A Very Hungry Black Hole Is Found, Gorging on Stars

It is a truism of modern astronomy that every galaxy has a hungry heart, to paraphrase Bruce Springsteen, in the form of a massive black hole gulping gas, dust and even stars.

Astronomers in Australia now say they have found the hungriest heart in all the cosmos. It is a black hole 20 billion times the mass of the sun eating the equivalent of a star every two days.

The black hole is growing so rapidly, said Christian Wolf, of the Australian National University, who led the team that found it in the depths of time, “that it is probably 10,000 times brighter than the galaxy it lives in.” So bright, that it is dazzling our view and we can’t see the galaxy itself. He and his colleagues announced the discovery in a paper to be published in the Publications of the Astronomical Society of Australia.

Black holes are a one-way gate to gravitational oblivion, according to Einstein’s theory of general relativity, but they can only swallow so much, depending on their size; the rest of the matter and energy gets splashed out across space, producing the fireworks popularly known as quasars.

The blaze from material swirling around this newly observed drainpipe into eternity — known officially as SMSS J215728.21-360215.1 — is as luminous as 700 trillion suns, according to Wolf and his collaborators. If it were at the center of our own galaxy, the Milky Way, it would be 10 times brighter than the moon and bathe the Earth in so many X-rays that life would be impossible.

Luckily it’s not anywhere nearby. It is in fact 12 billion light years away, which means it took that long for its light to reach us, so we are glimpsing this cataclysm as it appeared at the dawn of time, only 2 billion years after the Big Bang, when stars and galaxies were furiously forming.

How it got so big so quickly after the Big Bang adds to a mystery about the origin of the supermassive black holes — often weighing in at more than 1 billion suns — that occupy the centers of galaxies. What came first? The black holes or the galaxies?

“How they grew to such mass so early after the Big Bang is a profound puzzle for physics,” the authors say in their paper.

Today it appears as a reddish pinprick of light in the southern constellation Piscis Austrinus. It was one of many potential quasars that showed up in the SkyMapper Southern Sky Survey being performed by Wolf and his colleagues, but so do many stars. Wolf and his colleagues weeded out the list by cross-matching it with new data just released by the GAIA spacecraft, which is triangulating the distances to stars, looking for objects that did not appear to move and were thus very, very far away.

“All this searching happened within 36 hours between a Saturday early morning and a Sunday afternoon,” Wolf recalled in an email. That evening they got to a telescope and observed their 10 best remaining black hole candidates. Five of them were drowned out by the full moon, another one was a distant quasar with a smaller black hole. “And one was this guy,” Wolf wrote in an email.

“When it was clear what we had found, I had a bottle of Champagne with my wife,” he said.