Astronomers observe jet reorientation in ‘Death Star’ black holes

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

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

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

The team then used the Chandra data to study pairs of cavities, or bubbles, in the hot gas that were created in the past by jets pushing the gas outward. The location of the large outer cavities shows the direction these rays were heading millions of years ago. The scientists 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,” said Francesco Ubertosi of the University of Bologna in Italy, who led the study. “These Death Star black holes are spinning and heading for new targets, like the fictional space station in Star Wars.”

X-ray and radio data indicate that the jets can change direction by nearly 90 degrees in some cases and on timescales ranging from one million years to several tens of millions of years.

“Because these black holes are probably more than 10 billion years old,” said 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 rapid. Changing the direction of giant black hole jets in about a million years is analogous to changing the direction of a new battleship in a few minutes.”

Scientists think that the jets 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 massive new stars. If the rays change direction by a large amount, they can suppress star formation in much larger regions of the galaxy.

“These galaxies are too distant to know whether the rays from the Death Star’s black holes damage the stars and their planets, but we are sure that they prevent many stars and planets from forming in the first place,” said 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 rays from each of these presumably spinning 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 jets is probably matter in the disk that spins around the black hole and falls inward. This process is thought to force the rays to be perpendicular to the disc. If the material is falling towards the black hole at an angle other than parallel to the disc, this could affect the direction of the black hole’s spin axis.

“It’s possible that material rapidly falling towards black holes at a different angle for long enough would pull their spin axes in a different direction,” said co-author Jan Vrtilek, also of CfA, “which would cause the beams to point in a different direction.” .”

The team also considered alternative explanations for the mismatch between the directions of the radio beams and the cavities. One alternative is that the gas in the cluster churns like wine in a glass swirled in a circle. Such whiplash may be caused by collisions between two galaxy clusters, which could move the voids.

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