rišé (#), rišegi (#), rišâl
1) Math.: The indicated root of a quantity, as denoted by an expression written under
the → radical sign.
M.E., from L.L. radicalis "of or having roots," from → radix "root."
Fr.: axe radical
Of two circles, the straight line containing all points P such that the lengths of the tangents from P to the two circles are equal.
nešâne-ye rišâl, ~ rišegi
Fr.: signe radical
The symbol √ placed before a number or quantity to indicate the extraction of the square root. The value of a higher (the n-th) root is indicated by a raised positive digit (n) in front of the symbol, as in 3√ (cube root). The first known occurrence of this symbol was in the book Die Cross, published in 1525, by the German mathematician Christoff Rudolff.
Plural form of → radius.
1); 2) râdio; 3) partow, râdio
1); 2) Short from radiophone and radio-telegraphy.
Râdio, loan from Fr., as above; partow→ ray.
Fr.: arc radio
A large number of narrow filaments in → radio continuum occurring toward the → Galactic Center, about 15 to 20 arc-minutes (some 50 parsecs in projection) north of → Sgr A*. The radio Arc is the prototype of → non-thermal filaments (NTFs) and resolves into a set of more than a dozen vertical filaments with lengths of about 30 pc distributed symmetrically with respect to the → Galactic equator (Yusef-Zadeh et al. 1984, Nature 310, 557). Among more than 100 NTFs found in the Galactic center region, the Arc is the only one known to show inverted spectrum with a → spectral index α = +0.3 (Law et al. 2008, ApJS 177, 515, and references therein). This implies a very hard energy spectrum of particles for a source of → synchrotron radiation.
râdio axtaršenâsi, axtaršenâsi-ye râdioi
Fr.: radio astronomie
The branch of astronomy that deals with the study of the Universe by means of → radio waves.
Fr.: sursaut radio
A burst of emission in the radio frequencies of the electromagnetic spectrum.
radio continuum emission
gosil-e peyvastâr-e râdio-yi
Fr.: émission de continuum radio
A → continuum emission with frequencies in the radio range of the electromagnetic spectrum.
Fr.: contrepartie radio
Fr.: émission radio
Fr.: flux radio
Total radiation in radio wavelengths going out from the 2π solid angles of a hemisphere. → flux.
radio flux density
cagâli-ye šârr-e râdioyi
Fr.: densité de flux radio
basâmad-e râdio-yi (#)
Fr.: fréquence radio
râdio kahkešân, kahkešân-e râdioyi
A galaxy that is extremely luminous at radio wavelengths between 10 MHz and 100 GHz. The radio luminosity of a strong radio galaxy (1037-1039 watts) can be up to a million times greater than the radio output of an ordinary galaxy and up to a hundred times greater than the optical luminosity of a galaxy such as the Milky Way. The optical counterparts of radio galaxies are usually an → elliptical galaxy. Radio galaxies often exhibit jet structure from a compact nucleus. They typically display two → radio lobes that are often approximately aligned with the jets observed in the optical and that may extend for millions of → light-years.
Fr.: interféromètre radio
An → interferometer designed for radio frequencies.
radio-šân, šân-e râdioyi
Fr.: jet radio
An → astrophysical jet appearing in the radio wavelengths of the electromagnetic spectrum.
Fr.: lobe radio
An extended region of diffuse radio emission, often dumbbell shaped, that surrounds a radio galaxy.
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.