منطقة هيدروجين II
Chini et al. (2012) identify this as a double-lined spectroscopic binary star system. It shows a stellar classification of O9.7 Iab, matching a massive O-type supergiant star. Along with the O-type star 16 Sgr (HD 167263), it is ionizing an H II region along the western edge of the molecular cloud L291.