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.
very late thermal pulse (VLTP)
tape-ye garmâyi-ye besyâr dir
Fr.: flash de l'hélium très tardif
In evolutionary models of → post-asymptotic giant branch stars, the occurrence of the helium shell burning when the star has reached the → white dwarf cooling track. This leads to the possibility of a violent → helium shell flash and expansion on a time-scale of ≤ 10 years. The rapid expansion and prompt change in surface composition observed in → Sakurai's Object are thought to be due to such a very late thermal pulse.
very low-mass star
setâre-ye besyâr kamjerm
Fr.: étoile de très faible masse
very massive star
setâre-ye besyâr porjerm
Fr.: étoile très massive
very small grain (VSG)
dâne-ye besyâr kucak
Fr.: très petit grain
A special type of carbonaceous → interstellar dust grains with a size ranging from 10 to 150 Å and consisting of tens to hundreds of atoms. In contrast to → big grains, VSGs are not in → thermal equilibrium. They can be heated to very high temperatures (~ 1000 K) by the absorption of a single photon. It is thought that VSGs are clusters of → PAH.
very-long-baseline interferometry (VLBI)
andarzanešsanji bâ pâye-xatt-e besyâr bozorg
Fr.: interférométrie à très longue base
A technique in radio interferometry in which the individual telescopes are not directly connected together, but instead make their observations separately with very accurate timings. The data are later sent to a central correlator to be combined. With this technique the individual telescopes can be arbitrarily far apart, and so the technique provides the highest resolution images in astronomy, typically down to a few milliarcseconds.
1) rag (#); 2) âvand
1) A tube or duct, as an artery or vein, containing or conveying
blood or some other body fluid.
M.E., from O.Fr. vessel "container, receptacle; ship," from L.L. vascellum "small vase or urn," also "a ship," alteration of L. vasculum, diminutive of vas "vessel."
1) Rag "blood vessel, vein; lineage, race, stock," from Mid.Pers.
rag, from Proto-Iranian *raha-ka-, from *raha-
"liquid, essence," + suffix -ka-; cf. Av. ranhā-
"name of a mythical stream;" Skt. rása-
"juice (of plants), liquid, essence," rásavant-, rasin-
"juicy;" L. ros "dew;" Lith. ràsa "dew;" O.C.S. rosa "dew."
To oscillate with a continuing periodic change relative to a fixed reference point or state of equilibrium. → oscillate.
From L. vibratus, p.p. of vibrare "to move quickly to and fro, shake" (cf. Lith. wyburiu "to wag the tail," Dan. vippe, Du. wippen "to swing," O.E. wipan "to wipe").
Šividan "to vibrate, move to and fro, to tremble," related to šodan, šow- "to go; to become;" Av. šiyav-, š(ii)auu- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro."
Verbal noun from → vibrate.
Fr.: énergie de vibration, ~ vibratoire
The energy due to the vibration of the molecules making up atoms (→ molecular vibration). A molecule in space can have energies in various forms: → rotational energy, vibrational energy, or electronic energy. These energies of molecules are → quantized and a particular molecule can exist in different rotational and vibrational → energy levels. The molecules can move from one level to another level only by a jump involving a finite amount of energy. → Quantum mechanics predicts that any molecule can never have zero vibrational energy, that is atoms can never be completely at rest relative to each other. The harmonically oscillating molecules can undergo vibrational changes determined by simple selection rules obtained from → Schrödinger equation.
basâmad-e šiveši (#)
Fr.: fréquence de vibration, ~ vibrationnelle
The frequency at which the atoms in a molecule vibrate. The frequencies of → molecular vibrations in diatomic molecules are in the order of 10-12 to 10-14 Hz. In such molecules, the only → vibrational mode available is along the bond. More complicated molecules have many types of vibration and stretching modes.
Fr.: mode de vibration, ~ vibratoire
Any of the ways in which a → molecule vibrates. Each vibrational mode has a different → frequency frequency. The number of vibrational modes of a molecule is determined by the number of atoms in it. The number of vibrational modes for a non-linear molecule is 3N - 6, where N is the number of atoms making up the molecule. For a linear molecule it is 3N - 5.
Fr.: transition vibrationnelle
Fr.: transition vibrationnelle-rotationnelle
A person or thing that suffers harm or death, from another or from some adverse act or circumstance.
M.Fr. victime, from L. victima "sacrificial animal."
Lišé, from Mid.Pers. lyš- / rêš- "to wound, hurt;" Pers. riš, rêš "wound;" Av. raēš- "to get hurt, suffer damage;" cf. Skt. reṣ "to get harmed."
Fr.: période victorienne
A series of 532 years, arising from the cycles of the Sun and Moon multiplied into one another. It was used by the Western churches for many years, in computing the time of Easter, till the → Gregorian calendar was established.
Named after Victorius (a French clergyman), who invented the period about the middle of the 5th century.
1) didâré; 2) didâri
1) (n.) The visual part of a television broadcast.
From L. video "I see," from videre→ vision.
Didâré, didâri, from didâr "vision, sight," verbal noun from didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen").