Photographer's Note

A backside view of the Cherenkov telescopes situated at the Roque de los Muchachos Observatory on La Palma, one of the Canary Islands, at about 2200 m above sea level.

In workshop is included a frontal view of one of the telescopes.

MAGIC (Major Atmospheric Gamma-ray Imaging Cherenkov Telescope) is a Imaging Atmospheric Cherenkov telescope. It detects particle showers released by cosmic gamma-rays, using the Cherenkov radiation, i.e., faint light radiated by the charged particles in the showers. With a diameter of 17 meters for the reflecting surface, it is the largest in the world.

A second MAGIC telescope (MAGIC 2) at a distance of 85 m from the first one has started taking data in July 2009.

MAGIC is sensitive to cosmic gamma rays with energies between 50 GeV and 30 TeV due to its large mirror; other ground-based gamma-ray telescopes typically observe gamma energies above 2-300 GeV. Satellite-based detectors detect gamma-rays in the energy range from keV up to several GeV).

The goals of the telescope are to detect and study primarily photons coming from:

Accretion of black holes in Active Galactic Nuclei
Supernova remnants
Some unidentified EGRET Sources
Gamma ray bursts
Annihilation of Dark matter

MAGIC has found pulsed gamma-rays at energies higher than 25 GeV coming from the Crab Pulsar. The presence of such high energies indicates that the gamma-ray source is far out in the pulsar's magnetosphere, in contradiction with many models.

MAGIC detected very high energy cosmic rays from the quasar 3c 279, which is 5 billion light years from Earth. This doubles the previous record distance from which very high energy cosmic rays have been detected. The signal indicated that the universe is more transparent then was previously thought based on data from optical and infrared telescopes.

MAGIC did not observe cosmic rays resulting from dark matter decays in the dwarf galaxy Draco. This strengthens the known constraints on dark matter models.

A much more controversial observation is an energy dependence in the speed of light of cosmic rays coming from a short burst of the blazar Markarian 501 on July 9, 2005. Photons with energies between 1.2 and 10 TeV arrived 4 minutes after those in a band between .25 and .6 TeV. The average delay was .030.012 seconds per GeV of energy of the photon. If the relation between the space velocity of a photon and its energy is linear, then this translates into the fractional difference in the speed of light being equal to minus the photon's energy divided by 21017 GeV.

The telescope has the following specifications:

A collecting area of 236 m consisting of 50 cm x 50 cm Aluminium individual reflectors
A lightweight carbon fibre frame
A detector consisting of 396 separate hexagonal photomultiplier detectors in the center
(diameter: 2.54 cm) surrounded by 180 larger photomultiplier detectors (diameter: 3.81 cm).

Data are transferred in analogue form by fibre optic cables
Signal digitization is done via an ADC (analog-digital converter) of frequency 2 GHz
The weight of the whole telescope is 40,000 kg
The reaction time to move to any section of the sky is up to 40 seconds

Physicists from over twenty institutions in Germany, Spain, Italy, Switzerland, Croatia, Finland, Poland, Bulgaria and Armenia collaborate in using MAGIC; the largest groups are at

Institut de Fsica d'Altes Energies (IFAE)
Universitat Autnoma de Barcelona, Spain
Universidad Complutense Madrid,Spain
Max-Planck-Institute for Physics, Munich, Germany
Dipartimento di Fisica and INFN, University of Padua, Italy
Tuorla Observatory Piikki, Finland
Dipartimento di Fisica and INFN, University of Siena, Italy
Dipatimento di Fisica and INFN, University of Udine, Italy
TU Dortmund University, Germany
University of Wrzburg, Germany
Institute for Particle Physics, Zrich, Switzerland
Institute for Nuclear Research and Nuclear Energy, Sofia, Bulgaria
Croatian MAGIC Consortium ( Institute Ruđer Boković, Zagreb; University of Split, Split; University of Rijeka, Rijeka), Croatia

(source : wikipedia)

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Additional Photos by Paul Bulteel (pauloog) Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 1393 W: 77 N: 1882] (11751)
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