Free Astronomy Magazine July-August 2016

PLANETOLOGY 37 JULY-AUGUST 2016 exoplanet system? T he Sun was born some 4.6 billion years ago in an environment similar to this stellar cluster (NGC 4755). The high concen- tration of stars implies that from time to time they get very close to each other. Dur- ing one such occurrence, the Sun could have stolen a planet from another star. [ESO] T he study by Mike Brown and Kon- stantin Batygin on the possible exis- tence in our solar system of a ninth planet located far beyond Neptune's orbit has led many astronomers to conduct fur- ther researches, using numerical simula- tions, in order to characterize with re- duced uncertainty the physical and dyna-