Space

Astronomers image 40-light-year-wide space donut

Astronomers image 40-light-yea...
An artist's rendition of the gigantic donut of gas that surrounds the supermassive black hole at the center of the galaxy M77
An artist's rendition of the gigantic donut of gas that surrounds the supermassive black hole at the center of the galaxy M77
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ALMA imaged the active galactic nucleus of the galaxy M77, and found a cloud of gas stretching out 20 light-years from the central black hole
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ALMA imaged the active galactic nucleus of the galaxy M77, and found a cloud of gas stretching out 20 light-years from the central black hole
ALMA determined the motion of the gas at the center of M77: blue is gas moving towards us, while red is that moving away from us
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ALMA determined the motion of the gas at the center of M77: blue is gas moving towards us, while red is that moving away from us
An artist's rendition of the gigantic donut of gas that surrounds the supermassive black hole at the center of the galaxy M77
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An artist's rendition of the gigantic donut of gas that surrounds the supermassive black hole at the center of the galaxy M77

The supermassive black holes lurking at the centers of galaxies have been known to chow down on anything unlucky enough to pass too close, but the opportunity to see that in action rarely occurs at the Milky Way's quiet core. Now, astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) observatory in Chile have imaged a very active black hole at the center of spiral galaxy M77, which is apparently feasting on the universe's largest donut.

The heart of M77 is what's known as an active galactic nucleus (AGN), meaning that gas and matter is constantly being sucked into the central black hole and giving off intense light. These active regions in the universe could help unlock the mysteries of how galaxies and the supermassive black holes at their cores develop in tandem.

Apart from the occasional spectacle, our own galactic center isn't very active, so astronomers need to look further away to find those clues. The team, made up of researchers from the National Observatory of Japan, SOKENDAI and Kagoshima University, used ALMA to image M77's galactic nucleus.

ALMA imaged the active galactic nucleus of the galaxy M77, and found a cloud of gas stretching out 20 light-years from the central black hole
ALMA imaged the active galactic nucleus of the galaxy M77, and found a cloud of gas stretching out 20 light-years from the central black hole

The team spotted a compact gaseous structure, resembling a gigantic donut, surrounding the black hole. The cloud stretches some 20 light-years out from the center, and is spinning around the black hole. The existence of these spinning torus structures has been hypothesized for decades, but according to the researchers, this marks the first time one has been directly observed.

"To interpret various observational features of AGNs, astronomers have assumed rotating donut-like structures of dusty gas around active supermassive black holes," says Masatoshi Imanishi, lead author on a paper describing the find. "This is called the 'unified model' of AGN. However, the dusty gaseous donut is very tiny in appearance. With the high resolution of ALMA, now we can directly see the structure."

ALMA determined the motion of the gas at the center of M77: blue is gas moving towards us, while red is that moving away from us
ALMA determined the motion of the gas at the center of M77: blue is gas moving towards us, while red is that moving away from us

The resolution of ALMA's images can't hog all the credit for the discovery. The researchers say it was also important to focus on specific molecular emission lines, and microwave emissions were detected from hydrogen cyanide (HCN) molecules and formyl ions (HCO+). Since these molecules only emit microwaves in dense gas, it tells the team a lot about the donut's density.

But there's more to the story. The researchers say that the torus isn't spinning perfectly in line with the black hole's gravity – instead, there's a high degree of randomness to its motion. That implies a violent past, which may have involved a collision with a smaller galaxy.

The research was published in Astrophysical Journal Letters.

Source: ALMA

9 comments
Chris74
Black holes have yet to be proven real. Just a fact. I also wonder how acurate these images can be from 1000s of light years away when we cant get clear images from/of Mars.
Bob
Artist renditions and a lot of assumptions. I'm beginning to wonder what proof means or is coming to mean in science.
ValeriyPolulyakh
In search of black holes and dark matter astrophysicists are relying on indirect observations. It would seem that the measurement of the event horizon of a black hole directly would be a direct evidence. However, by the nature of a horizon, any real measurement of the event horizon will be indirect. The Event Horizon Telescope will get picture of the silhouette of the Sgr A* which is due to optical effects of spacetime outside of the event horizon. The result will be determined by the simple quality of the resulting image that does not depend on the properties of the spacetime within the image. So, it will be also indirect and an existence of BH is a hypothesis. https://www.academia.edu/12468184/Are_there_Black_Holes_and_Dark_Matter_in_the_Milky_Way
Don Duncan
"...a high degree of randomness to its motion." In other words, the motion has not been explained yet. When it is, it won't be random. That's because "random" is not descriptive of the phenomena. It is a confession of ignorance. It describes the observer's state of mind vis a vie the observation, not the event. I assume the adjective "high degree" was used because of a speculation that the unexpected spin could be due to a galactic collision.
CzechsterMarek
Forty light years? How fast would I have to drive to get across it if the traffic wasn't bad?
DomainRider
The mass of the object can be calculated from the orbits and masses of the stars around it. If the mass is greater than a certain limit and the object is smaller than a certain size (i.e. not a star), it must be some kind of exotic superdense object that might as well be callled a 'black hole'.
donmr
Pretty much everything you think is real is your brain's interpretation of the stream of data from all its sensors. Much can be learned from indirect observation. Generally what we think we know as biggest, smallest or farthest goes up by an order of magnitude with frequency. A black hole is where you can sail your ship to the edge and then fall off into the abyss.
Riaanh
I get a feeling that a lot of commentators on this forum tend to have a misconception of science. No matter what the politicians say, science is never settled. Science consists of theories, some beter proven than others. Because of the complexity of the universe, which the little bugger called the Quantom theory is aptly demonstrating to us, we actually know nothing about anything. The best we can do is postulate a theory, and let our fellow scientist prove it, reject it or propose another theory. That is the best we can do within our physical limitiations.
Grunchy
Nah, my car exists (scientifically!) because I can grab a hammer and bash away at a ball joint. If I wanted definitive proof of a Black Hole, I reckon I'd like to blast a 50 kW laser beam at it, which is supposed to disappear at the Event Horizon. If you can't do something concrete with something, it makes no difference if it's Real or not. Galaxies could actually be Fake News for all any of us knows, there's absolutely no way to interact with them. Most anything you read about celestial bodies is the most tenuous of scientific hypothesis. But same like Religion, is there any way to prove it wrong? Not exactly.