The hexatriynylide ion is the first anion that has been detected in space by radioastronomical means in 1995.
M. C. McCarthy, C. A. Gottlieb, H. Gupta, and P. Thaddeus,
Laboratory and Astronomical Identification of the Negative Molecular Ion C₆H^–
Astrophys. J. 652, L141–L144 (2006)
reported microwave and millimeter-wave transitions of the molecule and the detection of two rotational transitions of this ion (J = 4 – 3 and 5 – 4) in TMC-1.
In addition, they identified this molecule as the carrier of B1377, a molecular species of unknown identity at the time the report was published and with a rotational B value of 1377 MHz. These lines have been found and attributed to an unknown species in
A Spectral-Line Survey Observation of IRC +10216 between 28 and 50 GHz by
K. Kawaguchi, Y. Kasai, S.-I. Ishikawa, and N. Kaifu,
Publ. Astron. Soc. Japan 47 853–876 (1995).

More recently, three transitions have been detected toward a low-mass protostar:
N. Sakai, T. Sakai, Y. Osamura, and S. Yamamoto,
Detection of C₆H^– toward the Low-Mass Protostar IRAS 04368+2557 in L1527
Astrophys. J. 667, L65–L68 (2007).

Contributor(s): H. S. P. Müller; 11, 2006; 1, 2008