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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 12948 Search : far
isotropy
  ایزوگردی، هم‌سان‌گردی   
izogardi, hamsângardi (#)

Fr.: isotropie   

The property by which physical properties are equal along all directions. → anisotropy.

Isotropy, noun of → isotropic.

issue
  ۱) برونای؛ ۲) بروناییدن   
1) borunây; 2) borunâyidan

Fr.: issue, question, problème   

1a) A result or outcome of something.
1b) The action of flowing or coming out.
1c) Each of a regular series of publications.
1d) An important topic or problem for debate or discussion.
2) Formally send out or make known (OxfordDictionaries.com).

M.E., from O.Fr. issue "a way out, a going out, exit; final event," from L. exire "to go out, go forth; become public; flow, pour forth," from → ex- "out," + ire "to go,"

Borunây, literally "what comes out, exits," from borun, → out, + ây- present stem of âmadan "to come, arrive, become," → precession.

iterate
  ایتریدن   
itaridan

Fr.: itérer   

1) To utter or to do something over again or repeatedly. → repeat.
2) Math.: → iteration.

Iterate "to do again, repeat," back-formation from iteration, from L. iterationem (nom. iteratio) "repetition," noun of action from iterare "to do again, repeat," from iterum "again, for the second time;" cf. Skt. itara- "the other (of the two), another."

Itaridan, from L. iter(um), Skt. itar(a-), as above, and Pers. dialects Kâšâni (Voništun) târ "the other;" Kurd. tir "the other" + -idan Pers. infinitive suffix.

iteration
  ایترش   
itareš

Fr.: itération   

A computational process involving a succession of approximations, which consists of repeating the operation by inputting the outcome of each preceding operation to improve the final result until a desired accuracy is achieved. Compare → repetition.

Verbal noun of → iterate.

iterative method
  روش ِ ایترشی   
raveš-e itareši

Fr.: méthode itérative   

A method of computation in mathematics using → iteration.

Iterative, characterized by or involving → iteration; → method.

Izar (ε Boötis)
  ایزار   
Izâr

Fr.: Izar   

A bright giant star in the constellation → Boötes lying 210 light-years away. It is a close double consisting of K0 and A0 dwarfs of magnitudes 2.5 and 4.6.

From Ar. Al-Izâr (الازار) "a cloth worn round the loins and passed between the legs," Ar. rendering of the Herdsman's skirt; → Boötes.

Jablonski diagram
  نمودار ِ یابلونسکی   
nemudâr-e Jablonski

Fr.: diagram de Jablonski   

An energy schematic representing the → electronic states of a → molecule and the → transitions between them. The vertical axis shows energies whereas → energy states are grouped horizontally according to their spin → multiplicity. Radiation-less transitions are symbolized by usual arrows, while → radiative transitions are represented by wavy arrows. The vibrational ground states of each electronic state are indicated with thick lines and the higher → vibrational states with thinner lines.

Named after Aleksander Jablonski (1898-1980), a Polish physicist who was an expert in the field of luminescence and atomic optics; → diagram.

Jacobi integral
  درستال ِ یاکوبی   
dorostâl-e Jacobi

Fr.: intégrale de Jacobi   

The integral admitted by the equations of a body of infinitesimal mass moving under the → gravitational attractions of two massive bodies, which move in circles about their → center of gravity. The Jacobi integral is the only known conserved quantity for the circular → restricted three-body problem. In the co-rotating system it is expressed by the equation: (1/2) (x·2 + y·2 + z·2) = U - CJ, where the dotted coordinates represent velocities, U is potential energy, and CJ the constant of integration (→ zero-velocity surface). The Jacobi integral has been used for two different purposes: 1) to construct surfaces of zero velocity which limit the regions of space in which the small body, under given initial conditions, can move, and 2) to derive a criterion (→ Tisserand's parameter) for re-identification of a → comet whose orbit has suffered severe perturbations by a planet. Also known as Jacobi constant.

Named after Karl Gustav Jacobi (1804-1851), a German mathematician who did important work on elliptic functions, partial differential equations, and mechanics; → integral.

Jacobian
  یاکوبی   
Jacobi

Fr.: jacobien   

Jacobian determinant, → Jacobian matrix.

Named after Karl Gustav Jacobi (1804-1851), a German mathematician who did important work on elliptic functions, partial differential equations, and mechanics. The "Jacobian" first appeared in an 1815 paper of the French mathematician Augustin Louis Cauchy (1789-1857), but Jacobi did write a detailed memoir about it in 1841.

Jacobian determinant
  آترمگر ِ یاکوبی   
âtarmgar-e Jacobi

Fr.: déterminant jacobien   

The determinant of a → Jacobian matrix formed by the n2 → partial derivative s of n functions of n variables.

Jacobian; → determinant.

Jacobian matrix
  ماتریس ِ یاکوبی   
mâtris-e Jacobi

Fr.: matrice jacobienne   

In → vector calculus, the matrix of all → first-order partial derivatives of a vector-valued → function.

Jacobian; → matrix.

Jalali calendar
  گاهشمار ِ جلالی   
gâhšomâr-e Jalâli (#)

Fr.: calendrier jalali   

An Iranian solar calendar, based on two successive passages of the Sun through the true → vernal equinox. It results from a reform undertaken by a group of astronomers led by Omar Khayyam (A.D. 1048-1131). The current → Iranian calendar is an improved version of the Jalali calendar.

