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

Same as → mid-infrared.

→ middle; → infrared.

A lunar → impact crater that is located in the southern part of the Moon's near side. Latitude: 41.0°S, longitude: 0.2°E, diameter: 52 km, depth: 3.35 km.

Named after the Iranian mathematician and astronomer Nasireddin Tusi (1201-1274), → Nasireddin couple.

A theorem put forward by the 13th century Persian mathematician and astronomer Nasireddin Tusi to generate linear motion from a combination of circular motions, and thus improve the geocentric model of Ptolemy. A circle of radius R rotates inside a circle of radius 2R. The smaller circle rotates at twice the speed of the larger one and in opposite direction. The initial tangent point will travel in linear motion back and forth along the diameter of the larger circle. A particular case of → hypocycloid curves.

Named for Nasireddin Tusi (1201-1274), director of Marâgha observatory who created the Ilkhani zij; → couple.

That region of the → electromagnetic spectrum covering shorter infrared wavelengths. It contains the → infrared windows between about 0.8 and 8 → microns, but the longer wavelength limit is not well defined. See also: → infrared radiation, → mid-infrared, → far-infrared, → submillimeter radiation.

→ near; → infrared.

A large area of the north polar region of Mars which is covered with alternating layers of water ice and dust. → South Polar Layered Deposits.

→ north; → polar; → layer; → deposit.

Preliminary reduction of observational data at a telescope simultaneously with their acquisition.

→ on-line; → reduction.

Characterized by → order; arranged according to a rule. → ordered tree.

→ order + -ed.

In → graph theory, a → tree in which the → children of each → vertex are ordered.

→ ordered; → tree.

1) Act of plundering or robbing; predatory behavior.
2) The preying of one animal on others.

Verbal noun, → prey.

Zoology: Any organism that exists by preying upon other organisms (Dictionary.com).

Agent noun from → prey.

1) Of, or relating to a predator.
2) Living by preying on other living animals.

Agent noun from → prey.

1a) Grammar: The part of a → sentence or → clause stating something about the → subject and usually consisting of a → verb. For example, in the sentence "The man opened the door," the subject is "the man" and the predicate is "opened the door."
1b) Logic: Something which is affirmed or denied concerning the subject in a → proposition.

1c) Math.: A → function whose values are statements about n-tuples of objects forming the values of its → arguments. For n =1 a predicate is called a "property" , for n> 1 a → relation; propositions may be regarded as zero-place predicates (encyclopediaofmath.org).
2a) To state, affirm, or assert (something) about the subject of a proposition.
2b) To make (a term, expression, etc.) the predicate of a proposition.

M.E., from M.Fr. predicat, from L. praedicatus "declared, proclaimed," p.p. of praedicare, from prae "beforehand," → pre-, + dicare "proclame," from stem of dicere "to speak, to say," from PIE root *deik- "to point out, to show," cognate with Pers. dis, → form, and andišidan, → think.

Farâsan from farâ- "before; toward, along; above, upon, over," → pro-, + san Proto-Ir. *sanh- "to declare, explain," related to soxan, → speech and pâsox, → response, sahân, → sentence.

The generic term for systems of → formal logic like → first-order logic and → second-order logic. Predicate logic contains → variables which can be quantified (→ quantify, → quantification).

→ predicate; → logic.

In a → formal language, a letter used to describe a → predicate or → relation. Also called → relation symbol.

→ predicate; → symbol.

That part of the electromagnetic spectrum, with a wavelength between 610 and 780 nm, that produces the impression of a variety of colors resembling that of blood.

M.E. red, from O.E. read (cf. Dan. rød, M.Du. root, Ger. rot), from PIE base *reudh- (cf. Av. raoidita- "red, reddish;" Skt. rudhirá- "red, bloody;" L. ruber "red;" Gk. erythros "red").

Sorx "red" (variants Tâleši sər, Kurd. sûr), from Mid.Pers. suxr "red;" O.Pers. θuxra-; Av. suxra- "red, of fire-color;" Ossetic syrx, surx "red;" cf. Skt. śukrá- "clear, pure, bright."

A concentration, on the → horizontal branch, of → red giant stars that roughly have the same intrinsic brightness. These core → helium burning stars are the metal rich equivalents of the better known → horizontal branch stars. Theoretical models predict that their absolute luminosity only weakly depends on their age and chemical composition.

→ red; → clump.

A star on the → horizontal branch which results from the evolution of a → red giant with an initial mass of ~ 1 Msun.

→ red; → clump; → star.

A small, cool, very faint, main sequence star whose surface temperature is under about 3500 K. Red dwarfs generally have masses of less than one-third that of the Sun. In the neighbourhood of the Sun the majority of stars are red dwarfs.

→ red; → dwarf.

A certain star of spectral type K or later that occupies the upper right portion of the → H-R diagram. Red giants are evolved stars that have exhausted their hydrogen fuel in the core. They may have a → luminosity up to 1000 times greater than → main sequence stars of the same → spectral type. Red giants belong to the → luminosity class III or II (bright giants). They are luminous because of their great size, but have a relatively low surface temperature. All normal stars are expected to pass eventually through a red-giant phase as a consequence of stellar evolution. When a main sequence star has converted approximately 10% of its hydrogen to helium, nuclear reactions in the core stop (→ Schönberg-Chandrasekhar limit). The → hydrostatic equilibrium is no longer maintained, and the core contracts while the outer layers expand and cool. This process produces the low surface temperature and large size (from 10 to 100 times that of the Sun) that characterize the red giant. In the core the temperature continues to rise. When it approaches 100,000,000 K helium will begin to fuse into carbon. → helium flash. Prominent bright red giants in the night sky include → Aldebaran and → Arcturus.

→ red; → giant.

The evolutionary path of a star that has exhausted its available hydrogen content in the core, between the → main-sequence turnoff and the → helium flash.

→ red giant; → branch.