Interstellar nitric oxide (NO) was first observed by Liszt & Turner in the OH/H₂ maser region of Sgr B2 in the late 1970s using the 11m Kitt Peak radio telescope. Their detection was limited to the doublet rotational lines at 150.2 and 150.5 GHz. This was followed by a second observation by Hollis et al. In addition, NO was observed by McGonagle et al. and Gerin et al. in L134N (also known as L183 or Lynds 183). NO was also observed by the latter study in five giants clouds. Other reports include the work of Ziurys et al. and Halfen et al.

Nitric oxide is known alternatively as nitrogen monoxide or the nitrosyl radical. It plays an important biological role in signaling, but it is also a toxic pollutant.