A nearby galaxy's odd behaviour has astronomers stumped, with some thinking it might be the result of an epic tussle between two supermassive black holes.
Mrk 1018 can't seem to decide how bright it's meant to be. It's one of 20 known galaxies which has turned the lights up or down, but one of only three which has done it twice.
It was originally classified as a Type 1 galaxy, but was reclassified as a Type 2 after getting a whole light brighter in the years following its discovery in 1974.
It spent three decades shining brightly, but has now been plunged into relative darkness, according to observations taken by the Very Large Telescope in Chile.
"It is very exciting to look at your data and see something you weren't expecting," says PhD student Rebecca McElroy at the University of Sydney, who first noticed the change.
A bunch of telescopes have since been turned on the galaxy in an effort to find out what's going.
There are two main theories - the first is that the supermassive black hole at the centre of the galaxy is being starved, "drawing in less matter and thus decreasing the brightness of its emission" according to Ms McElroy.
The second is a lot more exciting - that a second supermassive black hole has fallen into the centre of the galaxy, messing with the "normal feeding process" of the original.
"We are very lucky to have caught the transition in time to continue observing it with several telescopes, in many different ways with a variety of instruments available for our follow-up observations," says Dr Bernd Husemann at the European Southern Observatory in Germany.
Mrk 1018 continues to get dimmer as the research goes on.
The latest findings were published in Astronomy & Astrophysics today.