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
two-dimensional flow
  تچان ِ دو-وامونی   
tacân-e do-vâmuni

Fr.: écoulement bi-dimensionnel   

A flow whose parameters are functions of time and two space coordinates (x and y) only. There is no variation in the z direction and therefore the same → streamline pattern could at any instant be found in all planes in the fluid perpendicular to the z direction (B. Massey, Mechanics of Fluids, Taylor & Francis, 2006).

two; → dimensional; → flow.

two-photon emission
  گسیل ِ دو-فوتونی   
gosil-e do-fotoni

Fr.: émission à deux photons   

The simultaneous emission of two photons whose sum of energies is equal to that of a single electron transition. The energy of each individual photon of the pair is not fixed, so that the spectrum of two-photon emission is continuous from the wavelength of that transition to infinity. In practice, there is a peak in wavelength distribution of the emitted photons. Two-photon emission is studied atomic physics with application in astrophysics, as it contributes to the continuum radiation from → planetary nebulae. It was recently observed in condensed matter and specifically in → semiconductors.

two; → photon; → emission.

TY CrA
     
TY CrA

Fr.: TY CrA   

A multiple stellar system embedded in a → reflection nebula (NGC 6726/6727) in the → Corona Australis star forming region. The three stars are within 1.5 → astronomical units of each other and lie at a distance of 129 pc. Two of its components form a → double-line eclipsing binary with an orbital period of almost 3 days. The primary is a → main sequence star (mass 3.16 solar masses, effective temperature 12,000 K) and the secondary a → pre-main sequence star (mass 1.64 solar masses, effective temperature 4,900 K) with an age of a few million years. A third spectroscopic component is in a wide orbit around the eclipsing pair. A fourth star is located at a projected distance of about 0.3 arcsecond (40 AU) from the compact tertiary system.

Corona Australis.

Tycho's star
  ستاره‌ی ِ توگو   
setâre-ye Tycho

Fr.: étoile de Tycho   

A → supernova of Type Ia in the constellation → Cassiopeia, which Tycho Brahe observed in November 1572. At its peak it was as bright as Venus and was visible in the daytime, reaching a magnitude of about -4. It is now visible as a → supernova remnant about 20 light-years across at a distance of about 7,500 light-years. It is associated with faint emission in the optical and X-rays, but is a strong radio source. Other designations: SN 1572, 3C 10, B Cas, 2U 0022+63.

Named after the Danish astronomer Tycho Brahe (1546-1601), who described the event; → star.

Tychonic model
  مدل ِ توگویی   
model-e Tychoyi

Fr.: modèle tychonique   

A hybrid of → geocentric and → heliocentric systems in which the Earth remains at the center, with the → Sun orbiting the Earth, but with all the other planets revolving about the Sun. Moreover, the fixed stars were located in a crystalline shell centered on the Earth.

Related to the Danish astronomer Tycho Brahe (1546-1601), who imagined the model; → model.

tympanum
  حجره   
hojré (#)

Fr.:tympan   

Thin brass disk inserted into the → mater of a → planispheric astrolabe. It carries the grid of → altazimuth coordinates shown in polar → stereographic projection for the → latitude of the specific observation locality. In addition to the main → vertical circles and the main → almucantars, the tympanum reproduces some elements of the → celestial sphere - the → celestial equator, the → tropic of Cancer, and the → tropic of Capricorn, as well as the hour lines for determining the unequal hours of day or night respectively from the Sun's position on the ecliptic or from the altitude of a star marked on the → rete (online museo galileo, VirtualMuseum).

From L. tympanum "drum," from Gk. tympanon "a drum, panel of a door," from root of typtein "to beat, strike."

Hojré, from Ar. hujrah "chamber."

Tyndall effect
  اسکر ِ تیندال   
oskar-e Tyndall

Fr.: effet Tyndall   

The observation whereby when light passes through a clear fluid holding small particles in suspension, the shorter blue wavelengths are scattered more strongly than the red. The effect is most commonly known as the → Rayleigh scattering.

Names for John Tyndall (1820-1893), who discovered the effect in 1859.

type
  گونه   
guné (#)

Fr.: type   

A group of items that have strongly marked and readily defined similarities.

M.E., from M.Fr., from L. typus "figure, image, form, kind," from Gk. typos "dent, impression, mark, figure, original form," from root of typtein "to strike, beat."

Guné "species; color; form; manner, kind;" Mid.Pers. gônak "kind, species;" Av. gaona- "color; body hair;" PIE base *góur- "(animal) body hair," genitive form *gunós.

Type 1 Seyfert (Sy 1)
  کهکشان ِ سیفرت ِ گونه‌ی ِ ۱   
kahkešân-e Seyfert-e guné-ye 1

Fr.: galaxie Seyfer de type 1   

A type of → Seyfert galaxy showing both broad and narrow spectral emission lines. The widths of the broad lines indicates velocities around 1000 km s-1. Sy 1 galaxies are also very bright sources of UV and X-ray emission.

type; → one; → Seyfert galaxy.

