A strange mass of hot gas is orbiting around arc A* with amazing speed

In the strange gravitational environment at the heart of our galaxy, astronomers have found a point of gas orbiting our supermassive black hole at breakneck speed.

Its properties help astronomers explore the space directly surrounding Sagittarius A* in search of answers about why the galactic center flashes and glows across the entire electromagnetic spectrum.

Their findings indicate that the black hole is surrounded by a clockwise rotating disk of material modified by a strong magnetic field.

And it confirms something we already knew: the space around the black hole becomes runaway.

says astrophysicist Maciek Wielgus of the Max Planck Institute for Radio Astronomy in Germany.

“This requires an astonishing speed of about 30 percent of the speed of light!”

Sgr A* got its big moment in the spotlight earlier this year when the Event Horizon Telescope collaboration unveiled an image of a black hole in the making.

Telescopes around the world worked together to take observations of the galactic center, which came together to reveal a cake-shaped ring of material orbiting Sgr A*, which has been heated to incredible temperatures.

One of the telescopes included in the collaboration is the Atacama Large Millimeter/ Submillimeter Array (ALMA), an array of radio telescopes located in the Atacama Desert in Chile.

While studying data from ALMA only, and in isolation from the rest of the collaboration, Wielgus and colleagues noticed something interesting.

In April 2017, in the midst of collecting data, the Galactic Center released a flare of X-rays. It was just a pure chance that this would happen while astronomers were collecting data for the Event Horizon Telescope project.

Previously, these long flares, observed at other wavelengths, were associated with blobs of hot gas circulating near the black hole and at very high speeds.

“What is really new and exciting is that such flares have so far only been present clearly in X-ray and infrared observations of the A* arc,” Wilgus explains. “Here we see for the first time a very strong indication that orbital hotspots are also present in radio observations.”

These flares are thought to be caused by the interaction of hot gas with a magnetic field, and the team’s analysis of ALMA data supports this idea.

The hot spot emits highly polarized or twisted light, and displays a signature of synchrotron acceleration—both of which occur in the presence of a strong magnetic field.

The glow in radio light could be caused by the cooling of the hot spot after the glow, becoming visible at longer wavelengths.

“We found strong evidence for the magnetic origin of these flares, and our observations give us an idea of ​​the engineering of the process,” says astrophysicist Monika Mościbrodzka of Radboud University in the Netherlands.

“The new data is very useful for constructing a theoretical explanation for these events.”

The team’s analysis of the light indicates that the hot spot is embedded in a magnetized disk. This is a disk of matter orbiting around the black hole and feeding it, but at a rate impeded by the magnetic field.

Through modeling that combined the data, the team was able to provide stronger constraints on the shape and motion of this magnetic field, and the formation and evolution of the hotspot within it.

But there is still a lot we don’t know. Looking at black holes is really tricky, and there are some strange inconsistencies when compared to infrared observations of other flares.

The team hopes that simultaneous infrared and radio observations of future hot spot flares will help resolve these flaws.

“We hope one day we can feel comfortable saying we ‘know’ what’s going on in A* arc,” Wilgus says.

The search was published in Astronomy and astrophysics.

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