Radio galaxy

A radio galaxy is a galaxy that compared to other galaxies is characterized by its unusually large distance and can be measured almost exclusively in the long-wavelength radio emission due to the cosmological (non- motion-dependent ) redshift. The energy source of the radio emission is an active galactic nucleus. Our galaxy is therefore for all of us observed radio galaxies a radio galaxy.

Radio galaxies are usually the optically brightest galaxies are usually elliptical galaxies and S0 galaxies. Nevertheless, their radiation outperform the radio range in the visible spectral range. In nearby galaxies, the radio emission, but is far weaker than the visible light.

The radio waves come from many radio galaxies two generally symmetrical to the core disposed emission areas that are substantially greater than the visible galaxy to several Mpc. On closer observation, these sometimes by thin jets of matter (English Jets) are connected to the galactic nucleus. Energy source of radio galaxies is a supermassive black hole in the galactic nucleus, on the one hand absorbs matter, but also in its vicinity ionized matter accelerated to speeds close to the speed of light, generated magnetic fields and ejects the material beams. The radio emission is produced by synchrotron radiation in the jets of matter and the areas where they impinge on the intergalactic medium.

Despite their great distance include some radio galaxies to the apparently brightest and first discovered radio sources in the sky, which are named after the constellation in which they were found. Example, Virgo A ( Messier 87) and Cygnus A. The us next radio galaxy Centaurus A ( NGC 5128 ) in the southern sky.

A long time they were the only close observation accessible galaxies in the distant Universe with redshifts about 1 Through their radio emission could - be identified, and unlike quasars, the galaxy is not in the visible light through her ​​- among many other objects faint in visible light core outshines.

The emission of radio galaxies can be used in order to determine the intergalactic magnetic field that is carried by the wind matter into space. To assumptions about the electron density are required.