RSGC1

RSGC1 is a massive young open star cluster in the Milky Way galaxy. It was discovered in 2006 in the data from infrared surveys. 
There are 12 red supergiants identified so far. These are massive young stars undergoing helium burning in their cores. There is also one yellow hypergiant, and one intermediate. The cluster is in the constellation Scutum at about 6.6 kpc from the Sun. It is at the intersection of the northern end of the Long Bar of the Milky Way and the inner portion of the Scutum–Centaurus Arm—one of its two major spiral arms.
The age of RSGC1 is estimated at 10–14 million years. The observed red supergiants with the mass of about 16–20 solar masses will become type II supernovas. The cluster is heavily obscured and has not been detected in the visible light. It lies close to other groups of red supergiants known as Stephenson 2, RSGC3 and Alicante 8. The mass of RSGC1 is estimated at 30 thousand solar masses, which makes it one the most massive open clusters in the Galaxy.