Detection of the carbon monoxide ion (CO⁺) in the interstellar medium and a planetary nebula

We report detection of the carbon monoxide ion (CO⁺) in the interstellar medium (M17SW) and a planetary nebula (NGC 7027). These detections are based on observations of three millimeter and submillimeter transitions in M17SW and one in NGC 7027. Chemical models suggest that CO⁺ should be most abundant where complex molecules are least likely to be present. In our search for CO⁺ we therefore minimized the chance of confusion while maximizing the probability of detection by observing regions whose chemistry is dominated by the effects of ultraviolet radiation.