What you’re seeing is V404 Cygni, a binary system consisting of a star and a black hole, some 7800 light-years away. It has lain quiet for the last 25 years, but a week ago, NASA’s Swift satellite noticed a burst of new activity.


V404 is a binary system, consisting of a star and a black hole orbiting one another. Matter flows from the star to the black hole, where it heats up and lets off all sorts of x-ray and gamma-ray waves, before vanishing into the black hole. The last time V404 was active was way back in 1989, but on June 15th, NASA’s Swift satellite started picking up renewed bursts of gamma rays.


V404 Cygni, seen before and after its awakening



In turn, Earth-based telescopes started to monitor V404 on other wavelengths, and started picking up intense x-ray flashes, according to Erik Kuulkers, Integral project scientist at the European Space Agency.

“The behaviour of this source is extraordinary at the moment, with repeated bright flashes of light on time scales shorter than an hour, something rarely seen in other black hole systems. In these moments, it becomes the brightest object in the X-ray sky – up to fifty times brighter than the Crab Nebula, normally one of the brightest sources in the high-energy sky.”

[ESA]