The gravitational-wave detection of exoplanets orbiting white dwarf binaries using LISA

So far, around 4,000 exoplanets have been discovered orbiting a large variety of stars. Owing to the sensitivity limits of the currently used detection techniques, these planets populate zones restricted either to the solar neighbourhood or towards the galactic bulge. This selection problem prevents us from unveiling the true galactic planetary population and is not set to change for the next two decades. Here, we present a detection method that overcomes this issue and that will allow us to detect massive exoplanets using gravitational-wave astronomy. We show that the Laser Interferometer Space Antenna (LISA) mission can characterize new circumbinary exoplanets orbiting white dwarf binaries everywhere in our Galaxy—a population of exoplanets so far completely unprobed—as well as detecting extragalactic bound exoplanets in the Magellanic Clouds. Such a method is not limited by stellar activity and, in extremely favourable cases, will allow LISA to detect planets down to 50 Earth masses.