Neutron stars have the strongest magnetic fields in the universe, and the only way to measure their surface magnetic field directly is to observe the cyclotron absorption lines in their X-ray energy spectra. The Insight-HXMT team has recently discovered a cyclotron absorption line with an energy of 146 keV in the neutron star X-ray binary Swift J0243.6+6124, corresponding to a surface magnetic field of more than 1.6 billion Tesla. After direct measurement of the strongest magnetic field in the universe at about 1 billion Tesla in 2020, the world records for the highest energy cyclotron absorption line and direct measurement of the strongest magnetic field in the universe have been broken.
