High Energy Stereoscopic System
Encyclopedia
IACT
The IACT or Imaging Atmospheric Cherenkov Technique is the method whereby very high energy gamma-ray photons in the 50 GeV to 50 TeV range can be detected by ground based telescopes. There are currently four major ground based telescopes including CANGAROO III, MAGIC, HESS and VERITAS...
) for the investigation of cosmic gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
s in the 100 GeV and TeV energy range. The acronym was chosen in honour of Victor Hess, who was the first to observe cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s.
The name also emphasizes two main features of the currently-operating 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
Crab Nebula
The Crab Nebula is a supernova remnant and pulsar wind nebula in the constellation of Taurus...
.
As with other gamma-ray telescopes, H.E.S.S. observes high energy processes in the universe. Gamma-ray producing sources include Supernova Remnants
Supernova remnant
A supernova remnant 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 material it sweeps up and shocks along the way.There are two...
, Active Galactic Nucleii
Active galactic nucleus
An active galactic nucleus is a compact region at the centre of a galaxy that has a much higher than normal luminosity over at least some portion, and possibly all, of the electromagnetic spectrum. Such excess emission has been observed in the radio, infrared, optical, ultra-violet, X-ray and...
and Pulsar Wind Nebulae
Pulsar wind nebula
A pulsar wind nebula is a nebula powered by the pulsar wind of a pulsar. At the early stages of their evolution, pulsar wind nebulae are often found inside the shells of supernova remnants...
. 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 predictions of Loop Quantum Gravity
Loop quantum gravity
Loop quantum gravity , also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the theories of quantum mechanics and general relativity...
.
H.E.S.S. is located on the Cranz family farm, Göllschau, in Namibia
Namibia
Namibia, officially the Republic of Namibia , is a country in southern Africa whose western border is the Atlantic Ocean. It shares land borders with Angola and Zambia to the north, Botswana to the east and South Africa to the south and east. It gained independence from South Africa on 21 March...
, near the Gamsberg
Gamsberg
The Gamsberg is a mountain in the Appenzell Alps, overlooking the region of Walenstadt in the canton of St. Gallen. Located in the Alvier group it is the culminating point of the range lying between Lake Walenstadt and Toggenburg....
, 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 gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
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 September 2011, there are 62 sources in the HESS catalogue.
External links
- High Energy Stereoscopic System Project (H.E.S.S.) on the internet
- Nature: High energy particle acceleration in the shell of a supernova remnant
- 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