The C₃N cyanoethynyl radical was observed initially by Guélin & Thaddeus in the circumstellar envelope IRC+10216, with subsequent detection by Friberg et al. in TMC-1 and TMC-2. Usually, an astronomical search depends upon the availability of experimental data, but these detections were based upon theoretical predictions and not confirmed until the subsequent laboratory work of Gottlieb at al. several years later, published in 1983.

C₃N is a radical formed when the H removed from cyanoethyne (cyanoacetylene), which has also been observed.