A supermassive black hole and its jet, all in one image

In May 2022, the Event Horizon Telescope (EHT) team released the first-ever radio image of M87’s central black hole. It was a stunning revelation based on observations made using a worldwide network of radio telescopes. Recently, they reposted a newer, sharper image of the black hole’s “ring of light.”

Now, a team of astronomers from Europe, Korea and China have taken things a step further. This week they released another amazing view of this monster, this time in a slightly different lineup of radio shows. It clearly shows the connection between the supermassive black hole, its ring of light and the famous high-speed jet.

This latest image was made using an extensive network of radio telescopes. They included the Global mm Very Large Baseline Array (GMVA), the Atacama Large Millimeter Array (ALMA), and the Greenland Telescope (GLT). Their combined observations showed very fine detail in the region around the galactic core. This is the first time that the three main parts of the object are in the same image.

The observations, taken in 2018, show the region of radio light emitted at a longer wavelength than the EHT image. It is 3.5 mm instead of 1.3 mm. “At this wavelength, we can see how the jet emerges from the emission ring around the central supermassive black hole,” says Thomas Krichbaum of the Max Planck Institute for Radio Astronomy. The material escaping from M87 is an astrophysical jet. It contains superheated (ionized) matter flowing at high speed along an axis of rotation.

Get an overview of the black hole

To understand the structures in the last image, we need to know more about them. We know that supermassive black holes at the heart of galaxies are extremely powerful gravitational sinks. Nothing can escape as they suck up just about everything in the neighborhood. The formation of these monsters is not yet well understood. But, we can observe what they do to their quarters.

In the case of M87, there is an accretion disk funneling matter into the black hole. On the other hand, the jet helps some materials to escape. Understanding how such a huge jet can be created is a long-standing problem in astronomy. It probably forms as a result of some kind of activity inside the surrounding accretion disk.

Jet formation likely also involves entangled magnetic fields. However, astronomers are still unclear on all the details. “We know that jets are ejected from the region surrounding black holes,” said Ru-Sen Lu of the Shanghai Astronomical Observatory in China, “but we still don’t fully understand how this actually happens. To study this directly, we need to observe the origin of the jet as close as possible to the black hole.”

The new image also shows how the base of the jet connects to the swirling disc of matter in the black hole. Previous observations showed separate views of this disk and the jet. It is therefore the first time that the two characteristics have been observed together. “This new image completes the picture by showing the region around the black hole and the jet at the same time,” said team member Jae-Young Kim from Kyungpook National University in South Korea and the Max Planck Institute for Radio Astronomy in Germany.

probe the ring

Another fascinating part of the study is the ring of light surrounding the supermassive black hole M87. It’s actually a kind of optical illusion. As matter spins around, it heats up through friction with other matter and interactions with magnetic fields. This causes it to emit light. The strong gravitational effect of the black hole bends and captures some of the light. This creates what looks like a ring. This can be seen in the EHT image of the M87 black hole.

The new sightings of the ring were made in 2018 and are now published with an article (below) discussing the science. The size of the ring observed by the GMVA grating is about 50% larger compared to the EHT image. “To understand the physical origin of the larger and thicker ring, we had to use computer simulations to test different scenarios,” explained Keiichi Asada of Academia Sinica in Taiwan. The results suggest that the new image reveals more matter falling towards the black hole than could be observed with the EHT.

More sightings planned for M87 black hole

This new observation of the jet and the black hole is the first next-generation view of the system. Future studies will continue with clustered radio telescope arrays. They will continue to probe the connection between black holes and their jets. “We plan to observe the region around the black hole at the center of M87 at different radio wavelengths to further study the emission from the jet,” noted Eduardo Ros of the Max Planck Institute for Radio Astronomy.

Simultaneous observations using this array and the EHT would allow the team to unravel all the complex actions that occur near the supermassive black hole. Not only will they be interested in the jet, but also in the physics and activities of the accretion disk where the jet launches. “The coming years will be exciting as we learn more about what is happening near one of the most mysterious regions in the universe,” Ros said.