An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

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; → large; → telescope.

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; → late; → thermal; → pulse.

A star with a typical mass of one-hundredth of the mass of the Sun (→ solar mass) and a luminosity of about one-millionth that of the Sun (→ solar luminosity). Same as → brown dwarf.

→ very; → low; → mass; → star.

A star of mass around 100 → solar masses. See also: → supermassive star, → massive star, → canonical upper limit.

→ very; → massive; → star.

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; → small; → grain.

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.

→ very; → large; → baseline; → interferometry.

1) A tube or duct, as an artery or vein, containing or conveying blood or some other body fluid.
2) Botany: A duct formed in the xylem, composed of connected cells that have lost their intervening partitions, that conducts water and mineral nutrients (Dictionary.com).

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."
2) Âvand "vessel," contraction of âbvand, literally "water utensil," from âb, → water, + vand "vessel, vase, cup," from bastan "to bind, shut," → shutter.

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."

1) The act of vibrating. The state of being vibrated.
2) A continuing → periodic  → oscillation relative to a fixed reference point or → equilibrium state.

Verbal noun from → vibrate.

Of or pertaining to → vibration. → vibrational mode.

→ vibration; → -al.

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.

→ vibrational; → energy.

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.

→ vibrational; → frequency.

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.

→ vibrational; → mode.

A transition between two → quantized  → levels of a → molecule that have different vibrational energies.

→ vibrational; → transition.

A slight change in the → energy level of a → molecule due to → vibrational transition and/or → rotational transition.

→ vibrational; → rotational; → transition.

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."

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) (n.) The visual part of a television broadcast.
Something that has been recorded on videotape, especially a movie or music performance.
2) (adj.) Of or pertaining to the electronic apparatus for producing the television picture.

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").

A → lunisolar calendar used now in Vietnam mainly for determining seasonal holidays and cultural events. It is in fact the → Chinese calendar computed for Hanoi. It has 12 months of 29 or 30 days each (→ synodic month) and the year totals 355 days. The → lunar year is therefore 11 days shorter than its solar counterpart. To keep up with the solar pace, every 19 years seven extra months are added to the calendar. In practice, approximately every third year an → embolismic month is included. The New Year, called Tet, begins at the second → new moon after the → winter solstice. The Vietnamese calendar has some minor differences with the Chinese calendar. For example, it uses the cat and buffalo instead of the Chinese rabbit and cow respectively in the → zodiac.

From Vietnam "Viets of the South," from Viet the people's name + nam "south;" → lunar; → calendar.

1) An instance of seeing or beholding; visual inspection.
2) Sight; vision (Dictionary.com).

M.E. v(i)ewe, from M.Fr. veue "sight," from V.L. *viduta, from *vidutus, from L. visus, p.p. of videre "to see," → vision.

Did, → vision.