Massive star cluster and nebulae, infrared Spitzer Space Telescope image. This star cluster (bright green, centre) is one of the most massive in the Milky Way galaxy. It is thought to be the source of previously unexplained outpourings of X-rays and gamma rays from this area. Nebulae (yellow) are also seen. The cluster contains 14 massive supergiant stars, which are on the verge of exploding as supernovae. The cluster was found by the Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE) Legacy project to see past obscuring dust in the plane of the Milky Way. This region of the sky is 18,900 light years from Earth, in the constellation Scutum. The results were obtained in 2004 and published in 2006.