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

A cosmological hypothesis, based on Einstein's relativity, in which the expanding Universe began from an exploding "primeval atom." In the Lemaître Universe the rate of expansion steadily decreases.

Named after Monsignor Georges Edouard Lemaître (1894-1966), a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer; → universe.

1) A subsidiary proposition, proved for use in the proof of another proposition.
2) Linguistics: A word considered as its citation form together with all the → inflected forms. For example, the lemma go consists of go together with goes, going, went, and gone.
3) An argument or theme, especially when used as the subject or title of a composition (Dictionary.com).

From L. lemma, from Gk. lemma "something received or taken; an argument; something taken for granted," from root of lambanein "to take," → analemma.

Nehak, from neh present stem of nehâdan "to place, put; to set," → position, + -ak a diminutive suffix of nouns.

A closed curve with two loops resembling a figure 8. It is represented by the Cartesian equation (x² + y²)² = a²(x² - y²), where a is the greatest distance from the origin (pole) to the curve. Its polar equation is r² = a² cos 2θ.

From L. Latin lemniscatus "adorned with ribbons," from lemniscus "a pendent ribbon," from Gk. lemniskos "ribbon;" First described by Jacques Bernoulli (1654-1705) in 1694.

A distance determined by the extent of something specified. → Jeans length

M.E. length(e), O.E. lengthu "length," from P.Gmc. *langitho, noun of quality from *langgaz (root of O.E. lang "long," cognate with Pers. derâz, as below) + -itho, abstract noun suffix. Cognate with O.N. lengd, O.Fris. lengethe, Du. lengte.

Derâzâ quality noun of derâz "long," variants Laki, Kurdi derež; Mid.Pers. drâz "long;" O.Pers. dargam "long;" Av. darəga-, darəγa- "long," drājištəm "longest;" cf. Skt. dirghá- "lon (in space and time);" L. longus "long;" Gk. dolikhos "elongated;" O.H.G., Ger. lang; Goth. laggs "long;" PIE base *dlonghos- "long;" tul loan from Ar. ţaul, used in → wavelength.

Same as → Lorentz contraction.

→ length; → contraction.

1) Having or being of great length; very long.
2) Tediously verbose; very long; too long (Dictionary.com).

From → length + -y.

Kešnâk "lengthy" (Bardsiri, Kermâni), from kešidan, kašidan "to draw, protract, trail, drag, carry," → tide. Bardesir, Kermân

A transparent optical component consisting of one or more pieces of optical glass with surfaces so curved (usually spherical) that they serve to converge or diverge the transmitted rays from an object, thus forming a real or virtual image of that object.

From L. lens (gen. lentis) "lentil," cognate with Gk. lathyros, on analogy of the double-convex shape.

Adasi, related to adas "lentil," from Ar. 'adas.
The original Pers. terms for lentil are: mažu, mažâné, (Gilaki, Tabari) marju, marji, murje, marjum, (Laki) noži, (Aftari) marju, Mid.Pers. mijûg "lentil;" cf. Skt. masura- "lentil."

→ optical system.

→ lens; → system.

An effect predicted by → general relativity whereby a rotating body alters the → space-time around it. This effect can be thought of as a kind of "dragging of inertial frames," as first named by Einstein himself. A massive spinning object pulls nearby objects out of position compared to predictions for a non-rotating object. The effect is important for rapidly rotating → neutron stars and → black holes, but that near Earth is extraordinarily small: 39 milli-arc second per year, about the width of a human hair seen from 400 meters away.

Named after Austrian physicists Joseph Lense (1890-1985) and Hans Thirring (1888-1976), who first discovered this phenomenon in 1918; → effect.

1) The act or effect produced by a lens, in particular a → gravitational lens.
2) Pertaining to the object that produces the lensing effect. → lensing galaxy.

From → lens + → -ing.

1) Lenzeš, verbal noun of lenzidan, verb formed from E. lens + -idan infinitive suffix.
2) Lenzandé, verbal adj. from lenzidan, as above.

Effect created by a → gravitational lens.

→ lensing; → effect.

A galaxy that acts as a → gravitational lens. The effect can also be due to a cluster of galaxies.

→ lensing; → galaxy.

An astronomical object that creates → gravitational lensing. See also → lensing galaxy.

→ lensing; → object.

An important quantity in the characterization of → gravitational lensing. The lensing potential is obtained by projecting the three-dimensional Newtonian potential on the lens plane and by properly re-scaling it. It is a two-dimensional analog to the → gravitational potential.

→ lensing; → potential.

Circular and elliptical features on the surface of → Europa with diameters ranging from 10 to 100 km. Many are domes that seem to have been pushed up from below. These domes might have been formed by warm water rising between the cold ices of the outer crust, in a scenario recalling the → magma chambers on Earth.

From L. lenticula "freckle," diminutive of lens (genitive lentis) "lentil," → lens.

Kakmak "freckle."

A lens-shaped galaxy, which is an enormous grouping of old stars with very little internal structure.

Lenticular "resembling a lentil in form," → lens; → galaxy.

The direction of an induced current is such as to oppose the cause producing it. The cause of the current may be the motion of a conductor in a magnetic field, or it may be the change of flux through a stationary circuit.

Named after Heinrich Friedrich Emil Lenz (1804-1865), German physicist, who published the law in 1834; → law.

The Lion. One of the most conspicuous → constellations in the northern hemisphere, at 10h 30m → right ascension, 15° north → declination. Leo is a constellation of the → Zodiac crossed by the Sun from August 10th to September 16th. Leo is visible from February through June. Its brightest star, α Leonis or → Regulus, is of the first magnitude. Abbreviation: Leo; Genitive: Leonis. The neighboring constellations are → Cancer, → Coma Berenices, → Crater, → Hydra, → Leo Minor, → Lynx, → Sextans, → Ursa Major, and → Virgo. Leo contains many bright stars, many of which were individually identified by the ancients. There are four stars of first or second magnitude, which render this constellation especially prominent. Apart from Regulus, the constellation is home to the bright stars → Denebola, the nearby star Wolf 359, and to a number of famous deep sky objects, among them galaxies Messier 65, Messier 66, Messier 95, Messier 96, Messier 105, and NGC 3628. There are two → meteor showers associated with the constellation. The → Leonids usually peak on November 17-18 every year and have a → radiant near the bright star Gamma Leonis. The January Leonids are a minor shower that peaks between January 1 and 7. Leo has 11 stars with known planets.

→ lion.

The Lesser Lion. A faint constellation in the northern hemisphere, at 10h 20m right ascension, 35° north declination. Abbreviation: LMi; genitive: Leonis Minoris.

→ Leo; Minor, from L. minor "lesser, smaller, junior," from PIE base *min- "small."

Šir, → Leo; kucak "small," (Mid.Pers. kucak "small"), related to kutâh "short, small, little," kudak "child, infant," kutulé, → dwarf, Mid.Pers. kôtâh "low," kôtak "small, young; baby;" Av. kutaka- "little, small."

A → dwarf galaxy recently discovered near the Milky Way in → neutral hydrogen → 21-centimeter line observations. Optical imaging observations indicate that it is located between 1.5 and 2.0 Mpc from the Milky Way. This places Leo P in the → Local Volume but beyond the → Local Group. The dwarf galaxy has extreme properties: it is the lowest-mass system known that contains significant amounts of gas and is currently forming stars (Katherine L. Rhode et al. 2013, AJ 145, 149).

→ Leo.