The octatetraynyl radical (C₈H) was detected by Cernicharo and Guélin in 1996 and published back-to-back with new experimental data on the molecule measured by McCarthy et al. (where the species was generated by spark discharge of acetylene). C₈H was detected toward IRC +10216 like many other highly unsaturated hydrocarbon species. 10 rotational transitions were matched to unknown features in two surveys of the source, one performed with the IRAM 30m telescope and other with the 45m telescope at Nobeyama by Kawaguchi et al. The column density of C₈H was refined in 2007 with observations of the 100m telescope in Green Bank.

The octatetraynyl radical is the radical of tetraacetylene (C₈H₂), also known as 1,3,5,7-ocatatetrayne, which is extremely unstable. The octatetraynyl anion has also been detected.