external photoelectric effect
oskar-e šid-barqi-ye boruni
Fr.: effet photoélectrique externe
The → photoelectric effect in solids where free electrons are emitted from the surface of a substance (e.g., → semiconductor) when radiation of appropriate frequency falls on it. Also called → photoemissive effect.
Fr.: travail externe
The work done by a thermodynamic system as it expands against its surrounding environment. It is equal to ∫pdV, where p is the applied external pressure and V the volume, integrated from the initial V1 to final V2.
Verbal noun of → externalize.
1) To make external; embody in an outward form.
1) Dimming of light by an intervening medium (the Earth's atmosphere or the interstellar medium).
It is usually due to both scattering and absorption.
Noun of extinct, from L. extinctus, p.p. of extinguere "to quench, wipe out," from → ex- "out" + stinguere "to quench," from PIE base *steig- "to prick, stick, pierce;" cf. Mod.Pers. tiz, tež, tig, tej, tij, tiq "sharp;" Av. tiγra- "pointed," tiγray- "arrow;" → deblur.
Xâmuši, noun of xâmuš "extinguished; silent," Mid.Pers. xâmôš "silent;" cf. Skt. amrs- "to bear patiently."
Fr.: coefficient d'extinction
Gradient of apparent magnitude with air mass.
Fr.: correction d'extinction
In → photometric calibration, the correction for energy loss undergone by radiation due to the → atmospheric extinction. Extinction correction is done using → standard stars observed at different → airmasses.
Fr.: courbe de l'extinction interstellaire
A graph representing the variation of the → interstellar extinction against → wavelength. Usually it displays the → normalized values of extinction as a function of (the → inverse) of the wavelength (in → microns). See, e.g., Sandage & Mathis, 1979, Ann. Rev. Astron. Astrophys. 17, 73.
Fr.: étoiles d'extinction
Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.
A facility at → European Southern Observatory (ESO)'s → La Silla Observatory funded by the European Research Council and the French Agence National de la Recherche with the purpose of detecting and studying → transiting → exoplanets. ExTrA will search for Earth-sized planets orbiting nearby → red dwarf stars. It uses three 0.6-metre telescopes. They regularly monitor the amount of light received from many red dwarf stars and look for a slight dip in brightness that could be caused by a planet passing across a star's disk and obscuring some of its light. The three ExTra telescopes collect light from the target star and four comparison stars and that light is then fed through optical fibres into a → multi-object spectrograph. This innovative approach of adding → spectroscopic information to traditional photometry helps mitigate the disruptive effect of Earth's atmosphere, as well as effects introduced by instruments and detectors, thus increasing the precision achievable.
ostar-, borun- (#)
Prefix meaning "outside; beyond the scope of; in addition to what is used or expected." Also extro-.
M.E., from L. extra, adverb and preposition, "outside, except, beyond," from exter "outward, on the outside."
Ostar-, from os-, → ex-, + -tar comparative suffix (Mid.Pers. -tar; Av. -tara; PIE base *-tero); borun-, from borun "out, the outside" (Mid.Pers. bêron, from bê "outside, out, away" + rôn "side, direction;" Av. ravan- "(course of a) river").
Of, pertaining to, or dealing with the space beyond the Milky Way.
axtaršenâi-ye ostar-kahkašâni, ~ borun-kahkašâni
Fr.: astronomie extragalactique
The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars.
extragalactic background light (EBL)
nur-e paszimine-ye ostarkahkeši
Fr.: lumière du fond extragalactique
The integrated intensity of all of the light emitted throughout the history of the Universe across the whole of the → electromagnetic spectrum, including those which are not individually detected. The EBL spectrum includes cosmological backgrounds associated with either primordial phenomena, such as the → cosmic microwave background radiation (CMBR), or photons emitted by stars, galaxies and → active galactic nuclei (AGN) due to → nucleosynthesis or other → radiative processes, including → dust scattering, → absorption and reradiation. The EBL may also contain signals that are diffuse and extended, including high-energy photons associated with dark matter particle decays or annihilation.
1) Beyond what is usual, ordinary, regular, or established.
Fr.: rayon extraordinaire
Math.: To estimate the value of a result outside the range of a series of known values.
From borun, → extra- + yâftan, yâbidan "to find, discover; to obtain, acquire;" Mid.Pers. ayâftan, ayâpênitan "to reach, attain;" Manichean Mid.Pers. 'y'b "to attain;" Parthian, Sogdian (+ *pati-) pty'b "to reach, obtain;" Av. ap- "to reach, overtake," apayeiti "achieved, reached;" Skt. âp- "to reach, gain," âpnoti "reaches, gains;" Gk. hapto, haptomai "to touch, cling to, adhere to;" L. apiscor "touch, reach;" PIE base *ap- "to take, reach."
Predicting the value of unknown data points by projecting a function beyond the range of known data points.
Verbal noun of → extrapolate.
Not belonging to the → solar system; outside, or originating outside, the solar system.
Fr.: planète extrasolaire