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 were detected with the 43 m Green Bank telescope and the 45 m Nobeyama telecope, respectively, at 22258 and 45827 MHz.

R. G. Urso, M. E. Palumbo, C. Ceccarelli, N. Balucani, S. Bottinelli, C. Codella, F. Fontani, P. Leto, C. Trigilio, C. Vastel, R. Bachiller, G. A. Baratta, C. S. Buemi, E. Caux, A. Jaber Al-Edhari, B. Lefloch, A. López-Sepulcre, G. Umana, and L. Testi
reported on
C₂O and C₃O in Low-mass Star-forming Regions
Astron. Astrophys. 628, Art. No. A72 (2019).
The C₂O observations were carried out with the IRAM 30 m telescope at 3 mm. Three fine structure components of the N = 4 - 3 rotational transition around 92.5 GHz were detected toward the prestellar core L1544. Only the strongest of these components was searched for and detected toward the protostellar Elias 18.

J. Cernicharo, M. Agúndez, C. Cabezas, B. Tercero, N. Marcelino, R. Fuentetaja, J. R. Pardo, and P. de Vicente
reported on the
Discovery of HCCCO and C₅O in TMC-1 with the QUIJOTE Line Survey
Astron. Astrophys. 656, Art. No. L21 (2021).

Contributor(s): H. S. P. Müller; 12, 2003; 09, 2012; 12, 2021