In 2019, scientists unveiled the first-ever images of a black hole, M87*. Those observations kickstarted a wave of new investigations into how black holes work, how they grow, and how they change. And now, after a few upgrades, the Event Horizon Telescope network is back with another bombshell centered on M87*—finding tantalizing evidence of previously unknown physics at the event horizon of the black hole itself.
In a series of images taken by the EHT between 2017 and 2021, scientists observed a completely unexpected reversal in the black hole’s magnetic fields—in other words, its polarization flipped. They also detected strange jets blasting out of M87*. The observations provide researchers their most detailed view yet of the black hole and, perhaps as a consequence, the extreme conditions surrounding it. The findings are set to be detailed in an upcoming Astronomy & Astrophysics paper.
“These results show how the EHT is evolving into a fully fledged scientific observatory, capable not only of delivering unprecedented images but also of building a progressive and coherent understanding of black hole physics,” said Mariafelicia De Laurentis, study co-author and an astronomer at the University of Naples Federico II in Italy, in a release.
Unexpected changes to a supermassive black hole
M87* is a supermassive black hole that sits at the center of the galaxy M87, which is located about 55 million light-years away from Earth. This behemoth is estimated to be more than six billion times the mass of our Sun. Such a gigantic black hole should exert huge gravitational influence on any matter nearby, as seen in the ring of bright, orange plasma in the image.
What caught astronomers by surprise, however, were stark shifts in the direction of the plasma spiral around M87*, technically known as its polarization pattern. It suggests that the area around M87* is an “evolving, turbulent environment where magnetic fields play a vital role in governing how matter falls into the black hole and how energy is launched outward,” the researchers explained.
“What’s remarkable is that while the ring size has remained consistent over the years-confirming the black hole’s shadow predicted by Einstein’s theory-the polarization pattern changes significantly,” said Paul Tiede, study co-lead author and an astronomer at the Center for Astrophysics at Harvard & Smithsonian.
“This tells us that the magnetized plasma swirling near the event horizon is far from static; it’s dynamic and complex, pushing our theoretical models to the limit,” he added.
A piece of the cosmic puzzle
The observations suggest the polarization pattern at M87* flipped direction in 2017, before spiraling the other way in 2021.
“It challenges our models and shows there’s much we still don’t understand near the event horizon,” said Jongho Park, another co-author of the paper and an astronomer at Kyunghee University in South Korea.
Black hole physics is, well, a bit of a black hole, with myriad unanswered questions and mysteries still to be solved. Any hint we can get helps to advance our science forward: Supermassive black holes like M87* are essential to how galaxies form stars, and they help distribute seeds of energy throughout the universe.
In particular, the powerful jets emitted by such large black holes are a “unique laboratory” for astrophysicists studying gamma rays or high-energy neutrinos, the researchers said, offering a rich array of information about the role of black holes in cosmic evolution.