A new image of the supermassive black hole at the center of the Milky Way galaxy reveals striking similarities with another black hole and hints at a jet hidden inside it.
According to a press release from the European Southern Observatory, the image was captured by the Event Horizon Telescope (EHT) collaboration research on the black hole was p ublished this week in The Astrophysical Journal Letters. It shows that supermassive black hole Sagittarius A* (Sgr A*) – located at the center of our galaxy – has strong and organized magnetic fields around its edges.
Sara Issaoun, NASA Hubble Fellowship Program Einstein Fellow at the Center for Astrophysics/Harvard & Smithsonian and co-lead of the project, described the magnetic fields as “strong” and “twisted.”
Sgr A* has this in common with the black hole at the center of the M87 galaxy. As black holes, both are regions of spacetime where gravity is so great that nothing can escape from them, even light.
These new photos of Sgr A* indicate that strong magnetic fields may also be common to all black holes.
“This similarity also hints toward a hidden jet in Sgr A*,” said the press release. It said “ previous studies of light around the M87 black hole (M87*) revealed that the magnetic fields around it allowed the black hole to launch powerful jets of material back into the surrounding environment.”
However, EHT Deputy Project Scientist Mariafelicia De Laurentis, a professor at the University of Naples Federico II, Italy, noted that they have not found one yet in Sgr A*.
In 2019, the first image of a black hole – that one at the center of M87 – was revealed. Then, the first image of Sgr A* was released in 2022.
“While the Milky Way’s supermassive black hole, which is roughly 27,000 light-years away from Earth, is more than a thousand times smaller and less massive than M87’s, the first-ever black hole imaged, the observations revealed that the two look remarkably similar,” said the ESO.
To find out, researchers decided to study Sgr A* with polarized light. This type of light oscillates in a preferred orientation.
“In the plasma around these black holes, particles whirling around magnetic field lines impart a polarization pattern perpendicular to the field,” the ESO explained. “This allows astronomers to see in increasingly vivid detail what’s happening in black hole regions and map their magnetic field lines.”
Harvard Black Hole Initiative Fellow and project co-lead Angelo Ricarte said that polarized light reveals a lot about the astrophysics, the properties of the gas, and mechanisms that take place inside of a black hole. However, the process is a bit complicated since Sgr A* moves so fast.
To get images of the black hole, researchers require sophisticated tools even more advanced than the one that captured of M87*.
“We were relieved that polarized imaging was even possible. Some models were far too scrambled and turbulent to construct a polarized image, but nature was not so cruel,” said EHT Project Scientist Geoffrey Bower from the Institute of Astronomy and Astrophysics, Academia Sinica, Taipei.
In fact, eight telescopes were joined to make a “virtual Earth-sized” telescope. To create some images, they needed to average multiple images of the fast-moving black hole.
“As the largest and most powerful of the telescopes in the EHT, [The Atacama Large Millimeter/submillimeter Array (ALMA)] played a key role in making this image possible,” said ESO’s María Díaz Trigo, European ALMA Programme Scientist. “ALMA is now planning an ‘extreme makeover’, the Wideband Sensitivity Upgrade, which will make ALMA even more sensitive and keep it a fundamental player in future EHT observations of Sgr A* and other black holes.”
The ESO-hosted Atacama Pathfinder Experiment (APEX) in Chile was also part of the network.
Next month, the EHT is scheduled to observe Sgr A* again. Every year, images improve and researchers hope to find a hidden jet as more are captured.
Lauren Barry