If, as it now seems, every single galaxy has a black hole at its heart, this can't be a coincidence. Perhaps black holes are an essential part of what galaxies are and how they work.

No one had expected that black hole size and galaxy size could possibly be related. It suggested some mysterious invisible connection between a galaxy and its black hole. But what this was was a mystery scientists would have to wait three years to solve.

The first breakthrough came when a new instrument was added to Hubble Space Telescope. This dramatically accelerated the discovery of new black holes, giving scientists a wealth of new potential leads to follow. For three years the data has been coming down to Earth. Amongst those who've been sifting through it, are two young competing researchers. What they were to discover this year would turn the world of cosmology on its head.

Everyday I go to work, I don't really know what's going to happen, but I can count that it's going to be something exciting every single day.

These past six months have been phenomenal in terms of black hole research. We've been extremely excited we were finding these black holes in, in, in numbers that we had never been able to do before.

Karl Gebhardt and Laura Ferrarese were trying to find the fundamental connection linking black holes and their galaxies. So they searched through all the different galaxy characteristics, looking for any new links that might give a clue. But it wasn't until they looked at the property called sigma that the mystery began to unravel.

Sigma is just a very, very fancy name for something that's actually very simple.

Sigma is the speed at which the stars are circling in the outer reaches of the galaxy. The stars at the edge of the galaxy are so far away from the black hole that they are completely unaffected by its gravity.

wealth: an abundance or profusion of something desirable

unravel: investigate and solve (a mystery or puzzle)