Two neutron stars spiral closer and collide. The result: a gravitational wave, a ripple in spacetime, a short gamma-ray burst, and a faint glow astronomers call a kilonova. But sometimes the signal passes by a massive galaxy. Its gravity acts like a lens: bending the path of light and gravitational waves, creating an echo — a repeated or amplified image.
The authors calculated how often future observatories will catch such lensed events. Gamma-ray telescopes, even with ten times the sensitivity of current ones, will see only one burst per decade — about 0.1 events per year. That's a tiny fraction of all lensed gravitational waves. But a telescope like RST (the Nancy Grace Roman Space Telescope, named after Nancy Grace Roman) could spot a kilonova in infrared light up to 0.5–0.6 times per year. And an X-ray observatory like ATHENA might catch up to five such events over a decade.
This approach turns every lensed merger into a mini-laboratory. Even rare events promise precise measurements if you know where to look. The scientists proposed a strategy: first catch the gravitational wave with detectors like Cosmic Explorer and Einstein Telescope, then point telescopes at known lensing galaxies in the same patch of sky. This boosts the chances of seeing a faint kilonova to 15–30% of cases.
A kilonova shines a thousand times brighter than a typical nova, but a hundred times fainter than a supernova, and fades within days. Without precise pointing, finding one is nearly impossible.
In the story 'Light of a Distant Earth,' astronomers catch a gravity-distorted signal from an alien civilization, but there the lens acts like a funhouse mirror, whereas here it's a precision instrument.