Mu Orionis

μ Orionis (latinised to Mu Orionis, abbreviated to μ Ori or Mu Ori) is a quadruple star system in the constellation Orion, similar to Mizar and Epsilon Lyrae with combined visual magnitude of 4.13. The four stars are known as Mu Orionis Aa, Mu Orionis Ab, Mu Orionis Ba, and Mu Orionis Bb. All four components are spectroscopic, with A and B systems only several tenths of an arcsec apart. The entire system is located approximately 155 Light Years from the Sun.

Mu Orionis Aa is an A5V dwarf and metallic line star, of effective temperature 8350 Kelvin, and apparent magnitude of +4.31. Mu Orionis Aa has 2.1 solar masses, and a radius of 2.9 solar radii and a luminosity 32x that of the Sun.

Mu Orionis Ab is a G5V dwarf orbiting Aa at a distance of 0.077 AU, .2x the orbit of mercury.

Mu Orionis Ba and Bb are F5V dwarfs with 1.4 solar masses and apparent magnitudes of 6.91. They are separated from eacu other by 0.078 AU.

μ Orionis falls just outside an unrelated planetary nebula Abell 12. The bright star makes detecting the faint nebula difficult and it has been nicknamed The Hidden.