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. The A and B systems are several tenths of an arcsecond apart. The entire system is located approximately 150 light years from the Sun.

Mu Orionis Aa is an A5V dwarf and metallic line star, of effective temperature $6,813.8 days$, and apparent magnitude of +4.31. Mu Orionis Aa has 2.1 solar masses, and a radius of and a luminosity 32 times that of the Sun.

Mu Orionis Ab is a G5V dwarf orbiting Aa at a distance of $0.274$, 0.2x 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 each other by $12.62 AU$.

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.