Fr.: équation de Fokker-Planck
A modified form of → Boltzmann's equation allowing for collision terms in an approximate way. It describes the rate of change of a particle's velocity as a result of small-angle collisional deflections.
After Dutch physicist Adriaan Fokker (1887-1972) and the German physicist Max Planck (1858-1947); → equation.
Fr.: plan galactique
sayyâre-ye qulpeykar (#)
Fr.: planète géante
High Accuracy Radial velocity Planet Searcher (HARPS)
A high-precision echelle spectrograph built for exoplanet findings and installed on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. HARPS has discovered dozens of exoplanets, making it the most successful planet finder behind the Kepler space observatory. HARPS can detect movements as small as 0.97 m s-1 (3.5 km h-1), with an effective precision of the order of 30 cm s-1, and a → resolving power of 120,000 (Mayor et al., 2003, ESO Messengar 114, 20).
Fr.: plan d'image
The plane in which is formed an image produced by an → optical system.
sayyâre-ye zirin (#)
Fr.: planète inférieure
A planet that orbits between the Earth and the Sun. Mercury and Venus are the only two inferior planets in the Solar System.
sayârehâ-ye daruni (#)
Fr.: planètes internes
The planets Mercury, Venus, Earth and Mars collectively. T hey are also known as the terrestrial planets.
interplanetary coronal mass ejections (ICME)
ešâneš-e andarsayyâreyi-ye jerm az tâj
Fr.: éjection de masse coronale interplanétaire
Fr.: poussière interplanétaire
Particles of dust in the → interplanetary medium. They are left-overs from the beginning of the solar system or from other sources such as sublimating comets. Their existence was first deduced from observations of → zodiacal light.
Fr.: gaz interplanétaire
Electrically charged particles of the solar wind and gas liberated from comets within the solar system.
interplanetary magnetic field
meydân-e meqnâtisi-ye andarsayyârei
Fr.: champ magnétique interstellaire
The magnetic field that is carried along with the solar wind and fills the solar system space. It is wound into a spiral structure by the rotation of the Sun. At the Earth's distance from the Sun, it has a strength of about 5 x 10-5 gauss.
Fr.: matière interplanétaire
Material existing in the space between solar system planets. It includes interplanetary gas and dust.
Fr.: milieu interplanétaire
The material contained in the → solar system in the space through which the planets travel. It consists of the smaller objects such as → asteroids, → comets, → meteorites and also a general pervading → interplanetary dust. Moreover a → plasma of charged particles streaming outward from the Sun in the form of the → solar wind contributes to the interplanetary medium.
Fr.: espace interplanétaire
Same as → interplanetary medium.
Fr.: planète intramercurienne
A hypothetical planet, named Vulcan, that once was believed to exist between the Sun and Mercury.
Fr.: plan invariable
Mechanics: For a rotating rigid body not subject to external torque, a plane which is perpendicular to the angular momentum vector of the body, and which is always tangent to its → inertia ellipsoid.
The quality of an imaging system which is characterized by → isoplanatism.
Izobirâh, from izo-, → iso-, + birâh "a devious path; a wanderer, who deviates, errs."
Fr.: angle isoplanatique
The angle in which the → point spread function of the atmosphere/telescope system is space invariant. Because of the presence of → turbulence in high layers of the atmosphere, this angle is extremely small, often only a few seconds of arc at visible wavelengths. See also → aplanatism.
pac-e izobirâh, teke-ye ~
Fr.: tache isoplanatique
The spatial region where the variation of the → point spread function of an imaging system is considered negligible.
In an imaging system, the unvarying of the → point spread function over an extended field of view.