An Etymological Dictionary of Astronomy and Astrophysics
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The flux of → radio waves that falls on a → detector per → unit → surface area of the detector per unit → bandwidth of the radiation per unit → time. The unit is → jansky.

→ radio; → flux; → density.

The → electromagnetic radiation with the frequency range between 3 → kiloherz (kHz) to 300 → gigahertz (GHz). See also → radio wave.

→ radio; → frequency.

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.

→ radio; → galaxy.

An → interferometer designed for radio frequencies.

→ radio; → interferometer.

An → astrophysical jet appearing in the radio wavelengths of the electromagnetic spectrum.

→ radio; → jet.

An extended region of diffuse radio emission, often dumbbell shaped, that surrounds a radio galaxy.

→ radio; → lobe.

The electromagnetic noise at radio wavelengths.

→ radio + → noise.

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; → pulsar.

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.

→ radio; → recombination line.

A signal in the → radio frequency region of the → electromagnetic spectrum.

→ radio; → signal.

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.

→ radio; → silence.

A point or small portion of the sky giving stronger radio emission than the sky in its vicinity.

→ radio; → source.

That part of the → electromagnetic spectrum that includes → radio waves.

→ radio; → spectrum.

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.

→ radio; → star.

Strong radio frequency radiation from the Sun, occurring in association with eruptions of solar flares or other causes of solar activity.

→ radio; → storm.

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.

→ radio; → sun.

A map or series of images of a region of sky obtained in → radio wavelengths of the → electromagnetic radiation.

→ radio; → survey.

A telescope whose receiver is sensitive to → radio waves.

→ radio; → telescope.

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).

→ radio; → wave.

The → electromagnetic radiation with a wavelength ranging from 1 mm to several 100 km. See so → radio wave.

→ radio; → wavelength.