At https://dailygalaxy.com/2025/07/astronomers-mysterious-object-solar-system/ … first spotted at the beginning of July by astronomers monitoring an asteroid warning system, it seems 31/ATLAS is the third object with an origin outside our solar system. This is over a period of a few recent years. It seems interstellar objects may be more common than previously thought – whizzing through the solar system and back out again. 31/ATLAS is around 12 miles in diameter, somewhat larger than Oumuamua and Comet 12/Borisov. It is unclear if the present object is a comet, or not. It is, however, striking in its brightness and can be seen over vast distances.
Interstellar objects are calculated via their orbits. Highly elliptical or hyperbolic trajectories suggest they will not return – unlike most comets which have orbits that bring them back, over and over again. 31/ATLAS is also moving very fast. Fast enough to escape the gravitational pull of our Sun.