In 2014, a tentative detection of the organometallic radical magnesium monoacetylide (MgCCH) toward the molecule-rich circumstellar shell IRC +10216 was reported by Agúndez et al. MgCCH is the gazillionth molecule detected with the IRAM 30m telescope on Pico Veleta in southern Spain. Four transitions (two doublets) around 89.4 and 99.3 GHz were tentatively assigned to MgCHH.

MgCCH is an acetylide formed by replacing one of the H atoms in acetylene with a metal atom. Other known magnesium astromolecules include magnesium isocyanide (MgNC), magnesium cyanide (MgCN), and hydromagnesium isocyanide (HMgCN). No other acetylide has been detected in the ISM, although the rotational spectrum NaCCH has been measured.

October 2019 - Cernicharo et al. have reported additional lines of MgCCH toward IRC +10216, thus confirming the initial detection.