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

The process of removing the → bias from a → flat-field or science → frame. → debias

Verbal noun of → debias.

In → spectroscopy, to → resolve a → blend into its constituent → spectral lines.

Deblend, from → de- + → blend.

Tuham, → blend, + zodudan "to polish, clean," Mid.Pers. uzdātan, Av. uzdā-, from uz-, → ex-, + dā- "make, create."

The process or state of separating or resolving into constituent → spectral lines.

Verbal noun of deblend, from → de- + → blend.

To → increase the → spatial resolution or the clearness of an → image. Same as → sharpen. See also → deconvolve.

Deblur, from → de- + → blur.

Tigidan "to sharpen," from tig "sharp," variants tiz, tež, tej, tij, tiq, Mid.Pers. tigr, têz, têž "sharp," O.Pers. tigra- "pointed," tigra.xauda- "pointed helmet (epithet of Scythians)," Av. tiγra- "pointed," tiγray- "arrow," tiži.arštay- "with the pointed spear," cf. Skt. tikta- "sharp, pungent, bitter," tejas- "sharpness, edge, point or top of a flame;" PIE base *st(e)ig- "to stick; pointed." Cognates in other IE languages: Gk. stizein "to prick, puncture," stigma "mark made by a pointed instrument," L. in-stigare "to goad," O.H.G. stehhan, Ger. stechen "to stab, prick," Du. stecken, O.E. sticca "rod, twig, spoon," E. stick.

The process or state of making an image sharper. → deblur; same as sharpening. → deconvolution.

Verbal noun of → deblur.

The remains of anything broken down or destroyed; rubble; ruins.
Astro.: → debris disk; → orbital debris.
Geology: An accumulation of loose fragments of rock.

From Fr. débris, from M.Fr. débriser "break down, crush," from O.Fr. debrisier, → de- + brisier "to break," from L.L. brisare.

Tifâl, from tif "rubbish, sweepings, debris" + -al relation suffix → -al.

A disk developing around a star after the dissipation of the → protoplanetary disk of gas and dust whose material was used in the formation of planets during the first 10 million years. The resulting debris disk is mainly composed of residual → planetesimals analogous to → asteroids, → comets, and → Kuiper Belt Objects in the Solar System. Their mutual collisions produce observable → dust emission in a belt encompassing the planetary system.

→ debris; → disk.

A → unit of electric → dipole moments, equal to 10^-18 → CGS units or 3.336 x 10^-30 → coulomb meter.

After Peter Joseph Wilhelm Debye (1884-1966), Dutch-born American, who made important studies in the conductivity of electricity by salt solutions and in the heat capacity of solids. He received the 1936 Nobel Prize in chemistry for his work on the structure of molecules.

The → Debye model at → low  → temperatures, where the → specific heat is proportional to the cube of the → absolute temperature, i.e. C_V ∝ T³.

→ debye; → law.

A characteristic length scale in a → plasma, determined by the temperature and number density of the charged particles. The Debye length (in cm) is given by the expression: λ_D = 743(T_e/n_e)^1/2, where T_e is the electron temperature in → electron-volts and n_e is the electron density in cm^-3. Particles which pass each other at distances smaller than the Debye length interact directly. Outside the Debye length particle interactions are dominated by collective effects. In typical laboratory plasmas the Debye length is small compared with the plasma dimension, so that collective effects are important.

→ debye (D); → length.

An extension of the → Einstein model accounting for → specific heats, based on the concept of → elastic waves in → crystals. In this model specific heat is given by: C_V = 9R[(4/x²)∫ y²/(e^y - 1)dy - x/(e^x - 1)], integrating from 0 to x, where R is the → gas constant, k is → Boltzmann's constant, x = hν_max/k, and y = hν/k. The parameter T_D = hν_max/k is the characteristic → Debye temperature of the crystal. At low temperatures the specific heat prediction by this model is in good agreement with observations (→ Debye law), in contrast to Einstein's model.

→ debye; → temperature.

The characteristic → temperature of the → crystal as given by the → Debye model of → specific heats.

→ debye; → temperature.

Prefix meaning "ten" and "ten times" used in terms belonging to the metric system.

