AI Insight
This theoretical study explores using future gravitational wave detectors to identify exoplanets orbiting compact binary systems (pairs of neutron stars or black holes) in distant galaxies. The method analyzes the "wobble" in the center-of-mass motion of merging compact objects caused by an orbiting planet, which leaves detectable signatures in gravitational wave signals. The researchers demonstrate that with next-generation detectors like the Einstein Telescope and DECIGO, it may be possible to detect these extragalactic exoplanets and estimate their masses within a factor of order one of their true values for a significant fraction of parameter configurations.
Why it matters
This work opens a completely new avenue for exoplanet discovery beyond our galaxy, extending the search for planets to extragalactic distances for the first time. If successful, this method could reveal planetary systems in environments vastly different from our Milky Way and provide insights into planet formation around extreme compact objects.
Understand the Science
arXiv:2607.09658v1 Announce Type: new
Abstract: Exoplanets are high-value targets for a variety of ground and space-based telescopes. All known exoplanets are Galactic, and a fraction of them orbit compact objects. In this work, we investigate the possibility of detecting extragalactic exoplanets orbiting stellar-mass compact binary coalescences (CBCs), such as binary neutron stars, neutron star-black holes, and binary black holes, using future gravitational wave (GW) detectors, including A+ (LIGO in O5), Einstein Telescope, and DECIGO. We use the technique of reconstructing an external potential’s profile by extracting information about the centre-of-mass (CoM) kinematics of a CBC encoded in the GWs it emits. In this work, the external potential is provided by the circum-CBC exoplanet, and the resulting signature on the GW waveform comes from the “wobble” of the CBC’s CoM around the CBC-exoplanet barycentre. As a proof of principle, we consider a few example CBCs detectable with future detectors and a range of circum-CBC exoplanet parameters in circular and eccentric orbits. We find that for a significant fraction of the range of parameters considered, we can identify the presence of a circum-CBC exoplanet by extracting its mass (up to an unknown orbital inclination angle) within a factor $mathcal{O}(1)$ of its true value, at $68%$ confidence.