A pair of neutron stars is like two heavy bowling balls slowly spiraling toward each other. They are born together from a binary system of massive stars, but it can take hundreds of millions of years before they finally collide. When they do, a short gamma-ray burst erupts — a brilliant explosion visible across half the universe.
Astronomers gathered a large collection of such flashes and tried to figure out how long it typically takes from a pair's birth to its demise. Earlier estimates suggested an average of several billion years — almost the age of Earth. The new analysis shows that pairs usually merge much faster: tens to hundreds of millions of years. The waiting time is at most 350 million years.
Why were previous estimates so large? The error lay in how we account for which bursts we can actually see. Telescopes only catch the brightest events, missing the faint ones. If you ignore this 'blindness,' the merger time gets artificially stretched. Correcting for this selection effect brought the numbers back into line.
Now astronomers can better predict how often neutron stars collide in the universe, and thus prepare more effectively to observe these events, and to search for the gravitational waves they generate.
as written by the authors arXiv:2601.03861
Short gamma-ray bursts (SGRBs) are thought to be primarily associated with binary neutron star (BNS) mergers. The SGRB population can therefore be scrutinized for signatures of the delay time between the formation of the progenitor massive star binary and the eventual merger, which could produce an evolution of the cosmic rate density of such events whose shape departs from that of the cosmic star formation history. We therefore studied a large sample of SGRBs within a hierarchical Bayesian framework, with a particular focus on the delay time distribution (DTD) of the population. Following previous studies, we modelled the DTD either as a power-law with a minimum time delay or as a log-normal function. We considered two models for the intrinsic SGRB luminosity distribution: an empirical luminosity function with a doubly broken power-law shape and another based on a quasi-universal structured jet model. Regardless of the chosen parametrization, we found average time delays of $$10\lesssim \langle \tau_\mathrm{d}\mathrm\rangle/\mathrm{Myr}\lesssim 900$$ and a minimum delay time of $$\tau_\mathrm{d,min}\lesssim 350\,\mathrm{Myr}$$, in contrast with previous studies that found long delay times of a few gigayears. We demonstrate that the cause of the longer inferred time delays in past studies most likely resides in an incorrect treatment of selection effects
Neutron star mergers are the only place in nature where gold is forged: the collision ejects so many heavy elements that they could make up several Earth-sized planets.