Scientists using the HESS Observatory in Namibia detected the highest energy gamma rays coming from a dead star called a pulsar. The energy of these gamma rays is 20 teraelectron volts, or about 10 trillion times the energy of visible light. As reported by an international group in the journal Nature AstronomyThis observation is difficult to reconcile with the theory of the generation of such pulsed gamma rays.

Pulsars are the dead remains of stars that explode spectacularly in supernovae. The explosions leave behind a small, dead star only 20 kilometers in diameter, spinning extremely fast and with a huge magnetic field.

HESS scientist Emma explains: “These dead stars are made up almost entirely of neutrons and are incredibly dense: a teaspoon of the material inside them has a mass of more than five billion tonnes, or about 900 times the mass of the Great Pyramid of Giza.” The co-author of the publication, Onja Wilhelmi, works at DESY.

Pulsars emit rotating beams of electromagnetic radiation similar to cosmic signatures. If its rays pass through our solar system, we will see bursts of radiation at regular intervals. These flashes, also called radiation pulses, can be looked for in different energy ranges of the electromagnetic spectrum.

Scientists believe that the source of this radiation is fast electrons that form in the pulsar’s magnetosphere and accelerate, moving towards its surroundings. The magnetosphere consists of plasma and electromagnetic fields that surround the star and rotate with it.

“During their journey outward, the electrons gain energy and release it in the form of observable beams of radiation,” says Bronek Rudak, from the Nicolaus Copernicus Center for Astronomy (CAMK PAN) in Poland and one of the co-authors.

Located in the constellation Vela (Ship’s Sail) in the southern sky, the Vela pulsar is the brightest pulsar in the radio range of the electromagnetic spectrum and the brightest persistent source of cosmic gamma rays in the giga-electronvolt (GeV) range. . . It rotates approximately eleven times per second. However, at higher than a few GeV its radiation stops abruptly, probably because the electrons reach the end of the pulsar’s magnetosphere and leave it.

But that’s not the end of the story: deep observations with HESS have now revealed a new component of radiation with even more energy, with energies up to tens of teraelectronvolts (TeV).

“This is approximately 200 times more energy than any radiation detected to date from this object,” says co-author Christo Venter of Northwestern University in South Africa. This very high-energy component occurs in the same phase ranges as that observed in the GeV range. To reach these energies, however, electrons may need to travel farther from the magnetosphere, but the spin radiation pattern must remain the same.

“This result challenges our previous knowledge of pulsars and requires a rethinking of how these natural accelerators work,” says Arash Giannati-Atai of the Astroparticle and Cosmology (APC) Laboratory in France, who led the study.

“The traditional scheme, in which particles are accelerated along magnetic field lines inside or slightly outside the magnetosphere, cannot adequately explain our observations. Perhaps we observe particle acceleration due to a process called the magnetic reconnection process outside the light cylinder, which still somehow maintains its spin pattern? But even this scenario is “There are difficulties in explaining how such extreme radiation occurs.”

Whatever the explanation, the Vela pulsar, along with its other high values, now officially holds the record as the most energetic gamma-ray pulsar ever detected.

“This discovery opens a new observation window for detecting other pulsars in the tens of teraelectronvolt range with current and future more sensitive gamma-ray telescopes, thus paving the way for a better understanding of hyperacceleration processes in strongly magnetized astrophysical objects,” says Giannati-Atai. Source