Unveiled Strong Magnetic Fields Spiraling At The Edge Of Milky Way’s Central Black Hole

New discovery by the Event Horizon Telescope (EHT) Team. Since 2022, researchers have been working on the observation of the supermassive black hole at the center of the Milky Way, Sagittarius A (Sgr A). Scientists have detected a magnetic vortex system at the edge of the event horizon, similar to the one at the center of the Galaxy M87.

*A view of the Milky Way supermassive black hole Sagittarius A in polarised light. Credits: ESO*

Observed in polarized light, it confirmed the first hypotheses. This suggested that all black holes could possess these powerful magnetic vortices. Regardless of the size of the two black holes (Sgr A is a thousand times smaller than that of M87) as reported by ESO – European Southern Observatory, the structure appears similar. This suggests to the team that the jets of material ejected by M87 could also occur on the outskirts of our Sgr A.

“What we’re seeing now are powerful magnetic fields, twisted and organized around the black hole at the center of the Milky Way. Together with Sgr A we learned that strong and organized magnetic fields are critical to how black holes interact with the gas and matter around them.”
— Sara Issaoun, NASA Hubble Fellowship Program Einstein Fellow at the Center for Astrophysics and co-lead of the project

Angelo Ricarte, a fellow at the Harvard Black Hole Initiative, explained how polarized light allows us to observe what is not possible with traditional observations: “With polarized light, we can observe glowing gas near black holes, and this makes us imagine the structure and strength of the magnetic fields that influence the dynamics of the flow of gas and matter entering and exiting the black hole.“

Hard phenomena to observe

However, studying the phenomenon in Sgr A* presents greater challenges compared to M87. Unlike the stable and easily observable material in M87, the material in Sgr A* is in constant motion.

As the team attempted to capture the swirling motion in their photograph, it proved difficult to generate even a non-polarized image. The initial image of Sgr A* had to be compiled from an average of multiple images due to the continuous movement of the black hole.

*This is the first image of Sgr A*, the supermassive black hole at the centre of our galaxy. It’s the first direct visual evidence of the presence of this black hole. Credits: EHT Collaboration*

“We were relieved that polarized imaging was possible. Some models were too confusing and turbulent to construct a polarized image, but Nature wasn’t so bad with us.”
— Geoffrey Bower, EHT project researcher at the Institute of Astronomy and Astrophysics of Academia Sinica in Taipei

The Worldwide Telescope Network

To observe Sgr A, as M87, eight telescopes act in atomic synchrony around the world, to create a virtual telescope the size of the Earth’s diameter, and form the EHT. The most powerful of the eight is the Atacama Large Millimeter/submillimeter Array (ALMA), of which ESO is a partner, and which enabled much of the making of this image.

This visible light wide-field view shows the rich star clouds in the constellation of Sagittarius (the Archer) in the direction of the centre of our Milky Way galaxy. Credits: ESO and Digitized Sky Survey 2

In conjunction with ALMA, which operates in northern Chile, the Atacama Pathfinder Experiment (APEX), hosted by ESO, played a crucial role in the network conducting the 2017 observations. Other key contributors included the 30-meter telescope of the Institut de Radioastronomie Millimétrique (IRAM), the James Clerk Maxwell Telescope (JCMT), the Large Millimeter Telescope Alfonso Serrano (LMT), the Submillimeter Array (SMA), the University of Arizona Submillimeter Telescope (SMT), and the South Pole Telescope (SPT).

Since then, the EHT has added to its network the Greenland Telescope (GLT), the IRAM NOrthern Extended Millimeter Array (NOEMA), and the 12-meter Arizona Telescope on Kitt Peak (KPNO).