Of all of the possible ways planets could orbit, how many configurations will remain stable over the billions of years of a star’s life cycle? Rejecting the large range of unstable possibilities — all the configurations that would lead to collisions — would leave behind a sharper view of planetary systems around other stars, but it’s not as easy as it sounds. “Separating the stable from the unstable configurations turns out to be a fascinating and brutally hard problem,” said Daniel Tamayo, a NASA Hubble Fellowship Program Sagan Fellow in astrophysical sciences at Princeton. https://bit.ly/2CJIq0o Related from Futurism: New AI Predicts Which Planets Are Going to Smash into Each Other