Pulsar planet

Pulsar planets are planets that are found orbiting pulsars, or rapidly rotating neutron stars. The first such planet to be discovered was around a millisecond pulsar and was the first extrasolar planet to be confirmed as discovered.

Pulsar planets are discovered through pulsar timing measurements, to detect anomalies in the pulsation period. Any bodies orbiting the pulsar will cause regular changes in its pulsation. Since pulsars normally rotate at near-constant speed, any changes can easily be detected with the help of precise timing measurements. The discovery of pulsar planets was unexpected; pulsars or neutron stars have previously gone supernova, and it was thought that any planets orbiting such stars would have been destroyed in the explosion.

In 1991, Andrew G. Lyne announced the first ever pulsar planet discovered around PSR 1829-10. However, this was later retracted, just before the first real pulsar planets were announced.

In 1992, Aleksander Wolszczan and Dale Frail announced the discovery of a multi-planet planetary system around the millisecond pulsar PSR 1257+12. These were the first two extrasolar planets confirmed to be discovered, and thus the first multi-planet extrasolar planetary system discovered, and the first pulsar planets discovered. There was doubt concerning the discovery because of the retraction of the previous pulsar planet, and questions about how pulsars could have planets. However, the planets proved to be real. Two additional planets of lower mass were later discovered by the same technique.

In 2000, the millisecond pulsar PSR B1620-26 was found to have a circumbinary planet (PSR B1620-26 b) that orbits both it and its companion white dwarf, WD B1620-26. This was announced as the oldest planet ever discovered, at 12.6 billion years old. It is currently believed to have originally been the planet of WD B1620-26 before becoming a circumbinary planet, and therefore, while discovered through the pulsar timing method, it did not form the way that PSR B1257+12's planets are thought to have.

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