Astronomers have spotted the most energetic light observed to date from a pulsar

2023-10-07 08:21:01

Scientists say they have detected the most energetic gamma rays coming from a pulsar, which might challenge our current understanding of these cosmic events.

The energy of these<10−12 m) ce qui correspond à des fréquences supérieures à 30 exahertz (>3×1019 Hz). They can have an energy ranging from a few keV1 to several hundred GeV. The discovery of gamma rays in 1900 is due to Paul Villard, French chemist (1860-1934), who observed this radiation during the deexcitation of an atomic nucleus resulting from a disintegration, this emission process is called gamma radioactivity .” href=” target=”_blank” rel=”noopener”>gamma rays was measured at 20 teraelectronvolts, or 10 times the energy of visible light, according to scientists using the telescope array of the High Energy Stereoscopic System (HESS) en Namibie.

Header image: artistic representation of the Vela pulsar, in the center, and its magnetosphere, the edge of which is marked by the luminous circle. The blue traces moving outward represent the trajectories of the accelerated particles. These produce gamma radiation along the arms of a rotating spiral by colliding with infrared photons emitted into the magnetosphere (in red). (Image credit: Science Communication Lab for DESY)

And pulsar is a type ofneutron starthat is to say the remnant of a star which exploded spectacularly in supernova. Neutron stars are considered pulsars when they spin extremely fast, releasing rotating beams of electromagnetic radiation.

Representation of a neutron star, also called a pulsar, in rapid rotation. (NASA Goddard)

According to NASA, most neutron stars are detected as pulsars because of the regular pulses of radiation they emit. They are sometimes described as “cosmic beacons” because of these regular flashes.

In this recent study, scientists examined the pulsar Vela, which rotates regarding 11 times per second, using the HESS observatory. According to the researchers, this observatory detected a new component of radiation at a much higher energy than previously observed.

Position of Vela in the Milky Way. (NASA/ DOE/ International LAT Team)

Below: the remains still called residual from supernova Vela, imaged in 2022 by the OmegaCAM of the VLT Survey Telescope in Chile. This vestige is located in the constellation Sails. (ESO/VPHAS+ team/Cambridge Astronomical Survey Unit)

According to Professor Christo Venter, of the HESS Collaboration and North West University in South Africa:

This result was approximately 200 times more energetic than any radiation ever previously detected from this object.

This result left the team perplexed, because classical models cannot explain the observations, according to Arache Djannati-Atai, of the French Astroparticles and Cosmology (APC) laboratory, who adds:

This result calls into question our previous knowledge of pulsars and forces us to reconsider the functioning of these natural accelerators. This discovery opens a new observation window for the detection of other pulsars in the tens of teraelectronvolt range with current and future more sensitive gamma-ray telescopes, paving the way for a better understanding of extreme acceleration processes in strongly magnetized astrophysical objects.

Presentation of the discovery by the Deutsches Elektronen-Synchrotron (DESY/ German electron synchrotron):

In August, researchers studying a pulsar located 4,500 light years from Earth discovered its strange behavior. The pulsar, called PSR J1023+0038 or J1023 for short, has been switching from one mode to another for regarding ten years: One in which the star emits high-frequency visible light, ultraviolet light and x-rays, and the other in which it darkens and emits low-frequency radio waves.

Material ejections might explain the mystery of a rapidly varying pulsar

The scientists deduced that, in the low-frequency mode, material falls toward the surface of the pulsar and is pushed outward by its jet. During this process, the material surrounding the star heats up, triggering J1023’s higher frequency mode.

The HESS study published in Nature Astronomy: Discovery of a radiation component from the Vela pulsar reaching 20 teraelectronvolts and presented on the Deutsches Elektronen-Synchrotron website (DESY/ German electron synchrotron): Scientists discover the highest energy gamma-rays ever from a pulsar.

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