2024-04-01 18:57:45
At the center of our Milky Way, a black hole is absorbing masses of matter. A new picture shows how we have to imagine Sagittarius A*.
The supermassive black hole at the heart of our galaxy has revealed a spectacular view of its magnetic fields. A new image from the EHT collaboration shows for the first time how they spiral and organize around the edge of Sagittarius A* in polarized light.
EHT Collaboration stands for “Event Horizon Telescope”. The alliance brings together telescopes and scientists from around the world to jointly research black holes – including astronomers from the Max Planck Institute for Radio Astronomy in Bonn, the Goethe University in Frankfurt am Main and Harvard University in the USA.
How was the recording made?
Despite its size of about four million solar masses, Sagittarius A* is largely inactive at the center of the Milky Way and therefore invisible to normal telescopes. It reveals its presence primarily through the movements of stars and gases in the galactic center.
The EHT’s coupled radio observatories were able to image “our” black hole for the first time in 2022. Shortly afterwards, radio data provided the first evidence of the movement of the hot plasma around the event horizon and its rotation.
Now the scientists in the EHT collaboration have been able to make the magnetic fields around Sagittarius A* visible for the first time. The polarization of the light emitted by the surrounding gas disk was observed, the scientists at the Max Planck Institute explain in a press release. In this way, the course of the magnetic field lines on the inner edge of the gravity trap could be mapped.
“By measuring the polarized light from hot, glowing gas near black holes, we can infer the structure and strength of the magnetic fields,” explained Angelo Ricarte of the Harvard Black Hole Initiative in a press release.
Electromagnetic radiation becomes polarized when it passes through certain filters, such as the lenses of polarized sunglasses or the lenses of a camera. This reduces reflections, reflections and glare on bright surfaces; this makes the image appear clearer. Polarized radiation also occurs in space and helps astronomers to sharpen their view of an object (Max Planck Institute).
However, this mapping was not easy for Sagittarius A* because the black hole is very turbulent and changes much faster than the larger and much quieter supermassive black hole M87*. “We now see that there are strong, ordered and twisted magnetic fields near Sagittarius A*,” reports Sara Issaou from the Harvard & Smithsonian Center for Astrophysics in the US.
Does Sagittarius A* have a jet?
However, the new EHT images also raise the question of whether our black hole could have a previously hidden jet (jets of matter containing high-energy particles emitted by black holes). There are faint traces of possible jet radiation, but this is not conclusive (read more about this here). “While we observed a very obvious jet in M87*, we have not yet been able to find it in Sagittarius A*,” explains Mariafelicia De Laurentis from the University of Naples Federico II.
Further clarity on these and other questions may be provided by the Event Horizon Telescope’s next observation campaign, scheduled for April 2024. The collaboration is also planning expansions of the telescope network and increased observation bandwidth and frequency over the next decade to enable even sharper images.