おうし座T型星
The infrared source IRS1 is close to σ Ori A. It has been resolved to a pair of low mass objects, a proplyd, and a possible third object. The brighter object has an M1 spectral class, a mass around , and appears to be a relatively normal low mass star. The fainter object is very unusual, showing a diluted M7 or M8 absorption spectrum with emission lines of hydrogen and helium. The interpretation is that it is a brown dwarf embedded within a proplyd that is being photoevaporated by σ Ori A. X-ray emission from IRS1 suggests the presence of an accretion disc around a T Tauri star, but it is unclear how this can fit with the proplyd scenario.