Astrophysicist Josep Trigo-Rodriguez of the Institute of Space Sciences near Barcelona, Spain, believes it is an interstellar object based on its odd path and extreme speed cutting through the solar system. He estimates its size at roughly 25 miles (40 kilometers) across.

A rare interstellar comet is flying through our solar system. Here's how—and when—you might be able to see Comet ATLAS from your backyard.