[8] The brightest component, B1, is known to be an eclipsing binary and its unresolved companion is generally called B5.

[5] The stars making up θ1 Orionis B are gravitationally bound, but their configuration is likely to be unstable and will eventually decay.

Its spectroscopic companion B5 is estimated to have a spectral type of G2 III from observations during the total eclipses.

[6] The unusual and changeable eclipses are thought to be caused by a translucent disc surrounding the secondary star.

It is seen nearly edge-on and variations in its opacity cause differences in the light curve shape.