Scientists may have detected signs of a planet transiting a star outside of the Milky Way, in what could be the first planet ever to be discovered outside our galaxy.

The possible exoplanet was discovered in the Whirlpool Galaxy -- the spiral galaxy Messier 51 (M51) -- by NASA's Chandra X-ray Observatory, NASA said in a press release on Monday.
An exoplanet is a planet outside of our solar system that normally orbits a star other than our own sun in our galaxy.

Until now, all other exoplanets have been found in the Milky Way, and most of them have been found less than 3,000 light-years from Earth.