An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -oi obj obs obt oct off old onl ope opp opt opt orb ord Ori ort Ost ove oxi > >>

Number of Results: 373
orbital migration
  کوچِ مداری   
kuc-e madâri

Fr.: migration orbitale   

Theoretical prediction according to which a → giant planet, formed in the outer regions of a → protoplanetary disk, could migrate inward by losing → energy and → angular momentum as the result of → gravitational interactions with the remnants of the disk. This orbital migration could explain the presence of giant gaseous Jupiter-like planets (→ hot Jupiters) very close to their host stars.

orbital; → migration.

orbital node
  گره ِ مداری   
gereh-e madâri

Fr.: nœud orbital   

One of the two points of intersection of the orbit of a secondary body with the plane of reference through the primary.

orbital; → node.

orbital period
  دوره‌یِ مداری   
dowre-ye medâri (#)

Fr.: période orbitale   

The time interval between two successive passages of an object through the same point in its orbit around another object.

orbital; → period .

orbital plane
  هامُنِ مداری   
hâmon-e madâri

Fr.: plan orbital   

The plane defined by the motion of an object about a primary body.

orbital; → plane .

orbital precession
  پیشایان ِ مداری   
pišâyân-e madâri

Fr.: précession orbitale   

Same as → relativistic precession.

orbital; → precession.

orbital resonance
  باز‌آوایی ِ مداری   
bâzâvâyi-ye madâri

Fr.: résonance orbitale   

The situation in which two orbiting objects exert a regular, periodic gravitational influence on each other and therefore their orbital frequencies are related by a ratio of two small → integers. Orbital resonance often results in an unstable interaction in which bodies exchange momentum and shift orbits until the resonance disappears. The resonance increases the eccentricity until a body approaches a planet too closely and the body is slung away.

orbital; → resonance.

orbital shrinkage
  درهم‌کشیدگیِ مداری   
darhamkešidegi-ye madâri

Fr.: rétrécissement de l'orbite   

The lessening in size of the orbit of a binary system composed of two compact objects (pulsars/black holes) due to loss of energy by the system, in particular through gravitational wave radiation. This loss will cause the two objects to approach closer to each other, the orbital period decreases and the binary companions will eventually merge.

orbital; shrinkage, from shrink, from M.E. schrinken, O.E. scrincan, from P.Gmc. *skrenkanan (cf. M.Du. schrinken, Swed. skrynka "to shrink."

Darhamkešidegi "shrinking, shriveling," from state noun of < i>darhamkešidé, from darham- "together, in eachother, toward eachother" (For etymology of dar-, → in-; for etymology of ham-, → com-) + kešidé "drawn, shrivelled, wrinkled," from Mod./Mid.Pers. kešidan, kašidan "to draw, protract, trail, drag, carry," dialectal Yaqnavi xaš "to draw," Qomi xaš "streak, stria, mark," Lori kerr "line;" Av. karš- "to draw; to plow," karša- "furrow;" Proto-Iranian *kerš-/*xrah- "to draw, plow;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base kwels- "to plow;" madâri, → orbital.

orbital velocity
  تندایِ مداری   
tondâ-ye madâri

Fr.: vitesse orbitale   

The velocity of an object in a given orbit around a gravitating mass. For a perfect circular orbit, the velocity is described by the formula V =√[G(M + m)/r], where G is the gravitational constant, M the mass of the primary gravitating body, m the mass of the orbiting object, and r the radius of the orbit.

orbital; → velocity.


Fr.: orbitographie   

In astronautics, the study of satellite orbits and precise determination of orbital elements which gives the exact position of the satellite.

orbital + → -graphy.

  ۱) رایه؛ ۲) رایاندن   
1) râyé; 2) râyândan

Fr.: 1) ordre; 2) ordonner   

1a) General: The way in which several items are arranged, as an indication of their relative importance or size or when each will be dealt with.
1b) Optics: → order of interference.
1c) Math.: The number of rows or columns of a → square matrix or → determinant.
1d) Math.: The highest → derivative appearing in a given → differential equation. For example,
d2y/dx2 + 2y (dy/dx) - 3 = 0
is a differential equation of order two.
2) To arrange, regulate, or dispose things in their proper places. See also: → disorder, → first-order differential equation, → first-order partial derivative, → first-order spectrum, → interference order, → order of a tensor, → order of interference, → order of magnitude.

