Namibian H.e.s.s. Telescope Discovers High Energy Rays

10 Oct 2023

The H.E.S.S. gamma ray telescope stationed near the Gamsberg some 100km west of Windhoek has detected a new component of higher energies from a burnt-out star.

These cosmic gamma quanta rays had an energy of up to 20 tera-electron volts (TeV).
They come from a pulsar, a burnt-out, dead star, and are the most energetic gamma rays ever discovered and measured by the H.E.S.S. Telescope.

This was disclosed in the magazine Nature Astronomy on 05 October 2023.

"This is about 200 times more energetic than all the radiation that has previously been measured from this object," says Christo Venter from the North-West University in South Africa, who was involved in the project.

The radiation recorded has around ten trillion times as much energy as visible light. “The observation is difficult to reconcile with the current theory for the generation of such pulsed gamma radiation,” said a press release from the German Electron Synchrotron (DESY) on Friday.

The H.E.S.S. Telescope array near Windhoek.
Photo: H.E.S.S. Collaboration, Stefan Schwarzburg.


Pulsars are the remnants of stars that have exploded spectacularly in what is called a supernova. The explosion leaves behind a small, dead star, of about 20 km in diameter, that rotates extremely quickly and has an enormous magnetic field, DESY explained.

"These dead stars consist almost entirely of neutrons with incredible density: a teaspoon of their material weighs more than five billion tons, which is about 900 times the weight of the Great Pyramid of Giza," explained H.E.S.S. scientist Emma de Oña Wilhelmi from DESY.

The H.E.S.S. Telescope array in Namibia detected that these incredible fast energy rays come from the Vela pulsar in the southern sky in the constellation “Sails of the Ship”.

Vela is the brightest pulsar in the radio band of the electromagnetic spectrum and the brightest sustained source of cosmic gamma rays in the giga-electron volt (GeV) range. Vela rotates about eleven times per second.

According to the current theory, the radiation comes from fast electrons that are accelerated and deflected by the pulsar's strong magnetic fields.

However, this newly discovered component occurs synchronously with radiation in the GeV range. In order to achieve these enormous energies, the electrons would have to be accelerated more than is actually possible in the magnetosphere. The rhythm of the emission must remain intact, according to DESY and the online publication

Typically, pulsars are expected to emit radiation with energies below tens of gigaelectronvolts (GeV). One gigaelectronvolt is equal to one billion electronvolts.

Vela – it was established - generates the “most energetic gamma rays” ever discovered coming from a pulsar.

"This result challenges our previous knowledge of pulsars and requires a rethinking of the theory of how these natural accelerators work," said Arache Djannati-Atai of the APC Astroparticle and Cosmology laboratory in France, who led the H.E.S.S. research.

Brigitte Weidlich

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