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The first quasars, discovered in the late 1950s, were identified as sources of intense radio emission. In 1960 astronomers observed objects whose spectra showed emission lines that could not be identified. In 1963, the American astronomer of Dutch origin Maarten Schmidt discovered that these unidentified emission lines in the spectrum of quasar 3C 273 were already known lines but showed a much stronger redshift than in any other known object.
One cause of the redshift is the Doppler effect, which shifts the wavelength of the light emitted by the celestial objects towards the red (longer wavelength) when the objects move away from Earth. Distant objects such as galaxies move away from Earth because of the expansion of the Universe. By their redshift, astronomers can calculate the speed of that distance.
By the end of the 1980s, several thousand quasars had been identified and the redshift of a few hundred of them had been determined. If we consider that the redshift is really caused by the galaxy moving away, these quasars would be moving away at a speed of more than 93% of the speed of light. According to Hubble's law, its distance would therefore be more than 10,000 million light years and its light would have been traveling practically throughout the existence of the Universe. In 1991, researchers from the Monte Palomar Observatory discovered a quasar at a distance of 12,000 million light years. Some quasars produce more energy than 2,000 galaxies. One of them, the S50014 + 81, can be 60,000 times brighter than our Milky Way.
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