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

The loci of various changes between two → states through which a → thermodynamic system passes during a → thermodynamic process.

→ thermodynamic; → path.

A measure of the energy level of a → thermodynamic system. It represents the amount of → work obtainable when the system undergoes a → change. The main types of thermodynamic potential are: → internal energy, → enthalpy, the → Helmholtz free energy, and the → Gibbs free energy.

→ thermodynamic; → potential.

An ordered set of → equilibrium states undergone by a → thermodynamic system. Thermodynamics processes have various types: → cyclic process, → reversible process, and → irreversible process, → isothermal process, → adiabatic process, → isentropic process.

→ thermodynamic; → process.

A quantity of substance or a working machine which in a well-defined way is set apart from its → environment. The boundary between the system and its surroundings can be real or an imaginary mathematical envelope. A thermodynamic system is not necessarily bound to a predefined geometry. Thermodynamic systems can be divided into three types: → open systems, → closed systems, and → isomated systems.

→ thermodynamic; → system.

A temperature scale, measured in → kelvin (K), that is related to the energy possessed by matter; it was formerly known as → absolute temperature. The zero point on the scale (0 K) is absolute zero. Thermodynamic temperature can be converted to temperature on the → Celsius scale by subtracting 273.15.

→ thermodynamic; → temperature.

A branch of physics concerned with the relations between heat and other forms of energy and how these affect temperature, pressure, volume, mechanical action, and work.

→ thermo-; → dynamics, coined by the Scottish physicist William Thomson (Lord Kelvin, 1824-1907), in 1849.

Of, relating to, or produced by electric phenomena occurring in conjunction with a flow of heat.

→ thermo- + → electric.

A phenomenon occurring when temperature differences exist in an electrical circuit, such as the → Peltier effect, the → Seebeck effect, and the → Thomson effect,

→ thermoelectric; → effect.

The electricity produced by heat or temperature difference in a conductor.

→ thermo- + → electricity.

An instability in the ocean water that occurs when a layer of warm salt water is above a layer of fresh cold water of slightly higher density. In this process the hot salt water cools off and then, after having reached a higher density than the fresh water, sinks down even in the presence of stabilizing temperature gradients. This phenomenon explains the large-scale water movements in the oceans called themohaline circulation. First discussed by Melvin E. Stern (1960, Tellus 12, 172). → thermohaline mixing.

Thermohaline, from → thermo- + haline, from Gk. hals (genitive halos) "salt, sea;" cf. L. sal; O.Ir. salann; Welsh halen; O.C.S. sali "salt;" O.E. sealt; cf. O.N., O.Fris., Goth. salt, Du. zout, Ger. Salz from PIE *sal- "salt."

Garmâšur, from garmâ-→ thermo- + šur "salty" (Mid.Pers. šôr "salty," šorag "salt land;" cf. Skt. ksurá- "razor, sharp knife;" Gk. ksuron "razor;" PIE base *kseu- "to rub, whet").

In stars, an instability phenomenon, reminiscent of the → thermohaline convection in the oceans, that takes place when layers of higher molecular weight occur above a region of lower molecular weight. A situation of heavier material being above lighter gas in a star can occur during the → helium flash when → helium burning does not start in the center but in the shell. Similarly, in → close binary systems it may happen that helium-rich material is transferred to a → main sequence star. Then a helium-rich outer layer is formed and the instability occurs at the interface between that layer and the original stellar material. This process can explain several surface abundance variations in stars. First discussed by S. Kato (1966, Publ. Astron. Soc. Japan 18, 374).

→ thermohaline; → mixing.

A theoretical interpretation for the → X-ray bursts observed toward → low-mass X-ray binary (LMXB) stars. According to models, X-ray bursts are produced on the surface of → neutron stars as a result of violent thermonuclear processes in a → hydrogen or → helium rich → layer. It is the → nuclear energy released in the → fusion of hydrogen and helium to heavier elements (e.g., Ni, Zn, and Se) in the → accreted matter which heats the upper layers of the neutron star so that X-rays are emitted from the surface (see, e.g., Taam, R.E., 1984, AIP Conf. Proc. 115, 263).

