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Oldest black hole found, and it may solve a cosmic mystery

Astronomers found the most distant black hole ever detected in X-rays (in a galaxy dubbed UHZ1) using the Chandra and Webb space telescopes. X-ray emission is a telltale signature of a growing supermassive black hole. This result may explain how some of the first supermassive black holes in the universe formed. These images show the galaxy cluster Abell 2744 that UHZ1 is located behind, in X-rays from Chandra and infrared data from Webb, as well as close-ups of the black hole host galaxy UHZ1.  (NASA)
By Joel Achenbach Washington Post

Two NASA space telescopes teamed up to scrutinize a distant galaxy and discovered something mind-boggling: a gargantuan black hole inside a galaxy that’s more than 13 billion years old. The “supermassive” object – hailed as the oldest black hole yet confirmed – has roughly the same mass as all the stars in that galaxy combined.

The discovery, published Monday in the journal Nature Astronomy, may help solve a cosmic mystery about supermassive black holes, which appear to have taken up residence in baby galaxies in the earliest era of the universe, not long after the big bang.

Black holes come in two varieties: stellar mass and supermassive. This is fairly self-explanatory. The stellar mass black holes might be roughly 10 to 100 times the mass of our sun. A supermassive black hole, a term without an ounce of hype, can be many millions or even billions of times heftier.

The residency of such monstrous black holes in the cores of virtually all galaxies – including our own – has fascinated astrophysicists, in part because their origin is unclear. The new report can’t fully resolve the issue, but it makes a strong case that at least for one galaxy, named UHZ1, the supermassive black hole didn’t grow gradually, but rather was supermassive from the get-go.

The report leveraged data from both the Chandra X-Ray Observatory and the James Webb Space Telescope. This is cosmic archaeology, using ancient light in the X-ray and infrared portions of the spectrum.

Chandra, in Earth’s orbit, has been studying the universe since it was launched in 1999. JWST, the newest member of the space telescope fleet in a solar orbit roughly a million miles from Earth, was launched on Christmas Day 2021. As an infrared telescope, it has enabled astronomers to look deeper into space and further back in time, collecting light from an era soon after the first stars began illuminating the universe and forming galaxies.

The light from UHZ1 was emitted 13.2 billion years ago, about 470 million years after the big bang. The observations, according to the new paper, show that the supermassive black hole at its core has roughly the same mass as the entire galaxy – “which is absolutely crazy,” said lead author Akos Bogdan, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.

Theorists have mulled two competing theories for the origin of supermassive black holes, known as light seed vs. heavy seed. In the light seed theory, a star will collapse into a stellar mass black hole and grow over time until it reaches supermassivity (which is not actually a word, but should be).

But in the heavy seed theory, a tremendous cloud of gas, rather than an individual star, does the consequential collapsing. There is no puny phase: As the cloud condenses and gravity does its work, the black hole forms at a supermassive scale.

“In this case, we can say with certainty that the black hole came from a heavy seed,” Bogdan said. “It is a pretty big deal.”

It’s just one galaxy, though, and thus one data point, so it won’t by itself resolve the debate.

“It’s not really possible to extrapolate from this single source to the whole galaxy population,” said Zoltan Haiman, a professor of astronomy and physics at Columbia University who studies early galaxies and was not part of the new report.

Haiman said the heavy seed model may include the formation, within the collapsing cloud, of a single gigantic star, which then collapses further into the black hole.

This is at once esoteric stuff and at the same time essential to the scientific understanding of how the universe came to look the way it does today. The Webb telescope was designed in large measure to probe deep into the early years of the universe and see what’s there.

More galaxies are coming under scrutiny, and it now appears that jumbo black holes will be foundational in the unfolding story.