Astronomers found black hole pairs that shouldn't exist, proving our math for how stars die is fundamentally broken.
April 15, 2026
Original Paper
A Path to Constraints on Common Envelope Ejection in Massive Binaries: Full Evolutionary Reconstruction of Three Black Hole X-ray Binaries
arXiv · 2604.10440
The Takeaway
When two massive stars are close together, they are supposed to go through a 'common envelope' phase where they eject their outer layers to become black holes. But this paper looked at three specific black hole systems and found that the energy required to eject those layers is physically impossible according to our current models—the math simply doesn't add up. It’s as if a car drove 1,000 miles on a single gallon of gas. This 'impossible' result means there is a massive source of energy or a physical process we are completely missing in our understanding of how stars merge. We are going to have to rewrite the textbook on how the most violent objects in the universe are born.
From the abstract
The massive binary common envelope (CE) phase plays a pivotal role in the formation of close black hole/neutron star (BH/NS) binaries, yet significant uncertainties remain in our understanding of this process. In this study, we aim to constrain the massive binary CE phase by systematically reconstructing three observed BH X-ray binaries (BHXBs): GRO J1655-40, SAX J1819.3-2525, and 4U 1543-47. Through comprehensive binary evolution simulations and parametric supernova (SN) modeling, we establish