The black hole at the heart of the Milky Way is like the monster lurking under your bed. It’s four million times the mass of the Sun, and about 15 million miles across – just waiting to gobble up anything that gets too close.

But compared to the black holes in many other galaxies, the one in the Milky Way is less like a monster and more like a dust bunny. The largest ones yet seen are thousands of times bigger. They’re known as ultra-massive black holes. Informally, they’re also called SLABs – stupendously large black holes.

Just which one is the biggest is uncertain – it’s hard to measure the mass of something that might be billions of light-years away. A recent candidate is in a structure known as the Cosmic Horseshoe. The gravity of a stupendously large galaxy “warps” the view of a galaxy behind it, creating what looks like a big, blue horseshoe.

In a recent study, astronomers combined a couple of techniques to measure the mass of the black hole in the foreground galaxy: 36 billion times the mass of the Sun. Researchers say the combo makes the measurement the most accurate for any candidate for the “biggest black hole” honors.

But other black holes could be bigger. The biggest candidate is known as Phoenix A. It could be up to about 25 thousand times the mass of the Milky Way’s black hole. But that number is highly uncertain. So the search for the biggest black hole continues.

Script by Damond Benningfield