An article published in the journal “Astronomy & Astrophysics” describes the discovery of the the most energetic pulses ever detected in a pulsar. An international team of scientists used the two MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov) telescopes at the Roque de los Muchachos Observatory on La Palma, Canary Islands, to observe the Crab pulsar.

Pulsars are neutron stars formed from the mass that remains after a star exploded in a supernova and collapsed to occupy a very small volume. The Crab pulsar, also known as PSR B0531+21 or PSR J0534+2200, is young in astronomical terms because the observation of the supernova that generated it together with the nebula surrounding it was recorded in 1054 and it’s “only” about 6,500 light years away from Earth. It has a mass which is about one and half times that of the Sun concentrated in a volume about 10 kilometers of diameter.

The name pulsar derives from the fact that these neutron stars emit very strong energetic pulses rotating around its own axis. The Crab pulsar rotates about 30 times per second and is surrounded by a very strong magnetic field that emits signals at very high energies, up to X-rays and gamma rays. For this feature, pulsars are considered kind of cosmic lighthouses. The particularity of this pulsar is that it reached energy levels much higher than those predicted by existing models.

In 2011, the MAGIC telescopes discovered high-energie electromagnetic emissions, confirmed by another observatory, the American VERITAS (Very Energetic Radiation Imaging Telescope Array System), the most powerful observatory for gamma rays in the northern hemisphere. The photons of the electromagnetic emissions had energies higher than 1 TeV (tera electron volt), even a hundred times higher than the previous measurements of that pulsar.

The study of the pulsar revealed that the beams of gamma ray photons at those high energies arrive at the same time as those in X-rays or radio frequencies. This means that all of the electromagnetic emissions originate from a very small region of the pulsar or that those at higher energies are generated by electrons that somehow keep the memory of lower energies emissions.

In essence, it’s not clear where higher energies emissions are generated because the observations don’t match the current models of pulsar behavior. The MAGIC telescopes, the largest in the world for gamma rays detections, were used for a total of over 300 hours to observe the Crab pulsar yet more data are still needed to understand its behavior. Discovering this anomaly is already a step forward because those events are the ones that allow to improve theoretical models and achieve scientific progress.

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