How does pulsar timing detect extrasolar planets?

Pulsar timing detects extrasolar planets by measuring the arrival times of the highly regular radio pulses emitted by a pulsar—a rapidly rotating neutron star.12

Because pulsars act as extremely precise cosmic clocks, any planet orbiting the pulsar exerts a gravitational tug on it, causing the pulsar to wobble. This motion changes the distance between the pulsar and the telescope on Earth, which in turn causes periodic variations in the arrival times of the pulses. By analyzing these timing residuals, astronomers can identify the presence of orbiting bodies and determine their orbital characteristics.1234

This technique is remarkably sensitive; while it is difficult to detect small planets around normal stars, pulsar timing can reveal planets with masses as small as that of Earth’s Moon. The first extrasolar planets ever discovered were found in 1992 around the pulsar PSR 1257+12 using this method at the Arecibo Observatory.245