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.
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
1) (adj.) Of or from outside the limits of the Earth.
Fr.: vie extraterrestre
Life that may exist and originate outside the planet Earth.
Farthest from the center or middle; outermost; exceeding the bounds of moderation. → extreme adaptive optics; → extreme HB star; → extreme horizontal branch star; → extreme infrared; → extreme mass ratio inspiral; → extreme ultraviolet; → extremely metal-poor star.
From L. extremus "outermost, utmost," superlative of exterus, "outer," comparative of ex "out of," → ex-.
Ostom "outermost, utmost" (Av. (ustəma- "outermost, highest, ultimate"), superlative of ost "out," → ex-, + -tom superlative suffix, from Mid.Pers. -tom (xwaštom "most pleasant," nevaktom "best," wattom "worst"), from O.Pers. -tama- (fratama- "first, front"); Av. -təma- (amavastəma- "strongest," hubaiδitəma- "most sweet-scented," baēšazyôtəma- "most healing," fratəma- "first, front"); cf. Skt. tama-.
extreme adaptive optics
nurik-e niyâveši-ye ostom
Fr.: optique adaptative extrême
An → adaptive optics system with high-contrast imaging and spectroscopic capabilities. Extreme adaptive optics systems enable the detection of faint objects (e.g., → exoplanets) close to bright sources that would otherwise overwhelm them. This is accomplished both by increasing the peak intensity of point-source images and by removing light scattered by the atmosphere and the telescope optics into the → seeing disk.
extreme HB star
Fr.: étoile EBH
Same as → extreme horizontal branch star.
extreme horizontal branch star (EHB)
setâre-ye šâxe-ye ofoqi-ye ostom
Fr.: étoile de la branche horizontale extrême
The hottest variety of stars on the → horizontal branch with temperatures ranging from 20,000 to 40,000 K. EHB stars are distinguished from normal horizontal branch stars by having extremely thin, inert hydrogen envelopes surrounding the helium-burning core. They are hot, dense stars with masses in a narrow range near 0.5 Msun. These stars have undergone such extreme mass loss during their first ascent up the giant branch that only a very thin hydrogen envelope survives. Stars identified as EHB stars are found in low metallicity globular clusters as an extension of the normal HB.