Fastest-growing black hole of past 9bn years may have been found, Australian-led astronomers say

Astronomers believe they have discovered the fastest-growing black hole of the past 9bn years.

The supermassive black hole consumes the equivalent of one Earth every second and has the mass of 3bn suns, they estimate.

Scientists discovered an extremely bright quasar, a luminous object powered by a supermassive black hole, using the SkyMapper Southern Sky Survey – a 1.3-metre telescope in Coonabarabran, New South Wales.

The object – J114447.77-430859.3, or J1144 for short – is 7,000 times more luminous than all the light from the Milky Way.

The lead researcher Dr Christopher Onken, of the Australian National University, said the supermassive black hole was “more or less halfway across the universe”.

“The light that we’re seeing from this growing black hole has been travelling to us for about 7bn years,” he said. The big bang occurred an estimated 13.8bn years ago.

J1144 was the most luminous quasar in the last 9bn years of cosmic history, the scientists found.

There are other similar sized black holes “but they all tend to be much earlier in the history of the universe where the mergers between galaxies was much more common”, Onken said.

The reason for J1144’s unusual luminosity is still unclear. “Maybe two big galaxies have collided and have funnelled a lot of gas in towards the black hole,” Onken said.

“People have been looking for these growing black holes since the early 1960s,” he said, adding that around 880,000 of them had been discovered and catalogued to date. “The fact that something so bright has escaped the many, many searches that have been conducted over the years is quite remarkable.”

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Why J1144 has eluded discovery for so long may be partly due to its position in the night sky. “Historically, people have avoided looking very close to the plane of the Milky Way age because there’s so many stars, there’s so many contaminants, that it’d be very hard to find anything more distant,” Onken said.

“There have been searches that stopped looking at 25 degrees … or even 20 degrees away from the plane of the Milky Way. This source is at 18 degrees away.”

While black holes are themselves not visible – their gravity is so great that not even light can escape them – they are observable because of the matter that swirls around them.

A side-by-side comparison of the sky from photographic plates observed in 1901 and 2018
A side-by-side comparison of the sky from photographic plates observed with a 20cm telescope (a one-hour exposure) in 1901 and the SkyMapper Southern Sky Survey’s 1.3-metre telescope using a CCD camera (and a 100-second exposure) in 2018. Photograph: Christopher Onken/Australian National University

Dr Fiona Panther, a gravitational wave astronomer at the University of Western Australia, who was not involved in the research, described black holes as “very, very messy eaters … if there’s a lot of gas and dust being pushed on to the black hole, it will actually spit a lot of it out.

“It will usually get spat out in massive jets … quasars are a particular type of black hole jet,” she said.

Almost every galaxy in the universe has a supermassive black hole at its centre, Panther said.

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While nothing beyond the event horizon can escape, black holes “don’t have any special sucking power beyond their gravitational ability to pull things towards them”, Onken said.

“If you took the sun and shrunk it down into a black hole … we’d be in perpetual night-time but the motions of the planets around the sun wouldn’t change very much because the mass hasn’t changed.”

“The Milky Way, our own galaxy, has a black hole that is 4m times larger than the sun,” Onken said.

J1144 is bright enough to be visible to amateur astronomers. “If you want to see it with your eye then you probably need a telescope that is 30 to 40cm across,” Onken said.

J1144 was first spotted by Adrian Lucy, a doctoral student, while searching for close pairs of binary stars in the Milky Way.

The research is not yet peer-reviewed; it has been published as a preprint and submitted to the Publications of the Astronomical Society of Australia.

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