Pulsars are a type of neutron star created in a supernova explosion at the end of a massive star’s life. A pulsar is a small object, about 20 kilometers in diameter, that rotates very quickly around its axis and emits a beam of electromagnetic radiation. This radiation can only be observed on Earth when the beam is directed towards Earth. Like a lighthouse, a rotating neutron star scans its beam around its surroundings. With each rotation, as its jet of radiation is directed towards Earth for a moment, astronomers observe a pulse of radiation. Thus we are able to accurately determine the rotation rate of pulsars. Thanks to this, we know that some of them need a few seconds to make a complete revolution, and others make several hundred revolutions in one second.
Although it is difficult to imagine an object with a diameter of 20 kilometers and the mass of the Sun rotating at a rate of several hundred revolutions per second, it has other surprising features.
Scientists studying the Vela pulsar (PSR J0835-4510), which formed in a Type II supernova explosion that occurred 11,000 years ago about 800 light-years away, have now observed that it is emitting surprisingly energetic radiation.
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The high-energy stereoscopic system in Namibia has been used to study a pulsar. Thanks to this instrument, it was possible to determine that the pulsar emits 20 trillion electron volts, which automatically makes it the most active pulsar in history. The results of the observations are described in detail in Scientific material Published in the journal Nature Astronomy. Scientists admit that it is currently difficult for them to explain how a pulsar is able to emit such intense radiation, and therefore it constitutes a kind of stress test for theories describing the evolution of stars.
A pulsar emits radiation as a result of a strong magnetic field that tears charged particles from the surface. Particles extracted in this way are ejected along magnetic field lines from the star’s magnetic poles. As knowledge about pulsars develops, scientists have discovered objects of this type emitting radiation of increasingly higher energies, on the order of a trillion electron volts (Pulsar Kraba, 2016).
In the latest research project, a team of scientists analyzed data collected during 80 hours of observing the pulsar using a network of radio telescopes in Namibia. These instruments look for the glow that arises when high-energy radiation emanating from distant parts of the universe hits particles in Earth’s atmosphere. The data identified 78 highly energetic particles that came from a pulsar about 1,000 light-years away in the constellation Saila. Measurements showed that the energy of these particles is 20 times that of a Crab pulsar.
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So the question arises as to how such energetic electromagnetic radiation is generated. Researchers suspect that the radiation emitted by the pulsar is amplified by collisions with other fast particles, such as electrons. However, the mechanism of this improvement is still unknown.
Either way, this is further evidence supporting the increasingly common belief among scientists that magnetic field lines thousands of kilometers away from the pulsar collide with each other and magnetic reconnection occurs, in which particles are launched at tremendous speeds into interstellar space. The only problem is that the Vela pulsar described above has already reached the limit on the amount of energy that can be produced in this way. If more energetic radiation is discovered soon, a new explanation will have to be sought.
