theory interpreting those scenarios, the re- quired core mass from which a gas giant can con- tinue to grow increases with the orbital period. Since for a nucleus of that kind, especially if at short distances from stars, is not easy to collect and retain the gas of the protoplan- etary disk, it could hap- pen that potential gas giants are unable to pass beyond the core stage. The end result of that “failure” should be a plan- et not much larger than Earth, but decidedly much heavier and thus more dense. A good candidate could have been Kepler- 10b, a rocky planet that based on the 2011 obser- vations (Batalha et al.) ap- T he building housing the Telescopio Nazio- nale Galileo, with the instrument clearly visible in- side its dome. Thanks to the powerful HARPS- N spectrograph, with which it was equipped a cou- ple of years ago, this 3.6 metres diameter tele- scope has allow- ed to discover the first mega-Earth. [TNG/G. Tessicini] Below, an inside view of the spec- trograph. [HARPS- N Consortium] might seem. The metallicity is, however, only one of the factors involved in plane- tary formation, and even though its role is now considered much more central than in the past, another determining factor in the