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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Number of Results: 13048 Search : far
turnoff
  رهگشت   
rahgašt

Fr.: tournant   

1) A small road that branches off from a larger one, or a place where one diverges from a former course.
2) An act of turning off.

turn; → off.

Rahgašt, from rah, variant râh "path, way," → Milky Way, + gašt, → turn.

turnoff point
  نقطه‌ی ِ رهگشت   
noqte-ye rahgašt

Fr.: tournant final de la séquence principale   

Same as → main-sequence turnoff.

turnoff; → point.

turnoff star
  ستاره‌ی ِ رهگشت   
setâre-ye rahgašt

Fr.: étoile du tournant final de la séquence principale   

A star that has ended → hydrogen burning in its core but is still burning hydrogen in a shell that surrounds the core, just before evolving into a → red giant.

turnoff; → star.

turquoise
  فیروزه   
firuzé (#)

Fr.: turquoise   

A greenish blue mineral consisting of aluminium phosphate colored by traces of copper.

From M.Fr. turquoise (M.E. turkeis), from O.Fr. turqueise "Turkish," because it was first brought to Europe from Turkestan. The gem does not occur in Turkey.

Mid.Pers. pirôzak, pirôcak, cf. Skt. peraja, peroja.

Tusi couple
  جفت ِ توسی، ~ ِ طوسی   
joft-e Tusi (#)

Fr.: couple de Tusi   

Nasireddin couple.

Named for Nasireddin Tusi (1201-1274), director of Marâgha observatory who created the Ilkhani zij; → couple.

Tusi's staff
  چوبدست ِ توسی   
cubdast-e Tusi

Fr.: bâton de Tusi   

Sharafeddin's staff.

Named after the Iranian mathematician and astronomer Sharafeddin Tusi (c1135-1213), who invented the instrument. Not to be confused with Nasireddin Tusi (1201-1274), → Nasireddin couple.

tutor
  آموختار   
âmuxtâr

Fr.: tuteur   

1) A teacher who instructs students without institutional connection.
2) A teacher of a rank below instructor in some US universities.

From tutor, M.E., from O.Fr. tutour "guardian, private teacher," from L. tutor "protector, watcher," from tutus, variant p.p. of tueri "to watch over," of unknown origin.

Âmuxtâr, literally "teacher," from âmuxtan, → teach, + -âr agent noun suffix (such as xaridâr).

tutorial
  آموختال   
âmuxtâl

Fr.: tutoriel   

1) A series of intensive lessons given to an individual student or to a small group of students.
2) Programmed instructions about running a particular → software package and often built into that package.

tutor + → -al.

Âmuxtâl, from âmuxtan, → teach, + → -al.

TW Hydrae
   TW هودرا   
TW Hudrâ

Fr.: TW Hydrae   

The nearest known → classical T Tauri star, situated some 56 → parsecs away in the constellation → Hydra, far from any → molecular cloud (abbreviated TW Hya). It is a variable star with large Hα-emission → equivalent width. TW Hya is similar in mass to the Sun, but is only about 8 million years old. The star appears to be → accreting from a remarkable → face-onprotoplanetary disk of dust and gas, resolved in images from the → Hubble Space Telescope. Stellar light scattered from the optically thick dust disk is seen from 20 to 230 AU. The → scattering profile indicates that the disk is → flared, not geometrically flat. TW Hya is accompanied by a group of other low-mass stars with similar ages and space motions, comprising the → TW Hydrae association. An → exoplanet of mass nearly 10 → Jupiters has been detected around TW Hya. It orbits the star with a period of 3.56 days at 0.04 AU, inside the inner rim of the disk.

Hydra.

TW Hydrae association
  آهزش ِ TW هودرا   
âhazeš-e TW Hudrâ

Fr.: Association TW Hydrae   

A young (≤ 100 million years) association of stars (abbreviated TWA) with at least 27 members, from → intermediate mass stars to planetary mass objects. Five of them, including → TW Hydrae, display signatures of → T Tauri stars. TWA is the first moving group of young nearby (≤ 100 → paesecs) stars to be identified.

TW Hydrae; → association.

twenty
  بیست   
bist (#)

Fr.: vingt   

A cardinal number, 10 times 2.

M.E.; O.E. twentig "group of twenty," from twegentwo; cf. O.Fris. twintich, Du. twintig, O.H.G. zweinzug, Ger. zwanzig.

Bist "twenty;" Mid.Pers. wist "twenty;" Av. vīsaiti "twenty;" cf. Skt. vimśati- "twenty;" Gk. eikosi "twenty;" L. uiginti "twenty."

twice
  دوبار   
dobâr (#)

Fr.: deux fois   

Two times, as in succession; on two occasions.

M.E. twies, from O.E. twiga, twigea "two times," from twi-, → two; cf. L. bis, Gk. dis, Skt. dvis, Av. biš.

Dobâr, from do, → two, + bâr "time, fold," from Mid.Pers. bâr; Proto-Ir. *uara-; cf. Av. var- "to choose; to convince;" Skt. vāra- "time, turn."

twilight
  نیمتاب   
nimtâb (#)

Fr.: crépuscule   

The diffused light from the sky when the Sun is below the → horizon, either from daybreak to → sunrise or, more commonly, from → sunset to → dusk or nightfall. There are three types of twilight: → astronomical twilight, → nautical twilight, and → civil twilight. They are divided on the basis of the → solar depression angle.

