We just caught two black holes merging in a messy, wobbling orbit, proving they aren't always the perfect, tidy pairs we expected.
March 25, 2026
Original Paper
Impact of eccentricity on the population properties of neutron star - black hole mergers
arXiv · 2603.22461
The Takeaway
Most black hole mergers involve orbits that have settled into perfect circles over millions of years. This discovery of a highly 'eccentric' or oval-shaped merger suggests the black hole was violently kicked into its partner by a third nearby star, revealing a much more crowded and chaotic life story than previously assumed.
From the abstract
We revisit the population properties of neutron star-black hole (NSBH) mergers using low-mass compact binary coalescences reported through GWTC-4. Employing pyEFPE, an inspiral-only waveform model that captures both orbital eccentricity and spin-induced precession, we reanalyse all binary neutron star (BNS) and NSBH events observed via gravitational waves. The BNS systems GW170817 and GW190425 are fully consistent with quasi-circular inspirals, while GW200105 stands out among the NSBH binaries a