Mu1 Scorpii (μ1 Sco, μ1 Scorpii) is a binary star system in the southern zodiac constellation of Scorpius. The combined apparent visual magnitude of the pair is +3.04, making it one of the brighter members of Scorpius. Based upon parallax measurements, the distance of this system from the Earth is roughly 500 light years (150 parsecs). This system is a member of the Scorpius-Centaurus Association, the nearest OB association of co-moving stars to the Sun.
μ1 Scorpii is an eclipsing binary of the Beta Lyrae type. Discovered to be a spectroscopic binary by Solon Irving Bailey in 1896, it was only the third such eclipsing pair to be discovered. This is a semidetached binary system where the secondary is close to filling its Roche lobe, or it may even be overflowing. The two stars revolve each other along a circular orbit with the components separated by 12.9 times the radius of the Sun. Due to occultation of each component by the other, the apparent magnitude of the system decreased by 0.3 and 0.4 magnitudes over the course of the binary's orbit, which takes 34 hours 42.6 minutes to complete.
The primary component is a B-type main sequence star with a stellar classification of B1.5 V. It has 8.5 times the mass of the Sun and 4.1 times the Sun's radius. The secondary member is a smaller B-type main sequence star with a classification of about B6.5 V, having 5.3 times the Sun's mass and 4.4 times the radius of the Sun. The effective temperature of the outer atmosphere for each star is 23,725 K for the primary and 16,850 K for the secondary. At these temperatures, the two stars glow with a blue-white hue.