The fastest-growing black hole in the universe eats a sun every 48 hours - and Australian astronomers have found it

NASA/JPL-CaltechAn artist’s impression supermassive black hole.

A “supermassive” black hole swallowing up the mass of our sun every two days has been found by Australian astronomers.

Astronomers at the Australian National University (ANU), led by Dr Christian Wolf of the Research School of Astronomy and Astrophysics, found the fastest-growing black hole known in the universe by looking back more than 12 billion years to what they call “the early dark ages of the universe”.

It takes a million years to grow by 1%, but given it’s already estimated to be as big as 20 billion suns, that means the black hole, also known as a quasar, is growing by around 66.5 million Earths annually.

Wolf said if it was at the centre of the Milky Way, it would appear 10 times brighter than a full moon as a pin-point star that would almost wash out all the stars in the sky.

Not that you’d know, because the x-rays emanating from it would make life on Earth impossible.

“This black hole is growing so rapidly that it’s shining thousands of times more brightly than an entire galaxy, due to all of the gases it sucks in daily that cause lots of friction and heat,” Wolf said.

Most of the energy coming from the quasar is ultraviolet light. Wolf’s team used the SkyMapper telescope at the ANU Siding Spring Observatory to detect the light in the near-infrared, because it had red-shifted over the billions of light years towards Earth.

“As the Universe expands, space expands and that stretches the light waves and changes their colour,” Wolf explained.

The European Space Agency’s Gaia satellite, which measures tiny motions of celestial objects, also helped out, confirming that ANU’s discovery was sitting still and thus likely to be a quasar.

What puzzles Wolf is how it grew so large, so quickly when the universe was just a toddler, but despite the fact that black holes this big are “exceedingly rare”, the ANU team are already on the hunt for other, faster-growing quasars. Improved technology on ground-based telescopes coming online over the next decade will also be able to directly measure the expansion of the universe using the very bright black holes.

Dr Wolf said one benefit from finding black holes is they act as backlighting to everything else out in the cosmos, making it easier to see.

“Scientists can see the shadows of objects in front of the supermassive black hole,” he said.

“Fast-growing supermassive black holes also help to clear the fog around them by ionising gases, which makes the universe more transparent.”

The research on the ANU find will be published in Publications of the Astronomical Society of Australia.

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