For the First Time, See the Mysterious Disks That Circle Black Holes

David Grossman
Photo credit: ALMA (ESO/NAOJ/NRAO), E.M. Murchikova; NRAO/AUI/NSF, S. Dagnello

From Popular Mechanics

In April, scientists stunned the world when they unveiled the first-ever picture of a supermassive black hole. Months later, the Atacama Large Millimeter/submillimeter Array (ALMA) is helping fill in the picture with the first ever shot of cool, interstellar gas wrapped around a supermassive black hole's center. The shot will give scientists a better understanding of the mysterious regions that surround black holes, their accretion disks.

Black holes are regions of space with the strongest gravitational pulls in the universe. They pull in matter so fast that they create what are known as accretion disks, something like an interstellar traffic jam. What happens is all that matter can't all fall in the hole at once, so the various objects take the form of a circular line to get destroyed.

The matter of an accretion disk, which can consist of gas, plasma, dust, or anything in the vicinity of the black hole, becomes white hot due to their rapid movement. How hot? Scientists estimate around 10 million degrees Celsius (18 million degrees Fahrenheit), which is around two-thirds as hot as the Sun. That bright, radiant whiteness helps scientists identify black holes.

ALMA captured the accretion disk of Earth's nearest black hole, known as Sagittarius A*, which is approximately 26,000 light-years from Earth.

"We were the first to image this elusive disk and study its rotation," says Elena Murchikova, a member in astrophysics at the Institute for Advanced Study in Princeton, New Jersey, and lead author on the paper showing the finding, in a press statement. "We are also probing accretion onto the black hole. This is important because this is our closest supermassive black hole. Even so, we still have no good understanding of how its accretion works. We hope these new ALMA observations will help the black hole give up some of its secrets."

According to the National Radio Astronomy Observatory, the new picture shows "roving stars, interstellar dust clouds, and a large reservoir of both phenomenally hot and comparatively colder gases."


Those colder gasses are only around a hundredth of a light-year away from Sagittarius A*. That's approximately 1000 times the distance from the Earth to the Sun, which is a long way in terms of human distance. But for a black hole, it's practically next door.

They were discovered through mapping the shifts in wavelengths of this radio light, thanks to the Doppler effect. The blue part of the picture shows images moving in the direction of Earth, and objects moving away from the Earth's direction look red. The crosshairs of the picture show the location of the black hole. The emissions are "stronger than expected," according to the paper's abstract in Nature.

There's clearly a lot left to learn about black holes and their accretion disks. But the more photos that come in, the more answers appear.

('You Might Also Like',)