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: 13116 Search : far
parallelogram
  پراسوبر   
parâsubar

Fr.: parallélogramme   

A four-sided → polygon whose opposite sides are parallel. A parallelogram all of whose angles are right angles is a → rectangle.

From Fr. parallélogramme, from L. parallelogrammum, from Gk. parallelogrammon "bounded by parallel lines," from parallelos, → parallel, + gramme "line," related to graphein "to write, draw" → -graph.

Parâsubar, from parâsu, → parallel, + bar, → side.

paramagnet
  پارامغنات   
pârâmeqnât

Fr.: para-aimant   

A paramagnetic substance, which possesses → paramagnetism.

para- + → magnet.

paramagnetic
  پارامغناتی   
pârâmeqnâti

Fr.: paramagnétique   

Relative to or characterized by → paramagnetism.

para- + → magnetic

paramagnetism
  پارامغنات‌مندی   
pârâmeqnâtmandi

Fr.: paramagnétisme   

The property of a substance that possesses a → magnetic permeability greater than that of a vacuum but significantly less than that exhibited by → ferromagnetism. In the absence of an external magnetic field the atomic → magnetic moments of the substance are randomly oriented and thus cancel each other out with no net total magnetic moment. Moreover the coupling between neighboring moments is weak. However, when a magnetic field is applied magnetic moments align with the direction of the field and so the magnetic moments add together. Therefore paramagnetic substances affect external fields in a positive way, by attraction to the field resulting in a local increase in the magnetic field. The → magnetization vanishes when the field is removed.

para- + → magnetism

parameter
  پارامون   
pârâmun

Fr.: paramètre   

General: Any of a set of physical properties whose values determine the characteristics or behavior of something. → impact parameter; → ionization parameter.
Math.: A constant or variable term in a function that determines the specific form of the function but not its general nature, as a in f(x) = kx, where k determines only the slope of the line described by f(x).

Mod.L. parametrum, from Gk. → para- + metron "measure," → meter.

Parâmun, from parâ-, → para-, + mun/mân "measure," as in Pers. terms pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl," from O.Pers./Av. mā(y)- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure."

parametric equation
  هموگش ِ پارامونی   
hamugeš-e pârâmuni

Fr.: équation paramétrique   

Any of a set of equations that defines the coordinates of the dependent variables of a curve or surface in terms of one or more independent variables or parameters.

parametric; → equation.

Paranal Observatory
  نپاهشگاه ِ پارانال   
nepâhešgâh-e Paranal

Fr.: Observatoire de Paranal   

An → ESO observatory, located on Cerro Paranal in the Atacama Desert, northern Chile, at 2,635 m altitude. It is about 120 km south of the town of Antofagasta and 12 km inland from the Pacific Coast. The Paranal Observatory hosts the → Very Large Telescope (VLT) with four 8.2 m telescopes. Each telescope provides one → Cassegrain and two → Nasmyth focus stations for facility instruments. One Nasmyth focus is available for visitor instruments. In addition each telescope is equipped with a → coudé focus station from which the light can be coherently combined in the interferometric focus. ESO also operates four 1.8 m Auxiliary Telescopes (ATs), that are used as an interferometric array (VISA) and a 4 m infrared survey telescope (VISTA). Currently, more than 10 instruments including two interferometric instruments (MIDI, AMBER) are operational and offered for science observations.

Paranal, the name of the mountain, in the Quechua language meaning "whirlwind;" → observatory.

parapegma
  پاراپگما   
pârâpegmâ

Fr.: parapegme   

An astronomical and meteorological calendar written by ancient Greeks from 450 B.C. during at least three centuries. The parapegma was an inscribed stone for public use. It had holes beside the inscription, in which a peg could be inserted next to the appropriate day. The term was later applied to purely written forms of such calendars, or almanacs; plural form parapegmata.

From → para- "next to" + pegma "something that fastens something else together," from pegnyein "to stick."

paraxial
  پر‌آسه‌ای   
parâse-yi

Fr.: paraxial   

Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian optics.

para-; → axial.

From par(â)-, → para-, + âseyiaxial.

paraxial ray
  پرتو ِ پر‌آسه‌ای   
partow-e parâse-yi

Fr.: rayon paraxial   

A ray that lies close to and almost parallel to the optical axis and behaves according to paraxial equations.

paraxial, → ray.

