Move over, giant meteor. Here’s what the largest comet would do to Earth
Out there, in the farthest recesses of the Solar System, a great existential threat lies in wait: the Oort cloud. Formed at the same time as the protostar that would become our Sun and the protoplanetary disk that would give rise to the planets, asteroids, and moons, it largely consists of the remnants of that same primitive material. Whatever wasn’t either boiled off by the Sun or locked up into the planetary, lunar, asteroidal, or Kuiper belt objects we have today persisted in series of objects, ranging from tiny to planet-sized, in a spheroidal cloud. The closest Oort cloud objects might “only” originate from a thousand times the Earth-Sun distance, but the full extent of this cloud reaches up to one or two light-years away. Today, these bodies, mostly a mix of ice-and-rock, remain in slow, quasi-stable orbits in the deepest recesses of our Solar System. But every once in a while, a chance gravitational encounter will perturb the orbit of one of those objects, and either eject it from the cloud into interstellar space …









