The pure carbon chain molecule pentatetraenediylidene, C5, has been detected in the circumstellar envelope of the famous carbon star CW Leo, aka IRC +10216, by
P. F. Bernath, K. H. Hinkle, and J. J. Keady,
Detection of C<sub>5</sub> in the Circumstellar Shell of IRC +10216,
Science 244, 562–564 (1989)
before it was actually detected in the laboratory. 16 P and R branch transitions of the ν3 band were detected around 2169 cm–1 of which 13 appear to be unblended.
Contributor(s): H. S. P. Müller; 08, 2010