In 2023 astronomers detected a low-frequency background of gravitational waves. By timing pulsars across the galaxy, they found a pervasive hum likely from merging supermassive black holes. It opened a new, ultralow-frequency window on the cosmos.
Pulsars as detectors
Nature provides the clock. Rapidly spinning neutron stars beat with extreme regularity. Tiny timing shifts betray passing waves.
A galaxy-scale array
The instrument is vast. Dozens of pulsars form a detector light-years across. Coordinated timing reveals the signal.
Black-hole origin
The source is likely massive. Merging supermassive black holes fit the spectrum best. Confirmation is building.
Years of data
Patience was required. The result rests on more than a decade of observation. Long baselines matter.
Multiple teams
Consensus grew. Independent collaborations reported consistent evidence. Agreement strengthens the case.
A new astronomy
The window is fresh. Ultralow-frequency waves probe the largest black holes. The field is just beginning.
The bottom line
Pulsar-timing arrays detected a galaxy-wide gravitational-wave background, likely from supermassive black-hole mergers. Independent teams agreed after a decade of data. It opened ultralow-frequency astronomy.
