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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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turn
  ۱) گردیدن، گشتن؛ گرداندن؛ ۲) گشت   
1) gardidan, gaštan; gardândan; 2) gašt

Fr.: 1) tourner; faire tourner; 2) tour, tournure   

1) To move, or cause to move, around, or partly around a center.
2) The action or an act of turning about a center or axis.

M.E. turnen; O.E. turnian "to rotate, revolve," also from O.Fr. torner "to turn," both from L. tornare "to turn on a lathe," from tornus "lathe," from Gk. tornos "lathe, tool for drawing circles."

Gardidan "to turn; turning," variant gaštan "to turn, to change;" Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- " to turn, bend."

turning point
  گشتگاه   
gaštgâh (#)

Fr.: tournant   

The closest point in the path of a sound wave to the center of a star, as studied in → asteroseismology. Starting from the surface, the sound wave first moves into the star almost straight toward the center. Its path then deflects, because of the increasing → sound speed, so that it misses the center of the star. After the turning point, the wave moves out again until it reaches the surface, where it is reflected. If exactly an integer number of wavelengths fits between two reflections at the surface, the sound wave corresponds to a → standing wave with a specific pattern of → node lines on the surface.

turn; → point.

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.

<< < -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 > >>