The detection of the cis-conformer of the sulfur-containing species thionylimide (HNSO) was reported in 2024 by Sanz-Novo and co-workers toward the central galactic cloud G+0.693-0.027 within the larger Sgr B2 cloud. The observations were made with the Yebes 40m telescope and the IRAM 30m telescope. It is the first astromolecule to be detected that contains S, O, and N. Previously, Esplugues and co-workers had searched unsuccessfully for cis-HNSO toward Orion KL, as reported in 2013. In other work, Mehnen and co-workers studied the collision behavior of HNSO, while Lattanzi and co-workers have measured the rotational spectrum of the less stable trans-HNSO conformer and Jiang and co-workers have studied the photochemistry of the HNSO conformers and other isomers containing H, N, S, and O.

HNSO is a cousin of sulfur dioxide (SO₂) with the =NH imine group replacing one of the doubly-bonded O atoms. The other O atom can also be replaced with a second =NH to form S(NH)₂, sulfur diimide, which has three conformers (cis,cis-,cis,trans-, and trans,trans-).