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
Tully-Fisher relation
  بازانش ِ تولی-فیشر   
bâzâneš-e Tully-Fisher

Fr.: relation Tully-Fisher   

An observed correlation between the luminosity of a spiral galaxy and its rate of rotation (measured from its 21 cm hydrogen line). This means that more luminous galaxies have stars that are moving faster. Knowing the rotational velocity of a spiral galaxy, this relation provides its absolute magnitude and then its distance. → Faber-Jackson relation.

Named after R. B. Tully and J. R. Fisher who first derived this relationship (1977, A&A 54, 661); → relation.

tumble
  ۱) کلتاو؛ ۲) کلتاویدن   
1) kaltâv; 2) kaltâvidan

Fr.:   

1) An act of tumbling or falling.
2a) To fall helplessly down, end over end, as by losing one's footing, support, or equilibrium; plunge headlong.
2b) To roll end over end, as in falling (Dictionary.com).

M.E. tum(b)len "to dance in acrobatic style;" perhaps from O.E. tumbian "dance about, tumble, leap;" maybe related to Du. tuimelen, O.H.G. tumon "to reel."

Kaltâv, from Kermâni keletow, Malâyeri kallatow "wobbling," from kal, kalleh "head" + tâv, tow, tâb "swing, twist," from tâbidan "to twist, to spin."

tumbling asteroid
  سیارک ِ کلتاونده، ~ کلتاوگر   
sayyârak-e kaltâvande, ~ kaltâvgar

Fr.:   

An asteroid whose rotational motion does not take place about its → principal axis. Such a behavior can be interpreted as a composition of two or more rotational periods, and described mathematically by a two dimensional → Fourier series (Pravec et al. 2005, Icarus, 173, 108).

The term was first used by A. W. Harris, 1994, Icarus, 107, 209. → tumble; → asteroid.

tumbling motion
  جنبش ِ کلتاوی   
jonbeš-e kaltâvi

Fr.:   

The motion of a solid body whose rotation axis is not fixed in space. For example, that of an asteroid that does not rotate about one of their principal axes. → tumbling asteroid.

tumble; → motion.

tungsten
  تنگستن   
tangestan (#)

Fr.: tungstène   

A very hard, silver-white to steel-gray metal with a body-centered cubic crystalline structure; symbol W. Atomic number 74; atomic weight 183.85; melting point about 3,410°C; boiling point 5,660°C; specific gravity 19.3 at 20°C. The chemical element was discovered by the Swedish chemist Carl-Wilhelm Scheele in 1781. Tungsten metal was first isolated by the Spanish chemists Don Fausto d'Elhuyar and his brother Don Juan Jose d'Elhuyar in 1783.

The name derives from the Swedish ng sten "heavy stone". The chemical symbol, W, is derived from the Ger. wolfram, which was found with tin and interfered with the smelting of tin.

Tunguska event
  رویداد ِ تونگوسکا   
ruydâd-e Tunguska (#)

Fr.: événement de la Toungouska   

The violent impact of a comet or meteorite in the Tunguska region of Siberia on 30 June 1908. The object exploded in the atmosphere before touching the ground at an estimated height of 5-10 km. Observers reported seeing a fireball as bright as the Sun. The explosion caused a shock wave that shook buildings and caused damage, though there was no loss of human life. The first expedition to the remote area of the explosion took place in 1927. An estimated 80 million trees covering more than 2,150 square km were flattened. The energy of the explosion is estimated to have been equivalent to that of about 15 → megatons of TNT , a thousand times more powerful than the atomic bomb dropped on Hiroshima in 1945.

From the name of the central Siberian region, Russ. Podkamennaya (Lower Stony) Tunguska River, today Krasnoyarsk Krai; → event.

tunnel effect
  اُسکر ِ تونل   
oskar-e tunel

Fr.: effet tunnel   

A phenomenon in quantum mechanics whereby a particle can penetrate and cross a potential barrier whose energy is greater than the particle's energy. The tunnel effect, forbidden in classical mechanics, is a direct consequence of the wave nature of material particles. Also called tunneling

M.E. tonel, from M.Fr. tonele, tonnelle "funnel-shaped net," feminine of tonnel,diminutive of tonne "tun, cask for liquids." Sense of "tube, pipe" developed in Eng. and led to sense of "underground passage."

