Atacama Large Millimeter Array (ALMA)
ârast-e bozorg-e milimetri-ye âtâkâmâ (ALMA)
Fr.: Grand réseau millimétrique Atacama
One of the largest ground-based astronomy projects and a major new facility for world astronomy located on the plain of the → Chajnantor Chilean Andes, San Pedro de Atacama, some 5000 m above sea level. ALMA will initially comprise 66 high precision antennas, with the option to expand in the future. There will be an array of fifty 12 m antennas, acting together as an → interferometer to capture → millimeter and → submillimeter wavelengths of 0.3 to 9.6 mm. It will have reconfigurable baselines ranging from 15 m to 18 km. A compact array of 7 m antenna and few 12 m diameter antennas (ACA) will be used to measure the diffuse emission. Resolutions as fine as 0''.005 will be achieved at the highest frequencies. Construction of ALMA started in 2003 and will be completed in 2012. The ALMA project is an international collaboration between Europe, Japan, and North America in cooperation with the Republic of Chile. ALMA is funded in Europe by the → European Southern Observatory (ESO). The first 12 m diameter antenna, built by Mitsubishi Electric Corporation for the National Astronomical Observatory of Japan, was handed over to ESO in 2008. It will shortly be joined by North American and European antennas. ALMA will allow astronomers to study the cool Universe, i.e. the molecular gas and tiny dust grains from which stars, planetary systems, galaxies, and even life are formed.
Atacama the name of a desert, west of the Andes mountains in Chile, covering a 1,000 km strip of land on the Pacific coast of South America; → large; → millimeter; → submillimeter; → array.
Expanded Very Large Array (EVLA)
A → radio interferometer array consisting of 27 25-meter diameter antennas located on the Plains of San Agustin in West-Central New Mexico. EVLA will operate at any frequency between 1.0 and 50 GHz and will have a continuum sensitivity improvement over the → VLA by factors of 5 to 20.The EVLA project is expected to be completed in 2012. See also the EVLA homepage.
Of more than average size, quantity, degree, etc.; of great scope or range.
From O.Fr. large "broad, wide," from L. largus "abundant, copious, plentiful," of unknown origin.
Bozorg "great, large, immense, grand, magnificient;" Mid.Pers. vazurg "great, big, high, lofty;" O.Pers. vazarka- "great;" Av. vazra- "club, mace" (Mod.Pers. gorz "mace"); cf. Skt. vájra- "(Indra's) thunderbolt," vaja- "strength, speed;" L. vigere "be lively, thrive," velox "fast, lively," vegere "to enliven," vigil "watchful, awake;" P.Gmc. *waken (Du. waken; O.H.G. wahhen; Ger. wachen "to be awake;" E. wake); PIE base *weg- "to be strong, be lively."
Large Magellanic Cloud (LMC)
Abr-e Bozorg-e Magellan (#)
Fr.: Grand Nuage de Magellan
The larger of the two Magellanic Cloud galaxies visible in the southern hemisphere at about 22 degrees from the South Celestial Pole. It is approximately on the border between the constellations → Dorado and → Mensa in a region of faint stars. The center of the LMC is approximately RA: 5h 23m 35s, dec: -69° 45' 22''. The LMC shines with a total → apparent visual magnitude of approximately zero. It spans an area of the sky about 9 by 11 degrees, corresponding to about 30,000 → light-years across in the longest dimension, for a distance of some 162,000 light-years. It has a visible mass of about one-tenth that of our own Galaxy (1010 Msun). The LMC and its twin, the → Small Magellanic Cloud, are two of our most prominent Galactic neighbors. The LMC is classified as a disrupted → barred spiral galaxy of type SBm, the prototype of a class of → Magellanic spirals. The galaxy is characterized by a prominent offset → stellar bar located near its center with the dominant → spiral arm to the north with two "embryonic" arms situated to the south. The → metallicity in the LMC is known to be lower than in the solar neighborhood by a factor 2 or more. Based on 20 → eclipsing binary systems, the distance to the LMC is measured to one percent precision to be 49.59±0.09 (statistical) ±0.54 (systematic) kpc (Pietrzynski et al., 2019, Nature 567, 200).
→ large; → Magellanic; → cloud.
Fr.: grand nombre
A → dimensionless number representing the ratio of
various → physical constants. For example:
large number hypothesis
engâre-ye adadhâ-ye bozorg
Fr.: hypothèse des grands nombres
The idea whereby the coincidence of various → large numbers would bear a profound sense as to the nature of physical laws and the Universe. Dirac suggested that the coincidence seen among various large numbers of different nature is not accidental but must point to a hitherto unknown theory linking the quantum mechanical origin of the Universe to the various cosmological parameters. As a consequence, some of the → fundamental constants cannot remain unchanged for ever. According to Dirac's hypothesis, atomic parameters cannot change with time and hence the → gravitational constant should vary inversely with time (G∝ 1/t). Dirac, P. A. M., 1937, Nature 139, 323; 1938, Proc. R. Soc. A165, 199.
→ large; → number; → hypothesis.
large Reynolds number flow
tacân bâ adad-e bozorg-e Reynolds
Fr.: écoulement à grand nombre de Reynolds
A turbulent flow in which viscous forces are negligible compared to nonlinear advection terms, which characterize the variation of fluid quantities. The dynamics becomes generally turbulent when the Reynolds number is high enough. However, the critical Reynolds number for that is not universal, and depends in particular on boundary conditions.
→ large; → Reynolds number; → flow.
Fr.: grande échelle
1) A scale representing measures that significantly override the usual ones of
the same kind.
Large Synoptic Survey Telescope (LSST)
teleskop-e bozorg-e hanvini barâye bardid
Fr.: Grand Télescope d'étude synoptique
Initial name given to → Vera C. Rubin Observatory.
Fr.: structure à grandes échelles
The distribution of galaxies and other forms of mass on large distance scales, covering hundreds of millions of → light-years.
Very Large Array (VLA)
ârast-e besyâr bozorg
Fr.: Very Large Array (VLA)
A radio interferometer consisting of 27 antennas, each 25 m in diameter, in a Y-shaped configuration. It is located about 100 km west of Socorro, New Mexico, and is operated by the United States National Radio Astronomy Observatory. The VLA has the resolution of a single antenna 36 km wide and the sensitivity of a dish 130 m across.
Very Large Baseline Array (VLBA)
ârast bâ pâye-xatt-e besyâr bozorg
Fr.: Very Large Baseline Array (VLBA)
A network of ten 25-m radio telescopes for → very-long-baseline interferometry (VLBI), operated by the U.S. National Radio Astronomy Observatory. Eight of the VLBA telescopes are distributed across the continental United States, while the other two are in Hawaii and the Virgin Islands, giving a maximum baseline of about 8,000 km and a resolution better than a milliarcsecond at its shortest wavelength.
Very Large Telescope (VLT)
tleskop-e besyâr bozorg
Fr.: Très Grand Télescope, VLT
An observing facility consisting of four 8.2 m telescopes, with the combined collecting area of a 16 m mirror, owned and operated by the European Southern Observatory at an altitude of 2635 m at the Paranal Observatory in Chile. The four reflecting unit telescopes are called Antu "Sun" in the language of Chile's indigenous Mapuche people, Kueyen "Moon," Melipal "Southern Cross," and Yepun "Venus." Each unit is equipped with several sophisticated instruments. The light of the individual telescopes can be combined using interferometric techniques to achieve superior resolution. → VLT Interferometer (VLTI). The wavelength range covered by the VLT is extremely wide, ranging from deep ultraviolet to mid-infrared.