Mu Crucis, Latinized from ü Crucis, is the seventh-brightest star in the constellation Crux commonly known as the Southern Cross. ü Crucis is a wide double star of spectral class B stars, magnitude 4.0 and 5.2 respectively. They lie about 370 light-years away, and both stars are likely physically attached. The brighter component is known as ü<sup>1</sup> Crucis or ü Crucis A, while the fainter is ü<sup>2</sup> Crucis or ü Crucis B.
ü<sup>1</sup> Crucis is the brighter of the two stars with an apparent magnitude of 4.0. It is a hot massive main sequence or subgiant star, over a thousand times as luminous as the sun.
ü<sup>2</sup> Crucis is the fainter of the pair. Its apparent magnitude is 5.2 and it is a Be star, a star spinning so quickly that it has ejected a disc of material that creates emission lines in its spectrum. The disc is inclined at 36ð to our line of sight.