Lightest known pair of neutron stars proves Einstein right yet again

Astronomers have discovered the lightest known pair of neutron stars — two ultradense stellar remnants that circle each other every 2 hours, 22 minutes, veering toward an inevitable collision about 82 million years from now.

By timing radio pulses from one of the stars, the researchers detected three subtle effects predicted by Albert Einstein 's general theory of relativity and found that the theory describes the pair's motion to within about 1% — proving the visionary physicist right yet again .

The researchers published their findings Sept.

15 in the journal Physical Review Letters .

Neutron stars are the collapsed cores of massive stars that exploded as supernovas.

Each packs more mass than the sun into a ball roughly 12 miles (20 kilometers) in diameter.

Some, called pulsars, spin rapidly and sweep beams of radio waves across the sky like cosmic lighthouses.

Their rotation is so steady that their pulses work as extraordinarily precise clocks.

Very few pulsars orbit another neutron star.

"There are only 30 such double neutron star systems, and the relativistic effects are very strong if they are in compact orbits," study co-author JinLin Han , an astronomer at the National Astronomical Observatories of the Chinese Academy of Sciences, told Live Science via email.

The first such pair, discovered in 1974 and known as the Hulse-Taylor binary, provided the first evidence for gravitational waves — ripples in space-time predicted by Einstein.

Such waves carry energy away from an orbiting pair, so its orbit should gradually shrink, and the Hulse-Taylor orbit shrank at just the rate Einstein's theory predicted.

Later, the "double pulsar," which completes an orbit every 2.45 hours, matched the predicted rate to within about 0.01%.

Eventually, this shrinking forces such pairs to merge, unleashing gravitational waves like those the Laser Interferometer Gravitational-Wave Observatory and Virgo interferometer picked up in 2017 .