The largest anion identified to date in space is C₈H^–, which goes by the formal (and tongue twisting) name octatetraynyl anion. The detection was reported in 2007 by three groups, initially in back-to-back ApJL papers by Brünken et al. and Remijan et al., followed within a few months by confirming observations reported by Kawaguchi et al. The detection of Brünken et al. was toward TMC-1 while that of Remijan et al. was toward IRC+10216; both groups used data collected with the 100m Robert C. Bird Green Bank Telescope. The detection of Kawaguchi et al. was also toward IRC +10216 based on observations with the 45m telescope at Nobeyama Radio Observatory. A total of 13 different transitions were observed by the three efforts. The detection was made possible by laboratory measurement of the rotational spectrum of C₈H^– by Gupta et al.

To date five anions have been detected in space in the gas phase. In addition to C₈H^–, the detections of the hexatriynyl (C₆H^–) and butadiynyl (C₄H^–) anions were both reported in 2007, while the detections of the cyanoethynyl (C₃N^–) and cyanobutadiynyl (C₅N^–) anions were reported in 2008, and the detection of the cyano (CN^–) anion was reported in 2010.