Supermassive black hole galaxies, COSMOS image. The blue dots in this field of galaxies, known as the COSMOS field (Cosmic Evolution Survey), show galaxies that contain supermassive black holes emitting high-energy X-rays. The black holes were detected by NASA's Nuclear Spectroscopic Array (NuSTAR), with 32 such black holes in this image. NuStar has observed hundreds of black holes across the whole sky. The other coloured dots are galaxies that host black holes emitting lower-energy X-rays, and were observed by NASA's Chandra X-ray Observatory. Chandra data show X-rays with energies between 0.5 to 7 kiloelectron volts, while NuSTAR data show X-rays between 8 to 24 kiloelectron volts. Image published in 2016.