Space and Physics
PUBLISHED
One of the most prominent features of supermassive black holes that are actively feeding is a jet of plasma. The jet can move at almost the speed of light and extend for many millions of light-years in some cases. New research shows that the jets are not stuck in place, but they can in fact change direction, sometimes even wildly.
The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.Researchers combined observations in X-rays and radio waves to spot potential changes in the directions of the jets. The fact that a change might happen is not an obvious fact. Once a black hole is accreting, it can release these powerful jets. The material falling into a black hole will arrange itself into a disk around it. The jets are influenced by the black hole's spin and direction, but not always.
The spin itself is difficult to estimate – a brand new approach used a destroyed star – but depending on the size of the disk, the direction of the jet might not align itself with the rotation of the black hole, meaning it can change significantly. In the 16 cases observed by the team, there was significant variation.
The radio observations are more detailed and can be used to work out the current direction of the jet. The X-ray observations are not as detailed, focusing on an area about 30 times wider, but they are crucial because they look at hot gas extending hundreds of light-years around the galaxy hosting the supermassive black hole. Researchers can see cavities in that gas that the jets carved millions of years ago. If the cavities are in a different direction, the jet must have moved.
And some have moved significantly. The comparison between the X-ray observations from NASA’s Chandra and the radio images from the Very Large Baseline Array (VLBA) show that the beams of galaxy Abell 478 changed direction by about 35 degrees. The ones of galaxy NGC 5044 changed direction by about 70 degrees.
“We found that about a third of the beams are now pointing in completely different directions than before,” lead author Francesco Ubertosi of the University of Bologna, said in a statement. “These Death Star black holes are swiveling around and pointing at new targets, like the fictional space station in Star Wars.”
There are some that changed direction by almost 90 degrees, and they did so in between one to 10 million years. Given that these objects are 10 billion years old (10,000 million years), this is a very quick change.
“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, of the Center for Astrophysics, Harvard & Smithsonian.
The study is published in The Astrophysical Journal.
