China’s FAST telescope finds the lightest known neutron-star pair
China’s FAST telescope has identified PSR J1856−0039, a neutron-star pair with a combined mass of 2.488 times the Sun’s and an orbit lasting 2.36 hours. Researchers say its orbital decay matches general relativity’s prediction, making the system a useful test of gravity and a rare window into the physics of dense matter.
Bottom line — The pair is expected to merge in about 82 million years, probably forming a heavier neutron star.
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China Daily and People’s Daily report that the pulsar weighs about 1.30 solar masses and its companion about 1.19.
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Phys.org says researchers observed the system in 17 FAST sessions from 2020 to 2025, measuring the arrival times of 253 pulses.
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The 2.36-hour orbit is the second-shortest known among confirmed double neutron-star systems, according to China Daily.
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Phys.org reports that the team measured three relativistic effects, including the orbit’s gradual shrinkage and the turning of its closest point.
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Han Jinlin told China Daily that only one or two known systems appear promising for measuring frame dragging.
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The researchers plan long-term monitoring to investigate the pulsar’s internal structure; Phys.org says the work could take about 10 years.