An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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A B C D E F G H I J K L M N O P Q R S T U V W X Y Z


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Number of Results: 13176 Search : in
Large Synoptic Survey Telescope (LSST)
  تلسکوپ ِ بزرگ ِ هنوینی برای ِ بردید   
teleskop-e bozorg-e hanvini barâye bardid

Fr.: Grand Télescope d'étude synoptique   

Initial name given to → Vera C. Rubin Observatory.

large; → synoptic; → survey; → telescope.

large-scale structure
  ساختار ِ بزرگ-مرپل   
sâxtâr-e bozorg-marpel

Fr.: structure à grandes échelles   

The distribution of galaxies and other forms of mass on large distance scales, covering hundreds of millions of → light-years.

large; → scale; → structure.

Larissa
  لریسا   
Larissa (#)

Fr.: Larissa   

The fifth of Neptune's known satellites. It orbits 73,600 km from Neptune and is a non spherical object about 208 × 178 km in size. It was discovered using NASA's Voyager 2 mission in 1989.

In Gk. mythology, Larissa is a princess of Argos (in central Greece) who, according to some, bore Poseidon three sons: Akhaios, Pelasgos and Pythios (though others gave these eponymous heroes different parents).

Larmor frequency
  بسامد ِ لارمور، فرگی ِ ~   
basâmad-e Larmor (#), feregi-ye ~ (#)

Fr.: fréquence de Larmor   

The frequency of precession of a charged particle describing a circular motion in a plane perpendicular to the magnetic induction in a uniform magnetic field.

Named after Joseph Larmor (1857-1942), an Irish physicist, the first to calculate the rate at which energy is radiated by an accelerated electron, and the first to explain the splitting of spectrum lines by a magnetic field; → frequency.

Larmor radius
  شعاع ِ لارمور   
šoâ'-e Larmor (#)

Fr.: rayon de Larmor   

The radius of the circular motion of a → charged particle moving in a → uniform magnetic field. Same as → gyroradius, → radius of gyration, → cyclotron radius. The Larmor radius (rL) is obtained by equating the → Lorentz force with the → centripetal force: qvB = mv2/rL, which leads to rL = p/(ZeB), where p is → momentum, Z is → atomic number, e is the → electron charge, and B is → magnetic induction. The frequency of this circular motion is known as the → gyrofrequency.

Larmor frequency; → radius.

Larmor's theorem
  فربین ِ لارمور   
farbin-e Larmor

Fr.: théorème de Larmor   

If a system of → charged particles, all having the same ratio of charge to mass (q/m), acted on by their mutual forces, and by a central force toward a common center, is subject in addition to a weak uniform magnetic field (B), its possible motions will be the same as the motions it could perform without the magnetic field, superposed upon a slow → precession of the entire system about the center of force with angular velocity ω = -(q/2mc)B.

Larmor frequency; → theorem.

Larson relation
  بازانش ِ لرسون   
bâzâneš-e Larson

Fr.: relation de Larson   

An → empirical relationship between the internal → velocity dispersion of → molecular clouds and their size. The velocity dispersions are derived from molecular → linewidths, in particular those of → carbon monoxide. It was first established on star forming regions and found to be: σ (km s-1) = 1.10 L (pc)0.38, where σ is the velocity dispersion and L the size. The relation holds for 0.1 ≤ L ≤ 100 pc. More recent set of cloud data yield: σ (km s-1) = L (pc)0.5. This relation indicates that larger molecular clouds have larger internal velocity dispersions. It is usually interpreted as evidence for → turbulence in molecular clouds. Possible sources of interstellar turbulence include the following processes operating at various scales: galactic-scale (→ differential rotation, → infall of extragalactic gas on the galaxy), intermediate-scale (expansion of → supernova remnants, → shocks, → stellar winds from → massive stars), and smaller-scale processes (→ outflows from → young stellar objects).

First derived by Richard B. Larson, American astrophysicist working at Yale University (Larson, 1981, MNRAS 194, 809). See Falgarone et al. (2009, A&A 507, 355) for a recent study; → relation.

