But there's lot of speculation what it might be: Maybe an asteroid, maybe a comet and maybe the first "interstellar object" to be observed and confirmed by astronomers.
In other words, the object appears to have originated from outside the solar system -- from somewhere else in our galaxy.
A/2017 U1 was discovered earlier this month by the University of Hawaii's Pan-STARRS 1 telescope on Haleakala during the course of its nightly search for near-Earth objects.
Rob Weryk, a postdoctoral researcher at the UH Institute for Astronomy, identified the moving object and submitted it to the Minor Planet Center.
He subsequently searched the Pan-STARRS image archive and found it was present in images taken the previous night, but was not initially identified by the moving object processing.
The object is less than a quarter-mile in diameter and is moving really fast.
And since its discovery, astronomers from around the world have pointing their telescopes toward it to try to figure out what it is.
"We have been waiting for this day for decades," said Paul Chodas, manager of the Center for Near-Earth Object Studies.
"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. So far, everything indicates this is likely an interstellar object, but more data would help to confirm it."