CTA 102, also known by its B1950 coordinates as 2230+114 (QSR B2230+114) and its J2000 coordinates as J2232+1143 (QSO J2232+1143), is a blazar-type quasar discovered in the early 1960s by a radio survey carried out by the California Institute of Technology.^[3] It has been observed by a large range of instruments since its discovery, including WMAP, EGRET, GALEX, VSOP and Parkes,^[1] and has been regularly imaged by the Very Long Baseline Array since 1995.^[4] It has also been detected in gamma rays, and a gamma-ray flare has been detected from it.^[5]

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.^[3] Follow-up observations were announced in 1965 by Gennady Sholomitskii, who found that the object's radio emission was varying;^[6] a public announcement of these results on April 12, 1965, caused a worldwide sensation.^[7] 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.^[3]

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.^[8]

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).^[9][10] This likely was the most luminous blazar state ever observed,^[11] with an absolute magnitude in excess of -32.

A new outburst began in December 2017, with increased gamma-ray^[12] and optical activity.^[13] As of 22 December 2017, it has reached magnitude +14.^[14]

• PSR B1919+21, the first pulsar discovered, mistaken for an alien radio signal
• HD 164595