Larson-Penston solution
  لویش ِ لرسون-پنستون   
luyeš-e Larson-Penston

Fr.: solution de Larson-Penston   

The analytical solution to the → hydrodynamic equations describing the → collapse of an → isothermal sphere. The Larson-Penston solution is → self-similar for a purely dynamical isothermal collapse with spherical symmetry. It corresponds to the collapse prior to the formation of a → protostar, and thus is suitable for the study of → pre-stellar cores. The Larson-Penston solution was extended by Shu (1977) to obtain a whole family of solutions for this problem.

Named after R. B. Larson (1969, MNRAS 145, 271) and M. V. Penston (1969, MNRAS 144, 425), who simultaneously, but independently, did this study.

laryngeal
  حنجره‌ای   
hanjare-yi (#)

Fr.: laryngé   

1) Of, pertaining to, or located in the larynx.
2) Phonetics: articulated in the larynx (Dictionary.com).

larynx; → -al.

laryngeal consonant
  هم‌آوای ِ حنجره‌ای   
hamâvâ-ye hanjare-yi

Fr.: son laryngé   

A consonant generated in the → larynx with the → vocal cords partly closed and partly vibrating. It is hypothesized that the → Proto-Indo-European language contained some laryngeal consonants (denoted by H).

laryngeal; → consonant.

larynx
  حنجره   
hanjaré (#)

Fr.: larynge   

A muscular and cartilaginous structure lined with mucous membrane at the upper part of the → trachea in humans, in which the → vocal cords are located (Dictionary.com).

From M.Fr. larynx, from M.L. from Gk. larynx (genitive laryngos) "the upper windpipe," probably from laimos "throat," influenced by pharynx "throat, windpipe."

Hanjaré, from Ar. Hanjarah.

laser
  لیزر   
leyzer (#)

Fr.: laser   

1) A device that generates an intense directional beam of → monochromatic and → coherent light by exciting atoms to a higher energy level and causing them to radiate their energy in phase. The high degree of collimation arises from the fact that excited atoms are are situated in a cavity bounded by two parallel front and back mirrors. A first photon stimulates an atom which emits a second photon, and so on thanks to the mirrors. The resulting photons are all identical. They have the same energy which gives them the same color and a unique direction. The first working laser, a pulsed ruby device, was developed by T. Maiman in 1959. See also → gas laser, → stimulated emission; → maser.
2) The light produced in this way.

Acronym for light amplification by stimulated emission of radiation, on pattern of → maser.

laser cooling technique
  تشنیک ِ سردش ِ لیزری   
tašnik-e sardeš-e leyzeri

Fr.: technique de refroidissement par laser   

A technique that uses a suitable arrangement of → laser beams and magnetic fields to capture → cesium (133Cs) atoms from a thermal vapor and slow the motion of the atoms, cooling them to just a few micro-kelvins above the → absolute zero. The technique allows trapping some 107 cesium atoms in a cloud a few millimeters in diameter in a few tenths of a second. At a temperature of 2 μK, the average thermal velocity of the cesium atoms is of the order of 1 cm s-1, so they stay together for a relatively long time. The laser cooling technique is the key tool which enabled the operation of an → atomic fountain clock.

laser; → cooling; → technique.

laser interferometer
  اندرزنش‌سنج ِ لیزری   
andarzaneš-sanj-e leyzeri

Fr.: interféromètre laser   

An optical instrument using laser → beams to form → interference pattern. There are two types of laser interferometers: → homodyne and → heterodyne. A homodyne interferometer, like → Michelson interferometer, uses a single-frequency laser source. A → heterodyne interferometer uses a laser source with two close frequencies.

laser; → interferometer.

Laser Interferometer Gravitational-Wave Observatory (LIGO)
  نپاهشگاه ِ موجهای ِ گرانشی با اندرزنش‌سنجی ِ لیزری   
nepâhešgâh-e mowjhâ-ye gerâneši bâ andarzaneš-sanji-ye leyzeri

