Black holes are some of the most mysterious, frightening, and — paradoxically — brightest objects in the cosmos.

In particular, supermassive black holes, which can outweigh the sun millions of times, sometimes flare with powerful bursts of X-ray light that can rival the energy output of hundreds of stars.

X-ray flares aren't visible to the naked eye and black holes don't emit visible light, as their name suggests. But astronomers can detect them in deep space with specially tuned telescopes.

Years of observing black holes show many of them are shrouded with glowing-hot plasma, called a corona, which is made from the sucked-in gases of nearby stars. Astronomers have long suspected the corona had something to do with X-ray flashes, but couldn't be certain. We usually only detect X-ray bursts long after they're made, not during their formation.

For the first time, however, astronomers recorded a supermassive black hole named Markarian 335 halfway through spewing out a burst of X-ray light. What's more, the flare happened right after the black hole shot a cloud of its hot plasmatic corona away at around 20% the speed of light.

"The corona gathered inward at first and then launched upwards like a jet," Dan Wilkins, an astronomer at Saint Mary's University, said in a press release.

Here's an artist's impression of what the ejection looked like:

NASA

Wilkins said we still don't know what causes a corona to launch and speed away from black holes, nor what about the phenomenon triggers a stream of X-rays known as a black-hole flare.

We'll need to see a black-hole flare from start to finish to find out more about the process.