Oskar, → effect; tunel, from Fr. tunnel, as above.

turbid
  تار   
târ (#)

Fr.: turbide   

Having sediment or foreign particles stirred up or suspended; obscured, muddy, such as turbid water.

From L. turbidus "muddy, full of confusion," from turbare "to confuse, disturb," from turba "turmoil, crowd," probably from Gk. tyrbe "turmoil;" cf. Pers. târ "dark, obscure, cloudy," Laki tur "balk, refractory, restive."

Târ "obscure, dark," variant târik "dark;" Mid.Pers. târig "dark," târ "darkness;" Av. taθra- "darkness," taθrya- "dark;" cf. Skt. támisrâ- "darkness, dark night," L. tenebrae "darkness;" Hittite taš(u)uant- "blind;" O.H.G. demar "twilight."

turbidity
  تاری   
târi (#)

Fr.: turbidité   

1) Meteo.: A measure of vertical extinction of solar radiation in the atmosphere. Turbidity is directly related to aerosol concentrations in the tropospheric and stratospheric layers. → visibility.
2) The cloudiness or haziness of a fluid caused by individual particles (suspended solids) that are generally invisible to the naked eye, similar to smoke in air.

turbid; → -ity.

turbine
  توربین   
turbin (#)

Fr.: turbine   

An engine or motor in which the → kinetic energy of a moving → fluid (water, steam, air, or hot gases) acts on the blades, vanes, or buckets of a → rotor to produce rotational motion that can be converted into electrical or mechanical power. In an impulse turbine the turbine is driven by free jets of fluid striking the blades. In a reaction turbine the turbine is driven by the reactive force of a fluid passing through the rotor blades. Turbines are used in hydroelectric power generators, ship propulsion systems, and jet aircraft engines.

From Fr. turbine, from L. turbinem (nominative turbo) "spinning top, eddy, whirlwind," related to turba "turmoil, crowd."

Turbin, loan from Fr., as above.

turbulence
  آشوبناکی   
âšubnâki (#)

Fr.: turbulence   

A state of hydrodynamic → flow in which the velocity at each point fluctuates rapidly and randomly so that only statistical properties can be recognized and subjected to analysis. Turbulence is the most striking manifestation of the non-linear nature of the laws of hydrodynamics, with the irregularity of flows increasing with the → Reynolds number measuring the strength of non-linear effects. The regime of intermediate Reynolds numbers corresponds to a highly non-universal regime of the onset of turbulence, whereas high Reynolds numbers, common in practical situations, characterize the regime of → developed turbulence. → laminar flow; → chaos.

From L. turbulentia, from turbulentus "full of commotion, restless," from turba "turmoil, crowd;" maybe related to Pers. târ "dark, obscure, cloudy," Laki tur "balk, refractory, restive."

šubnâki, from âšub "turmoil, disturbance," âšoftan "to agitate, disturb;" Mid.Pers. âšôb "confusion, turmoil," âšoftan "to destroy, disturb;" Av. xšuf- "to tremble;" cf. Skt. ksobh- "to stagger, begin to swing, tremble;" Pol. chybac "to rock, move to and fro;" Lith. skubus "hasty, fast;" Goth. afskiuban "to shove;" O.E. scufan "to shove;" PIE base *k(w)seubh-, + -nâk state suffix, -i noun suffix.

turbulence decay
  تباهی ِ آشوبناکی   
tabâhi-ye âšubnâki

Fr.: dissipation de turbulence   

The process whereby turbulence evolves by exchanging energy, leading to → dissipation.

turbulence; → decay.

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.

<< < -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 > >>