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: 12948 Search : far
turbulent
  آشوبناک   
âšubnâk (#)

Fr.: turbulent   

The quality of a flow that undergoes → turbulence.

Adj. from → turbulence.

turbulent boundary layer
  لایه‌یِ کرانیِ آشوبناک   
lâye-ye karâni-ye âš:ubnâk

Fr.: couche limite turbulente   

The layer in which the Reynolds stresses are much larger than the viscous stresses. When the → Reynolds number is sufficiently high, there is a turbulent layer adjacent to the → laminar boundary layer.

turbulent; → boundary; → layer.

turbulent core model
  مدل ِ مغزه‌ی ِ آشوبناک   
model-e maqze-ye âšubnâk

Fr.: modèle de cœur turbulent   

A star formation scenario whereby → massive stars form from gravitationally bound → pre-stellar cores, which are supersonically → turbulent and in approximate pressure equilibrium with the surrounding protocluster medium. The high → accretion rates that characterize such media allow accretion to overcome the radiation pressure due to the luminosity of the star. The core is assumed to → collapse via an → accretion disk to form a single star or binary. The core density structure adopted is ρ ∝ r-k, with k = 1.5 set from observations. This choice affects the evolution of the accretion rate, which increases linearly with time. The high densities in regions of massive-star formation lead to typical time scales for the formation of a massive star of about 105 years (McKee & Tan 2003, ApJ 585, 850).

turbulent; → core.

turbulent flow
  تچان ِ آشوبناک   
tacân-e âšybnâk

Fr.: écoulement turbulent   

A → flow characterized by → turbulence. In other words, a flow in which the motion at any point varies unpredictably in direction and magnitude. See also → laminar flow; → transitional flow.

turbulent; → flow.

turbulent Jeans mass
  جرم ِ جینز ِ آشوبناک   
jerm-e Jeans-e âšubnâk

Fr.: masse de Jeans turbulente   

The characteristic mass for → cloud fragmentation in a → turbulent medium. While the standard → Jeans mass depends simply on the gas mean → density and → temperature, and fragmentation is purely gravitational, turbulent Jeans mass depends strongly also on the → Mach number (Chabrier et al. 2014, arXiv:1409.8466).

turbulent; → Jeans; → mass.

turbulent plasma
  پلاسمای ِ آشوبناک   
plasmâ-ye âšubnâk

Fr.: plasma turbulent   

A plasma characterized by a → turbulent flow regime.

turbulent; → plasma.

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."

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir 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 coo cor cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>