This article is about the astronomical phenomenon. Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study For the geological phenomenon see radiohalo. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit Radiohalos are microscopic spherical shells of discolouration in rocks such as Granite, or Biotite caused by the inclusion of Radioactive

Radio halos are large-scale areas of radio emission found in clusters of galaxies. Galaxy groups and clusters are the largest Gravitationally bound objects to have arisen thus far in the process of cosmic structure formation They do not have an obvious galaxy counterpart, as opposed, for example, to radio galaxies which have AGN counterparts. Radio galaxies and their relatives radio-loud Quasars and Blazars, are types of Active galaxy that are very luminous at radio wavelengths (up An active galactic nucleus ( AGN) is a compact region at the centre of a Galaxy which has a much higher than normal luminosity over some or all of the Electromagnetic Their cause is still debated, but they may come to exist due to reacceleration of mildly relativistic particles (electrons) happening during a merger event between galaxy clusters: the generated turbulent motions of the intra-cluster plasma drive Magneto-Hydrodynamical Waves, which couples with mildly relativistic particles (i. e. of energy on the level of 10²MeV) and accelerate them up to energy of 10GeV or more. They are found at the centre of clusters. Radio relics are similar features found at the edge of clusters, even though their driving mechanism should be different (emitting electrons are more likely accelerated not by turbulence, but by shock waves instead). Radio Relics are diffuse Synchrotron Radio emission found in the peripheral regions of Galaxy clusters

They are likely to result from synchrotron radiation originating from electrons, moving in the intracluster magnetic field of around 0. 1 - 3 μ G. ^[1]

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