3.5 billion light years from Earth — a significant chunk of the way across the visible Universe — lies a monster. It's called OJ287, and it's an active galaxy, one with a tremendous amount of energy blasting out of its nucleus. It's classified as a blazar, one of the most luminous objects in the Universe, with energy pouring out of it across the electromagnetic spectrum, from radio waves all the way up to high-energy gamma rays.
The power source for this galaxy is a black hole in its center that is abjectly soul-crushing in its proportions: It has a mass of 18.4 billion times the mass of the Sun — that's the mass of a small galaxy, except it's all compressed down into a single object. This not only makes it a supermassive black hole — it's one of the most massive known.
A maelstrom surrounds it, a swirling disk of gas and dust light years across. Near the center, just outside the black hole itself, the material is moving at very nearly the speed of light, and is unimaginably hot. Friction heats it, since material moving farther out from the black hole is revolving around it more slowly, causing intense collisions between particles in the disk. It's so hot and so huge that it is hugely luminous, which is how we can see this object at all from so far away.
You'd think this would be enough superlatives for any object. But there's more. Oh my yes, there's more.
You see, OJ 287’s black hole isn't alone. It's a binary black hole, with a second one orbiting it. This companion is only — only! — 150 million times the Sun's mass. For comparison, the supermassive black hole in the center of the Milky Way is about 4 million solar masses, so even this smaller one in OJ 287 positively dwarfs ours.
It orbits the bigger one every 12 years, traveling along an elongated elliptical path that takes it to within 500 billion kilometers of its bigger compatriot. That's a long way in human terms (it's about 100 times the distance of Neptune from the Sun), but remember the scale of what we're talking about here: The accretion disk around the primary black hole is trillions of kilometers wide, so the secondary black hole plunges right through the disk, twice per orbit. And when it does, all hell breaks loose.
Its immense gravity draws in a huge amount of material from the disk, which heats up massively as it falls in. Even though the disk itself is still quite hot at that location anyway, this event dumps even more energy into it, creating two huge rapidly expanding bubbles of gas superheated to 100,000°C, nearly 20 times hotter than the surface of the Sun. This creates an intense flare of brightness from the disk, which grows rapidly at first as the bubbles expand, then dims as the bubbles get so big and spread out they become transparent.
How intense are they, you ask? Well, at their maximum they put out a trillion times as much light as the Sun. A trillion. That's more luminous than our entire galaxy, and the flares last for days.
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