CCO has been detected first toward TMC-1:
M. Ohishi, H. Suzuki, S.-I. Ishikawa, C. Yamada, H. Kanamori, W. M. Irvine, R. D. Brown, P. D. Godfrey, N. Kaifu,
Detection of a new carbon-chain molecule, CCO
Astrophys. J. 380, L39–L42 (1991).
The N_J = 1₂ – 0₁ and 2₃ – 1₂ transitions werev detected with the 43 m Green Bank telescope and the 45 m Nobeyama telecope, respectively, at 22258 and 45827 MHz.

Contributor(s): H. S. P. Müller; 12, 2003; 09, 2012