A small asteroid or comet that has been spotted racing through our solar system may have come from elsewhere in the galaxy, U.S. space scientists say, possibly marking the first such interstellar visitor observed from Earth.

The mystery object, so far known only as A/2017 U1, was discovered earlier this month by a researcher using a sophisticated telescope system at the University of Hawaii that continually scans the universe for such phenomenon.

"We have been waiting for this day for decades," said Paul Chodas, manager of the National Aeronautics and Space Administration's Center for Near Earth Object Studies at the Jet Propulsion Laboratory in Pasadena, California.

"It's long been theorized that such objects exist - asteroids or comets moving around between the stars and occasionally passing through our solar system - but this is the first such detection," Chodas said.