An emitting/receiving device in which the echo of a pulse of microwave radiation is used to detect and locate distant objects.
From ra(dio) d(etecting) a(nd) r(anging).
Graphic display of measurements by a → radar of mineral deposits on a planetary surface.
Emanating from a common central point; arranged like the radii of a circle.
Fr.: migration radiale
The process whereby a → disk star changes its → galactocentric distance. Radial migration involves → angular momentum transfer, resulting from → resonances created by transient → density waves such as → bars or → spiral arms in → galactic disks. According to → galactic dynamics models, → churning is the main cause of radial migration. Radial migration of stars plays an important role in shaping the properties of galactic disks.
Fr.: mouvement radial
A motion away from or toward a central point or axis.
Fr.: spoke radial
Any of short-lived (generally lasting less than 24 hours) radial features that periodically appear over the outer half of → Saturn's → B ring, when the ring tilt angle is small. These features revolve at the same rate as the planet's → magnetic field and maintain their shape over much of the course of their existence even though they extend tens of thousands of kilometers across the rings. It is believed that the tiny particles that make up these spokes are electrically charged and temporarily "frozen" into the planet's magnetic field (Ellis et al., 2007, Planetary Ring Systems, Springer).
Fr.: vitesse radiale
The component of a three-dimensional velocity vector of an object directed along the line of sight. It is measured by examining the Doppler shift of lines in the spectrum of astronomical objects.
radial velocity curve
xam-e tondâ-ye šo'â'i
Fr.: courbe de vitesse radiale
A curve describing the variation of the radial velocity of a star, due to the Doppler effect, under the gravitational effect of a secondary body (companion or exoplanet). The amplitude of these variations depends upon the mass of the secondary and its distance from the star.
radial velocity method
raveš-e tondâ-ye šo'â'i
Fr.: méthode de vitesses radiales
The technique based on the analysis of the → radial velocity curve, used to detect the presence of an invisible secondary around a host star. This method holds the majority of exoplanet discoveries.
A unit of angular measure; one radian is that angle with an intercepted arc on a circle equal in length to the radius of the circle.
From radi(us) + -an an originally adj. suffix.
1) Generally, the → radiant energy
per unit → solid angle per unit of
→ projected area of the → source.
It is usually expressed in → watt per
→ steradian per → square
→ meter (W m-2 sr-1). Same as
Tâbešmandi, noun from tâbešmand "possessing radiation," from tâbeš, → radiation, + -mand a suffix denoting possession; Mid.Pers. -ômand suffix forming adjectives of quality.
1) tâbandé, tâbeši; 2) tâbsar
1) Sending out rays of light; bright; shining.
M.E., from M.Fr. radiant, from L. radiantem (nominative radians) "shining," pr.p. of radiare "to shine, radiate," → radiation.
Fr.: dérive de radiant
Fr.: énergie radiative
šâr-e tâbeši (#)
Fr.: flux radiatif
Rate of flow of energy as → radiation.
Fr.: intensité de rayonnement
A measure of the amount of radiation emitted from a point expressed as the radiant flux per unit solid angle leaving this source.
From L. radiat(us), p.p. of radiare "to shine, to beam" + -ate verbal suffix.
Tâbidan, variants tâftan "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."
Fr.: radiation, rayonnement
Verbal noun of → radiate.
kamarband-e tâbeš (#), ~ tâbeši (#)
Fr.: ceinture de radiations
A ring-shaped region in the → magnetosphere of a planet in which charged particles are trapped by the planet's magnetic field. The radiation belts surrounding Earth are known as the → Van Allen belts.
Fr.: constante de rayonnement
Same as → radiation density constant.