The radio galaxy IC 310 in the Perseus constellation is approximately 260 million light years away from Earth. Astronomers assume there is a supermassive black hole at its centre. This black hole was the setting for an extremely powerful outburst of gamma rays which was observed by the MAGIC telescopes on La Palma in the Canary Islands ("Black hole lightning due to particle acceleration at subhorizon scales"). The source exhibited one of the fastest radiation variations which researchers have ever been able to detect in an extragalactic object at these energies.
In the course of the outburst, the strength of the measured radiation from the core of the IC 310 galaxy varied within only five minutes, much to the surprise of the researchers. Yet the event horizon of the black hole – the boundary surface in space-time beyond which events are no longer visible – is three times the distance between Sun and Earth, i.e. 450 million kilometres. Light would need at least 25 minutes to travel this distance.