The Hamilton Spectator

Voracious Black Hole At the Dawn of Time

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Astronomer­s claimed recently that they had discovered what might be the hungriest, most luminous object in the visible universe — a supermassi­ve black hole that was swallowing a star a day. That would be the mass equivalent of 370 suns a year disappeari­ng down a cosmic gullet 11 billion years ago at the dawn of time.

In a paper published in Nature Astronomy, Christian Wolf of the Australian National University and his colleagues from Australia and Europe called the object at the center of a newly discovered quasar, J0529-4351, “the fastest growing black hole in the universe.”

According to their estimates, this black hole was one of the most massive ever found: 17 billion times as massive as the sun. But other astrophysi­cists have questioned the methods by which the mass and luminosity of the quasar had been estimated.

“It does seem like an extreme object,” said Daniel Holz, a theoretica­l astrophysi­cist at the University of Chicago. But, he added, “I would be shocked if this turned out to be the most luminous quasar on the sky.”

He wrote in an email, “There’s this weird game we play in astronomy where we’re always looking for the biggest, the brightest, the youngest, the oldest, etc.”

Quasars look like stars. They emit improbable torrents of energy, outshining all the stars in the galaxy in which they are embedded. Astronomer­s have concluded that this energy is produced by matter falling into giant black holes. Just as a bathtub cannot drain in an instant, matter can disappear down the cosmic drain only at a rate, called the Eddington limit, depending on the black hole’s size. The rest is trapped in a swirling disc radiating energy, making

black holes the brightest objects in the universe.

Dr. Wolf and his team identified J0529-4351 as a quasar after observing it with a telescope at Siding Spring Observator­y in Australia. Follow-up spectrogra­phic measuremen­ts with the Very Large Telescope in Chile allowed them to estimate the size of the accretion disc and the speed of the gas within it.

That in turn led them to conclude that the black hole was some 17 billion solar masses and was accreting mass at the Eddington limit.

“In this process its accretion

disc alone releases a radiative energy that is equivalent to the output from between 365 and 640 trillion suns,” the astronomer­s wrote in their paper.

Acknowledg­ing that all estimates of these distant early universe black hole masses were uncertain by a large margin, Dr. Wolf said that new instrument­s — including a high-resolution instrument called Gravity on the Very Large Telescope, and the upcoming Extremely Large Telescope under constructi­on in Chile — should be able to get a well-defined image of the rotating storm disc, leading to an accurate black hole mass.

At its observed rate of growth, Dr. Wolf said, the quasar’s black hole would have doubled every 30 million years, which would have allowed the black hole’s mass to grow to 17 billion suns within three billion years after the Big Bang.

But it was unlikely, he added, that black holes grow at their maximum rates all the time. He said black holes only intermitte­ntly reach their Eddington limits, when a feast presents itself. Even more massive black holes have been discovered in the early universe by telescopes like the James Webb Space Telescope, but none are as luminous as J0529-4351.

That has led some astronomer­s to speculate that many of these black holes had primordial origins, predating stars and galaxies, and started out very massive.

“I am myself coming around to the idea that black holes formed before the galaxies did, and were the seeds around which galaxies formed rather than the other way around,” Dr. Wolf said. “This has been proposed decades ago, but was considered too crazy to become mainstream.”

 ?? M. KORNMESSER/EUROPEAN SOUTHERN OBSERVATOR­Y, VIA ASSOCIATED PRESS ?? An artist’s concept of the quasar J0529-4351. Astronomer­s said its black hole was the fastest growing in the universe.
M. KORNMESSER/EUROPEAN SOUTHERN OBSERVATOR­Y, VIA ASSOCIATED PRESS An artist’s concept of the quasar J0529-4351. Astronomer­s said its black hole was the fastest growing in the universe.

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