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

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.

A → microorganism with the ability to thrive in extreme environmental conditions that would kill other species. These conditions include high temperatures, very low temperatures, high pressures, high levels of radiation, and high concentrations of salt in water.

→ extreme; → -phile.

A maximum or minimum value of a function in a specified interval.

From L. extremus, → extreme.

Ostomé, from ostom, → extreme + noun suffix -é, from Mid.Pers. -ag.

Not essential or inherent; not forming part of or belonging to a thing. → intrinsic.

Extrinsic, from L.L. extrinsecus "outward," from extrim- + secus "beside," from sequi "to follow."

Borungin, from borun "out, the outside" (Mid.Pers. bêron, from bê "outside, out, away" + rôn "side, direction;" Av. ravan- "(course of a) river") + -gin adj. suffix, contraction of âgin "filled."

Photoconductivity due to the addition of impurities or external causes.

→ extrinsic; → photoconductivity.

Šidhâzandegi, → photoconductivity; borungin, → extrinsic.

A semiconductor, such as silicon, whose responsive properties can be altered by the addition of impurities. Copper- and mercury-doped germanium are both examples of this semiconductor material.

→ extrinsic; → semiconductor.

A star whose variation in apparent brightness is not due to changes in the star itself but to some external cause, such as eclipsing by a companion.

→ extrinsic; → variable; → star.

The organ of vision that detects light.

O.E. ege (Mercian), eage (W. Saxon), from P.Gmc. *augon, from PIE *ok^w- "to see;" cf. Av. aši- "(both) eyes;" Skt. áksi- "eye;" Gk. osse "(both) eyes;" Goth. augo; O.C.S. oko; Lith. akis; L. oculus; Arm. ac-kh "eye."

Cašm, from Mid.Pers. cašm, Av. cašman- "eye," ākas- "to look," from prefix ā- + Proto-Iranian *kas- "to look, appear," cf. Skt. cáksus- "seeing."

The distance between the eyepiece of a telescope and the location of the exit pupil. This is where the observer's eye should be positioned to see the entire field of view of the eyepiece. Also termed eye distance.

→ eye; relief, from M.E. relef, from O.Fr. relief "assistance," from relever "to raise," from L. relevare "to raise, alleviate," from re- intensive prefix, + levare "to lift up, lighten."

Cašm nehâd "eye position," from cašm, → eye, + nehâd "position, placing, posture," contracted form of nehâdan "to place, put;" Mid.Pers. nihâtan; Av. ni- "down; into," → ni-, + dā- "to put; to establish; to give," dadāiti "he gives;" cf. Skt. dadāti "he gives;" Gk. didomi "I give;" L. do "I give;" PIE base *do- "to give."

The necessary precautions that must be taken in order to avoid damaging the eyes when watching a → solar eclipse. The only time that the Sun can be viewed safely with the naked eye is during a → total eclipse, when the Moon completely covers the disk of the Sun. It is never safe to look at a → partial eclipse or → annular eclipse, or the partial phases of a total solar eclipse, without the proper equipment and techniques. Even when 99% of the Sun's surface (the → photosphere) is obscured during the partial phases of a solar eclipse, the remaining crescent Sun is still intense enough to cause permanent retinal damage, especially when viewed through binoculars or other optical aids (F. Espenak, NASA).

→ eye; safety, M.E. sauvete, from O.Fr. salvetet, from M.L. salvitatem "safety," from L. salvus, cognate with Pers. har "all, each, every," → holo-.

Gazand "damage, injury," Mid.Pers. wizend, ultimately from *ui-jan-, from *ui- "apart, away from," → expand, + *jan- "to beat, strike," cf. Pers. zan-, zadan "to beat, strike," → beat; cašm, → eye
Zilegi, → security.

A device consisting of a pair of glass or plastic lenses worn in a frame in front of the eyes to help correct imperfect vision or protect the eyes from light, dust, and the like. Also called glasses, spectacles.

→ eye; → glass.

Eynak, probably related to âyené "mirror," âbginé "glass" (Mid.Pers. êwênag "mirror," from *âdênak, from Proto-Iranian *ādayanaka-, from prefix ā- + the root of Av. dā(y)- "to see," didāti "sees" (cf. Mod.Pers. didan "to see," Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" O.Pers. dī- "to see;" Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen") + suffix -ak). Other obsolete Pers. equivalents for eyeglasses are cešm-e farangi "Frank/European eye" and âyene-ye farangi "Frank/European glass." And it seems that the oldest mention of eyeglasses in Pers. is by the poet Jâmi (1414-1492), who calls it farangi šišé "Frank/European glass." These paradigms support the relation between eynak and âyené. As for the more recent term sam'ak "hearing aid," which is invoked to relate eynak to eyn (Ar. 'ayn "eye"), it may have been coined on the model of eynak supposing that eyn means "eye."

A → lens system, also known as an → ocular, used to → magnify the → image formed by the → objective of a → telescope.

→ eye; → piece.

Cašmi "ocular," adj. of cašm→ eye + -i adj. suffix.