Phosphaethyne (HCP) was detected toward IRC +10216 by Agúndez et al. in 2007. Four consecutive rotational transitions were observed using the IRAM 30m telescope. Milam et al. confirmed the detection in 2008 and observed HCP toward both IRC +10216 and CRL 2688, also known as the Egg nebula, a protoplanetary system. An earlier attempt reported in 1990 by Turner et al. to detect HCP toward IRC +10216 was unsuccessful.