Supermassive black holes in the universe are like a raucous choir singing in the language of X-rays. When black holes pull in surrounding matter, they let out powerful X-ray bursts. This song of X-rays, coming from a chorus of millions of black holes, fills the entire sky -- a phenomenon astronomers call the cosmic X-ray background. The blue dots in this field of galaxies, known as the COSMOS field, show galaxies that contain supermassive black holes emitting high-energy X-rays. The black holes were detected by our Nuclear Spectroscopic Array, or NuSTAR, which spotted 32 such black holes in this field and has observed hundreds across the whole sky so far. Credits: NASA/JPL-Caltech #chandra #nasa #space #stars #xray #nasabeyond #blackhole #galaxy #astronomy #science #nustar #cosmos #song