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Very-high-energy Gamma Ray
Very-high-energy gamma ray (VHEGR) denotes gamma radiation with photon energies of 100 GeV (gigaelectronvolt) to 100 TeV (teraelectronvolt), i.e., 1011 to 1014 electronvolts. This is approximately equal to wavelengths between 10−17 and 10−20 meters, or frequencies of 2 × 1025 to 2 × 1028 Hz. Such energy levels have been detected from emissions from astronomical sources such as some binary star systems containing a compact object. For example, radiation emitted from Cygnus X-3 has been measured at ranges from GeV to exaelectronvolt-levels. Other astronomical sources include BL Lacertae, 3C 66A Markarian 421 and Markarian 501. Various other sources exist that are not associated with known bodies. For example, the H.E.S.S. catalog contained 64 sources in November 2011. Detection Instruments to detect this radiation commonly measure the Cherenkov radiation produced by secondary particles generated from an energetic photon entering the Earth's atmosphere. This method is calle ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The MAGIC Telescope At Night
''The'' () is a grammatical Article (grammar), article in English language, English, denoting persons or things already mentioned, under discussion, implied or otherwise presumed familiar to listeners, readers, or speakers. It is the definite article in English. ''The'' is the Most common words in English, most frequently used word in the English language; studies and analyses of texts have found it to account for seven percent of all printed English-language words. It is derived from gendered articles in Old English which combined in Middle English and now has a single form used with pronouns of any gender. The word can be used with both singular and plural nouns, and with a noun that starts with any letter. This is different from many other languages, which have different forms of the definite article for different genders or numbers. Pronunciation In most dialects, "the" is pronounced as (with the voiced dental fricative followed by a schwa) when followed by a consonant s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cosmic Rays
Cosmic rays 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 Solar System in our own galaxy, and from distant galaxies. Upon impact with Earth's atmosphere, cosmic rays produce showers of secondary particles, some of which reach the surface, although the bulk is deflected off into space by the magnetosphere or the heliosphere. Cosmic rays were discovered by Victor Hess in 1912 in balloon experiments, for which he was awarded the 1936 Nobel Prize in Physics. Direct measurement of cosmic rays, especially at lower energies, has been possible since the launch of the first satellites in the late 1950s. Particle detectors similar to those used in nuclear and high-energy physics are used on satellites and space probes for research into cosmic rays. Data from the Fermi Space Telescope (2013) have been interpreted as evidence ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ultra-high-energy Gamma Ray
Ultra-high-energy gamma rays are gamma rays with photon energies higher than 100 TeV (0.1 PeV). They have a frequency higher than 2.42 × 1028 Hz and a wavelength shorter than 1.24 × 10−20 m. The existence of these rays was confirmed in 2019. In a 18 May 2021 press release, China's Large High Altitude Air Shower Observatory (LHAASO) reported the detection of a dozen ultra-high-energy gamma rays with energies exceeding 1 peta-electron-volt (quadrillion electron-volts or PeV), including one at 1.4 PeV, the highest energy photon ever observed. The authors of the report have named the sources of these PeV gamma rays PeVatrons. Importance Ultra-high-energy gamma rays are of importance because they may reveal the source of cosmic rays. Discounting the relatively weak effect of gravity, they travel in a straight line from their source to an observer. This is unlike cosmic rays which have their direction of travel scrambled by magnetic fields. Sources that produce cosmic rays will ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Attojoule
The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied. It is also the energy dissipated as heat when an electric current of one ampere passes through a resistance of one ohm for one second. It is named after the English physicist James Prescott Joule (1818–1889). Definition In terms of SI base units and in terms of SI derived units with special names, the joule is defined as One joule can also be defined by any of the following: * The work required to move an electric charge of one coulomb through an electrical potential difference of one volt, or one coulomb-volt (C⋅V). This relationship can be used to define the volt. * The work required to produce one watt of power for one second, or one watt-second (W⋅s) (compare kilowatt-hour, which is 3.6 megajoules). This relationship can be ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landau–Pomeranchuk–Migdal Effect
In high-energy physics, the Landau–Pomeranchuk–Migdal effect, also known as the Landau–Pomeranchuk effect and the Pomeranchuk effect, or simply LPM effect, is a reduction of the bremsstrahlung and pair production cross sections at high energies or high matter densities. It is named in honor to Lev Landau, Isaak Pomeranchuk and Arkady Migdal. Overview A high energy particle undergoing multiple soft scatterings from a medium will experience interference effects between adjacent scattering sites. From uncertainty as the longitudinal momentum transfer gets small the particles wavelength will increase, if the wavelength becomes longer than the mean free path in the medium (the average distance between scattering sites) then the scatterings can no longer be treated as independent events, this is the LPM effect. The Bethe–Heitler spectrum for multiple scattering induced radiation assumes that the scatterings are independent, the quantum interference between successive scatterings c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Muon
