A binary star system with a neutron star has set a world record for the strength of the magnetic field. Scientists took measurements and were stunned by the results – the strength of the magnetic field is at the level of 1.6 billion Tesla (16 trillion Gauss), which exceeds the record of 1 billion Tesla, set in 2020. This figure is about 150 million times higher than the magnetic force in the most powerful MRI machine in the world.
To determine this value, high-energy physicists led by Ling-Da Kong from the Chinese Institute studied the X-ray spectrum of the system, looking for cyclotron absorption lines during a powerful flare of the system in 2017 using the Insight-HXMT space telescope. During the observations, the lines were observed at 146 keV.
Astronomers know that neutron stars have very strong magnetic fields. Some of them are so powerful that they are called magnetars. However, it is not always possible to measure these fields.
Magnetic field strength measurements
The Swift J0243.6+6124 binary system consists of a neutron star and its larger companion. A neutron star orbits its neighbor with a 28-day period. The powerful gravitational field of a neutron star extracts gas from a companion star, forming an accretion disk. The plasma in the disk is influenced by both gravitational and magnetic fields, and matter falls on the surface of the neutron star along the magnetic field lines, emitting X-rays at the same time. The stronger the magnetic field, the more energy X-rays can absorb electrons, so a high energy absorption line provides a measurement of the field near the surface of the star. As neutron stars rotate, these X-rays form pulses that astronomers notice on Earth. This makes it possible to measure the strength of the magnetic field of these powerful objects.
Usually X-ray pulsars are observed in other galaxies. But Swift J0243.6+6124 is the first one found in the Milky Way. Its relative proximity to Earth allowed astronomers to test the hypothesis that the brightness of these objects is a consequence of extreme magnetic fields. The 146 keV absorption line became the proof that astronomers were looking for. Moreover, the 1.6 billion Tesla field turned out to be about 10 times stronger than astronomers estimated using several indirect methods.
According to Astrophysical Journal Letters
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