nufe-ye râdioyi (#)
Fr.: bruit radio
The electromagnetic noise at radio wavelengths.
râdio-tapâr, pulsâr-e râdio-yi
Fr.: pulsar radio
A → pulsar that emits → pulses in → radio waves. The bulk of discovered pulsars are radio pulsars. There is a small number of pulsars that emit at optical wavelengths, X-ray wavelengths, and gamma-ray wavelengths.
radio recombination line
xatt-e bâzmiyâzeš-e râdioyi
Fr.: raie de recombinaison radio
A → recombination line whose wavelength lies in the radio range of the electromagnetic spectrum. Radio recombination lines are the result of electronic transitions between high energy levels (n > 50) in an atom or ion.
Fr.: signal radio
Fr.: silence radio
A condition in which all fixed or mobile equipments capable of radio transmitting in an area are kept inoperative, typically for the duration of some sensitive time period. The term has both military and civilian applications.
râdio-xan, xan-e râdioyi
Fr.: radio source, source radio
A point or small portion of the sky giving stronger radio emission than the sky in its vicinity.
Fr.: spectre radio
râdio setâré, setâre-ye râdioyi
Fr.: étoile radio
A star which is a source of emission at radio frequencies. Radio stars include pulsars, flare stars, binary star systems in which mass is transferred from one component to the other, and some X-ray stars.
tufân-e radioyi (#)
Fr.: orage radio
Strong radio frequency radiation from the Sun, occurring in association with eruptions of solar flares or other causes of solar activity.
xoršid-e râdioyi (#)
Fr.: Soleil radio
The image of the Sun obtained from its electromagnetic radiation in radio frequencies. The apparent size of the radio Sun depends of the frequency of the signal, since different radio frequencies originate from various atmospheric layers of the Sun.
Fr.: relevé radio
râdio-teleskop (#), teleskop-e râdioyi (#)
Fr.: radio télescope
A telescope whose receiver is sensitive to → radio waves.
mowj-e râdioyi (#)
Fr.: ondes radio
The → electromagnetic radiation with the longest → wavelengths (and lowest energies), ranging from 0.3 mm to several km. Radio waves form a very broad category, which includes the → submillimeter waves (with a wavelength of 0.3-1 mm) and → microwave regions (1 mm to several cm).
Fr.: longueur d'onde radio
rowzane-ye râdioyi (#)
Fr.: fenêtre radio
A range of electromagnetic radiation in the radio frequencies to which the Earth's atmosphere is transparent.
kuâsâr-e râdioyi-ye xorušân
Fr.: quasar puissant en radio
A quasar that has the same characteristics as a → radio-quiet quasar with the addition of having strong radio emissions.
kuâsâr-e râdioi-ye ârâm
Fr.: quasar faible en radio
A type of quasar with weak radio emission. These types of quasars have strong emissions in both the optical and X-ray spectra. Within the optical spectrum, both broad and narrow emission lines are present. Their host is usually an elliptical galaxy, but less commonly, it might be a spiral. → radio-load quasar.
Kuâsâr→ quasar; → radio; ârâm "quiet" (Mid.Pers. râm "peace," râmenidan "to give peace, pleasure," râmišn "peace, pleasure;" Av. ram- "to stay, rest;" cf. Skt. ram- "to stop, stand still, rest, become appeased;" Gk. erema "quietly, gently;" Goth. rimis "rest;" Lith. rãmas "rest").
Possessing, or pertaining to, → radioactivity.
sen yâbi-ye partow-žirâ
Fr.: datation radioactive
Determining the age of an object from the → radioactive decay of its constituting material. The technique consists of comparing the → abundance ratio of a → radioactive isotope to its → decay product. This will yield the number of half-lives that have occurred since the sample was formed. More specifically, if an object is made up of 50 % decay product then it has gone through 1 → half-life. 75% decay product equals 2 half-lives, 87.5% decay product equals 3 half-lives, 93.76% decay product equals 4 half-lives, and so on. For example, the decay product of → uranium-238 (238U) is → lead-206 (206Pb). The half-life of 238U is 4.5 billion years. Hence, if the sample has gone through two half-lives, it is 9 billion years old. See also: → radiocarbon dating.
Fr.: désintégration radioactive
Spontaneous emission by a nucleus of photons or particles.