An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -ne Nao nat nea neg nes neu New New Nix nom non non nor nov nuc nul num > >>

Number of Results: 356

Fr.: Nix   

The second satellite of → Pluto discovered in 2005 by astronomers using the → Hubble Space Telescope images. It has an estimated diameter of between 46 and 137 km and an orbital period of 24.9 days. Also called Pluto II (P2).

Nix, from Nyx in Gk. mythology the goddess of darkness and night. The conversion of "i" into "y" was to avoid conflict with the asteroid 3908 Nyx.

no boundary hypothesis
  انگاره‌ی ِ گیتی بی کران ِ آغازین   
engâre-ye giti bi karân-e âqâzin

Fr.: l'hypothèse de l'Univers sans limite initiale   

The proposal whereby the → Universe would not have begun with a → singularity. Instead, the → Big Bang would be an ordinary point of → space-time. The proposal, advanced by James Hartle and Stephen Hawking (1983) results from an attempt to combine aspects of → general relativity and → quantum mechanics. Based on an imaginary time assumption, it predicts a closed Universe that would start at a single point, that can be compared to the North Pole of the Earth on a two-dimensional space. Before the → Planck era there was space, but the real time began with the Big Bang event. → Hartle-Hawking initial state.

boundary; → hypothesis.

no hair theorem
  فربین ِ بی‌مویی، ~ کچلی   
farbin-e bimu-yi, ~ kacali

Fr.: théorème de calvitie   

There are only three parameters that can be applied by an outside observer relating to a → black hole: → mass, → electric charge, and → angular momentum. The collapse of a star into a black hole wipes out all other details of its structure, and the observer can never discover any other properties of the star which formed the black hole. In other words, none of its characteristics leave any trace outside the black hole, and that is what is meant by "hair."

No, M.E., from O.E. na "never, no," cognate with Pers. na, nâ, → non-; → hair; → theorem.

Farbin, → theorem; bimuyi, noun from bimu "without hair," from bi- "without" (→ in-) + mu, → hair.
Kacali "baldness," from kacal "bald," also "crooked, bandy-legged," from kajal, from kaj "crooked, curved, bent" + → -al; probably unrelated to kal "bald," → colure.

Noachian era
  دوران ِ نوحیانه   
dowrân-e Nuhiyâné

Fr.: ère noachienne   

>Noachian era = dowrân-e Nuhiyâné     دوران ِ نوحیانه

Fr.: ère noachienne

The oldest geological era on Mars, which started from the planet's birth and lasted until about 3.8 billion years ago. Features such as dried-up river valleys and delta features suggest that the climate may have been warmer and wetter. It is believed also that lakes and oceans could have existed. → Amazonian era; → Hesperian era.

The oldest geological era on Mars, which started from the planet's birth and lasted until about 3.8 billion years ago. Features such as dried-up river valleys and delta features suggest that the climate may have been warmer and wetter. It is believed also that lakes and oceans could have existed. → Amazonian era; → Hesperian era.

Noachian, named for → Noachis Terra "Land of Noah;" → era.

Noachis Terra
  زمین ِ نوحیانه   
zamin-e Nuhiyâné

Fr.: Noachis Terra   

An extensive southern terrain of the planet Mars. One of the oldest terrains on Mars, it lies roughly between the latitudes -20° and -80° and longitudes 30° west and 30° east.

L. Noachis Terra "Land of Noah."

Zamin "land," → earth; Nuhiyâné adj. of Nuhi "related to Nuh," from Nuh (نوح) "Noah."

noble gas
  گاز ِ هوپد   
gâz-e huped

Fr.: gaz rare   

A gaseous chemical element that does not readily enter into chemical combination with other elements. Examples are helium, argon, krypton, xenon, and radon. Same as → inert gas.

