On October 26th, NASA announced that a 'comet or small asteroid' from beyond our solar system was paying us a visit. The significance being this is the first time NASA has tracked an outside 'visitor,' and theories have already popped up as to whether this object really is a comet or asteroid, or if it could possibly be something more.
First spotted on October 19th, this is the first 'interstellar object,' that NASA will be able to track entering our solar system and (hopefully?) leaving. The Minor Planet Center (MPC) has temporarily named it A/2017 U1, and it has been described as having the most 'extreme orbit' observed by scientists. So fast, in fact, that experts predict it will zoom past our solar system never to return again. Well, it was nice of A/2017 U1 to take this trip in time for Halloween, just like our other favorite extraterrestrial.