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

A fairly long-lived step in the evolution of → low-mass and → intermediate-mass stars when helium burning shifts from the center to a shell around the core. At this phase the stellar luminosity is provided almost entirely by → helium shell burning. The He-shell burning generally adds mass to the growing carbon/oxygen core, resulting in → degenerate matter due to its increasing density.

→ early; → AGB; → phase.

A spectrograph that uses an echelle grating to disperse the light.

→ echelle grating; → spectrograph.

The space around a star in which a planet would experience external conditions that are not incompatible with the existence of life.

Ecosphere, from eco-, → ecology, + → sphere.

Bumsepehr, from bum "eco-," → ecology, + sepehr, → sphere.

An elongated structure of → interstellar dust and gas which absorbs the radiation from background stars in an → H II region. These structures are the denser remnants of → molecular clouds from which → massive stars are formed. Elephant trunks are eventually dissipated by the action of the → ionizing radiation and → stellar wind of the associated massive stars. A remarkable example of these structures is displayed by the → HST image of the → Eagle Nebula as → pillars of obscuring matter protruding from the interior wall of a dark molecular cloud. Some → Bok globules may represent the remaining densest fragments of elephant trunks.

M.E. elephant, from O.Fr. olifant, from L. elephantus, from Gk. elephas "elephant, ivory," probably from a non-I.E. language, likely via Phoenician; trunk, from M.E. trunke, O.Fr. tronc, from L. truncus "stem, trunk, stump."

Xortum "the proboscis of an elephant," loanword from Ar. xartum; fil, pil "elephant," from Mid.Pers. pil "elephant;" O.Pers. piru- "ivory."

An elongated dark structure of gas and dust in the → H II region IC 1396. It spans about 5 degrees on the sky in the constellation → Cepheus, about 2400 → light-years from the Earth. The Elephant Trunk Nebula is believed to be site of star formation, containing several very young stars. It is an example of → elephant trunks associated with star forming regions.

→ elephant trunk; → nebula.

Special stress laid upon, or importance attached to (Dictionary.com).

From L. emphasis, from Gk. emphasis "significance, implied meaning," from emphainein "to show, indicate," from en "in" + phainein "to show." It developed a sense of "extra stress" laid on a word or words to make the significance clear, or to show their importance.

Barâvaž, present stem of barâvažidan, literally "to speak loudly," from bar- "on, upon, up," → over-, + âvaž variant of âvâz "voice, sound, noise, clamour," cf. Sariqoli awuj "voice, sound," Wakhi awôγ "voice, sound," related to vâž, → word.

To give → emphasis to; lay stress upon; stress (Dictionary.com).

→ emphasis + → -ize.

1) Uttered, or to be uttered, with emphasis; strongly expressive.
2) Using emphasis in speech or action (Dictionary.com).

From Gk. emphatikos, variant of emphantikos, from emphainein, → emphasis.

Barâvaži, from barâvaž + -i adj. suffix.

In → graph theory, a graph with any number of → vertices which do not have → edges.

→ empty; → graph.

A → morphism from an → object to itself.

→ endo-; → morphism.

A table of computed positions occupied by a celestial body over successive intervals of time such as daily; plural ephemerides.

From L. ephemeris "day book, diary," from Gk. ephemeris "diary, account book," from ephemeros "short-lived, lasting but a day," from → epi "on, upon" + hemerai, dative of hemera "day."

Ruzij, from ruz, → day + zij "astronomical table," from Mid.Pers. zig "astronomical table," originally "string," since the lines of a table were compared to strings used on a weaver's instrument, variant zih, meaning "cord, string" (Modern Persian zeh "cord, string"); Av. jiiā- "bow-string;" cf. Skt. jiyā- "bow-string;" PIE base *g^whi- "thread, tendon" (from which derive also Gk. bios "bow;" L. filum "thread;" Russ. žca "thread").

86,400 → ephemeris seconds.

→ ephemeris; → day.

A fictitious meridian that rotates independently of the Earth at the uniform rate implicitly defined by → Terrestrial Dynamical Time (TDT).

→ ephemeris; → meridian.

The length of a tropical second (1/31,556,925.97474 of the tropical year) on 1900 January 0.5 → ephemeris time.

→ ephemeris; → second.

The uniform time-scale used as the independent variable to calculate the orbits in the solar system prior to 1984. Ephemeris Time was adopted in 1960 to deal with irregularities in the → Earth's rotation that had been found to affect the course of mean solar time. The definition of Ephemeris Time is based on Newcomb's analytical theory of the Earth's motion around the Sun (Newcomb 1898), according to which the geometric mean longitude of the Sun with respect to the Earth-Moon barycenter is expressed by:
L = 279° 41' 48".04 + 129 602 768".13 T + 1''.089 T²,
where L refers to the → mean equinox of date while T measures time from noon 1900 January 0 GMT in Julian centuries of 36525 days. Ephemeris Time is therefore defined as the instant near the beginning of the calendar year A.D. 1900 when the mean longitude of the Sun was 279° 41' 48''.04, at which instant the measure of ET was 1900 January 0, 12h precisely. In this system the fundamental unit was the → ephemeris second, which was defined so that the → tropical year at the epoch 1900.0 should be exactly 31 556 925,9747 seconds of ephemerides. Ephemeris Time was inconvenient in many ways and was supeseded with the → Terrestrial Dynamical Time (TDT), whose fundamental unit is the SI second.

→ ephemeris; → time.

The passage of a celestial body or point across the → ephemeris meridian.

→ ephemeris; → transit.

A → morphism f : Y → X if, for any two morphisms u,v : X → Z, u f = v f  implies u = v.

→ epi-; → morphism.

The region between the → event horizon and the → stationary limit of a rotating → Kerr black hole. It is possible for a particle falling inside the ergosphere to break into two parts, one of which will fall into the black hole and the other will come out.

→ erg + → sphere.

→ spheres of Eudoxus.

→ spheres of Eudoxus.

An inoffensive word or phrase substituted for one considered offensive or hurtful, especially one concerned with religion, sex, death, or excreta (TheFreeDictionary.com).

From Gk. euphemismos, from euphemizein "speak with fair words, use words of good omen," from → eu- "well," + pheme "speech, voice, talk," from phanai "to speak," ultimately from PIE *bha- "to speak, tell, say;" cf. Skt. bhanati "speaks;" L. fari "to say," fabula "tale, story," fama "talk, rumor, report; reputation;" Armenian ban, bay "word, term."

Xošguyi, xošzabâni, literally "pleasant talking, ~ speach," from xoš "well, pleasant," → eu- + guyi verbal noun of goftan "to say, talk, speak," → logic; zabâni, from zabân, → language.