Noble, from O.Fr. noble, from L. nobilis "well-known, famous, of superior birth," earlier gnobilis, literally "knowable," from gnoscere "to come to know" (Fr. connaître; Sp. conocer); cognate with Pers. šenâxtan "to know, discern, distinguish, be acquainted with;" Mid.Pers. šnâxtan, šnâs- "to know, recognize," dânistan "to know;" O.Pers./Av. xšnā- "to know, learn, come to know, recognize;" cf. Skt. jñā- "to recognize, know," jānāti "he knows;" Gk. gignoskein "to know, think, judge;" P.Gmc. *knoeanan; O.E. cnawan; E. know; Rus. znat "to know;" PIE base *gno- "to know;" → gas.

Gâz, → gas; huped "noble," from Mid.Pers. hupid "noble," from hu- "good, well" (Mid.Pers. hu-; O.Pers. hu- "good, well" (ukāra- "having good people"); Av. hu-, hū- "well, good, beautiful" (hu-kərp- "well-shapen," hūxta- "well spoken," hu-manah- "good-minded"); cf. Skt. su- "good" (svasti "well-being, good luck," sumánas- "good-minded," sūktá- "well spoken"); L. from Gk. eu "well," combining form of eus "good" (hu-gies "healthy"); Gallic su-; O.S. su-; Welsh hy-; PIE base *su-) + pid "father," variant of pidar; Mod.Pers. pedar "father" (O.Pers. pitā- "father;" Av. patar-; Skt. pitár-; Gk. pater; L. pater, O.H.G. fater).

sufâr (#)

Fr.: entaille, encoche   

The end part of an → arrow having a notch for holding the bowstring.

M.E. nok(ke); of uncertain origin; cf. Swedish nock "notch;" also M.L.G. nokk, Dutch nok "tip of a sail."

Sufâr "the notch in the arrow which receives the string," also "the eye of needle," related to softan, sombidan "to pierce;" Mid.Pers. sôftan "to pierce, bore;" cf. Pashtu suray, Wakhi sərv "hole, cavity," Munji surv "hole," Yidgha surv, Kurd. sontin; Proto-Ir. sup, sub, sump, sumb "to pierce."

noctilucent cloud
  ابر ِ شب‌تاب   
abr-e šabtâb

Fr.: nuage nocturne lumineux   

The highest clouds in the Earth's atmosphere, at altitudes between 75 and 90 km. They resemble thin cirrus clouds with a bluish or silverish color, and are visible only during twilight.

From nocti- combining form of L. nox, → night, + L. lucent p.p. of lucere "to shine," from luxlight; → cloud.

Abr, → cloud, + šabtâb "noctilucent," from šab, → night, + tâb present stem of tâbidan "to shine," → luminous.

gerehi (#)

Fr.: nodal   

Relating to or of the nature of a node.

node; → -al.

nodal line
  خط ِ گره‌ها   
xatt-e gerehhâ

Fr.: ligne des noeuds   

The line connecting the ascending and descending nodes of an orbit.

nodal; → line.

nodal point
  نقطه‌ی ِ گرهی   
noqte-ye gerehi

Fr.: point nodal   

Any of the two points on the axis of a → lens system, such that if the → incident ray passes through one, travelling in a given direction, the emergent ray passes the other in a parallel direction.

nodal; → point.

nodal regression
  پسرفت ِ گرهی   
pasraft-e gerehi

Fr.: regression nodale   

For a ring inclined to the planet's equator, the points at which the ring crosses the equator (nodes) slowly move around the planet (regress) in a direction opposite to that of the ring's orbital motion. (Ellis et al., 2007, Planetary Ring Systems, Springer).

nodal; → regression.

gereh (#)

Fr.: nœud   

1) A point of zero → amplitude in a system of → stationary waves. See also → antinode.
2) A → junction point in a network.
3) Same as → orbital node; see also → lunar node.

From L. nodus "knot."

Gereh "knot," from Mid.Pers. grih "knot;" Sogdian γr'nš "knot, bond, joining;" Khotanese grantha- "knot;" cf. Skt. granthi- "knot."

nodical month
  ماه ِ گرهی، ~ گوزهری   
mâh-e gerehi (#), ~ gowzahri (#)

Fr.: mois draconitique   

The time interval between two successive passages of the Moon through its ascending node (27.212220 days, i.e., 27 days 5 hours 5 minutes 35.8 seconds). Nodical month is important for predicting eclipses. Also called → draconic month.

