Pulsar stars have revealed that the mysterious black holes being detected by our gravity sensors are likely not leftovers from the Big Bang.
April 29, 2026
Original Paper
Constraints on the Primordial Black Hole Abundance using Pulsar Parameter Drifts
arXiv · 2604.22634
The Takeaway
Many scientists believed that the massive black holes we see colliding in deep space were primordial, meaning they formed during the birth of the universe. This study tracked the tiny timing drifts of rotating pulsar stars to see if these ancient black holes were floating around. The data showed far fewer of these objects than the theory predicted. This effectively rules out primordial black holes as the source of the signals we are picking up with our detectors. It forces physicists to look for other explanations for where these massive dark objects came from.
From the abstract
Primordial black holes (PBHs) provide a compelling interpretation for the binary black holes (BBHs) observed by ground-based gravitational-wave (GW) detectors, especially for those BBHs in the theoretical mass gap. In the early Universe, the scalar perturbations required to produce such PBHs inevitably generate scalar-induced GWs (SIGWs). These SIGWs peak in the sub-nanohertz band, and manifest secularly as measurable jerk-like drifts in the second derivative of pulsar spin periods. In this Lett