An interstellar object was spotted last month by the "Pan-STARRS One" telescope in Hawaii.
The International Astronomical Union is calling it an "interstellar asteroid", the first of its kind.
Astronomers say the object could carry secrets on how other solar systems have formed. But such objects are extremely difficult to spot.
Experts say between one and 10 of those visitors drop by our solar system annually. But they move so fast, it's extremely difficult to see or study them.