A polarized photograph of the M87 black hole.
In 2019, the Event Horizon Telescope (EHT) team took the first image of the black hole region in galaxy M87. The image shows bright ring-like structures with the black hole shadowed in the central region. This marked another important step in our understanding of these most exotic objects.
Two years later, the image was upgraded: it now has polarization information.
“We now see the next crucial piece of evidence to understand the behavior of magnetic fields around black holes and how activity in this very compact region of space drives powerful jets far beyond the Milky Way.” Monika Mościbrodzka, an assistant professor at Radboud Universiteit (Netherlands), said in a statement.
Polarization is a property of light that tends to oscillate in a particular direction. It has a wide range of applications in our daily lives, from polarized glasses that show us vivid 3D movies to polarized sunglasses that help us filter out glare. It can also be a powerful tool for astronomers, as it reveals the structure of magnetic fields in very powerful magnetized plasmas.
Andrew Chael of Princeton University said in the same statement, “The newly released polarized images are a key to understanding how magnetic fields cause black holes to “eat” matter and emit powerful jets. The key.”
The M87 black hole is a very active and extreme black hole because it consumes large amounts of surrounding matter and emits relativistic plasma jets. The jet is so bright that it can extend thousands of light years from the black hole.
However, the origin of this jet is still unknown to astronomers. In particular, the size of the jet may exceed the size of galaxy M87, but it comes from a tiny region smaller than our solar system.
Moreover, the reason why the light coming from the vicinity of a black hole is polarized is because the mechanism that produces the radiation is synchrotron radiation, which is the crucial radiation process that occurs in nuclear reactors. Therefore it is also crucial to understand this physical mechanism in extreme environments, such as near a black hole.
“The observations suggest that the magnetic field at the edge of the black hole is strong enough to push the hot gas back and help it resist the pull of gravity. Only gas that spills out of the magnetic field ends up falling into the black hole.” Jason Dexter, an assistant professor at the University of Colorado, Boulder (USA), explained in the same statement.
To observe the M87 black hole, the EHT collaboration linked eight telescopes around the world, including the Atacama Large Millimeter/Submillimeter Array (ALMA) and the Atacama Pathfinder Experiment (APEX), to create a virtual Earth-sized telescope. Using an advanced technique called radio interferometry, the EHT has the resolution to see credit card-sized objects on the lunar surface.
“With ALMA and APEX, which improve image quality by being located in the south by increasing the geographic distribution of the EHT network, European scientists were able to play a central role in the study.” ” ALMA, with its 66 antennas, dominates the overall signal collection of polarized light, while APEX is essential for image calibration,” said Ciska Kemper, an ALMA scientist at the European Southern Observatory (ESO), in a statement.
“ALMA data are also crucial in the calibration, imaging and interpretation of EHT observations, which provide tight constraints on theoretical models explaining the behavior of matter near the apparent horizon of black hole events,” added Ciriaco Goddi, a scientist at Radboud University, in the above statement. The Leiden Observatory in the Netherlands led a follow-up study, which relied only on ALMA observations.
” The EHT is progressing rapidly, with upgrades to the network technology and the addition of new observatories. We hope that future EHT observations will reveal the magnetic field structure around black holes more accurately and provide us with more information about thermal physics.” Jong-Ho Park of the Institute of Astronomy and Astrophysics, Academia Sinica, Republic of China, concluded in the above statement.
This new work is described in two papers in Astrophysical Journal Letters, and another follow-up study was published in Astrophysical Journal Letters.
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