From Fr. déca-, from L. deca-, dec-, from Gk. deka "ten;" cf. Av. dasa "ten," Mod.Pers. dah "ten," Skt. dasa, PIE *dekm (Dan. ti, Du. tien, Ger. zehn, E. ten, Fr. dix).

Dekâ-, from Fr. as above.

1a) To become decomposed.
1b) Of a radioactive nucleus, to disintegrate spontaneously into one or more different nuclei, accompanied by the emission of → alpha particles, → beta particles, → positrons, and/or → gamma rays.
2a) Decomposition.
2b) Of a spacecraft, a gradual decrease in the radius of its orbit over time, caused by aerodynamic drag of the atmosphere and other forces. The rate of orbit decay rises as the spacecraft falls and encounters increasing atmospheric density, eventually resulting in reentry. → alpha decay; → beta decay; → dark matter decay; → decay chain; → decay constant; → decay mode; → decay product; → decay time; → inverse beta decay; → Ohmic decay time; → orbit decay; → radioactive decay; → turbulence decay.

From O.Fr. decair, from V.L. *decadere "to fall off," from L. cadere "to fall," PIE base *kad- "to fall" (cf. Pers. Gilaki katan "to fall," ba.ka.tam "I fell," dakatan "to fall (in a marsh, in a pit)," vakatan "to fall from tiredness, be exhausted," fakatan "to fall from (lose) reputation," Pers. Laki: katen "to fall," kat "he fell," beko "fall!," Pers. Tabari: dakətə "fallen," dakətən "to crash down," dakət.gu "stray cow," Arm. chacnum "to fall").

Tabâhidan, verbal form of tabâhi, noun form of tabâh "spoiled, ruined, destroyed," Mid.Pers. tapâh "spoiled, destroyed." Maybe related to Mod.Pers. tâb "affliction, pain, torment; heat, burning," tab "fever," tâbidan, tâftan "to shine," tafsidan "to become hot," Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth," cf. Skt. tap- "to spoil, injure, damage; to suffer; to heat, be/become hot," tapati "burns," L. tepere "to be warm," tepidus "warm," PIE base *tep- "warm."

A series of nuclear decays produced by successive → daughter products, when the daughters are themselves → radioactive. For example, the decay chain N₁→ N₂→ N₃→ ... in which the parent nuclide N₁ decays to the daughter N₂, which in turn decays to N₃. Each → radionuclide in the decay chain can → branch to more than one daughter.

→ decay; → chain.

A constant of proportionality occurring in the formula expressing spontaneous → decay of → radionuclides. The number of atoms decaying is given by N = N₀e^-kt, where N₀ is the number of nuclei in the given volume of the substance at instant t = 0, N is the number of nuclei at t, and k is decay constant. Decay constant is related to → half-life by τ = ln2/k, roughly 0.693/k.

→ decay; → constant.

A possible type of decay of a → radionuclide or → elementary particle. In general, a given particle may decay by more than one decay mode. Usually the number of decay modes is one or two. There are, however, → nuclides which have many decay modes; for example the nuclide ¹¹Li has seven decay modes.

→ decay; → mode.

A → stable nuclide or → radioactive nuclide formed by the → disintegration of a → radioactive isotope, either directly or as a result of a → decay chain. Also called → daughter product. For example, the decay product of ²³⁸U is ²⁰⁶Pb, after passing through the following chain: ²³⁸U → ²³⁴Th (4.5 billion yr) → ²³⁴Pa (24 days) → ²³⁴U (1 min) → ²³⁰Th (245,000 yr) → ²²⁶Ra (76,000 yr) → ²²²Rn (1,600 yr) → ²¹⁸Po (3.8 d) → ²¹⁴Pb (3 m) → ²¹⁴Bi (27 m) → ²¹⁴Po (160 microseconds) → ²¹⁰Pb (22 yr) → ²¹⁰Bi (5 d) → ²¹⁰Po (138 d) → ²⁰⁶Pb.

→ decay; → product.

The time required for the amplitude of a vibrating system to decrease to 1/e of its initial value.
Of an orbiting object, its lifetime in a non stable orbit.

→ decay; → time.

(v.intr.) To slow down. (v.tr.) To decrease the velocity of.

From → de- + (ac)celerate, from → accelerate.

Vâšetâbidan, from vâ-→ de- + šetâbidan, → accelerate.