Spotted: signs of a potential planet about 28 million light-years away 🔎 🪐 For the first time, astronomers may have detected an exoplanet candidate outside of the Milky Way galaxy. Exoplanets are defined as planets outside of our solar system. All other known exoplanets and exoplanet candidates have been found in the Milky Way, almost all of them less than about 3,000 light-years from Earth. This new result is based on transits, events in which the passage of a planet in front of a star blocks some of the star's light and produces a characteristic dip. Researchers used our NASAChandraXray Observatory to search for dips in the brightness of X-rays received from X-ray bright binaries in the spiral galaxy Messier 51, also called the Whirlpool Galaxy (pictured here). These luminous systems typically contain a neutron star or black hole pulling in gas from a closely orbiting companion star. They estimate the exoplanet candidate would be roughly the size of Saturn, and orbit the neutron ...