Type 2 Seyfert (Sy 2)
  کهکشان ِ سیفرت ِ گونه‌ی ِ ۲   
kahkešân-e Seyfert-e guné-ye 2

Fr.: galaxie Seyfer de type 2   

A type of → Seyfert galaxy showing only narrow emission lines and weak UV and X-ray emissions but strong IR emission.

type; → two; → Seyfert galaxy.

Type I burst
  بلک ِ گونه‌ی ِ I   
belk-e gune-ye I

Fr.: sursaut de type I   

A burst of → X-rays observed toward → low-mass X-ray binary (LMXB)s. It is characterized by a sharp increase in → luminosity, which lasts 1-10 s, followed by the peak and a slow decrease, which can last from ~ 10s to 100s. Observationally, X-ray bursts manifest as a bright peak of emission on top of the persistent emission powered by → accretion. See also → Type II burst.

type; → burst.

Type I error
  ایرنگ ِ گونه‌ی ِ I   
irang-e gune-ye I

Fr.: erreur de type I   

Statistics: An error made if a → hypothesis is rejected when it should be accepted. → Type II error.

type; → error.

Type I migration
  کوچ ِ گونه‌ی ِ I   
kuc-e gune-ye I

Fr.: migration de type I   

An → orbital migration of low-mass → planets in which no gap is created in the → protoplanetary disk. According to planetary models, beyond a critical core mass for the forming planet, a gap in the protoplanetary disk is created. The critical mass depends on the mass and → metallicity of the disk and therefore it does not have a singular value, but has been shown to be between about 10-30 Earth masses. Compare with → Type II migration.

type; → migration.

Type I supernova
  ابر-نو-اختر ِ گونه‌ی ِ I   
abar-now-axtar-e gune-ye I

Fr.: supernova de type I   

A type of supernova whose spectra lacks hydrogen lines. Its → light curve exhibits a sharp maximum with a gradual decrease. Typical magnitudes MV = -14 to -17. Ejecta velocities about 10,000 km/sec. Type I supernovae have several subtypes: → Type Ia, → Type Ib, and → Type Ic.

Type I initially introduced by R. Minkowski (1941, PASP 53, 224); → type; → supernova.

Type I tail
  دم ِ گونه‌ی ِ I   
dom-e gune-ye I

Fr.: queue de type I   

The → gas tail of of a comet.

type; → tail.

Type Ia supernova
  ابر-نو-اختر ِ گونه‌ی ِ Ia   
abar-now-axtar-e gune-ye Ia

Fr.: supernova de type Ia   

A → Type I supernova that presents a singly-ionized silicon (Si II) absorption feature at 6150 Å near peak brightness. Type Ia SNe are believed to result from mass → accretion to a carbon-oxygen → white dwarf in a → close binary system. When the white dwarf mass exceeds the → Chandrasekhar limit, the → degenerate electron pressure can no longer support the accumulated mass and the star collapses in a thermonuclear explosion producing a supernova. The → peak luminosity of SNe Ia is set by the radioactive decay chain 56Ni → 56Co → 56Fe, and the observed photometric correlation between the peak luminosity and the time-scale over which the → light curve decays from its maximum is understood physically as having both the luminosity and → opacity being set by the mass of 56Ni synthesized in the explosion. Type Ia supernovae occur in all types of galaxies. Type Ia SNe are used as → standard candles in determining cosmological distances, after normalizing their light curves with the → Phillips relation.

type; → supernova.

Type Ib supernova
  ابر-نو-اختر ِ گونه‌ی ِ Ib   
abar-now-axtar-e gune-ye Ib

Fr.: supernova de type Ia   

A → Type I supernova that has neutral helium line (He I) at 5876 Å, and no strong silicon (Si II) absorption feature at 6150 Å. Type Ib supernovae are believed to result from the evolution of → massive stars.

type; → supernova.

Type Ic supernova
  ابر-نو-اختر ِ گونه‌ی ِ Ic   
abar-now-axtar-e gune-ye Ic

Fr.: supernova de type Ia   

A → Type I supernova that shows weak or no helium lines and no strong silicon (Si II) absorption feature near 6150 Å. Type Ic supernovae are believed to result from the evolution of → massive stars.

type; → supernova.

Type II burst
  بلک ِ گونه‌ی ِ II   
belk-e gune-ye II

Fr.: sursaut de type II   

A burst of → X-rays observed toward → low-mass X-ray binary (LMXB)s and characterized by quick succession of bursts with recurrence intervals as short as ~ 7 s. Type II X-ray bursts look similar to → Type I bursts, but they are thought to be related with spasmodic episodes of → accretion.

type; → burst.

Type II error
  ایرنگ ِ گونه‌ی ِ II   
irang-e gune-ye II

Fr.: erreur de type II   

Statistics: An error made if a → hypothesis is accepted when it should be rejected. → Type I error.

type; → error.

<< < -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 > >>