Astronomers using ESA’s XMM-Newton X-ray observatory have discovered, for the first time, a pair of supermassive black holes in orbit around one another in an ordinary galaxy. This artist’s impression shows a binary supermassive black hole system in the galaxy SDSS J120136.02+300305.5. Image credit: ESA / C. Carreau. Most massive galaxies in the Universe are thought to harbor at least one supermassive black hole at their center. Two supermassive...