EHT Collaboration
- A new photo of the supermassive black hole at our galaxy's core looks different from those before it.
- A groundbreaking collaboration of black-hole-imaging scientists published it on Wednesday.
- The photo may reveal a magnetic secret about the structure of all supermassive black holes.
The supermassive black hole at the heart of our galaxy has a side you've never seen before.
A new image reveals powerful magnetic fields swirling around our hometown black hole, which is called Sagittarius A* (pronounced "A-star").
The image is the latest innovation of a groundbreaking scientific collaboration called the Event Horizon Telescope (EHT), which rallied telescopes across the planet to focus on one black hole together, effectively creating an observatory as big as Earth.
It was just five years ago when EHT released the first-ever photo of a supermassive black hole, a feat which was thought to be impossible for decades. That's because black holes are objects so dense that not even light can escape them, making them invisible.
What is visible, however, is the disc of ultra-hot material circling around a black hole, which you can see in the image below of a supermassive black hole at the center of a galaxy called Messier 87.
Event Horizon Telescope Collaboration/Maunakea Observatories via AP
It wasn't long after that Sagittarius A* got its moment in the limelight.
Sagittarius A*'s 2022 portrait, below, looked quite similar to that of Messier 87, even though Sagittarius A* is about 1,000 times smaller than Messier 87's black hole.
Event Horizon Telescope collaboration
But the new image released on Wednesday is different. It shows our galaxy's black hole in polarized light, which occurs when light waves oscillate in a preferred direction.
The new view, below, reveals a clear polarization pattern in the particles circling the black hole — which means they're being affected by powerful magnetic fields spiraling around the edge of Sagittarius A*.
EHT Collaboration
"What we're seeing now is that there are strong, twisted, and organized magnetic fields near the black hole at the center of the Milky Way galaxy," Sara Issaoun, an astrophysicist at the Harvard and Smithsonian Center for Astrophysics and co-lead of the project, said in a press release.
A clue about the secret structure of supermassive black holes
Sagittarius A* is 27,000 light-years away from Earth, so this image represents a very tiny point in the sky.
"This appears the same size in the sky as a donut on the moon," Issaoun said at a press conference presenting the first image of it in 2022.
But the discovery of the magnetic field lines offers a major clue about the behavior of supermassive black holes across the universe, and how they eat the material surrounding them.
EHT had previously imaged its first black hole, Messier 87, in polarized light as well, though it doesn't look quite as striking:
EHT Collaboration
Since both black holes have similar structures of magnetic fields, despite their immense difference in size, the EHT scientists now suspect that all supermassive black holes might have magnetic structures like this.
"We've learned that strong and ordered magnetic fields are critical to how black holes interact with the gas and matter around them," Issaoun said.
The discovery also suggests that, like Messier 87, Sagittarius A* could have a jet of radiation and high-speed particles shooting out of the black hole. We just can't see it yet.
NASA's Goddard Space Flight Center/CI Lab
The telescope observations that led to this new image took place in 2017, but EHT is poised to cast its gaze at Sagittarius A* again in April.
Issaoun and her collaborators published their findings in two papers in The Astrophysical Journal Letters on Wednesday.
Bigger black hole breakthroughs may be in store
Further imaging with new innovative techniques and technologies could reveal even more secrets of supermassive black holes, both big and small.
EHT even aims to capture video of our galaxy's black hole, possibly by the end of the decade, Michael Johnson, an astrophysicist on the project, told Business Insider at a meeting of the American Astronomical Society in January.
"We think we're just scratching the surface of what can be done," Johnson said in a presentation at that meeting. "Even more exciting science is yet to come."
To that end, EHT recently added a telescope in Greenland to its worldwide array.
Incorporating satellites into that array, and thereby expanding the EHT observatory into space, could allow scientists to study dozens of black holes instead of just two. According to Johnson, that's likely to happen within a decade.