M.E., cognate with Du. tweelicht, Ger. zwielicht, from twi- a combining form meaning "two, twice," but it appears to refer to "half" light, rather than the fact that twilight occurs twice a day + → light.

Nimtâb, from nim, nimé, → half, + tâb "light," present stem of tâbidan "to shine," → luminosity.

twinkling
  چشمک   
cešmak (#)

Fr.: scintillation   

A shining with intermittent light, as the twinkling of the stars. → scintillation.

M.E. twinklen (v.), O.E. twinclian, frequentative of twincan "to wink, blink;" related to M.H.G. zwinken, Ger. zwinkern.

Cešmak "twinke," from cešm, → eye, + -ak relation suffix.

twins paradox
  پارادخش ِ همزادها   
pârâdaxš-e hamzâdhâ

Fr.: paradoxe des jumeaux   

A thought experiment in special relativity, according to which if one of a pair of twins (A) remains on Earth, and the other (B) travels at a speed near the speed of light, B will be younger than A upon returning to Earth. In fact there is no paradox, because the two perspectives, A and B's, are actually not completely symmetric. There is no fixed time difference between the events, and different observers experience different intervals of time between the same two events. In fact, B returns younger than A because only B travels in a non-inertial (accelerating) reference frame. From A's point of view, B experiences time dilation, but from B's point of view the distance traveled is shortened because of length contraction. If B leaves in the year 2000 and returns in 2020, for A 20 years have elapsed. For B it depends on his travel speed. If has has moved as fast as 86% of the speed of light for him 10 years have passed. If his speed has been 99.5% of the speed of light the travel duration for him has been 2 years. This effect has been verified experimentally by measurements with atomic clocks.

Twin M.E.; O.E. twinn; cf. O.N. tvinnr, O.Dan. tvinling, Du. tweeling, Ger. zwillung; → paradox.

Pârâdaxš, → paradox; hamzâdhâ, plural of hamzâd "twin," literally "born together," from ham- "together" → syn- + zâd "born," from zâdan "to bring forth, give birth" (Mid.Pers. zâtan; Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" cf. Skt. janati "begets, bears," janitár "progenitor, father;" Gk. genetor "progenitor;" L. gignere "to beget," nasci "to be born," as above, PIE base *gen- "to give birth, beget").

two
  دو   
do (#)

Fr.: deux   

A cardinal number, 1 plus 1. → two-color diagram; → two-photon emission.

M.E., from O.E. twa, feminine and neuter form of twegen "two," from P.Gmc. *twai (cf. O.S., O.Fris. twene, twa, O.N. tveir tvau, Du. twee, O.H.G. zwene, zwo, Ger. zwei, Goth. twai), cognate with Pers. do, as below.

Do "two," from Mid.Pers. do; Av. dva-; cf. Skt. dvi-; Gk. duo; L. duo (Fr. deux), di; Lith. dvi; O.C.S. duva; PIE base *duwo.

Two Micron All Sky Survey (2MASS)
     
2 MASS

Fr.: 2MASS   

An astronomical → survey conducted from 1997 to 2001 of the entire sky in near-infrared J, H, and K bands (wavelengths 1.25, 1.65, and 2.17 microns respectively). The aim was to detect and characterize point sources brighter than about 1 → mJy in each band, with → signal-to-noise ratio greater than 10, using a pixel size of 2".0. Two automated 1.3-m telescopes were used, one at Mt. Hopkins, AZ, and one at CTIO, Chile. 2MASS is currently producing the following data products: 1) A digital atlas of the sky comprising approximately 4 million 8' × 16' images, having about 4" spatial resolution in each of the wavelength bands. 2) A point source catalog containing accurate positions and fluxes for 300 million stars and other unresolved objects. 3) An extended source catalog containing positions and total magnitudes for more than 1,000,000 galaxies and nebulae.

two; → micron; → all-sky survey.

two-body problem
  پراسه‌ی ِ دو جسم   
parâse-ye do jesm

Fr.: problème à deux corps   

In classical mechanics, the study concerned with the dynamics of an isolated system of two particles subject only to the Newtonian gravitational force between them. The problem can be separated into two single-particle problems with the following solutions. The equation of the → center of mass is governed by the equation of the same form as that for a single particle. Moreover, the motion of either particle, with respect to the other as origin, is the same as the motion with respect to a fixed origin of a single particle of → reduced mass acted on by the same internal force. See also → three-body problem, → n-body problem.

two; → body; → problem.

two-body system
  راژمان ِ دو جسم   
râžmân-e do jesm

Fr.: système à deux corps   

A → dynamical system consisting of two masses that interact via → central forces.

two; → body; → system.

two-color diagram
  نمودار ِ دو رنگ   
nemudâr-e do rang

Fr.: diagramme deux couleurs   

A graph on which two color indices such as B-V and U-B are plotted, one along each axis, for a sample of stars or other objects, such as stars.

two; → color; → diagram.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu 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 Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg 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 Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad 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 Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>