These are the most powerful sources of visible, infrared and radio emission of radiation. The dimensions of quasars do not exceed several light days, that is, 10 ^ 13–10 ^ 14 m. The luminosity of quasars is 10 ^ 12 – 10 ^ 13 of the luminosity of the Sun. The brightest quasar 3C 273 is visible as a 12.6m star, located at a distance of about 3 billion sv. years and emits more energy in the optical range than the brightest galaxies. Apparently, quasars are the nuclei of distant galaxies in a state of very high activity.
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