Scientists of the Event Horizon Telescope (EHT) discovered the presence of powerful, organized magnetic fields spiraling from the edge of the supermassive black hole Sagittarius A* (Sgr A*), at the center of the Milky Way.
Seen in polarized light for the first time, this new image of the “monster lurking” at the heart of the Milky Way revealed the existence of a magnetic field structure strikingly similar to that of the galaxy M87 black hole, suggesting that strong magnetic fields may be common to all black holes. This similarity also points to a hidden jet in Sgr A*.
The research is published in two articles in the journal The Astrophysical Journal Letters, led by the EHT collaboration, in which more than 300 researchers from Africa, Asia, Europe, North America and South America are involved.
2022, key year
In 2022, in press conferences around the world – also in Spain – scientists unveiled the first image of Sgr A*. Although the Milky Way's supermassive black hole, which is about 27,000 light years away from Earth, is more than a thousand times smaller and less massive than that of M87 (the first photographed), observations revealed that the two are quite similar.
This made the scientific community wonder if, regardless of their appearance, they both shared traits. To find out, the team decided to study Sgr A* in polarized light, describes a statement from the European Southern Observatory (ESO).
Previous studies of the light around M87 (M87*) revealed that the magnetic fields in its surroundings allowed the black hole to launch powerful jets of material back into the surrounding environment. Based on this work, new images revealed that the same thing may be happening in Sgr A*.
“What we are seeing now is that there are strong magnetic fields, twisted into a spiral and organized near the black hole at the center of the Milky Way”summarizes Sara Issaoun, from the Harvard & Smithsonian Center for Astrophysics (USA).
Light is an oscillating or moving electromagnetic wave that allows objects to be seen. Sometimes, light oscillates in “a preferred orientation”, called “polarized” and although it surrounds us, for human eyes it is indistinguishable from “normal” light, explains the ESO.
“By imaging polarized light from the hot, glowing gas near black holes, we are directly deducing the structure and strength of the magnetic fields that thread the flow of gas and matter on which they feed, and in turn “At the same time, they expel,” says Angelo Ricarte, from Harvard.
He won't stay still for the photo
But imaging black holes with polarized light isn't as easy as putting on a pair of polarized sunglasses, and this is particularly true of Sgr A*, which changes so quickly that it won't stay still for photos.
Imaging requires sophisticated tools beyond those previously used to capture M87*, a much more stable target.
Mariafelicia De Laurentis of the University of Naples Federico II in Italy says the data indicates that both black holes have strong magnetic fields, suggesting this may be a universal and perhaps fundamental characteristic.
Another similarity could be a jet; although scientists photographed a very obvious one at M87*, they have not yet found it at Sgr A*.
To observe the Milky Way's black hole, the collaboration brought together eight telescopes around the world to create a virtual Earth-sized telescope, the EHT. ALMA, of which ESO is a partner, and APEX, both in northern Chile, were part of the network that carried out the observations, carried out in 2017.