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

Of, pertaining to, or dealing with the space beyond the Milky Way.

From → extra- + → galactic.

The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars.

→ extragalactic; → astronomy.

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.

→ extragalactic; → background; → light.

1) Beyond what is usual, ordinary, regular, or established.
2) Exceptional in character, amount, extent, degree, etc. (Dictionary.com). → unordinary.

→ extra-; → ordinary.

When a beam of → unpolarized light is incident on a → doubly refracting crystal, there will be two refracted rays. The ray for which → Snell's law does not hold.

→ extraordinary; → ray.

Math.: To estimate the value of a result outside the range of a series of known values.

From → extra- + (inter)polate, → interpolate.

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.

→ extra-; → solar.

A planet which belongs to a star other than → Sun, and therefore does not belong to our → solar system; same as → exoplanet.

→ extrasolar; → planet.

A → planatary system around a star other than the Sun. Same as → exoplanetary system .

→ extrasolar; → system.

1) (adj.) Of or from outside the limits of the Earth.
2) (n.) A hypothetical extraterrestrial being; → alien.

→ extra- + → terrestrial.

Life that may exist and originate outside the planet Earth.

→ extraterrestrial; → life.

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-.

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; → adaptive; → optics.

Same as → extreme horizontal branch star.

→ extreme horizontal branch star.

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.

A portion of the far infrared radiation, including wavelengths between 100 and 1,000 microns.

→ extreme; → infrared.

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; → mass; → ratio; → inspiral.

A part of the ultraviolet radiation with wavelengths between 50 and 300 Angstöms.

→ extreme; → ultraviolet.

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.

→ extreme; → metal; → poor; → star.