Skip to main content

Black holes all look like donuts, regardless of their size

The release of a remarkable image of the black hole at the center of our galaxy isn’t only an incredible scientific achievement — it also agrees precisely with predictions about what black holes are and how these strange objects are formed by the power of gravity.

The black hole, called Sagittarius A*, is a type called a supermassive black hole, which is found at the center of almost all galaxies. Ours is on the smaller end for such giants: At 4.3 million times the mass of the sun, it’s much smaller than other monsters like the one is Messier 87 which was imaged in 2019 and which is 6.5 billion times the mass of the sun.

The EHT Collaboration created a flurry of images of Sagittarius A*, using ray tracing, a technique that visualizes the properties of the black hole based on data collected with the radio telescope array and predictions made by Einstein's theory of general relativity. The images shown here were created by UArizona's Chi-kwan Chan.
The EHT Collaboration created a flurry of images of Sagittarius A*, using ray tracing, a technique that visualizes the properties of the black hole based on data collected with the radio telescope array and predictions made by Einstein’s theory of general relativity. The images shown here were created by UArizona’s Chi-kwan Chan. Ben Prather/EHT Theory Working Group/Chi-Kwan Chan

However, images of these two black holes look notably similar, both showing a distinctive donut shape. And that agrees precisely with physicists’ predictions, which said that black holes would appear the same no matter what size they are.

Recommended Videos

“The fact that the light appears like a ring, with the black shadow inside, tells you it’s purely gravity,” black hole researcher Dimitrios Psaltis of the University of Arizona explained in a statement. “It’s all predicted by Einstein’s theory of general relativity, the only theory in the cosmos that does not care about scale.”

This scaling is unusual because most things that exist at different scales look very different — Psaltis gives the example of an ant and an elephant, which look very different because of, among other factors, the way their mass is supported. But black holes aren’t like that, it seems, as they are the same whether big or small. Messier 87 is 1,500 times more massive than Sagittarius A* and is vastly larger as well, as you can see in a comparison image from the European Southern Observatory. But the two look very similar.

Size comparison of the two black holes imaged by the Event Horizon Telescope (EHT) Collaboration: M87*, at the heart of the galaxy Messier 87, and Sagittarius A* (Sgr A*), at the centre of the Milky Way.
Size comparison of the two black holes imaged by the Event Horizon Telescope (EHT) Collaboration: M87*, at the heart of the galaxy Messier 87, and Sagittarius A* (Sgr A*), at the center of the Milky Way. EHT collaboration (acknowledgment: Lia Medeiros, xkcd)

That means that even very small black holes, if we were able to image them, would look like the images of Sagittarius A* and Messier 87. They would all show that similar donut shape.

“Wherever we look, we should see donuts, and they all should look more or less the same,” Psaltis said, “and the reason this is important — besides the fact that it confirms our prediction – is that nobody likes it. In physics, we tend to dislike a world where things don’t have an anchor point, a defined scale.”

Georgina Torbet
Georgina has been the space writer at Digital Trends space writer for six years, covering human space exploration, planetary…
Event Horizon Telescope can now take images of black holes that are 50% sharper
Illustration of the highest-resolution detections ever made from the surface of Earth

The Event Horizon Telescope project, the group that took the first-ever image of a black hole, has made another historic breakthrough, making the highest-ever resolution observations of space taken from the Earth's surface. The project uses facilities around the globe to turn the Earth itself into a giant observatory, which is capable of taking highly precise measurements of distant galaxies.

The latest observations made use of the Atacama Large Millimeter/submillimeter Array (ALMA), a large array of radio telescopes located in Chile, as well as other facilities in Spain, France, and Hawaii. To get higher-resolution images than previous observations, scientists weren't able to make the telescope bigger -- as it was already the size of the Earth -- so they observed at a higher frequency instead.

Read more
Hubble finds mysterious and elusive black hole
An international team of astronomers has used more than 500 images from the NASA/ESA Hubble Space Telescope spanning two decades to detect seven fast-moving stars in the innermost region of Omega Centauri, the largest and brightest globular cluster in the sky. These stars provide compelling new evidence for the presence of an intermediate-mass black hole.

An international team of astronomers has used more than 500 images from the NASA/European Space Agency (ESA) Hubble Space Telescope spanning two decades to detect seven fast-moving stars in the innermost region of Omega Centauri, the largest and brightest globular cluster in the sky. These stars provide compelling new evidence of the presence of an intermediate-mass black hole. ESA/Hubble & NASA, M. Häberle (MPIA)

There's something strange about black holes. Astronomers often find small black holes, which are between five times and 100 times the mass of the sun. And they often find huge supermassive black holes, which are hundreds of thousands of times the mass of the sun or even larger. But they almost never find black holes in between those two sizes.

Read more
NASA 360-degree video shows what it’s like to plunge into a black hole
A black hole according to NASA's 360-degree video.

360 Video: NASA Simulation Shows a Flight Around a Black Hole

If you were having a bad day, plunging into a black hole would be enough to really top it off. Apparently, you’d experience a process known as “spaghettification” in which the black hole’s enormous gravitational force would compress your entire body while stretching it out at the same time, leaving you a bit noodle-like. Falling into a supermassive black hole would be a slightly less horrendous experience, apparently.

Read more