The exoplanet detection technique that uses precise variations in radio pulses from neutron stars is pulsar timing.
A pulsar is a rapidly rotating neutron star that emits radio beams like a cosmic lighthouse. Because its pulses arrive with extraordinary regularity, astronomers can measure tiny departures from the predicted arrival times. An orbiting planet makes the pulsar wobble around the system’s common center of mass, changing the signal’s travel time and producing a recognizable timing pattern.
Pulsar timing is exceptionally sensitive. It can reveal planets much less massive than Earth and can also show gravitational interactions between multiple planets. However, pulsars are uncommon, and planets around them are difficult environments for life because of intense radiation.
In 1992, Aleksander Wolszczan and Dale Frail used this method to identify planets around PSR B1257+12, the first confirmed planets found beyond the Solar System. Pulsar timing is not the same as transit photometry: it measures pulse arrival times rather than a dip in a star’s brightness.