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.
→ extreme; → horizontal; → branch; → star.
Fr.: infrarouge extrême
A portion of the far infrared radiation, including wavelengths between 100 and 1,000 microns.
extreme mass ratio inspiral (EMRI)
forupicé bâ vâbar-e ostom-e jerm
Fr.: orbite plongeante d'un trou noir binaire, au rapport de masse extrême
A compact stellar remnant (e.g., a → white dwarf, → neutron star, or → black hole) that undergoes → inspiral into a much more massive object (→ supermassive black hole found → galactic centers). EMRIs are potential sources of low-frequency → gravitational waves. Predictions of the EMRI event rates span a wide range, from ~ 10-9 to 10-6 yr-1 per galaxy (Merritt et al. 2011, Physical Review D 84, 044024). See also → resonant relaxation.
extreme ultraviolet (EUV)
Fr.: ultraviolet extrême
A part of the ultraviolet radiation with wavelengths between 50 and 300 Angstöms.
→ extreme; → ultraviolet.
extremely metal-poor star (EMPS)
stâre-ye ostomâné kamfelez
Fr.: étoile extrêmement pauvre en métaux
A star with an iron abundance [Fe/H] < -3 found in a → galactic halo. These stars, whose → metallicity is typically less than one thousandth of the solar value, are believed to have formed shortly after the → Big Bang, 13.7 billion years ago. The number of such stars depends on the primordial → initial mass function. If the IMF were steep, there could, in principle, be a lot of EMPSs formed at high → redshifts. Thus many of them could have ended up in the halos of galaxies. See also → Population III star.