In a forthcoming article in the journal Astronomy and Astrophysics, Sánchez Sáez and her co-authors conclude that what they have been watching is the creation of an “active galactic nucleus” — a region at the center of a galaxy that shines extremely brightly as dust and gas are sucked into the black hole, creating a cosmic light show.

The researchers say black holes, upward of 100,000 times the size of the sun, exist at the center of most galaxies, including the Milky Way.

But the black hole in this galaxy, located 300 million light-years away in the constellation Virgo, is unusual in that it is clearly visible.

“These giant monsters usually are sleeping and not directly visible,” Claudio Ricci, an astronomer from Diego Portales University in Chile who co-wrote the study, said in the release. “In the case of SDSS1335+0728, we were able to observe the awakening of the massive black hole, [which] suddenly started to feast on gas available in its surroundings, becoming very bright.”

Unlike its better-known counterparts, this suddenly-not-so-boring galaxy doesn’t yet have a name. Astronomers refer to it as SDSS1335+0728.

Galaxies do light up for other reasons, such as supernova explosions or tidal disruption events — when a star gets too close to a black hole and is torn apart.

The researchers haven’t ruled out the possibility that what they are witnessing is an unusually slow tidal disruption event. Those typically last for weeks, less than a year at most. If it is a tidal event, it would be the longest and faintest ever recorded, the researchers say.

SDSS1335+0728 is still getting brighter, four years later. The researchers compared data from before and after December 2019 and found the galaxy is now radiating much more light at ultraviolet, optical and infrared wavelengths. It also started emitting X-rays in February.

“This behavior is unprecedented,” Sánchez Sáez said.