Millisecond pulsar

A neutron star that emits pulses of radiation while rotating hundreds of times per second. Most are spun up by accreting matter from a companion star.

Accretion: The growth of a celestial body as it draws in matter from its surroundings. Matter transferred from a companion carries angular momentum that can accelerate the neutron star.
Binary star: A system of two stars bound to each other by gravity. A companion commonly supplies the matter that recycles a neutron star into a millisecond pulsar.
Pulsar timing: The measurement of pulse arrival times to study a pulsar and its surroundings. Stable millisecond-pulsar signals reveal tiny changes in motion, orbit, and propagation.
Normal pulsar: A pulsar rotating more slowly than a millisecond pulsar, usually born in a supernova and gradually losing spin. Its slower rotation and lack of accretion-driven recycling contrast with the usual millisecond-pulsar history.
Angular momentum: A conserved physical quantity measuring rotational motion. Accreted matter spins up the neutron star by transferring angular momentum.
Stellar evolution: The physical changes a star undergoes over its lifetime. The companion’s evolution determines when and how it transfers mass to the neutron star.
Pulsar timing array: A network of precisely timed millisecond pulsars used to detect correlated variations caused by gravitational waves. Millisecond pulsars provide the long-term clocks that make the array possible.
Magnetar: A neutron star powered largely by the decay of an exceptionally strong magnetic field. Magnetars are distinguished by extreme magnetic activity rather than millisecond rotation.
Neutron star: A compact stellar remnant composed mostly of densely packed neutrons. Millisecond pulsars are rapidly rotating neutron stars.
Roche-lobe overflow: Mass transfer that begins when a star expands beyond the region gravitationally bound to it in a binary system. It can feed the accretion that spins up a millisecond pulsar.

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