A team of astronomers examined 16 supermassive black holes in galaxies with hot gas detected in X-rays by Chandra. Using radio data from the VLBA, they studied the directions of particle beams a few light-years away from the black holes. This analysis provided a picture of the current aim of each beam from Earth. Each black hole emits two beams in opposite directions.
The team also used Chandra data to study pairs of cavities in the hot gas created by the beams pushing gas outwards. The positions of large outer cavities show where the beams were pointed millions of years ago. The researchers compared the directions of the radio beams with the directions of the cavities.
"We found that about a third of the beams are now pointing 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 swiveling around and pointing at new targets, like the fictional space station in Star Wars."
X-ray and radio data suggest that the beams can change direction by nearly 90 degrees over timescales ranging from one million to tens of millions of years.
"Considering that these black holes are likely more than 10 billion years old," said co-author Gerrit Schellenberger of the Center for Astrophysics | Harvard and Smithsonian (CfA), "we consider a large change in direction over a few million years to be fast. Changing the direction of the giant black hole beams in about a million years is analogous to changing the direction of a new battleship in a few minutes."
Scientists believe that beams from black holes and the cavities they create play a key role in star formation within galaxies. The beams inject energy into the hot gas around the galaxy, preventing it from cooling enough to form large numbers of new stars. If the beams change direction significantly, they can inhibit star formation across much larger areas of the galaxy.
"These galaxies are too distant to tell if the beams from the Death Star 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," said co-author Ewan O'Sullivan, also from CfA.
One major question is how these black hole beams reorient. The direction of the beams, aligned with the black hole's rotation axis, suggests they point along a line connecting the poles.
An important power source for these beams is likely matter in a disk spinning around the black hole and falling inward. This process forces the beams to be perpendicular to the disk. If material falls toward the black hole at a different angle, it could affect the direction of the black hole's rotation axis.
"It's possible that material rapidly falling towards the black holes at a different angle for long enough would drag their rotation axes in a different direction," said co-author Jan Vrtilek, also from CfA, "causing the beams to point in a different direction."
The team also explored other explanations for the misalignment between the radio beams and cavities. One possibility is that gas is sloshing around in the cluster, which might be caused by collisions between clusters of galaxies. However, evidence of sloshing in both aligned and misaligned clusters argues against this theory.
The paper led by Francesco Ubertosi was published in the Jan. 20, 2024, issue of The Astrophysical Journal. The authors include Schellenberger, O'Sullivan, Vrtilek, Simona Giacintucci from the Naval Research Laboratory, Laurence David and William Forman from CfA, Myriam Gitti from the University of Bologna, Tiziana Venturi from the National Institute of Astrophysics-Institute of Radio Astronomy, Christine Jones from CfA, and Fabrizio Brighenti from the University of Bologna.
Research Report:Jet reorientation in central galaxies of clusters and groups: insights from VLBA and Chandra data
Related Links
Chandra X-Ray Center
Understanding Time and Space
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