→ thermonuclear; → flash.

A nuclear reaction in which two or more atomic nuclei fuse into a single heavier nucleus by a collision of the interacting particles at extremely high temperatures. Chains of thermonuclear reactions, such as the → proton-proton chain and the → CNO cycle, account for the energy radiated from the Sun and more massive stars.

→ thermo- + → nuclear; → reaction.

1) The uncontrolled → fusion of hydrogen into helium.
2) A → thermonuclear reaction process occurring at electron → degenerate conditions in stellar material, such as in → Type Ia supernovae.

→ thermonuclear; → runaway.

Vâžireš, → reaction; garmâhaste-yi, → thermonuclear; legâm gosixté literally "rampant, unrestrained," from legâm "bridle, rein" + gosixté "broken off, torn away," p.p. of gosixtan "to tear away, to break off."

Same as → type Ia supernova

→ thermonuclear; → supernova.

The region of the upper atmosphere in which temperature increases continuously with height, starting at roughly 100 km. The thermosphere includes the exosphere and most of the ionosphere.

→ thermo-; → sphere.

A device for maintaining a system at constant temperature by automatically terminating or restoring the heating or cooling source. It consists of a temperature sensing instrument connected to a switching device. The sensing device is often a bimetallic strip which triggers a simple electric switch.

→ thermo- + → -stat.

1) A controlled and structured list of terms or descriptors usually with a cross-reference system used in subject analysis and information retrieval in a particular field.
2) More generally, a work that lists words arranged and grouped according to their semantic similarities, including synonyms and sometimes antonyms. This is different from the dictionary, which contains definitions and pronunciations. The first major work of this kind in English is Peter Mark Roget's Thesaurus of English words and phrases, Classified and Arranged so as to Facilitate the Expression of Ideas (1852).

From L. thesaurus "treasury, treasure," from Gk.  thesauros  "treasure, treasury, storehouse," from root of  tithenai "to put, to place," → thesis.

Vâžganj, from vâž, → word, + ganj "treasure," from Mid.Pers. ganj "treasure."

1) A proposition put forward for consideration, especially one to be discussed and proved or to be maintained against objections.
Philo.: The first of three stages in Hegelian dialectic; the inevitable transition of thought, by contradiction and reconciliation, from an initial conviction to its opposite and then to a new, higher conception that involves but transcends both of them. → antithesis; → synthesis.
2) A dissertation based on original research, especially as work toward an academic degree.

M.E., from L., from Gk. thesis "a proposition; a setting down, something set down," from root of tithenai "to place, put, set," cognate with Pers. dâdan "to give," as below.

1) Dâyan "giving, setting down," from O.Pers./Av. dā- "to give, grant, put," dadāiti "he gives;" Mid.Pers./Mod.Pers. dâdan "to give; to put" (cf. Skt. dadáti "he gives;" Gk. tithenai "to place, put, set," didomi "I give;" L. dare "to give, offer;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do;" PIE base *dhe- "to put, to do") + -y- epenthetic vowel + -an noun/adjective suffix appearing in many words (such as rowzan, mihan, barzan, rasan, barzan, rowšan).
2) Dâyan-nâme, from dâyan "thesis" + nâme "diploma, letter" (Mid.Pers. nâmag "book, letter, inscription," from O.Pers./Av. nāman- "name;" cf. Skt. nama-; Gk. onoma, onuma; L. nomen; PIE *nomen-).
Pâyân-nâme, literally "ending, final diploma," from pâyân "end," → terminal + nâme.

The proper name of the → extrasolar planet  → Pollux b.

In Greek and Roman mythology, Thestias was the patronym of Leda, → Pollux's mother.