“There’s a new interstellar comet in the neighbourhood!,” tweets NASA’s Jet Propulsion Laboratory. Discovered by the Chilean ATLAS observatory with supporting observations dating back to June, 3I/ATLAS arrives from the direction of the Sagittarius constellation and poses no threat to Earth. Currently 420 million miles away and estimated at 5-20 km in diameter, it will make its closest solar approach on October 30th—just inside Mars’ orbit—before becoming observable again in December.