Figure 11-4 RIVUXG Hidden Stars Revealed by Infrared Telescope The Flame Nebula, also known as NGC 2024, hides a cluster of young, blue, massive stars that (a) are invisible when studied with visible light, but (b) are revealed by infrared observations that easily see through the dust. Redder looking stars in the image are more heavily embedded within the nebula than the bluer stars (many of which are in the foreground). The cluster is thought to be less than one million years old.