THE MYSTERY OF THE BIGGEST BLACK HOLE IN THE UNIVERSE

Black holes are big. Very big. But physics makes it almost impossible for them to grow. Here's how one black hole defied the odds to swell to gargantuan proportions

- DR BECKY SMETHURST

The first image taken of a black hole, the picture that finally turned artists' impressions into a reality, was of the supermassive black hole at the centre of the galaxy Messier 87. Most supermassive black holes are found in the centres of galaxies. They sit in the gravitational driving seat as the hundreds of billions of stars in the surrounding systems happily orbit them, just like the planets orbit the Sun at the centre of our Solar System.

The black hole at the centre of Messier 87 lies at the more massive end of the supermassive scale, cramming a mass that's six billion times that of the Sun (six billion solar masses) into an area the size of Neptune's orbit. But as huge as that might sound (especially when compared to the black hole at the centre of the Milky Way, which is a mere four million solar masses), it's by no means the most massive black hole that we know of.

That title goes to TON 618, which is an astonishing 66 billion solar masses. It's so big that astronomers had to invent a new term to describe it; hence, TON 618 is what's become known as an ultramassive black hole. 

To give you an idea of just how mindbogglingly big TON 618 is, imagine taking all the stars in the Milky Way and squishing the matter in them down to create a black hole. Even if you did that, you would still be a few billion Suns worth of matter shy. So how did TON 618 become such a behemoth?

SPAGHETTI AND PIZZA

Black holes are made of vast amounts of matter that have accumulated in one spot and been packed together as densely as possible, to the point where the gravitational pull from the accumulation is so strong that not even light can escape it.