An Etymological Dictionary of Astronomy and Astrophysics
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A radio galaxy that shows broad optical emission lines. → broad-line region.

→ broad; → line; → radio galaxy.

An object emitting intense energy in radio wavelength from a small, unresolved central region.

→ compact; → radio source.

Radio waves emanating from extraterrestrial sources.

→ cosmic; → radio; → noise.

A localized source on the celestial sphere that can be observationally separated at radio wavelengths from its background emission.

→ discrete; → radio; → source.

A → galaxy that emits radio energy from two regions located on opposite sides of the galaxy.

→ double; → lobe; → radio; → source.

A bright → burst of → radio emission lasting only a few milliseconds, and thought to be of → extragalactic origin. The first ever detected such burst, called the → Lorimer burst, was in 2007. It lasted only 5 milliseconds, but the single radio → pulse was dispersed over a wide range of frequencies (→ dispersion measure). This suggested a → cosmic origin for the burst, because the radiation must have passed through very distant → intergalactic clouds to be so highly dispersed. The second FRB was detected in 2012 in archival data from the Parkes Radio Telescope, the same telescope through which the original burst was seen. No temporally coincident → X-ray or → gamma ray signature was identified in association with the bursts. Most recent results suggest FRBs as a new population of explosive events at cosmological distances of up to 3 → giga  → parsecs, that is → redshifts of 0.5 to 1. While physical interpretations for this phenomenon remain speculative, they are thought to involve highly → compact objects, such as → neutron stars. See also → blitzar.

The term fast radio burst was coined by Thornton et al., 2013, Science, 341, 53 (arXiv:1307.1628); → fast; → radio; → burst.

The 500 m diameter → radio telescope which is the largest → single-dish antenna in the world. It is an Arecibo type telescope nestled within a natural basin in China's remote and mountainous Dawodang, Kedu Town, in southeastern China's Guizhou Province. The → reflector consists of 4,450 triangular panels, each with a side length of 11 m. More than 2,000 → actuators are used, according to the feedback from the measuring system, to deform the whole reflector surface and directly correct for → spherical aberration. Several detectors are used to cover a frequency range of 70 MHz to 3 GHz.

→ five; → hundred; → meter; → aperture; → spherical; → radio; → telescope.

A diffuse radio signal that originates outside the solar system. It is strongest in the direction of the Galactic plane.

→ galactic; → radio; → noise.

A quasar with detectable radio emission.

→ quasi-; → stellar; → radio; → source.

1) An apparatus for receiving or transmitting radio broadcasts.
2) Pertaining to the → radio waves of the → electromagnetic radiation.
3) As a prefix, indicating → radition or → radioactivity.

1); 2) Short from radiophone and radio-telegraphy.
3) Combining form of → radiation.

Râdio, loan from Fr., as above; partow→ ray.

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.

→ radio; → arc.

The branch of astronomy that deals with the study of the Universe by means of → radio waves.

→ radio; → astronomy.

A burst of emission in the radio frequencies of the electromagnetic spectrum.

→ radio; → burst.

A → continuum emission with frequencies in the radio range of the electromagnetic spectrum.

→ radio; → continuum; → emission.

The representation in → radio wavelengths of an astronomical object that has emission in other parts of the → electromagnetic spectrum.

→ radio; → counterpart.

→ Electromagnetic radiation carried by → radio waves.

→ radio; → emission.

Total radiation in radio wavelengths going out from the 2π solid angles of a hemisphere. → flux.

→ radio; → flux.

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.