Astronomers observe the reorientation of jets in ‘Death Star’ black holes

Huge black holes shoot powerful particles into space – and then change their aim to shoot at new targets. This discovery, made using NASA’s Chandra surrounding galaxies and beyond.

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

Using radio data from the VLBA, they studied the directions of beams (also called jets) of particles fired several light years away from the black holes. This gives scientists a picture of where each beam is currently pointed, as seen from Earth. Each black hole fires two beams in opposite directions.

The team then used data from Chandra to study pairs of voids, or bubbles, in the hot gas that formed in the past as the jets pushed gas out. The locations of large outer cavities indicate the direction in which these rays were pointing millions of years earlier. The researchers then compared the directions of the radio beams with the directions of the pairs of cavities.

“We found that about a third of the rays now point in completely different directions than before,” says Francesco Ubertosi of the University of Bologna in Italy, who led the study. “These Death Star black holes spin around and point to new targets, like the fictional space station in Star Wars.”

The X-ray and radio data indicate that the beams can change direction over nearly 90 degrees in some cases, and over timescales between a million years and several tens of millions of years.

“Taking into account that these black holes are probably more than 10 billion years old,” says co-author Gerrit Schellenberger of the Center for Astrophysics, Harvard & Smithsonian (CfA). “We consider a large change in direction over a few million years to be fast. Changing the direction of the giant black holes in about a million years is analogous to changing the direction of a new battleship in a few minutes.”

Scientists think the jets from black holes and the cavities they carve play a major role in the number of stars formed in their galaxies. The jets pump energy into the hot gas in and around the galaxy, preventing it from cooling enough to form huge numbers of new stars. If the beams change direction significantly, they could prevent star formation in much larger parts of the Milky Way.

“These galaxies are too far away to tell whether the jets from Death Star’s black holes are damaging stars and their planets, but we are confident they are preventing many stars and planets from forming in the first place,” says co-author Ewan O’. Sullivan, also from CfA.

One of the biggest open questions is how these black hole beams spin like this. The direction of the beams from each of these giant black holes, which are likely spinning, is believed to be aligned with the black hole’s axis of rotation, meaning the beams point along a line connecting the poles.

A major energy source for these beams is likely matter in a disk orbiting the black hole and falling inward. This process is believed to force the rays to be perpendicular to the disk. If material falls towards the black hole at a different angle, which is not parallel to the disk, it can affect the direction of the black hole’s axis of rotation.

“It is possible that material falling towards the black holes at a different angle quickly and for long enough drags their rotation axes in a different direction,” says co-author Jan Vrtilek, also from CfA, “which causes the beams to move in a different direction.” point in direction. .”

The team also considered alternative explanations for the discrepancy between the directions of the radio beams and the cavities. One alternative is that gas is swirling around in the cluster, like wine in a glass spinning in a circle. This kind of sloshing can be caused by collisions between two clusters of galaxies, which can set the voids in motion.

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