Incredible first view of the magnetic fields surrounding our Milky Way’s supermassive black hole

The team that gave us the very first image of a black hole has released a new image of Sagittarius A*, the supermassive black hole at the center of the Milky Way, this time seen in polarized light for the first time. The image captured the magnetic field structures orbiting the black hole, similar to those around M87*, indicating that “strong, twisted and organized” magnetic fields are common among black holes.

The Event Horizon Telescope is a collaboration that uses radio telescopes around the world to form an Earth-sized combined array, large enough to image a black hole. If your eye had the same resolution, you could see a donut on the surface of the moon. It has given us the first image of our own Sagittarius A* (Sgr A*) and the much larger and more powerful black hole at the center of the massive elliptical galaxy Messier 87. In 2021 it captured the magnetic fields of M87*, the first ever for a black hole, using polarized light.

Now, for the first time, the team has used the polarization of light to image the magnetic fields of Sgr A*. Light is made by oscillating electromagnetic waves and when it oscillates in a preferred direction, we call it polarized. This is how 3D glasses work: the two lenses have different polarization that allows only part of the light to pass through, allowing our brains to create a 3D image in our heads. Polarized light helps reduce the glare from bright light sources, allowing the team to get a sharper view of the edge of the black hole and map the magnetic field lines present there.

“For the first time we have obtained polarimetric images at the scale of the event horizon of the black hole at the center of our Milky Way, Sgr A*,” said Professor Mariafelicia De Laurentis, EHT Deputy Project Scientist and Professor at the University of Naples Federico II . IFLScience.

“Thanks to the polarization of light, these images reveal a surprisingly detailed and orderly magnetic structure around the black hole. It is important that these images are presented in polarized light because it allows us to ‘see’ and understand the geometry of the magnetic field. around the black hole, a crucial aspect that cannot be captured with non-polarized light alone.”

A side-by-side comparison of the two images of the black holes, which show a similar magnetic field, shown as bright thin lines across their roughly donut shapes.  The lines wrap around the entire shape

The magnetic structures surrounding both M87* and Sagittarius A* are remarkably similar, despite the difference in size.

Image credits: EHT collaboration

The plasma around a supermassive black hole moves along the magnetic field lines, because plasma consists of charged particles. The swirling of these particles creates a polarization pattern on the light that is perpendicular to the magnetic field. Measuring the polarization tells us exactly how the magnetic field wraps around the supermassive black hole.

“Polarization is important in the study of black holes because it gives us information about the geometry and dynamics of the magnetic fields around the black hole,” explains Professor De Laurentis. “These fields play a key role in accretion processes and jet emissions. influencing the observation of black holes and our understanding of the physics governing these extreme objects.”

Accretion and aircraft emissions are not things that our friendly neighborhood supermassive black hole often participates in. As far as black holes go, Sagittarius A* is fairly quiet and calm, which is a good thing because even 26,000 light-years away an active supermassive black hole can have an impact. These objects could determine the fate of an entire galaxy.

But for M87*, these magnetic fields are crucial for releasing powerful jets. The supermassive black hole has been observed to release jets of particles that travel at nearly the speed of light and extend about 5,000 light-years from M87*. Seeing the same magnetic structures that drive far-reaching events in M87 in our own supermassive black hole suggests that these are underlying mechanisms common to all black holes.

“These magnetic fields are crucial in controlling the accretion of matter in black holes and the ejection of energetic jets, which are among the most spectacular phenomena in the universe,” Professor De Laurentis told IFLScience. “Understanding these fields allows us to explore the extremes. conditions near black holes, testing theories of gravity and magnetohydrodynamics in regimes where the effects of Einstein’s general theory of relativity play a crucial role.”

This image of Sagittarius A* is another step forward in better understanding black holes and how they affect their host galaxies, and is also a fantastic testbed for theoretical models of black hole activity.

“These observations represent a technical milestone and demonstrate the capabilities of current astronomical instruments and methodologies. They set a precedent for future observation campaigns and theoretical studies, and pushed the boundaries of our understanding of the universe,” Professor De Laurentis told IFLScience.

The next-generation Event Horizon telescope will be even better.

The research has been published in two articles in The Astrophysical Journal Letters.

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