New images of the universe’s most photogenic dark hole provide insight into the mysterious behavior of a black hole.
For the first time, we look at the source of a colossal plasma jet pouring into space from the edge of the supermassive black hole M87*. It’s also the first time we’ve seen the shadow of a black hole and its jet in the same image, and the sight should help astronomers figure out how these massive streams of plasma are generated.
“We know that jets are ejected from the region surrounding black holes,” says astronomer Ru-Sen Lu of the Shanghai Astronomical Observatory in China, “but we still don’t fully understand how this actually happens. To study it directly, we need to observe it.” the origin of the jet as close as possible to the black hole.”
Black holes, as we all know, are famous for not emitting anything that we can detect. They are so dense that the spacetime around them actually warps into a closed sphere, so no velocity in the universe is sufficient to reach escape velocity. But the space just outside the boundary of this ball – what we call the event horizon – is a different matter.
Here is a region of extremes where gravity reigns supreme. Any nearby material is drawn into its trap, swirling into a disk of material that pours into the black hole like water down a drain. Friction and gravity heat this material, causing it to glow; That’s what we saw in the now-famous image of M87, first released in 2019 based on data collected in 2017 by the Event Horizon Telescope (EHT) collaboration.
But not all material is inevitably drawn beyond the event horizon. Some of it skims the edge before being launched into space from the black hole’s polar regions, forming jets capable of traveling at a significant percentage of the speed of light and crashing long distances into interstellar space.
Astronomers believe that this material is deflected from the inner edge of the disk along magnetic field lines beyond the event horizon. These magnetic field lines accelerate the particles so that when they reach the poles, they are launched into space at high speed.
It is wide trains; specifics are more difficult to determine. We know that M87* is a jet that reaches 100,000 light-years at radio wavelengths, about the diameter of our own galaxy. So in 2018, astronomers used powerful radio telescopes combined to form the Global mm-VLBI Array (GMVA) to see if they could see in detail the region from which the jets originate. It collected data at a longer wavelength than EHT, revealing different information.
“M87 has been observed for many decades, and 100 years ago we knew the jet was there, but we couldn’t put it into context,” says Lu. “With GMVA, including the leading instruments at NRAO and GBO, we’re observing at a lower frequency, so we’re seeing more detail, and now we know we need to see more detail.”
Located about 55 million light-years away, the galaxy M87 hosts a supermassive black hole about 6.5 billion times the mass of the Sun, actively accreting matter from the disk around it. The image taken by the EHT showed for the first time the shadow of this black hole, a dark region in the middle of a ring of glowing material that has been distorted by the gravitational bending of spacetime.
The new image shows a wider area of space than the EHT image. This reveals that the volume of plasma around M87* is much larger than seen in the EHT image, in addition to the source of the jet.
“The original EHT imaging revealed only part of the accretion disk surrounding the center of the black hole. By changing the observation wavelengths from 1.3 millimeters to 3.5 millimeters, we can see more of the accretion disk and now the jet,” says astronomer Tony Minter from the National Radio Astronomy Observatory. “It revealed that the ring around the black hole is 50 percent larger than we previously thought.”
The new image also revealed new information about how the jet is launched from the region of space around the black hole, confirming that magnetic field lines do indeed play a crucial role in sucking up material to be launched as jets.
But they are not acting alone. A strong wind emanates from the disk itself, powered by radiation pressure. This wind, as seen in the image, contributes to the formation of M87’s jet.
It’s a pretty major breakthrough in black hole science, but researchers aren’t done yet. There is much more to see across the radio spectrum and the M87* has proven to deliver.
“We plan to observe the region around the black hole at the center of M87 at different radio wavelengths to further study the jet emission,” says astronomer Eduardo Ross of the Max Planck Institute for Radio Astronomy in Germany. “The next few years will be exciting as we learn more about what’s going on near one of the most mysterious regions of the universe.”
The study has been published Nature.
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