The methyl radical (CH₃) was detected toward Sgr A* (the galactic center) by Feuchtgruber et al. in 2000 with the Infrared Space Observatory (ISO). Unlike most observed interstellar astromolecules, the methyl radical has no dipole moment and thus can't be detected with pure rotational spectroscopy. However, two of the distinctive rovibrational features of CH₃ were observed. Knez et al. reported confirming evidence of CH₃ toward NGC 7538 IRS 1 in 2009.

Contrary to VSEPR theory logic, the methyl radical is planar. The images below depict the ν₂ vibrational mode that gives rise to the observed features (left), the bonding diagram for CH₃ showing the singly occupied 2p orbital on C (center), and an isodensity surface for that orbital (right).

vibrational mode	bonding diagram	singly occupied orbital