Fr.: décalage Doppler
Effect of the relative motion of a wave source (light, sound) and the observer. If the source is moving away, the wavelength is stretched (shifted toward lower frequencies). If the source is approaching, the wavelength is compressed (shifted toward higher frequencies). These effects, known as Doppler shifts, are in the case of light waves called redshift and blueshift, respectively.
Fr.: tomographie Doppler
A technique using a series of Doppler-shifted line profiles at different orbital phases in cataclysmic variable stars (CVs) to image the compact system in the light of a particular emission line. Although developed for CVs, the method has wider applications. An alternative method is → eclipse mapping.
Mâhi-ye zarrin, zarrin mâhi (#)
The Swordfish. A constellation in the southern hemisphere near → Reticulum and → Pictor. It contains most of the → Large Magellanic Cloud which laps over to some extent into the neighboring constellation → Mensa. The south → ecliptic pole also lies within this constellation. Abbreviation: Dor, Genitive: Doradus.
Dorado, from Sp., from L.L. deaurutus, p.p. of deaurare "to gild," from → de- + aurium "gold." Dorado (Coryphaena hippurus) is a surface-dwelling fish found in off-shore tropical and subtropical waters worldwide. It is distinguished by dazzling golden colors on the sides.
Mâhi "fish," from Mid.Pers. mâhik, Av. masya-, cf.
Skt. matsya-, Pali maccha-.
Fr.: produit scalaire
Same as → scalar product.
O.E. dott "speck, head of a boil," perhaps related to Norw. dot "lump, knot," Du. dot "knot, wisp;" cognate with O.H.G. tutta "nipple;" → product.
1) Composed of two like parts or members.
From O.Fr. duble, from L. duplus "twofold" (Gk. diplos "double"), from duo "two" + -plus "fold."
Dotâyi, from dotâ, from do "two," akin to L. duo, + tâ "fold, plait, ply; piece, part," Mid.Pers. tâg "piece, part."
Fr.: intégrale double
The simplest case of a → multiple integral.
pulsâr-e dotâyi, tapâr-e ~ (#)
Fr.: pulsar double
A → binary pulsar consisting of two pulsars. The only known example is PSR J0737-3039 (A and B), discovered in 2003 (Burgay et al. Nature 426, 531). The rotation periods of the pulsars are 22.7 and 2.8 milliseconds respectively. Each of them has a mass about 1.3 times that of the Sun and revolves around their → center of gravity with a period of 2.4 hours. According to the theory of → general relativity, such a binary should lose energy through the emission of → gravitational waves. As deduced from the change in orbital period, the separation of the pulsars is reducing by about 7 mm per day, in exact agreement with theory. It is expected that the pulsars will eventually merge in about 85 million years.
Fr.: double réfraction
Formation of two refracted rays of light from a single incident ray; property of certain crystals, notably calcite.
Fr.: racine double
double shell burning
suzeš-e puste-ye dotâyi
Fr.: combustion double coquille
A situation in the evolution of an → asymptotic giant branch star whereby both hydrogen and helium shells provide energy alternatively. As the burning → helium shell approaches the hydrogen-helium discontinuity, its luminosity decreases because it runs out of the fuel. As a consequence, the layers above contract in response, thus heating the extinguished → hydrogen shell until it is re-ignited. However, the shells do not burn at the same rate: the He burning shell becomes thermally unstable and undergoes periodic → thermal pulses.
šekâf-e dotâyi (#)
Fr.: fente double
A pair of adjacent holes or slits made on a dark and plane surface, used in optical experiments, such as interference and diffraction.
setâre-ye dotâyi (#)
Fr.: étoile double
An apparently single star which better observational resolution shows it to be a pair of closely lying stars. They may or may not be physically related.
Fr.: vision double
Same as → diplopia.
double white dwarf
sefid kutule-ye dotâyi
Fr.: naine blanche double
A → double-lined binary with two → white dwarf components. Short-period double white dwarfs can lose → orbital angular momentum by emitting → gravitational radiation and if the total mass of the binary exceeds the → Chandrasekhar limit, their eventual → merger might produce a → Type Ia supernova.
double-degenerate binary system
râžmân-e dorin-e dobâr vâgen
Fr.: système binaire doublement dégénéré
A system of evolved → binary stars in which both → components have ejected their envelopes and evolve toward → white dwarf stage. So far a half dozen double-degenerate → binary systems are known, for example Henize 2-248 (M. Santander-Garcia et al., 2015, 518, 5).
hambaz-e do paxši
An instability involving two layers of fluid with opposite gradients of properties. Same as → fingering instability. See also → salt finger. Double-diffusive instabilities commonly occur in any astrophysical fluid that is stable according to the → Ledoux criterion, as long as the entropy and chemical stratifications have opposing contributions to the dynamical stability of the system. They drive weak forms of convection, and can cause substantial heat and compositional → mixing. Two cases can be distinguished. In fingering convection, entropy is stably stratified (∇ - ∇ad < 0), but chemical composition is unstably stratified (∇μ < 0); it is often referred to as → thermohaline convection by analogy with the oceanographic context in which the instability was first discovered. In oscillatory double-diffusive convection, entropy is unstably stratified (∇ - ∇ad > 0), but chemical composition is stably stratified (∇μ > 0); it is related to semiconvection, but can occur even when the → opacity is independent of composition (P. Garaud, 2014, arXiv:1401.0928).
Fr.: binaire à double raies
double-lined eclipsing binary
dorin-e gerefti-ye doxatté
Fr.: binaire à éclipse à double raies
double-lined spectroscopic binary
dorin-e doxatte-ye binâbnemâyik
Fr.: binaire spectroscopique à double raies
Same as → double-lined binary.
double-lobed radio source
xan-e râdioyi bâ lap-e dotâyi
Fr.: radio source à double lobe
A → galaxy that emits radio energy from two regions located on opposite sides of the galaxy.