Energy-releasing black hole. Computer artwork of the energy-releasing black hole in galaxy MCG -6- 30-15, seen from above. The energy around this black hole was measured by astronomers, using ESA's XMM-Newton X-ray observatory. It was found to be greater than expected. The extra energy is thought to be rotational energy extracted when the black hole's spin is slowed by the twisting of magnetic field lines close to its border (event horizon). The gravity in this region is strong enough to twist the fabric of space-time, resulting in the tightening of the magnetic field lines that slows the spin of the hole. The energy released by the slowed hole heats surrounding gas.