Also found in: Dictionary, Thesaurus, Wikipedia.
radio sourceA celestial object whose radio emissions may be detected with a radio telescope. Within our Solar System these sources include Jupiter and the Sun, both of which emit powerful radio bursts. Galactic radio sources include pulsars, supernova remnants, H I and H II regions, maser sources, and the galactic center itself. Synchrotron emission from cosmic rays in the Galaxy gives rise to a diffuse background radiation, centered broadly on the galactic plane but having several spurs away from it (see interstellar medium). This background radiation may limit the sensitivity of a radio telescope, especially at frequencies below about 400 megahertz.
Extragalactic radio sources include spiral galaxies (whose H I and carbon monoxide emissions may be used to map the distribution of hydrogen within them), radio galaxies, and quasars. An extragalactic radio source is often classified according to the spatial distribution of the radio emission shown on a radio map of the source. See radio-source spectrum; radio-source structure.