Within all those systems, they found only one exoplanet. The team targeted more than 200 total star systems within these galaxies using the Chandra X-ray Observatory and the European Space Agency's XMM-Newton. The new research, published in Nature Astronomy, examined three galaxies: M51, M101, and M104. '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 study lead Rosanne Di Stefano of the Harvard-Smithsonian Center for Astrophysics in a press release. To find the distant planet hiding in this system, astronomers relied on X-ray data rather than more standard visual observations. Residing some 28 million light-years away near the heart of the Whirlpool Galaxy (M51), the binary system M51-ULS-1 consists of either a neutron star or a black hole that's tangoing with a more standard companion star. Astronomers believe they've spotted the first extragalactic exoplanet beyond our own galaxy.
