Editing Astronomical radio source (section)

===Radio galaxies===
Many galaxies are strong radio emitters, called [[Radio galaxy|radio galaxies]]. Some of the more notable are [[Centaurus A]] and [[Messier 87]].

[[Quasar]]s (short for "quasi-stellar radio source") were one of the first point-like radio sources to be discovered. Quasars' extreme [[redshift]] led us to conclude that they are distant active galactic nuclei, believed to be powered by [[black hole]]s. [[Active Galactic Nucleus|Active galactic nuclei]] have jets of charged particles which emit [[synchrotron radiation]].  One example is [[3C 273]], the optically brightest quasar in the sky.

Merging [[Galaxy groups and clusters|galaxy clusters]] often show diffuse radio emission.<ref>{{cite web|url=http://www.arcetri.astro.it/~buttery/thesis/node69.html |title=Conclusion|access-date=2006-03-29 |url-status=dead |archive-url=https://web.archive.org/web/20060128231925/http://www.arcetri.astro.it/~buttery/thesis/node69.html |archive-date=2006-01-28 }}</ref>