About 24,000 light-years from Earth in the constellation Cassiopeia, astronomers have discovered a neutron star, the existence of which cannot be explained by any of the current theories. The fact is that the star throws out jets (very powerful plasma streams moving at an incredible speed), but at the same time it has a very strong magnetic field. According to modern theories, the ejection of jets from neutron stars is possible only if the strength of their magnetic field is 1000 times less than that of the discovered one. The discovery of scientists was described by the journal Nature.
When the life cycle of stars by a mass several times the mass of the Sun comes to an end, they explode into supernovae, leaving behind neutron stars. These stars are distinguished by an extreme degree of density and a very powerful force of gravity, while having a very small radius - about 10-20 kilometers. Neutron stars, like black holes, are capable of emitting jets - powerful streams of particles accelerated almost to the speed of light. Previously, it was believed that neutron stars with a very strong magnetic field cannot create jets, but the observation of astronomers led by Van den Einden of the University of Amsterdam in the framework of the ICRAR project using the VLA telescope shows that this opinion turned out to be erroneous.
The object of the scientists' study was the star Swift J0243.6 + 6124, discovered in October 2017 by the Swift space telescope. It is part of a binary system, slowly rotates and pulls on the material of another companion star, according to researchers, the size of the sun much larger than it. Moreover, the strength of its magnetic field is 10 trillion times higher than that of our star.
While observing the object with the VLA telescope, scientists discovered that during pulsations, not only X-rays, but also radio emission are emitted from the star. In addition, the brightness of the system in the radio range began to weaken, when the maximum X-ray emission was reached, and then it decreased. This behavior is usually observed in systems with a jet.
Modern theories suggest that a stream of particles accelerated to high speeds is triggered by a magnetic field in the inner parts of the accretion disk. However, with a very strong magnetic field of the star, this field will suppress the creation of a jet, preventing disk matter from reaching the surface of the star. Nevertheless, the observations of scientists indicate that there are probably other mechanisms for the formation of jets. According to one of the assumptions, the formation of plasma streams may depend on the rotation of the neutron star, and not on the strength of the magnetic field in the region of the accretion disk, as is typical for other systems with neutron stars. Scientists believe that slowly rotating neutron stars will have a weaker jet. At least, judging by the observational data, such a feature is observed in the Swift J0243.6 + 6124 system.
According to the researchers, the neutron star Swift J0243.6 + 6124 may represent a whole class of similar objects. However, their radio emissions are too weak to be detected by today's scientific instruments. Scientists believe that updating the same VLA will allow finding other similar systems and understanding how jets are formed in neutron stars.
Nikolay Khizhnyak
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