86: Extragalactic X-Ray Exoplanet

We've spotted thousands of planets around other stars in our own Milky Way. But when we look at other galaxies, it's mostly impossible to see individual stars — let alone any planets orbiting them. Recently, astronomers spotted what looks suspiciously like a transit event in the signal from a bright x-ray binary system in the whirlpool galaxy. Could it be an exoplanet? Emily runs throuugh all the ways this might *not* be the case, and we're left with a tantalising "well ... maybe”.