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Astroboffins spy the most greedy black hole yet gobbling a Sun a day

It farts out enough energy to irradiate all life on Earth

Astronomers have spotted the greediest supermassive black hole going through the fastest growth spurt some 12 billion years ago.

The humongous hole, codenamed QSO SMSS J215728.21-360215.1, is the staggering size of about 20 billion suns, and grows at a rate of 200 million suns over a million years. It has a voracious appetite and gobbles a mass equivalent to twice that of our Sun every two days to sustain itself.

"If we had this monster sitting at the centre of our Milky Way galaxy, it would appear 10 times brighter than a full moon. It would appear as an incredibly bright pin-point star that would almost wash out all of the stars in the sky," said Christian Wolf, lead author of the study and a researcher from the Australian National University.

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The energy comes from the accretion disk. It’s a plate of gas and dust swirling around the supermassive black hole that will eventually get devoured. As the material spirals inwards during the feeding process, gravitational and frictional forces heat the accretion disk to temperatures hot enough, where it starts to emit electromagnetic radiation.

In this case, it’s mostly ultraviolet light and x-rays. “Again, if this monster was at the centre of the Milky Way it would likely make life on Earth impossible with the huge amounts of x-rays emanating from it," Wolf said.

Scary but useful

Black holes at the centre of galaxies, which can be quasars, often reach masses over ten billion times the mass of the Sun. Supermassive ones like this one are exceedingly rare, as they normally form very early on in the universe.

The team of researchers found the void with SkyMapper, an optical telescope in Australia, and the European Space Agency’s Gaia satellite, and NASA’s Wide-field Infrared Survey Explorer.

As the universe expanded, the electromagnetic waves emitted by the quasar take longer to reach Earth and their wavelength is stretched. The ultraviolet and x-ray light now appears as infrared, making it possible for the researchers to detect the quasar.

The energy radiated from supermassive black holes ionizes the surrounding gas and contributes cosmic reionization, where neutral atoms break apart into their constituent parts: electrons and nuclei.

These particles will eventually merge back together again to form new atoms, so scientists can use this to study how the first elements formed in the universe.

Finding objects like this ancient quasar will also help scientists probe the expansion of the universe. They are also useful as bright reference points for GPS and space navigation, and could provide the most sensitive measurements of the rate of expansion.

“We don't know how this one grew so large, so quickly in the early days of the Universe. The hunt is on to find even faster-growing black holes," Wolf said.

The research is expected to be published in the Publications of the Astronomical Society of Australia (here is the free arXiv version). ®

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