CTA-102

In 1963 Nikolai Kardashev proposed that the then-unidentified radio source could be evidence of a Type II or III extraterrestrial civilization on the Kardashev scale. Follow-up observations were announced in 1965 by Gennady Sholomitskii, who found that the object's radio emission was varying; a public announcement of these results on April 12, 1965, caused a worldwide sensation. The idea that the emission was caused by a civilization was rejected when the radio source was later identified as one of the many varieties of a quasar.

The American folk rock band The Byrds whimsically reflected the original view that CTA-102 was a sign of extraterrestrial intelligence in their song "C.T.A.-102" from their 1967 album Younger Than Yesterday.

In late 2016 CTA 102, usually glowing around magnitude +17, had a bright outburst in visible light to magnitude +11 (~250 times brighter than usual). This likely was the most luminous blazar state ever observed, with an absolute magnitude in excess of -32.

A new outburst began in December 2017, with increased gamma-ray and optical activity. As of 22 December 2017, it has reached magnitude +14.

CTA 102 displays a radio structure mainly made of a radio core and two other components. There is also a double knot feature. Additionally, it also has two radio lobes described having flux densities of 170 and 75 mJy, with a jet found as curved according to high resolution imaging by Very Long Baseline interferometry at 15 GHz. This jet contains jet components moving with apparent velocities of 15.4 ± 0.9c.

The quasar is also classified to be highly polarized with a flat radio spectrum, and such belongs to a classification of optically violent variable quasars.