Binary neutron star

A compact binary system in which two neutron stars orbit their shared center of mass. Its orbit loses energy through gravitational radiation, often ending in a merger.

Gravitational-wave emission: The production of gravitational waves by accelerating masses, especially when their motion changes the distribution of mass asymmetrically. The stars radiate orbital energy this way, causing their separation to shrink.
GW170817: A gravitational-wave signal from a binary neutron-star merger detected on 17 August 2017. It provided the first direct gravitational-wave observation of a neutron-star merger.
Binary stellar evolution: The evolution of two gravitationally bound stars as their mass exchange and mutual influence alter their lifecycles. Most known systems descend from massive stellar binaries whose evolution shapes both remnants.
Equation of state of neutron stars: A relation describing how pressure, density, and other thermodynamic quantities behave inside neutron-star matter. Merger waveforms and remnants constrain the extreme-density matter relation.
Inspiral: The progressively faster orbital phase in which a compact binary loses energy and its components draw closer. This phase drives a binary neutron star toward merger and sweeps through gravitational-wave detectors’ bands.
PSR B1913+16: A binary pulsar system containing two neutron stars, one of which is observed as a radio pulsar. Its measured orbital decay supplied early evidence for gravitational-wave energy loss.
Core-collapse supernova: The explosive collapse of a massive star’s core after it can no longer support itself against gravity. Each neutron star forms in a supernova, whose impulse can disrupt or preserve the binary.
Standard siren: A gravitational-wave source whose waveform provides a distance estimate, enabling measurement of cosmic expansion when paired with a redshift. A binary neutron-star signal can yield distance independently of the traditional distance ladder.
Neutron star merger: The collision and coalescence of two neutron stars, producing gravitational waves and often electromagnetic radiation. It is the endpoint of orbital decay and a source of heavy elements.
PSR J0737−3039: A double-pulsar system in which both neutron stars are detected as radio pulsars. Its precise timing allows unusually stringent tests of relativistic binary dynamics.

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