Astronomers Capture Dazzling New Image of the Black Hole at the Milky Way's Center

Astronomers have captured the first-ever image of magnetic fields circling the supermassive black hole at the center of our Milky Way galaxy.

The fields have a similar structure to those around the black hole at the center of Messier 87, a massive elliptical galaxy in the constellation Virgo. This finding suggests that strong magnetic fields may be a common feature of all black holes, the researchers report in a pair of papers published today in the Astrophysical Journal Letters.

“This spiral pattern that we see swirling around the black hole indicates that the magnetic fields must also be a spiral pattern whirling around—and that they’re very strong and very ordered,” Sara Issaoun, a co-leader of the research and an astronomer at the Center for Astrophysics, Harvard & Smithsonian, says to BBC Science Focus’ Tom Howarth.

The new image “shows that strong and ordered magnetic fields are critical to how black holes interact with the gas and matter around them,” Issaoun tells Space.com’s Robert Lea.

In 2019, researchers made history by capturing the first-ever image of a black hole, the one at the center of Messier 87. A black hole is a densely packed region of matter that has such a strong gravitational pull that not even light can escape its grasp.

Two years ago, astronomers shared the first image of the black hole residing in our home galaxy, called Sagittarius A*. Located around 27,000 light-years from Earth, Sagittarius A* has the mass of 4.3 million suns. But it pales in comparison to M87*, Messier 87’s black hole, which has a mass 6.5 billion times that of our sun.

Given their different sizes, researchers were surprised to find that the two black holes actually looked very similar, making them question whether the pair of behemoths had other traits in common, according to a statement from the Center for Astrophysics, Harvard & Smithsonian.

Both of the prior, groundbreaking images were taken with the Event Horizon Telescope (EHT), a global network of radio observatories at sites in the United States, Mexico, Chile, Spain and other countries that work together to image black holes.

To take the new image, researchers again turned to the EHT. This time, they imaged Sagittarius A* in polarized light, which is made up of waves that vibrate in only one orientation. This allowed the researchers to map the magnetic field lines of the black hole, per the statement.

“M87* and Sgr A* are different in a few important ways: M87* is much bigger, and it’s pulling in matter from its surroundings at a much faster rate,” Michi Bauböck, a co-author of the research and an astrophysicist at the University of Illinois Urbana-Champaign, says in the statement. “So, we might have expected that the magnetic fields also look very different. But in this case, they turned out to be quite similar, which may mean that this structure is common to all black holes.”

“A better understanding of the magnetic fields near black holes helps us answer several open questions—from how jets are formed and launched to what powers the bright flares we see in infrared and X-ray light,” he adds.

The magnetic fields surrounding Sagittarius A* (right) look very similar to those that surround M87* (left). This finding suggests strong magnetic fields may be a common feature among black holes. EHT Collaboration

M87*’s magnetic fields allow it to eject jets of material into its surroundings. Astronomers have not been able to spot such jets around Sagittarius A*. But the similarity between the two black holes’ magnetic fields suggests Sagittarius A* could have a hidden jet.

“There’s this really exciting hint that there may be some additional structure,” Ziri Younsi, a co-author of the research and astrophysicist at University College London, tells New Scientist’s Alex Wilkins. “There might be something going on that’s quite exciting in the center of the galaxy, and I think that these results we’re going to need to follow up.”

If our own galaxy’s black hole also has a jet, it could help astronomers understand the history of the Milky Way.

“In the host galaxy, the jets kick-start star formation—and can also quench it,” Issaoun says to the BBC. “So there’s a really interesting interlink between the dynamics of these jets coming from these black holes and the host galaxy’s evolution.”