Chinese astronomers find lightest known binary neutron star system, testing Einstein's gravity
A team in China discovered PSR J1856-0039, the lowest-mass binary neutron-star pair recorded, offering a new laboratory for general-relativity tests.
Chinese astronomers, led by Han Jinlin at the National Astronomical Observatories, used the Five-Hundred-Meter Aperture Spherical Telescope (FAST) to uncover PSR J1856-0039, the lightest binary neutron-star system yet observed, with a combined mass of roughly 2.488 solar masses. The system consists of a rapidly rotating pulsar (23.4 ms spin) and a companion weighing about 1.19 solar masses, orbiting each other every 2.36 hours.
Measurements of the pulsar’s pulse arrival one outlet reveal orbital decay at a rate of 1.28 × 10⁻¹² s s⁻¹, periastron precession of about 17.6 degrees per year, and an Einstein delay, all aligning with Einstein’s general-relativity predictions to within 1 %. These findings provide a stringent test of gravity in extreme conditions and may improve models of neutron-star interiors, supernova mechanisms, and the synthesis of heavy elements. Ongoing observations could also enable future probes of frame-dragging effects such as the Lense-Thirring precession.
Why it matters
The discovery offers a precise new test of Einstein's gravity and insights into neutron-star physics and heavy-element formation.
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