Nodical adj. of → node; → month.

Mâh, → month; gerehi, adj. of gereh, → node; gowzahridraconic month.

Noether's theorem
  فربین ِ نوتر   
farbin-e Noether

Fr.: théorème de Noether   

A → symmetry in a physical system leads to a → conserved quantity. For example, symmetry under → translation corresponds to conservation of → momentum, symmetry under → rotation to conservation of → angular momentum, and symmetry in → time to conservation of → energy. The Noether symmetry theorem is a fundamental tool of modern theoretical physics and the calculus of variations, allowing to derive conserved quantities from the existence of variational symmetries.

Named in honor of the German-American woman mathematician Amalie Emmy Noether (1182-1935), who published the theorem in 1918 ("Invariante Variationsprobleme," Nachr. D. König. Gesellsch. D. Wiss. Zu Göttingen, Math-phys. Klasse 1918: 235-257).

nufé (#)

Fr.: bruit   

1) The → random → fluctuations that are always associated with a measurement that is repeated many times over. Any unwanted disturbance, random or → systematic, which contaminates the → signal from an object under study. More specifically:
2) Electronics: An undesired signal within the useful frequency band.
3) Acoustics: Any extraneous sound tending to interfere with the perception of wanted sound.
See also:
atmospheric noise, → background noise, → cosmic radio noise, → dark current noise, → Galactic radio noise, → Johnson-Nyquist noise, → noise source, → noise temperature, → noise voltage, → noise-equivalent power, → photon noise, → quantum noise, → radio noise, → random noise, → readout noise, → receiver noise, → Schottky noise, → shot noise, → signal-to-noise ratio, → speckle noise, → stationary noise, → system noise, → thermal noise, → white noise.

Noise, of obscure origin; it has been related to O.Fr. noise "uproar, brawl," apparently from L. nausea "disgust, annoyance," literally "seasickness." Alternatively the O.Fr. word is traced to L. noxia "hurting, injury, damage."

Nufé "noise," related to Mod.Pers. noyidan "to cry loud, lament," navidan, nâvidan "to lament," noyé, nôyah "plaint, mown," navâ "sound, song," (with prefix *uz-) zenudan, zenav-, zonudan "to wail," Ossetic niwyn/newun "to howl," O.Khotanese nuva- "to make a noise," Yaqnâvi nuyok "crying, howling," novva "sound," Shahmirzâdi nâv- "to cry; cf. Skt. nav- "to sound loudly, roar," náva- "show of joy or triumph;" L. nuntius "messenger," adnuntiare "to annoince;" Tocharian AB nu- "to roar, PIE *neu- "to shout".

noise source
  خن ِ نوفه   
xan-e nufé

Fr.: source de bruit   

An electronic device designed to generate known amounts of radio noise in order to test and calibrate the receivers of radio telescopes.

noise; → source.

noise temperature
  دمای ِ نوفه   
damâ-ye nufé

Fr.: température de bruit   

A means for specifying the noise generated as unwanted → electromagnetic radiation in a receiver system or one of its components. It is usually measured in terms of the equivalent temperature in a → Rayleigh-Jeans spectrum. Noise temperature is used mainly in radio astronomy.

noise; → temperature.

noise voltage
  ولتاژ ِ نوفه   
voltâž-e nufé

Fr.: voltage de bruit   

Fluctuations of electric potential in a physical system due to spontaneous disturbances in the system.

noise; → voltage.

noise-equivalent power
  توان ِ هم‌ارز ِ نوفه   
tavân-e ham-arz-e nufé

Fr.: puissance équivalente de bruit   

A measure of the sensitivity of an electronic detector, defined as the power input to the detector that will create a signal to noise ratio of one for an integration time of half a second.

noise; → equivalent; → power.

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