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

Same as → true celestial equator.

→ true; → equtor.

The intersection of the → ecliptic with the → true celestial equator for a given epoch. It is derived from the → mean equinox accounting for the → nutation.

→ true; → equinox.

A large circle of the → celestial sphere whose plane is perpendicular to the radius of the Earth through the point. Same as → astronomical horizon. The → visible horizon usually lies lower than the true horizon. See also → dip of the horizon.

→ true; → horizon.

The geographic north defined by the rotational pole of the Earth, as opposed to magnetic north defined by the geomagnetic north pole.

→ true; → north.

The coordinates of an object for a given date, with respect to the true equator and the true equinoxes for the instant of time in question.

→ true; → position.

The → sidereal time with respect to the → true equinox.

→ true; → sidereal; → time.

The Sun as seen in the sky, also referred to as the → apparent Sun; in opposition to → mean Sun.

→ true; → Sun.

A young → massive star cluster in the → Carina Nebula, lying about 10 arcmin to the north-west of → Trumpler 16. It comprises several → O-type stars. In particular, its core contains at least three very early O-type stars; → HD 93129.

From a catalog by Robert J. Trumpler (1886-1956), the Swiss-American astronomer who studied the → open clusters at Lick Observatory (1930). He was the first to produce a definite evidence of the existence of → interstellar reddening, due to → absorption, and to estimate its magnitude.

A → massive star, and the most populous cluster of the → Carina Nebula. It contains several → O-type stars and three known → Wolf-Rayet stars in addition to the famous → LBV star → Eta Carinae. Trumpler 16 is probably older than → Trumpler 14.

→ Trumpler 14.

To shorten by cutting off a part.
Math.: 1) To shorten a number by dropping a digit or digits; e.g. to shorten 3.438 to 3.4.
2) To remove portions of solids falling outside a set of symmetrically placed planes.

From L. truncatus "cut off," p.p. of truncare "to maim, cut off," from truncus "mutilated, cut off."

Kol kardan "to cut off the end of; to dock a tail," from kol "docked, short," variants in a large number of dialects: kola, kalta, kel, kelma, koc, kall, kor, kul in Gilaki, Tâleši, Lori, Malâyeri, Hamedâni, Qâeni, and others, cf. Av. kaurvô- "bald, docked," kaurvôduma- "with a bald tail," kaurvôgaoša- "with bald ears;" cf. Gk. kol(os) "docked" (kolouros "dock-tailed;" L. colurus) + kardan "to do, to make" (Mid.Pers. kardan, O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "makes," cf. Skt. kr- "to do, to make," krnoti "makes," karma "act, deed;" PIE base k^wer- "to do, to make").

The act or process of truncating, as → disk truncation.

Verbal noun from → truncate.

1) The quality of being true, genuine, actual, or factual.
2) Something that is → true as opposed to → false.
3) Logic: The correct corresponding of a → proposition with a → fact. See also → truth value, → partial truth.

M.E. treuthe; O.E. trêowth "faith, faithfulness, fidelity; quality of being true," from triewe, treowe "faithful," → tue, with suffix *-itho-th.

Noun from râstin, → true, + noun suffix -i.

A → total function from → truth values to truth values (a sequence of truth values).

→ truth; → function.

A table with columns and rows that lists the resultant → truth value of the given → sentences for each of the possible combinations of truth values to the simple sentences out of which the given sentences are constructed.

→ truth; → value.

The quality of a logical → proposition (or a formal → symbol) which describes the relation of a proposition to → truth. The traditional → formal logic admits only two contradictory values, → true or → false. In → symbolic logic, more specifically in → polyvalent logics, other truth values are used (such as possible, impossible, undetermined, probable, random, etc.).

→ truth; → value.

A huge wave, caused by undersea earthquakes, volcanic eruptions, or, more rarely, by asteroid or meteoroid impact (as in the case of the K-T extinction).

From Japanese tsunami, from tsu "harbor" + nami "waves."

1) A long hollow cylinder of metal, glass, rubber, or other material used to transport or contain liquids or gases.
2) An electronic device in which electrons operate in a gas or in vacuo inside a closed envelope.

M.E., from M.Fr. tube, from L. tubus "tube, pipe," of unknown origin.

Lulé "tube, pipe; roll," dialectal Lori, Laki lil, Laki lul "wanderer;" Hamadâni lul "spiral, coil."

Same as → flow tube.

→ tube; → tube.

Bundles of lines of electrical intensity into which the vector field of electrical force can be divided. Same as tube of force, field tube.

→ tube; → flux.

The Toucan. A constellation of the southern hemisphere, at approximately 0h right ascension, -65° declination, represented as a toucan, a brightly colored South American bird with a very large, thick bill. Tucana contains the second most prominent → globular cluster in the sky, 47 Tucanae, and the → Small Magellanic Cloud. Abbreviation: Tuc; genitive: Tucanae. The constellation was one of twelve created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman Houtman between 1595 and 1597, and it first appeared in Johann Bayer's Uranometria of 1603.

From Fr., from Portugese tucano, from tucan (onomatopoeia) in the language spoken by the Tupi Indians in Brazil.