NASA has detected signs of what could be a planet orbiting a star outside of the Milky Way galaxy for the first time in history.Hints of the new exoplanet - the name given to a world that orbits a star - was detected in Messier 51, also known as M51 or the Whirlpool Galaxy.The NASA's Chandra X-ray Observatory detected the possible planetary signals by observing transits, which causes light to dim as a planet passes in front of the star.The planet would be located around 28 million light-years away from the Milky Way. (NASA/CXC/M.Weiss)"We are trying to open up a whole new arena for finding other worlds by searching for planet candidates at X-ray wavelengths, a strategy that makes it possible to discover them in other galaxies," said Rosanne Di Stefano of the Center for Astrophysics at Harvard and Smithsonian (CfA) in Cambridge.So far almost 5000 "exoplanets" have been found by all of these have been detected within our own galaxy, the Milky Way.An exoplanet in M51 would be about 28 million light years away."If a planet exists in this system, it likely had a tumultuous history and violent past," the space agency wrote on its website."An exoplanet in the system would have had to survive a supernova explosion that created the neutron star or black hole."
