RSGC1
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.