From O.Fr. ordre, from earlier ordene, from L. ordinem (nominative ordo) "row, rank, arrangement."

Râyé, noun related to râyânidan "to regulate, set in order," from Mid.Pers. râyânīdan "to arrange, organize," from rây- (Mod.Pers. ârây-, ârâyeš, ârâyidan "to arrange, adorn"), ârây-, ârâstan "to arrange, adorn;" O.Pers. rād- "to prepare," rās- "to be right, straight, true," rāsta- "straight, true" (Mod.Pers. râst "straight, true"); Av. rāz- "to direct, put in line, set," razan- "order;" Gk. oregein "to stretch out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" Skt. rji- "to make straight or right, arrange, decorate;" PIE base *reg- "move in a straight line;" see also → direct.

order of a tensor
  رایه‌ی ِ تانسور   
râye-ye tânsor

Fr.: ordre de tenseur   

The maximum number of the indices (→ index) of a tensor.

order; → tensor.

order of interference
  رایه‌یِ اندرزنش   
râye-ye andarzaneš

Fr.: ordre d'interfrérence   

A whole number which characterizes a particular position of an interference fringe according to whether there is interference arising from one, two, three, etc. wavelength difference of path. Same as → interference order

order; → interference.

order of magnitude
  رایه‌یِ بُرز   
râye-ye borz

Fr.: ordre de grandeur   

Value of a number or of a physical quantity given roughly, usually expressed as a power of 10. Thus, 2.5 x 105 and 6.4 x 105 are of the same order of magnitude, and 2 x 107 is 2 orders of magnitude greater than either.

order; → magnitude.


Fr.: ordinal   

1) Of or relating to an order, as of animals or plants.
2) Of or relating to order, rank, or position in a series.
3) → ordinal number.

M.E., from O.Fr., from L.L. ordinalis "denoting order or place in a series," from L. ordo (genitive ordinis) "row, series," → order; → -al.

order; → -al.

ordinal number
  عدد ِ رایه‌یی   
adad-e râye-yi

Fr.: nombre ordinal   

1) A number which defines the position or rank of something in a series, in contrast to → cardinal number. For example, first, second, tenth, etc.
2) In → set theory, the order type of a → well-ordered set. Also called ordinal.

ordinal; → number.


Fr.: ordinaire   

Usual; normal. → ordinary ray; → ordinary year.

M.E. ordinarie, from O.Fr. ordinarie, from L. ordinarius "regular, usual, orderly," from ordo (genitive ordinis) "order" + -arius-ary.

Šunik "ordinary," from Mid.Pers. šônik, šônig "ordinary, customary," from šôn "kind, manner, sort, way" + -ik, → -ic.

ordinary differential equation
  هموگش ِ دگرسانه‌ای شونیک   
hamugeš-e degarsâneyi-ye šunik

Fr.: équation différentielle ordinaire   

A → differential equation in which the unknown function depends on only one → independent variable, as contrasted with a → partial differential equation.

ordinary; → differential; → equation.

ordinary point
  نقطه‌ی ِ شونیک   
noqte-ye šunik

Fr.: point ordinaire   

The point M0(x0,y0) of the curve F(x,y) = 0, where at least one of the partial derivatives ∂F/∂x and ∂F/∂y does not vanish. → singular point

ordinary; → point.

ordinary ray
  پرتوِ شونیک   
partov-e šunik

Fr.: rayon ordinaire   

The ray that has an → isotropic speed in a → doubly refracting crystal. It obeys → Snell's law upon refraction at the crystal surface. See also → extraordinary ray

ordinary; → ray.

ordinary year
  سال ِ شونیک   
sâl-e šunik

Fr.: année ordinaire   

A → calendar year that contains 365 days and therefore is not a → leap year.

ordinary; → year.

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