Australian scientists have discovered the fastest growing black hole known in the universe.

It is growing at a rate of 1 per cent every 1 million years, and it is so big it is consuming a mass equivalent to our Sun every two days.

A long time ago, in a galaxy far, far away...

For those trying to unlock the secrets of the universe, the bigger a black hole is, the better.

And Dr Christian Wolf and his team at the ANU's Research School of Astronomy and Astrophysics have found a monster.

"What's really important in this business is now to actually find the most massive ones because they are the hardest ones to explain," he says.

Supermassive black holes — or quasars — are hard to find among the billions of stars in the universe.

The ultra-violet light emitted from the quasar was detected by the SkyMapper telescope at the ANU Siding Spring Observatory.

There is a supermassive black hole at the centre of our own galaxy, but compared to this one, it's a lightweight.

"That one has a mass of 5 million solar masses — that is 40,000 times less mass than the one that we have now found," Dr Wolf says.

"We estimate that this black hole has a mass of at least 20 billion times the mass of the Sun."

What did the first quasars look like? An artist's impression shows a primordial quasar as it might have been, surrounded by sheets of gas, dust, stars, and early star clusters. ( Illustration: Wolfram Freudling et al. (STECF), ESO, ESA, NASA )

And it's a good thing this monster black hole isn't at the centre of our Milky Way.

As well as its ravenous appetite, it would likely emit so many X-rays, life probably couldn't exist.

But don't panic — Dr Wolf says it won't suck us in.

"We don't have to be afraid of that. It is very far away," he says.

"The light has travelled for 12 billion years until it reached us and we were now able to see this.

"So this means it's far, far away in another galaxy and it will never drift and come over here."

Could this have triggered the big bang?

This supermassive quasar was around when the 13.8-billion-year-old universe was only about 1.2 billion years old.

That's a puzzle for scientists, who don't understand how quasars grew so big, so early in the history of the universe.

Professor Tamara Davis, an astrophysicist at the University of Queensland, says it has implications for our understanding of how it all began.

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"There's a big mystery about how these supermassive black holes form, because we don't understand how something could get that big that quickly; our normal theories don't work," she says.

"And it might mean that there were seeds to these black holes in the very early universe.

"During the birth of the universe, some really massive seeds were created that these black holes then formed around.

"So, it actually has implications for how the universe began and what mechanism triggered the big bang."

The findings have been accepted for publication in the Publications of the Astronomical Society of Australia (PASA).