Parenago catalog
  کاتالوگ ِ پارناگو   
kâlâlog-e Parenago

Fr.: catalogue de Parenago   

A catalog of stars in the → Orion Nebula created by P. P. Parenago in 1954 (Publ. Astr. Inst. Sternberg, Band 25, p. 393-437, Moskau).

Pavel Petrovich Parenago (1906-1960), a Soviet astronomer.

parent
  پرمار   
permâr

Fr.: parent   

1) General: A father or a mother. A precursor, or → progenitor.
2) Physics: A → nuclide that upon → radioactive decay or → disintegration yields a specific nuclide (the → daughter). See also → parent cloud, → parent element, → parent galaxy, → parent molecule.

From O.Fr. parent, from L. parentem (nominative parens) "father or mother, ancestor," from parere "to bring forth, give birth to, produce," from PIE base *per- "to bring forth"

Permâr, literally "father-mother" (as in Sogd. māt-pitri "parent"), from Gilaki per, → father, + Gilaki mâr, → mother.

parent cloud
  ابر ِ پرمار   
abr-e permâr

Fr.: nuage parent   

Usually of a newborn star, the molecular cloud in which the star has formed.

parent; → cloud.

parent element
  بن‌پار ِ پرمار   
bonpâr-e permâr

Fr.: élément parent   

A radioactive element that spontaneously decays into a new substance. The product of this decay is known as a "daughter" element.

parent; → element.

parent galaxy
  کهکشان ِ پرمار   
kahkešân-e permâr

Fr.: galaxie parente   

Of a high redshift supernova, the galaxy in which the event has occurred.

parent; → galaxy.

parent molecule
  مولکول ِ پرمار   
molekul-e permâr

Fr.: molécule parente   

The molecule initially produced when a comet nucleus sublimates, soon changed to different daughter molecules because of solar radiation.

parent; → molecule.

parhelion
  پراهور   
parâhur

Fr.: parhélie   

An atmospheric optical phenomenon, seen as a bright spot sometimes appearing at either side of the → Sun, often on a luminous ring or → halo and at the same angular elevation as the Sun. Parhelia are caused by the → refraction and → reflection of → sunlight by → ice crystals suspended in the Earth's → atmosphere. Also called mock Sun or sundog.

From Gk. parhelion "a mock Sun," from → para- "beside" + helios "sun," → helio-.

Parâhur, from parâ-, → para-, + hur "sun," → helio-.

parity
  همالی   
hamâli (#)

Fr.: parité   

1) General: Equality, as in amount, status, or character; equivalence; correspondence; similarity; analogy. Opposite of disparity.
2) Physics: The principle of space-inversion invariance.
An operation that reverses the algebraic sign of the coordinate axes used to describe a system, i.e. (x, y, z) → (-x, -y, -z). The parity principle is important in quantum mechanics because the wave functions which represent particles can behave in different ways upon transformation of the coordinate system. The parity is 1 (or even) if the wave function of the system is unchanged by an inversion of the coordinate system; it is -1 (or odd) if the wave function is changed only in sign. Parity is conserved in strong interactions, but not in weak ones.
3) Math.: The attribute, of an integer, of being even or odd. Thus, it can be said that 8 and 12 have the same parity, whereas 5 and 16 have opposite parity.
See also: → charge-parity symmetry, → even parity, → parity conservation, → parity symmetry, → parity violation.

From M.Fr. parité, from L.L. paritas "equality," from L. adj. par "equal."

Hamâli, quality noun of hamâl, → pair (equivalent 2).

parity conservation
  پتایش ِ همالی   
patâyeš-e hamâli

Fr.: conservation de parité   

In quantum mechanics, the condition of parity in strong and electrodynamic interactions, where it remains constant and does not change with time. In other words, parity conservation implies that Nature is symmetrical and makes no distinction between right- and left-handed rotations or between opposite sides of a subatomic particle. Thus, for example, two similar radioactive particles spinning in opposite directions about a vertical axis should emit their decay products with the same intensity upward and downward. Same as → parity symmetry.

parity; → conservation.

parity symmetry
  همامونی ِ همالی   
hamâmuni-ye hamâli

Fr.: symétrie de parité   

The invariance of physical laws under a transformation that changes the sign of the space coordinates. Parity symmetry is sometimes called mirror symmetry. It is known that the parity symmetry is violated in some weak interactions, while it is well preserved in all other three interactions (gravitational, electromagnetic, strong). Same as → P-symmetry and → parity conservation.

parity; → symmetry.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc 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 Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg 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 > >>