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Supermassive black holes shoot powerful beams of particles into space and then change their aim to fire at new targets. This discovery, made using NASA’s Chandra X-ray Observatory and the US National Radio Astronomy Observatory’s (NSF) Very Long Baseline (VLBA) National Radio Astronomy Observatory (NRAO), shows what kind of widespread impact black holes can have on the surrounding them galaxy and beyond.

A team of astronomers looked at 16 supermassive black holes in galaxies surrounded by hot gas detected in X-rays from Chandra. The report was published in The Astrophysical Journal.

Using radio data from the VLBA, they investigated the directions of the beams – also known as jets – of particles shot several light-years away from the black holes. This gives scientists a picture of where each beam is currently aimed as seen from Earth. Each black hole shoots two beams in opposite directions.

The team then used data from Chandra to examine pairs of cavities, or bubbles, in the hot gas that were created in the past by the rays pushing gas outward. The location of the large outer cavities indicates the direction these rays were pointing millions of years earlier. The researchers then compared the directions of the radio beams with the directions of the cavity pairs.

“We found that about a third of the rays now point in completely different directions than before,” said Francesco Ubertozzi of the University of Bologna in Italy, who led the study. “These black holes on the Death Star are spinning and pointing at new targets, like the fictional space station in Star Wars.”

The X-ray and radio data show that the rays can change directions by nearly 90 degrees in some cases and on time scales between a million years and a few tens of millions of years.

“Given that these black holes are probably more than 10 billion years old,” said co-author Gerrit Shellenberger of the Harvard-Smithsonian Center for Astrophysics (CfA). “We think a big change in direction in a few million years is fast.” Changing the direction of the rays of a giant black hole in about a million years is analogous to changing the direction of a new battleship in a few minutes.”

Scientists believe that the rays from black holes and the cavities they carve out play an important role in how many stars form in their galaxies. The rays pump energy into the hot gas in and around the galaxy, preventing it from cooling enough to form vast numbers of new stars. If the rays change direction by large amounts, they can reduce star formation in much larger regions of the galaxy.

“These galaxies are too distant to tell whether the rays from the Death Star’s black holes damage the stars and their planets, but we are confident that they prevent many stars and planets from forming in the first place,” said co-author Ewan Oh ‘ Sullivan, also of CfA.

One of the biggest open questions is how these black hole beams spin like this. The direction of the rays from each of these possibly rotating giant black holes is thought to be aligned with the black hole’s spin axis, meaning that the rays are directed along a line connecting the poles.

An important source of energy for these rays is likely matter in a disk that orbits the black hole and falls inward. This process is thought to force the rays to be perpendicular to the disc. If the material falls towards the black hole at a different angle that is not parallel to the disk, it can affect the direction of the black hole’s spin axis.

“It is possible that material rapidly falling towards the black holes at a different angle for a long enough time pulls their spin axes in a different direction,” said co-author Jan Vrtilek, also of CfA, “so that the beams are directed in a different direction.”

The team also looked at alternative explanations for the discrepancy between the directions of the radio beams and the cavities. One alternative is that the gas is sloshing around in the cluster like wine in a glass swirling around. A splash like this could be caused by collisions between two galaxy clusters, which could move the voids around.

However, the researchers found evidence of sloshing in both aligned and misaligned clusters, arguing against the possibility that sloshing causes cavities to move over long distances.