In space, a dormant system can reactivate at any time, even after decades of inactivity. One recent example is the reawakening of the V404 Cygni system, which consists of a black hole and an orbiting companion star.
Astronomers noticed the pair had become energized for the first time in about 26 years. The initial signs included a flare of gamma rays noticed by a telescope on NASA’s Swift satellite followed by an X-ray burst detected by the International Space Station.
The scientific community has since rallied to observe the phenomenon which involves “repeated bright flashes of light on time scales shorter than an hour, something rarely seen in other black hole systems,” according to one expert.
During these bursts, it becomes up to fifty times brighter than any other source in their sky.
The system, which is located nearly 8,000 light years away from Earth in the Milky Way galaxy, has experienced spikes in activity every 20 to 30 years. This is when enough residual material from the star is collected that the black hole begins to feed on it.