orbital phase 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 curve 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 plane hâmon-e madâri Fr.: plan orbital The plane defined by the motion of an object about a primary body. |
orbital precession pišâyân-e madâri Fr.: précession orbitale Same as → relativistic precession. → orbital; → precession. |
orbital resonance 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 shrinkage 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 k^{w}els- "to plow;" madâri, → orbital. |
orbital speed tondâ-ye madâri Fr.: vitesse orbitale Same as → orbital velocity. |
orbital velocity 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. |
orbitography madârnegâri Fr.: orbitographie In astronautics, the study of satellite orbits and precise determination of orbital elements which gives the exact position of the satellite. |
osculating orbit 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. |
parabolic orbit madâr-e sahmi Fr.: orbite parabolique An orbit whose overall shape is like a parabola; it is the limiting case between an elliptical orbit (eccentricity less than 1) and a hyperbolic orbit (eccentricity larger than 1). The speed necessary to form a parabolic orbit is known as the escape velocity. |
polar orbit madâr-e qotbi (#) Fr.: orbite polaire A spacecraft orbit that passes over, or close to, the geographic poles of the Earth or some other solar system object. |
polar orbiting satellite mâhvâré bâ madâr-e qotbi Fr.: satellite en orbite polaire A satellite that revolves around the Earth in an almost north-south orbit, passing close to both poles. The orbits are sun synchronous, allowing the satellite to cross the equator at the same local time each day. These satellites orbit at a height of 830-880 km and take about 100 minutes to complete a turn around the Earth. |
prograde orbit madâr-e farârow Fr.: orbite prograde Same as →prograde motion. → prograde motion; → orbit. |
resonance orbit madâr-e bâzâvâyi Fr.: orbite de résonance An orbit which is in → orbital resonance with another orbit. |
retrograde orbit madâr-e pasraft Fr.: orbite rétrograde An orbit with an inclination between 90° and 270° such as those of some comets and small asteroids orbiting the Sun. → retrograde; → orbit. |
spin-orbit coupling jafsari-ye espin-madâr, jofteš-e ~ Fr.: couplage spin-orbite 1) Astro.: A relationship between the orbital period of one body around another
and its rotational period on its axis. The relationship results from tidal forces
between the two bodies. For example, the rotation period of the Moon equals its revolution
period around the Earth. |
stationary orbit madâr-e istvar Fr.: orbite stationnaire An orbit in which the satellite revolves about the primary at the angular rate at which the primary rotates on its axis. From the primary, the satellite thus appears to be stationary over a point on the primary. → stationary; → orbit. |
synchronous orbit madâr-e hamgâm Fr.: orbite synchrone → synchronous; → orbit. |
tadpole orbit madâr-e vagizi Fr.: orbite en forme de têtard A shorter → horseshoe orbit confined to the → Lagrangian points L4 or L5. |