This graph shows variation in the X-ray luminosity of the black-hole binary system V404 Cygni, as observed with the IBIS/ISGRI instrument on ESA's Integral gamma-ray observatory at energies between 20 and 40 keV compared to the Crab Nebula (pink). On 15 June 2015, V404 Cygni started showing signs of extraordinary activity, something that had not happened since 1989. The renewed activity is likely caused by material slowly piling up in the disc, until eventually reaching a tipping point that dramatically changes the black hole's feeding routine for a short period. Illustration credits: Carlo Ferrigno, Integral Science Data Centre, Geneva, Switzerland/Jerome Rodriguez, Cea-Saclay, France/Marion Cadolle Bel, Max-Planck Computing and Data Facility, Garching Germany.
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