The Scutum–Centaurus Arm (also known as Scutum-Crux arm), is a long, diffuse curving streamer of stars, gas and dust that spirals outward from the proximate end of the Milky Way's central bar. As the Milky Way is a spiral galaxy, this feature is termed a spiral arm. In fact, the Milky Way is a barred spiral galaxy, and like many barred spirals it is believed to have two major spiral arms, not four as was previously believed. The Scutum–Centaurus Arm lies between the minor Carina–Sagittarius Arm and Perseus Arm—the second major arm. The Scutum–Centaurus Arm arm starts near the core as the Scutum Arm, then gradually turns into the Centaurus Arm.
The region where the Scutum–Centaurus Arm arm connects to the bar of the galaxy is rich in star-forming regions. In 2006 a large cluster of new stars containing 14 red supergiant stars was discovered there and named RSGC1. In 2007 a cluster of approximately 50,000 newly formed stars named RSGC2 was located only a few hundred light years from RSGC1; it is thought to be less than 20 million years old and contains 26 red supergiant stars, the largest grouping of such stars known. Other clusters in this region include RSGC3 and Alicante 8.