Fr.: Observatoire d'ondes gravitationnelles par interférométrie laser   

A facility dedicated to the detection and measurement of cosmic → gravitational waves. It consists of two widely separated installations, or detectors, within the United States, operated in unison as a single observatory. One installation is located in Hanford (Washington) and the other in Livingston (Louisiana), 3,000 km apart. Funded by the National Science Foundation (NSF), LIGO was designed and constructed by a team of scientists from the California Institute of Technology, the Massachusetts Institute of Technology, and by industrial contractors. Construction of the facilities was completed in 1999. Initial operation of the detectors began in 2001. Each LIGO detector beams laser light down arms 4 km long, which are arranged in the shape of an "L." If a gravitational wave passes through the detector system, the distance traveled by the laser beam changes by a minuscule amount -- less than one-thousandth of the size of an atomic nucleus (10-18 m). Still, LIGO should be able to pick this difference up. LIGO directly detected gravitational waves for the first time from a binary → black hole merger (GW150914) on September 14, 2015 (Abbott et al., 2016, Phys. Rev. Lett. 116, 061102). The Nobel Prize in physics 2017 was awarded to three physicists (Rainer Weiss, Barry C. Barish, and Kip S. Thorne) for decisive contributions to the LIGO detector and the observation of gravitational waves. LIGO had a prominent role in the detection of → GW170817, the first event with an → electromagnetic counterpart.

laser; → interferometer; → gravitational; → wave; → observatory.

Laser Interferometer Space Antenna (LISA)
  آنتن ِ فضایی ِ اندرزنش‌سنج ِ لیزری   
ânten-e fezâyi-e andarzanešsanj-e leyzeri

Fr.: Observatoire d'ondes gravitationnelles par interférométrie laser   

A collaborative project between → NASA and → ESA to develop and operate a space-based gravitational wave detector sensitive at frequencies between 0.03 mHz and 0.1 Hz. LISA detects gravitational-wave induced strains in → space-time by measuring changes of the separation between fiducial masses in three spacecraft 5 million km apart. Ultimately, NASA and ESA decided in 2011 not to proceed with the mission. LISA was not the highest ranked mission in the 2010 Decadal Survey and funding constraints prevented NASA from proceeding with multiple large missions (http://lisa.nasa.gov). → LISA pathfinder.

laser; → interferometer; → space; → antenna.

last
  واپسین   
vâpasin (#)

Fr.: dernier   

Occurring or coming after all others, as in time, order, or place. → last contact, → last quarter

Last, from O.E. latost (adj.) and lætest (adv.), superlative of læt (adj.) and late (adv.); cognate with O.Fris. lest, Du. laatst, O.H.G. laggost, Ger. letzt.

Vâpasin, from vâ-, as intensive prefix, → de-, + pasin, from pas "after, afterward, behind; finally, at last" (Mid.Pers. pas "behind, before, after;" O.Pers. pasā "after;" Av. pasca "behind (of space); then, afterward (of time);" cf. Skt. pazca "behind, after, later;" L. post "behind, in the rear; after, afterward;" O.C.S. po "behind, after;" Lith. pas "at, by;" PIE base *pos-, *posko-) + -in superlative suffix.

last (v.)
  پاییدن   
pâyidan

Fr.: durer   

To continue in time; go on; endure.

M.E. lasten, from O.E. læstan "to continue, endure;" cf. Goth. laistjan "to follow after," Ger. leisten "to perform, achieve,"), from PIE root *lois- "furrow, track."

Pâyidan "to watch, observe; remain or continue in existence, last," variants pâsidan, pâhidan; Mid.Pers. pây- "to protect, guard;" Sogdian p'y "to observe, protect, watch over;" O.Pers. pā- "to protect," pāta- "protected;" Av. pā- "to protect," pāti "guards," nipā(y)- (with ni-) "to watch, observe, guard," nipātar- "protector, watcher," nipāθri- "protectress;" cf. Skt. pā- "to protect, keep," tanû.pā- "protecting the body," paś.pā- "shepherd;" Gk. poma "lid, cover," poimen "shepherd;" L. pascere "to put out to graze," pastor "shepherd;" Lith. piemuo "shepherd;" PIE base *pā- "to protect, feed."

last contact
  پرماس ِ واپسین   
parmâs-e vâpasin

Fr.: dernier contact   

Same as → fourth contact at an eclipse.

last; → contact.

last quarter
  چارک ِ واپسین   
cârak-e vâpasin

Fr.: dernier quartier   

One of the phases of the Moon that appears when it is 90 degrees west of the Sun. Approximately one week after a full moon, when half of the Moon's disk is illuminated by the Sun. → first quarter.

last; → quarter.


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<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>