Astronomers have a new, more complete picture of the supermassive black hole at the center of a galaxy 55 million light-years from Earth – the first black hole ever to be imaged.
While the first image of this black hole and its shadow was released in 2019, the new image released Wednesday shows the cosmic body in polarized light.
Think about your polarized sunglasses, which help reduce glare and reflections of brightness. Light can also be polarized when it’s emitted in hot regions of space near magnetic fields.
In this case, analyzing how the light around this black hole at the center of the M87 galaxy is polarized allowed astronomers a sharper view and the ability to map magnetic field lines near its inner edge. The scientists also discovered that a significant amount of light around the black hole is polarized.
The Event Horizon Telescope collaboration used a global network of telescopes in April 2017 to capture the first-ever picture of a black hole, which the team shared in 2019. It was the first direct visual evidence that black holes exist, the researchers said.
In the new image, astronomers have been able to learn more about how the black hole launches energetic jets of material moving near the speed of light.
These bright jets of energy and matter extend about 5,000 light-years from the center of the galaxy. While most matter near the edge of a black hole falls inside it, some of the matter is able to escape just before and is blasted out in the jets.
They were able to learn about the gas that actually produces the light in the image, as well as how the black hole grows, said study coauthor Jason Dexter, a coordinator of the EHT theory working group and assistant professor at the University of Colorado Boulder.
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The role of magnetic fields
“Polarized light tells us about magnetic fields near the black hole, how strong they are and how they connect the black hole’s accretion (eating habits) and the jet of plasma it’s able to eject out of the entire galaxy,” said study coauthor Sara Issaoun, a doctoral student in astrophysics at Radboud University in the Netherlands.
“Magnetic fields are a key element to understanding gas processes and feeding habits of black holes, and this is the very first time we’re able to see them at play so close to a black hole event horizon.”
The event horizon is defined as the boundary marking the limits of a black hole, which means nothing can cross that threshold and then escape it – including light.
The gas around a black hole is moving incredibly fast due to the pull of gravity. Speed heats the gas to billions of degrees, causing atoms to separate and forming plasma of loose electrons and protons. These charged particles moving extremely fast create electromagnetic forces, Issaoun explained.
“Magnetic fields created play a role in how the gas moves, how turbulent it is, and how much gas can make it to the black hole and how much gets flung out at nearly the speed of light in an outflow or jet,” she said. “The production of these jets of plasma is the most powerful and energetic process in the entire universe and still quite a puzzle to unravel, and we believe magnetic fields play a key role in launching and maintaining this process.”
In the polarized image, astronomers realized that the magnetic field is actively pushing back and resisting the motions of the gas that is dragged around the black hole. This means that the magnetic fields at the edge of the black hole are strong enough to help the hot gas resist the pull of gravity.
“Such ‘strong’ magnetic fields are capable of launching the most powerful jets, and their presence would have important implications for how black holes grow,” Dexter said.
8 radio telescopes capture black hole
In the new image, streaks can be seen showing light oscillating in a specific direction that indicate the strength of the magnetic field.
Imaging this activity is no easy feat.
In their attempt to capture an image of a black hole, scientists combined the power of eight radio telescopes around the world using a technique called Very-Long-Baseline-Interferometry, according to the European Southern Observatory, which is part of the EHT. This effectively creates a virtual telescope around the same size as the Earth itself.
The resolution created by this could measure the length of a credit card on the surface of the moon, the researchers said.
The EHT collaboration could also shed more light on the evolution of the black hole over the course of a year, based on the data the team already has collected, Issaoun said. The collaboration will observe the M87 black hole again to gather more information about the black hole and its jet.
“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” said study author Monika Mościbrodzka, a coordinator of the EHT polarimetry working group and assistant professor at Radboud University, in a statement.