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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orbital element
  بُن‌پارِ مداری   
bonpâr-e madâri

Fr.: élément orbital   

Any of the six parameters needed to specify the → orbit of an object around a → primary body (such as a planet around the Sun or a satellite around the Earth) and give its position at any instant. Two of them define the size and the form of the orbit: → semi-major axis (a) and → eccentricity (e). Three angular values determine the orbit position in space: the → inclination (i) of the object's → orbital plane to the reference plane (such as the → ecliptic), the → longitude of ascending node (Ω), and the → argument of periapsis (ω). And finally the sixth element is the → time of periapsis passage which allows calculating the body's position along the orbit at any instant.

orbital; → element.

orbital energy
  کاروژِ مداری   
kâruž-e madâri

Fr.: énergie orbitale   

The → sum of the → potential energy and the → kinetic energy of an object in → orbit.

orbital; → energy.

orbital inclination
  درکیلِ مداری   
darkil-e madâri

Fr.: inclinaison orbitale   

An → orbital element that defines the angle between the orbital plane of a solar system body (planet, comet, asteroid) and the plane of the ecliptic. The orbital inclination of the Earth's orbit is 0°; those of Mercury, Venus, and Mars are 7.01°, 3.39°, and 1.85° respectively.

orbital; → inclination .

orbital maneuver
  مانوور ِ مداری   
mânovr-e madâri

Fr.: mainoeuvre orbitale   

The moving of a spacecraft between two different orbits resulting from a change in its velocity (acceleration). Generally, manoeuvres are caused by → thrust from the spacecraft's motors.

orbital; → maneuver.

orbital manoeuvre
  مانوور ِ مداری   
mânovr-e madâri

Fr.: mainoeuvre orbitale   

orbital maneuver.

orbital; → manoeuvre.

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 parameter
  پارامون ِ مداری   
pârâmun-e madâri

Fr.: paramètre orbital   

orbital element.

orbital; → parameter.

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 phase
  فاز ِ مداری   
fâz-e madâri

Fr.: phase orbitale   

In → photometry of → binary stars or → two-body systems, the number of whole or fractional orbits completed, from the point the photometry begins. The point is conventionally chosen as the position at which the → primary star eclipses the → secondary star, and therefore the → light curve is at a minimum. The phase keeps counting indefinitely, thus the secondary star gets eclipsed at phase 0, 1, 2, 3, and so on. At these phases the primary lies between the secondary and the observer. An orbital phase of 0.5 corresponds to halfway through the binary orbit, 0.75 is three-quarters the way through, and so on.

orbital; → phase.

orbital phase curve
  خم ِ فاز ِ مداری   
xam-e fâz-e madâri

Fr.: courbe de la phase orbitale   

The photometric variability induced by the → orbital motion in a → two-body system.

orbital; → phase.

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 speed
  تندای ِ مداری   
tondâ-ye madâri

Fr.: vitesse orbitale   

Same as → orbital velocity.

orbital; → speed.

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.

orbiter
  مدارگرد   
madârgard

Fr.: orbiteur   

A → spacecraft or → satellite designed to orbit a planet or other → solar system body.

orbit; → -er.

orbitography
  مدارنگاری   
madârnegâri

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.

osculating orbit
  مدارِ آبوسنده   
madâr-e âbusandé

Fr.: orbite osculatrice   

The Keplerian orbit that a satellite would follow after a specific time t if all forces other than central inverse-square forces ceased to act from time t on. An osculating orbit is tangent to the real, perturbed, orbit and has the same velocity at the point of tangency.

osculating; → orbit.

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