A new image from the Event Horizon Telescope collaboration, which includes researchers and telescopes at the University of Arizona, has discovered powerful, spirally organized magnetic fields from the edge of the supermassive black hole Sagittarius A*, or Sgr A* .
The Event Horizon Telescope (EHT) collaboration, which in 2022 presented the first image of Sagittarius A*, the black hole at the center of our Milky Way, has captured a new view of the massive object, this time in polarized light. For the first time, astronomers were able to measure polarization, a signature of magnetic fields, this close to the edge of the black hole. The lines mark the orientation of the polarization, which is related to the magnetic field around the black hole’s shadow. Image credit: EHT Collaboration
Observed for the first time in polarized light, this new view of the monster lurking at the center of our Milky Way galaxy revealed a magnetic field structure strikingly similar to that of a much more massive black hole, known as M87*, in the center. of the galaxy M87, suggesting that powerful magnetic fields could be common to all black holes. This similarity also hints at a hidden jet in Sgr A*. The results were published March 27 in The Astrophysical Journal Letters.
Scientists revealed the first image of Sgr A*, located about 27,000 light-years from Earth, in 2022, revealing that although the supermassive black hole in the Milky Way is more than a thousand times smaller and less massive than that of M87, it looks remarkably similar. This made scientists wonder if the two shared any common traits aside from their appearance. To find out, the team decided to study Sgr A* in polarized light. Previous studies of the light around M87* revealed that the magnetic fields around the giant black hole allowed it to launch powerful jets of material into the environment. Building on this work, the new images revealed that the same could be true for Sgr A*.
Boris Georgiev, EHT postdoctoral researcher at the UArizona Stewards Observatory and co-author of the study, said: “The consistency of the magnetic field structures around Sgr A* and M87* suggests that the processes by which holes blacks power and eject jets into their environment may be universal, despite their large differences in size and mass. »
“What we’re seeing now is that there are strong, twisted, organized magnetic fields near the black hole at the center of the Milky Way,” said Sara Issaoun, an Einstein Fellow in NASA’s Hubble Fellowship Program at Astrophysics Center | Harvard & Smithsonian and co-leader of the project. “In addition to the fact that Sgr A* has a polarization structure strikingly similar to that observed in the much larger and more powerful black hole M87*, we have learned that strong and orderly magnetic fields are essential to how black holes interact with the gas and matter around them. them. »
Light is a moving oscillation of electric and magnetic fields that allows us to see objects. Sometimes the light swings in a preferred direction
orientation, also called polarized. Although polarized light surrounds us, to human eyes it is indistinguishable from “normal” or unpolarized light. In the plasma around these black holes, particles swirling around the magnetic field lines impart a polarization pattern perpendicular to the field. This allows astronomers to see in increasingly vivid detail what is happening in black hole regions and to map their magnetic field lines.
“By imagining polarized light from hot, glowing gas near black holes, we directly infer the structure and strength of the magnetic fields that guide the flow of gas and matter from which the black hole feeds and ejects,” he said. said Angelo Ricarte, Harvard Black Hole. Initiative Fellow and co-leader of the project. “Polarized light tells us a lot more about astrophysics, the properties of gas and the mechanisms that occur when a black hole feeds. »
But imaging black holes in polarized light isn’t as simple as putting on a pair of polarized sunglasses, and that’s especially true for Sgr A*, which changes so quickly that it doesn’t stay still for photos . Imaging the supermassive black hole requires sophisticated tools, beyond those previously used to capture M87*, a much more stable target. EHT principal investigator and paper co-author Dan Marrone, a professor of astronomy at Steward Observatory, and his team developed instruments that detected polarized radio waves for this result.
“In the same way that polarized light can tell us the orientation of the surface it bounces off, like windows or roads, it can also show us the orientation of magnetic fields around black holes,” Marrone said . “Since the magnetic fields change rapidly around Sgr A*, transforming the EHT observations into polarized images presented a significant challenge. We are really proud that our data contains enough information.
Scientists say they are excited to have images of the two supermassive black holes in polarized light because these images, and the data that accompany them, offer new ways to compare and contrast black holes of different sizes and environments. As technology improves, the images will likely reveal even more secrets about black holes and their similarities or differences.
“These results help us improve our computational models and theories and give us a better idea of what happens near the event horizon of a black hole,” added the co-author. Chi-kwan ChanProfessor of astronomy at UArizona who focuses on theoretical modeling of black holes.
The EHT has made several observations since 2017. Each year, the images improve as the EHT incorporates new telescopes, greater bandwidth, and new observing frequencies.
“We are developing hardware and software to automate EHT observations, allowing the EHT to make more frequent observations in the future to capture films of black holes,” said Amy Löwitz, EHT research scientist at Steward Observatory which leads the EHT Agility project.
Such observations, spread over several months, constitute one of the main objectives of the EHT for the years to come, according to Remo Tilanus, professor at UArizona and head of operations of the EHT who supervises the observation campaigns and the technical developments.
“With Project Agility’s capabilities, we should be able to see material swirling around the M87* and being ejected into its jets,” Tilanus said.
Expansions planned for the next decade will also enable high-fidelity movies, could reveal a hidden jet in Sgr A*, and allow astronomers to observe similar polarization features in other black holes. There are even plans to extend the EHT into space, providing much sharper images of black holes and enabling much more powerful studies of black hole rotation and the mechanisms that power black hole jets.
EHT is expected to observe Sgr A* again in April, which will keep the EHT UArizona team busy. Along with Lowitz and Georgiev, postdoctoral researcher Andrew Thomas West and graduate student Jasmin Washington are currently preparing the submillimeter telescope on Mount Graham and the Arizona Radio Observatory’s 12-meter radio telescope on Kitt Peak for the upcoming observation.
Washington, who participated in the 2021 shadowing campaign as a first-year graduate student, said she enjoyed the experience and is excited to be able to return this year.
“We will be observing with more telescopes than ever before, which will give us better coverage and more sensitivity to make these polarized measurements,” she said.
West added: “Measuring with very high fidelity how these sources have changed since they were last observed will inform our models and allow us to answer fundamental questions about the physics in these extreme environments – it’s very exciting!” »
Source: University of Arizona
Originally published in The European Times.
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