BINARY STAR APOCALYPSE

摘要

Not all two-star systems have stars close enough for one planet to orbit both. In some cases, the stars are so far apart that planets could orbit one star, while the other lurks hundreds of billions of kilometres away. You might think such worlds would be as serene as those around solo stars. But the second star could spell doom, says Nathan Kaib of Northwestern University in Evanston, Illinois. In the outer reaches of our solar system, objects in the Oort cloud are nudged to and fro by galactic tides and the gravity of passing stars. This sends some of them, which we see as comets, careening into our neighbourhood on highly elongated orbits.