You may not see the black holes, but the surroundings aren’t. And for the first time, astronomers directly measured the overheated “corona” surrounding one of these universe giants.
The Supermassive Black Hole, RX J1131, is approximately 6 billion light years from Earth and rotates in more than half the light. The monster itself remains hidden, but it excavates nearby gas and dust, heats it to millions of degrees, and burns as a quasar, one of the brightest objects in the universe. Corona, the halo of superheated gas, spans approximately 50 astronomical units and is the size of the solar system.
This measurement was made possible by a rare cosmic alignment that creates a “double zoom” that depicts a foreground galaxy about 4 billion light years from Earth acting like two stacked magnifying glasses, creating a landscape of the environment right in the vicinity of the black hole.
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“This is the first time that such a measurement has been made,” Matos Libach, a senior researcher at Leiden University in the Netherlands, told Live Science. “In principle, we found a new way to see something very close to a black hole going on.”
The results detailed in Prelint before its soon appearance in Journal Astronomy & Astrophysics provide a new tool for investigating extreme environments around black holes on scales that are too small to solve even the best telescopes.
“This doesn’t look right.”
Because the galaxy in the foreground is so large, its enormous gravity bends and enlarges the light of the Rx J1131, creating four different images of the quasar through a phenomenon known as a strong gravity lens. When the Rybak team reanalyzed data from a decade ago collected by Chile’s Atacama Large Millimeter/Submillimeter Array (Alma) radio telescopes, they noticed small flickers in the brightness of these images.
“Within a few days of looking at the data, I realized, ‘OK, this doesn’t look right,'” recalls Rybak. “It’s not even my main area of study, but it’s become like a pet project we’ve been pursuing.”
If the source of these variations comes from around the black hole itself, all images will be brighter and darker. However, follow-up observations for 2022 revealed that images flickered independently of one day apart.
“It’s a smoking gun. It has to be something along the way,” Libac said.
That “something” is a microlens, where individual stars in the foreground galaxy act as small lenses, temporarily expanding various parts of the corona of the Quasar. Because COVID is so compact, these small amplifications produced independent flicker observed across images, the authors say in a new study.
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Related: Stephen Hawking’s long-standing black hole theory has finally been confirmed – scientists hear that the two-event vision blends into one
“We saw this flicker with data that we couldn’t explain otherwise,” Libac told Live Science. By analyzing these flickers, the team was the first to measure the width of the COVID-19 solar system.
New window to black holes
Not only will researchers be able to map corona, but the new measurements provide a potential window into the magnetic field surrounding black holes, scientists said in their study.
Previous studies have shown that a strong magnetic field regulates how much gas enters and how much is expelled, essentially controlling the way black holes grow over time. Although it is very difficult to measure these fields directly, theoretical models suggest a millimeter wave emission of corona, that is, a link between light-generating from rapidly moving electrons that spiral around the magnetic field line – its size and magnetic field strength.
“Understanding how these black holes grow is the main possibility here,” Libac said.
This measurement is particularly pronounced as millimeter wave light was previously considered largely static, even for months or years. “But this was one of those moments when I realized, ‘No, things change, and they change a lot,'” Libac said.
To track and compare millimeters of radiation across different wavelengths, the team is also planning to collect additional data from NASA’s Chandra X-Ray Observatory, the only X-ray telescope with sufficient spatial resolution to capture certain features of such a small lens. However, with large proposals for budget cuts that have sparked a strong backlash from the scientific community, the 26-year-old flagship telescope is unlikely to continue these observations.
Instead, future progress will likely depend on Alma. Alma has expanded into a low frequency band that covers the brightest wavelengths of black hole coronas.
Complementing Alma, the Vera C. Rubin Observatory excels in high resolution optical imaging, a standard way to discover lensed quasars like the RX J1131. The telescope, whose first image was revealed in June, discovered thousands of these systems, and is expected to allow astronomers to study optical flickering with unprecedented accuracy. “Rubbin is an innovative tool to do this,” Libac said.
With increasingly sensitive telescopes, astronomers are just beginning to explore the numerous sources that fly through the millimeter-wave sky.
“The exciting part is something we don’t know yet,” Libac said.
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