High Energy Stereoscopic System (H.E.S.S.) is a system of imaging atmospheric Cherenkov telescopes (IACTs) for the investigation of cosmic

gamma ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

s in the

photon energy Photon energy is the energy carried by a single photon. The amount of energy is directly proportional to the photon's electromagnetic frequency and thus, equivalently, is inversely proportional to the wavelength. The higher the photon's frequenc ...

range of 0.03 to 100 TeV. The

acronym An acronym is a type of abbreviation consisting of a phrase whose only pronounced elements are the initial letters or initial sounds of words inside that phrase. Acronyms are often spelled with the initial Letter (alphabet), letter of each wor ...

was chosen in honour of Victor Hess, who was the first to observe

cosmic ray Cosmic rays or astroparticles are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the ...

s. The name also emphasizes two main features of the installation, namely the simultaneous observation of air showers with several telescopes, under different viewing angles, and the combination of telescopes to a large system to increase the effective detection area for gamma rays. H.E.S.S. permits the exploration of gamma-ray sources with intensities at a level of a few thousandth parts of the flux of the

Crab Nebula The Crab Nebula (catalogue designations M1, NGC 1952, Taurus A) is a supernova remnant and pulsar wind nebula in the constellation of Taurus (constellation), Taurus. The common name comes from a drawing that somewhat resembled a crab with arm ...

. H.E.S.S. consists of five telescopes: four with mirrors just under 12 m in diameter, arranged as a square with 120 m sides, and one larger telescope with a 28 m mirror, located at the centre of the array. The four 12 m telescopes began operation in 2004, with the 28 m telescope added as an upgrade (called H.E.S.S. II) in 2012. As with other gamma-ray telescopes, H.E.S.S. observes high energy processes in the universe. Gamma-ray producing sources include

supernova remnant A supernova remnant (SNR) is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, and consists of ejected material expanding from the explosion, and the interstellar mat ...

active galactic nuclei An active galactic nucleus (AGN) is a compact region at the center of a galaxy that emits a significant amount of energy across the electromagnetic spectrum, with characteristics indicating that this luminosity is not produced by the stars. Such e ...

and

pulsar wind nebula A pulsar wind nebula (PWN, plural PWNe), sometimes called a plerion (derived from the Greek "πλήρης", ''pleres'', meaning "full"), is a type of nebula sometimes found inside the shell of a supernova remnant (SNR), powered by winds generate ...

e. It also actively tests unproven theories in physics such as looking for the predicted gamma-ray annihilation signal from WIMP dark matter particles and testing

Lorentz invariance In a relativistic theory of physics, a Lorentz scalar is a scalar expression whose value is invariant under any Lorentz transformation. A Lorentz scalar may be generated from, e.g., the scalar product of vectors, or by contracting tensors. While ...

predictions of

loop quantum gravity Loop quantum gravity (LQG) is a theory of quantum gravity that incorporates matter of the Standard Model into the framework established for the intrinsic quantum gravity case. It is an attempt to develop a quantum theory of gravity based direc ...

. H.E.S.S. is located in the Khomas highlands of

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

near the Gamsberg mountain, an area well known for its excellent optical quality. The first of the four telescopes of Phase I of the H.E.S.S. project went into operation in Summer 2002; all four were operational in December 2003. In 2004 H.E.S.S. was the first IACT experiment to spatially resolve a source of cosmic

s. In 2005, it was announced that H.E.S.S. had detected eight new high-energy gamma ray sources, doubling the known number of such sources. As of 2014, more than 90 sources of teraelectronvolt gamma rays were discovered by H.E.S.S. In 2016, the HESS collaboration reported deep gamma ray observations which show the presence of petaelectronvolt-protons originating from

Sagittarius A* Sagittarius A*, abbreviated as Sgr A* ( ), is the supermassive black hole at the Galactic Center of the Milky Way. Viewed from Earth, it is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south o ...

, the supermassive black hole at the centre of the Milky Way, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt galactic cosmic rays.

References

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External links

High Energy Stereoscopic System Project (H.E.S.S.)
on the internet

* ttp://www.sciencemag.org/cgi/content/abstract/307/5717/1938 ''Science'': A new population of very high energy gamma-ray sources in the Milky Way
''New Scientist'': Number of very high-energy gamma ray sources doubles

Aspera European network portal

HESS experiment
record on

INSPIRE-HEP INSPIRE-HEP is an open access digital library for the field of high energy physics (HEP). It is the successor of the Stanford Physics Information Retrieval System (SPIRES) database, the main literature database for high energy physics since the 1 ...

Gamma-ray telescopes Astronomical observatories in Namibia Particle experiments

See also

References

External links