Jalali, from the name of the ruler Jalâleddin Malek Šâh of the Saljuqid dynasty, who ordered the reform; → calendar.

James Webb Space Telescope (JWST)
  دوربین ِ فضایی ِ جیمز وب، تلسکوپ ~ ~ ~   
durbin-e fazâyi-ye James Webb, teleskop ~ ~ ~

Fr.: Télescope spatial James Webb   

A large, infrared space telescope with a mirror 6.55 m in diameter, scheduled for launch in 2018. JWST's instruments will work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range (0.6 to 28 μm). The scheduled instruments are Near IR Camera (NIRCam, field of 2.2 x 4.4 arcmin, wavelength range 0.6-5 μm), Near IR Spectrograph (NIRSpec, 3.5 x 3.5 arcmin, 0.6-5 μm, resolving powers of ~ 100, ~1000, and ~3000), Mid IR Instrument (MIRI, 1.4 x 1.9 arcmin, 5-27 μm, R ~ 3000), and Fine Guidance Sensor (FGS, 2.3 x 2.3 arcmin, 0.6-5 μm, R ~ 100). The successor to the → Hubble Space Telescope will be placed in an orbit about 1.5 million km from the Earth, at the → Lagrangian point L2. The JWST project is a → NASA-led international collaboration with the → European Space Agency and the Canadian Space Agency. The scientific goals of JWST can be grouped under four broad topics: first light after the Big Bang; galaxy formation; birth of stars and protoplanetary systems; and planetary systems and the origins of life.

Named in honor of James E. Webb (1906-1992), who headed NASA from 1961 to 1968, overseeing all the manned launches in the Mercury through Gemini programs, until before the first manned Apollo flight; → space; → telescope.

jansky (Jy)
  جنسکی   
jansky (#)

Fr.: jansky   

The unit of → radio flux density in → radio astronomy, equivalent to 10-26watts per square meter per → hertz.

Named in 1973 by the International Astronomical Union in honor of Karl Guthe Jansky (1905-1950), an American engineer of Czech descent who first identified radio waves from beyond the Solar System.

Janus
  یانوس   
Yânus (#)

Fr.: Janus   

The sixth of Saturn's known satellites. With a mean diameter of about 178 km it orbits Saturn at a distance of 150,000 km. Discovered by the French astronomer Audouin Dollfus (1924-) in 1966.

Janus was the god of gates and doorways in Roman mythology. He was also thought to represent beginnings, hence he lent his name to January, the first month of the year. He was depicted with two faces looking in opposite directions.

jasper
  یشم   
yašm (#)

Fr.: jaspe   

A colored form of natural silica, SiO2, which is a precious stone.

M.E. jaspe, jaspre, from M.Fr., O.Fr. jaspe, from L. iaspidem (nominative iaspis), from Gk. iaspis "jasper," via an Oriental language, probably an Eastern Iranian language, see below.

Yašm, variants, yasp, yasb, yašf "jasper;" Sogd. iešp "jasper," iešpênê "of jasper, crystalline."

Jeans
  جینز   
Jeans

Fr.: Jeans   

Named after Sir James Hopwood Jeans (1877-1946), English mathematical physicist, astrophysicist, and popularizer of science. He made important contributions to theoretical astrophysics, especially to the theory of stellar formation.

Jeans instability
  ناپایداری ِ جینز   
nâpâydâri-ye Jeans

Fr.: instabilité de Jeans   

An instability that occurs in a → self-gravitating  → interstellar cloud which is in → hydrostatic equilibrium. Density fluctuations caused by a perturbation may condense the material leading to the domination of gravitational force and the cloud collapse. The advent of instability involves a threshold called the → Jeans length or the → Jeans mass.

Jeans; → instability.

Jeans length
  درازای ِ جینز   
derâzâ-ye Jeans (#)

Fr.: longueur de Jeans   

The critical size of a homogeneous and isothermal interstellar cloud above which the cloud is unstable and must collapse under its own gravity. Below this size the cloud's internal pressure is sufficient to resist collapse. The Jeans length is defined by: λJ = (π cs2/Gρ)1/2 = 0.2 pc (T/10 K)1/2(nH2/104 cm-3)-1/2, where cs is the → sound speed, G is the → gravitational constant, ρ is the gas density, T is the gas temperature, and nH2 is the molecular hydrogen density.

Jeans; → length.

Jeans mass
  جرم ِ جینز   
jerm-e Jeans (#)

Fr.: masse de Jeans   

The → minimum mass for an → interstellar cloud below which the → thermal pressure of the gas prevents its → collapse under the force of its own → gravity. It is given by the formula MJ = (π5/2 / 6) G -3/2ρ0-1/2cs3, where G is the → gravitational constant, ρ0 the initial → density, and cs the isothermal → sound speed. It can be approximated to MJ ~ 45 (TK) 3/2 (ncm-3) -1/2 in units of solar masses, where TK is the temperature in → Kelvin, and ncm-3 the gas density per cm3. High density favors collapse, while high temperature favors larger Jeans mass. See also: → thermal Jeans mass, → turbulent Jeans mass.

Jeans; → mass.

<< < -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 > >>