A muon ( ; from the Greek letter mu (μ) used to represent it) is an elementary particle similar to the electron, with an electric charge of −1 '' e'' and a spin of , but with a much greater mass. It is classified as a lepton. As with other leptons, the muon is not thought to be composed of any simpler particles; that is, it is a fundamental particle. The muon is an unstable subatomic particle with a mean lifetime of , much longer than many other subatomic particles. As with the decay of the non-elementary neutron (with a lifetime around 15 minutes), muon decay is slow (by subatomic standards) because the decay is mediated only by the weak interaction (rather than the more powerful strong interaction or electromagnetic interaction), and because the mass difference between the muon and the set of its decay products is small, providing few kinetic degrees of freedom for decay. Muon decay almost always produces at least three particles, which must include an electron o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extensive Air Shower
An air shower is an extensive (many kilometres wide) cascade of ionized particles and electromagnetic radiation produced in the atmosphere when a ''primary'' cosmic ray (i.e. one of extraterrestrial origin) enters the atmosphere. When a particle, which could be a proton, a nucleus, an electron, a photon, or (rarely) a positron, strikes an atom's nucleus in the air it produces many energetic hadrons. The unstable hadrons decay in the air speedily into other particles and electromagnetic radiation, which are part of the particle shower components. The secondary radiation rains down, including x-rays, muons, protons, antiprotons, alpha particles, pions, electrons, positrons, and neutrons. The dose from cosmic radiation is largely from muons, neutrons, and electrons, with a dose rate that varies in different parts of the world and based largely on the geomagnetic field, altitude, and solar cycle. Airline crews receive more cosmic rays if they routinely work flight routes that take ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chicago Air Shower Array
The Chicago Air Shower Array (CASA) was a significant ultra high high-energy astrophysics experiment operating in the 1990s. It consisted of a very large array of scintillation detectors located at Dugway Proving Grounds in Utah, USA, approximately 80 kilometers southwest of Salt Lake City. The full CASA detector, consisting of 1089 detectors began operating in 1992 in conjunction with a second instrument, the Michigan Muon Array (MIA), under the name CASA-MIA. MIA was made of 2500 square meters of buried muon detectors. At the time of its operation, CASA-MIA was the most sensitive experiment built to date in the study of gamma ray and cosmic ray interactions at energies above 100 TeV (1014 electronvolts). Research topics on data from this experiment covered a wide variety of physics issues, including the search for gamma rays from Galactic sources (especially the Crab Nebula and the X-ray binaries Cygnus X-3 and Hercules X-1) and extragalactic sources (active Galactic nuclei and ga ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VERITAS
Veritas is the name given to the Roman virtue of Honesty, truthfulness, which was considered one of the main virtues any good Roman should possess. The Greek goddess of truth is Aletheia (Ancient Greek language, Ancient Greek: ). The German philosopher Martin Heidegger argues that the truth represented by ''aletheia'' (which essentially means "unconcealment") is different from that represented by ''veritas'', which is linked to a Roman understanding of rightness and finally to a Nietzschean sense of justice and a will to power. In Roman mythology, Veritas (), meaning Truth, is the Goddess of Truth, a daughter of Saturn (mythology), Saturn (called Cronus by the Greeks, the Titan (mythology), Titan of Time, perhaps first by Plutarch), and the mother of Virtus (deity), Virtus. She is also sometimes considered the daughter of Jupiter (mythology), Jupiter (called Zeus by the Greeks), or a creation of Prometheus. The elusive goddess is said to have hidden in the bottom of a holy well. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
La Palma
La Palma (, ), also known as ''La isla bonita'' () and officially San Miguel de La Palma, is the most north-westerly island of the Canary Islands, Spain. La Palma has an area of making it the fifth largest of the eight main Canary Islands. The total population at the end of 2020 was 85,840, of which 15,716 lived in the capital, Santa Cruz de La Palma and about 20,467 in Los Llanos de Aridane. Its highest mountain is the Roque de los Muchachos, at , being second among the peaks of the Canaries only to the peaks of the Teide massif on Tenerife. In 1815, the German geologist Leopold von Buch visited the Canary Islands. It was as a result of his visit to Tenerife, where he visited the Las Cañadas caldera, and then later to La Palma, where he visited the Taburiente caldera, that the Spanish word for cauldron or large cooking pot – "caldera" – was introduced into the geological vocabulary. In the center of the island is the Caldera de Taburiente National Park; one of four nation ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
MAGIC (telescope)
MAGIC (Major Atmospheric Gamma Imaging Cherenkov Telescopes, later renamed to MAGIC Florian Goebel Telescopes) is a system of two IACT, Imaging Atmospheric 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. MAGIC detects particle showers released by 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 was the largest in the world before the construction of High Energy Stereoscopic System, H.E.S.S. II. The first telescope was built in 2004 and operated for five years in standalone mode. A second MAGIC telescope (MAGIC-II), at a distance of 85 m from the first one, started taking data in July 2009. Together they integrate the MAGIC telescope stereoscopic system. MAGIC is sensitive to cosmic gamma rays with photon energy, photon energies between 50 GeV (later lowered to ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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