It’s become clear that the Milky Way is full of planets. And the Milky Way is unremarkable compared to many other galaxies, which, in all likelihood, are also rich with planets.

But there’s a big difference between “likely” and having evidence that planets exist outside of our galaxy. And the methods that have allowed us to spot planets in the Milky Way simply won’t work at such huge distances. But this week, researchers announced that a method they’d proposed may have turned up the first indication of a planet in another galaxy. The data was sitting in the archives of a couple of X-ray telescopes.

Long-distance eclipse

Almost every planet we know about was identified by one of two methods: either by watching a planet’s gravitational influence on the wavelengths of light produced by a star, or by watching the reduction in light as it passes between us and its host star. At the moment, we simply don’t have hardware with the resolution needed for these methods to work well with other galaxies, which generally appear as collections of stars so dense that distinguishing one star from another is nearly impossible.