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

The locus of a point the sum of whose distances from two fixed points is constant.

From O.Fr. ellipse, from L. ellipsis "ellipse," also, "a falling short, deficit," from Gk. elleipsis "an omission," from el-, variant of en-, + leip-, stem of leipein "to leave" + suffix -sis.

Beyzi, from Ar.

A three-dimensional geometric figure resembling a flattened sphere. It is generated by rotating an ellipse around one of its axes.

From → ellipse + → -oid.

Relating to or having the form of an → ellipse. Same as → elliptical.

From Gk. elleiptikos "pertaining to an ellipse," from elleipein "to fall short, leave out," from en- "in" + leipein "to leave," + → -ic.

Beyzigun, from beyzi, → ellipse, + -gun, from gun "resembling; manner, fashion; color" (Mid.Pers. gônak "kind, species;" Av. gaona- "color").

That part of → annual aberration proportional to the → eccentricity of the Earth's orbit.

→ elliptic; → aberration.

Pertaining to or having the shape of a geometric ellipse.

→ elliptic; → -al.

A galaxy whose structure is smooth without spiral arms and ellipsoidal in shape. Ellipticals are redder than spirals of similar mass. Giant ellipticals contain over 10¹² solar masses, whereas dwarf ellipticals have masses as low as 10⁷ solar masses.

→ elliptical; → galaxy.

The → polarization of an → electromagnetic radiation in which the electric vector at any point in the path of the beam describes an ellipse in a plane perpendicular to the propagation direction. Elliptical polarization results from the combination of two perpendicular → linearly polarized waves whose → phase difference is other than 0, 90, or 180°. The form of the ellipse is determined by the amplitudes of the component waves and the phase difference. → Linear polarization and → circular polarization can be considered as limiting cases of elliptical polarization.

→ elliptical; → polarization.

Light exhibiting → elliptical polarization.

→ elliptic; → polarized; → light.

The degree of divergence of an ellipse from a circle.

From elliptic-, from elliptical + → -ity.

Beyzigi, from beyzi, → ellipse, + -igi, → -ity.

Same as → Alnath.

→ Alnath.

To draw out to greater length; lengthen; extend.

From L.L. elongatus "lengthened out," p.p. of elongare "to make longer, to remove to a distance," from → ex- "out" + longus "long;" PIE base *dlonghos- "long;" cf. Av. darəga-, darəγa- "long," drājištəm "longest;" Mod.Pers. derâz "long," dir "late; long;" Skt. dīrghá- "long (in space and time);" Gk. dolikhos "long;" P.Gmc. *langgaz (Ger. lang; O.N. langr; M.Du. lanc; Goth. laggs "long;" E. long).

DerâzidanDerâzeš "to elongate," from derâz "long," Mid.Pers. drâz "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" PIE *dlonghos- "long," as above.

Made longer; long and narrow.

Past participle of → elongate.

An → elliptical orbit with a high → eccentricity.

→ elongated; → orbit.

1) Increase in length per unit of original length.
2) The angular distance of a planet from the Sun as seen from the Earth. An elongation of 0° is called → conjunction; one of 180° is called → opposition; and an elongation of 90° is called → quadrature.

→ elongate; → -tion.

A → dimensionless quantity used in → magnetohydrodynamics to describe the relative balance of → Lorentz forces to → Coriolis forces. It is given by: Λ = σB²/(ρΩ), where σ s the → electrical conductivity of the fluid, B is the typical → magnetic field strength within the fluid, ρ is the fluid → density, and Ω is the → angular velocity. A typical value for the Earth is Λ ~ 1.

Named after Walter Maurice Elsasser (1904-1991), American theoretical physicist of German origin; → number.

The brightest star in the constellation → Draco, with a visual magnitude of V = 2.23 and color B - V +1.52. It is a cool (4000 K) → giant star of spectral Type K5 III, lying 148 → light-years. Gamma Draconis has a luminosity 600 times that of the Sun and a diameter 50 times that of the Sun. It crosses the sky near the zenith point for England, a nd this was the reason why James Bradley (1693-1762) observed γ Draconis when he was trying to detect parallax and so calculate the distance. He found that the star undergoes a yearly shift of a form quite different from that expected from parallax. In a 1728 paper, Bradley announced his discovery and explained the effect as due to the → aberration of starlight . Variant names: Etamin, Etanin; Ettanin, other designations: HR 6705, HD 164058.

From Ar. At-Tinnin (التنین) "the great serpent," the Ar. rendition of the Greek constellation → Draco.

A transient upper atmospheric phenomenon occurring over a → thunderstorm in the lower → ionosphere. Elves result from especially powerful electromagnetic radiation pulses that are generated from certain lightning discharges (→ sprite). As the energy passes upwards through the base of the ionosphere it causes the gases to briefly glow for less than a thousandth of a second. This makes elves virtually impossible to see with the naked eye. Elves occur at a height of around 90-95 km, and can expand outward to several hundred kilometers in diameter, like giant expanding doughnuts.

Short for: Emission of Light and Very low-frequency perturbations from Electromagnetic pulse sources.

From E. elf "(in folklore) a small often malicious fairy; goblin; sprite;" O.E. elf, ælf, ylfe; cf. O.S. alf, O.N. alfr, Ger. alp, of unknown origin.

To flow out, issue, or proceed, as from a source or origin; come forth; originate; arise (Dictionary.com).

From L. emanatus, p.p. of emanare "flow out," figuratively "arise from, proceed from."

Runemudan "to appear, come out," literally "to show face," from ru "face," → surface, + nemudan "to show," → display.

An act or instance of emanating; something that emanates or is emanated.

→ emanate; → -tion.

A newborn star which is tightly enveloped by a surrounding cloud of gas and dust.

Ebedded p.p. of embed, from en- + bed from O.E. bed "bed," from P.Gmc. *badjam "sleeping place dug in the ground" (O.H.G. betti; Ger. bett); PIE base *bhedh- "to dig, pierce;" cf. Gk. bothyros "pit;" L. fodere "to dig," fossa "ditch;" → star.

Setâré, → star; forupušidé, p.p. of forupušidan, from foru- "below; beneath; down, downwards;" Mid.Pers. frôt "down, downwards;" O.Pers. fravata "forward, downward;" Skt. pravát- "a sloping path, the slope of a mountain" + pušidan "to cover, conceal, clothe; to wear clothes;" Mid.Pers. pôšidan, pôš- "to cover, put on, wear;" cf. Mid.Pers. pôst; Mod.Pers. pust "skin, hide;" O.Pers. pavastā- "thin clay envelope used to protect unbaked clay tablets;" Skt. pavásta- "cover;" Proto-Indo-Iranian *pauastā- "cloth."