One of the longest observed astromolecules, cyanotetraacetylene (HC9N) has been known since the 1978 report of its discovery by Broten et al. toward Heiles' cloud 2 (usually identified as TMC-1 in recent years). One of the co-authors on the discovery paper was Sir Harry Kroto, who passed away this year.

H Kroto

HC₉N has been observed in various sources since 1978, including toward circumstellar envelopes such as IRC+10216 and CRL2688. It was also detected toward the low-mass protostar IRAS 04368. The most recent detection of HC₉N was toward Serpens South 1a.

With this entry, I've finally featured each of the full series of detected cyanopolyyne compounds, HC_2n+1N for n=1-5, as Astromolecule of the Month. Here's the full set with links to their respective pages:

	cyanoacetylene
	cyanodiacetylene
	cyanotriacetylene
	cyanotetraacetylene
	cyanopentaacetylene