The Event Horizon Telescope (EHT) has captured stunning, newly revealed images of the supermassive black hole that lies at the heart of the galaxy M87. The EHT made this black hole, known as M87*, famous in April 2019 when it was revealed as the first black hole ever imaged by humanity.
These images of M87*, located around 55 million light-years from Earth, show that the polarization of the magnetic fields around the black hole reversed over a period of four years. The new observations of M87* also show the telltale signs of a jet of matter emerging from around the black hole, with its base connected to the bright ring around the outer boundary, or “event horizon,” around M87*.
The images could help scientists further develop theories of how matter behaves in the extreme environments around supermassive black holes, which have masses of millions or even billions of suns and are found at the hearts of all large galaxies.
“The fact that the polarization pattern flipped direction from 2017 to 2021 was totally unexpected,” EHT team member Jongho Park, a researcher at Kyunghee University in South Korea, said in a statement. “It challenges our models and shows there’s much we still don’t understand near the event horizon.”
The observations showed the ring of superheated, highly magnetized gas, or plasma, flowing one way around this 6.5-billion-solar-mass black hole in 2017, then settling in 2018 before reversing and spiraling in the opposite direction in 2021. And, to make matters more intriguing, not everything about the plasma changed between 2017 and 2021.
“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 [of general relativity], the polarization pattern changes significantly,” said team co-leader Paul Tiede, an astronomer at the Center for Astrophysics | 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.”
The changing polarization of plasma around M87* seems to indicate an evolving and turbulent environment around this black hole, which could be impacting how it feeds on surrounding matter. The cause of the reversal isn’t clear yet, but it could be the result of the magnetic structure of the plasma combined with external effects.
The newly released images also allowed the team to home in on the base of the jet of particles erupting from around M87* at near-light speed with the EHT for the first time. This is an important breakthrough, because jets like this one, which are comprised of particles channeled to the poles of black holes by magnetic fields, are thought to represent one of the ways supermassive black holes sculpt the galaxies in which they sit by pumping vast amounts of energy into their surroundings.
The new images also illustrate changes that the EHT itself has undergone. The final image, collected in 2021, is sharper due to the addition of two new telescopes, Kitt Peak in Arizona and NOEMA (Northern Extended Millimeter Array) in France, to the 25 Earth- and space-based instruments that make up the EHT network, which boosted the project’s sensitivity.
“These results show how the EHT is evolving into a fully fledged scientific observatory, capable not only of delivering unprecedented images, but of building a progressive and coherent understanding of black hole physics,” said EHT scientist Mariafelicia De Laurentis, an astronomer at the University of Naples Federico II in Italy. “Each new campaign expands our horizon, from the dynamics of plasma and magnetic fields to the role of black holes in cosmic evolution. It is a concrete demonstration of the extraordinary scientific potential of this instrument.”
Future images from the EHT are set to improve thanks to upgrades to two telescopes in its network, the Greenland Telescope and the James Clerk Maxwell Telescope. Thus, the EHT will continue playing a crucial role in our understanding of black hole physics for years to come, team members said.
“Year after year, we improve the EHT — with additional telescopes and upgraded instrumentation, new ideas for scientific explorations, and novel algorithms to get more out of the data,” said team co-leader Michael Janssen, of Radboud University in the Netherlands. “For this study, all these factors nicely conspired into new scientific results and new questions, which will certainly keep us busy for many more years.”
The team’s research was published in the August edition of the journal Astronomy & Astrophysics.