While extragalactic “rogue” planets – not orbiting any star – have been reported before, the new exoplanet is the first to be detected orbiting stars in another galaxy. And not just any galaxy … but M51, the beautiful Whirlpool, 23 million light-years away.
In recent decades, astronomers have found over 4,000 exoplanets, or worlds orbiting other stars. They range from small, rocky planets to huge gas giants, but they all have one thing in common. Every exoplanet found orbiting a star has so far resided in our own Milky Way galaxy. That makes sense, since the Milky Way’s own stars are the stars closest to us, cosmically-speaking. But now scientists at the Harvard-Smithsonian Center for Astrophysics – led by Rosanne Di Stefano – have used X-ray data to take the giant step across extragalactic space, to find the first evidence for a planet orbiting stars in another galaxy.
The planet, still a candidate at this point, appears to orbit a binary star system – two stars in a mutual orbit – in the glorious Whirlpool Galaxy (M51), a galaxy we see face-on, at a staggering 23 million light-years from Earth.
This article compliments of EarthSky.org