Black holes are beams of glowing particles that change targets over time

Black holes seem to offer endless fascination to astronomers. This is at least partly due to the extreme physics going on in and around them, but sometimes, it can go back to the cultural points that got them interested in astronomy in the first place. That seems to be the case for the authors of a new paper on the motion of jets emerging from black holes. Dubbing those black holes the “Death Star,” the researchers used data from the Very Long Baseline Array (VLBA) and the Chandra X-ray Observatory to see where these black holes were emitting jets of superheated particles. And over time they discovered that they did something that even the Death Star could do – move.

The black holes at the center of the study were the supermassive ones at the centers of galaxies. Importantly, they were all surrounded by hot gases that were visible to Chandra’s X-ray sensors. The planes themselves were clearly visible in the data, but other important information was hidden there, namely, pockets of no gas, which were pushed by the planes.

Every black hole has jets of particles in two opposite directions. As those jets blow away gas and dust, they open a pocket in the space surrounding the black hole. These are visible in the X-ray data due to the lack of signal from those regions. The researchers hypothesized that jets must conform to the pockets of free space they create.

Black holes are known to spin for a while – as Fraser discusses.

However, they found that, in at least 6 of the 16 black holes they were studying, the jets had completely changed direction so that the missing pockets of gas were no longer aligned with the jets currently emitted by the black hole. In some cases, these changes added up to a 90-degree shift in the direction the planes were facing. Even more impressively, they appeared to move on a relatively small time scale, with estimates ranging from 1 to 10 million years. That’s a blink of an eye for a black hole over 10 billion years old.

So why is this important? Cosmologists theorize that these disruptive jets set an upper limit on the number of stars that form in the black hole’s host galaxy. They don’t let the surrounding gas and dust cool enough to start forming stars and rocky planets. So while it’s not clear whether the particle jets themselves are baking any planets forming like the current Death Star, it’s clear that moving the jets around would cause an even more massive disruption to the star formation process. In theory, this means that galaxies containing these moving jets would have fewer stars, but that’s a study for another paper.

Understanding exactly why this is happening may also need to be explored in another paper, but the authors have a few theories. Matter orbiting the black hole and falling into it can cause the black hole to spin, causing the jets it emits to move with it.

How a black hole forms may hold the key to understanding why its jets move over time. Fraser discusses how this happens.

Another explanation is that the gas is moving around the galaxy without being affected by the rays. Essentially, gasless “voids” in a galaxy are remnants of other cosmological forces and have nothing to do with black hole radii. However, the authors do not think this is likely, because galaxy mergers that could be a source of causing the “destruction” occurred in both galaxies that had motional beams and those that did not. One would expect the cavities to be present in both types if they were caused by galaxy mergers rather than the motions of particle jets.

As always, there is more science to be done. Thanks to the wonderful world of video streaming, a whole generation of young scientists inspired by the same Death Star can do just that.

Learn more:
Chandra – Spotted: ‘Death Star’ Black Holes in Action
Ubertos etc. – Jet reorientation in central cluster and cluster galaxies: insights from VLBA and Chandra data
UT – It is confirmed. The M87 Black Hole is actually spinning
UT – The Milky Way’s Black Hole is spinning as fast as it can

Main image:
Image from the Chandra Radio Dataset and VLBA jets of a black hole with “cavities” surrounding it.
Credit: X-ray: NASA/CXC/Univ. of Bologna/F. Ubertos; Radio Inset: NSF/NRAO/VLBA; Image processing: NASA/CXC/SAO/N. Wolk

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