Scutum–Centaurus Arm

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.

The Milky Way has been posited since the 1950s to have four spiral arms; numerous studies contest or nuance this number.

[1] In 2008, observations using the Spitzer Space Telescope failed to show the expected density of red clump giants in the direction of the Sagittarius and Norma arms.

[2] In January 2014, a 12-year study into the distribution and lifespan of massive stars[3] and a 2013-reporting study of the distribution of masers and open clusters[4] both found corroboratory, though would not state irrefutable, evidence for four principal spiral arms.

In 2007 a cluster of approximately 50,000 newly formed stars named RSGC2 was located only a few hundred light years from RSGC1.