This cluster is estimated about 2–7 million years old,[1] and is approaching the Solar System at 22 km/s. The cluster belongs to the young Scorpius OB1 association in the neighboring Sagittarius Arm of the Milky Way. Zeta1 Scorpii (spectral type O8 and magnitude 4.71.[2]) is the brightest star in the association, and one of the most radiant stars known in the galaxy.[3]