Seeing a black hole jet in a new light
The University of Michigan originally published this story in its Michigan News on October 28, 2024. Edits by EarthSky.
Researchers led by the University of Michigan have pored over more than two decades of data from NASA’s Chandra X-Ray Observatory, looking closely at the high-energy jet of particles being blasted across space by the supermassive black hole at the center of the giant galaxy Centaurus A.
The new study is the latest effort in a small but growing body of research that’s digging deeper into data to spot subtle, meaningful differences between radio and X-ray observations.
David Bogensberger, lead author and a postdoctoral fellow at U-M said:
A key to understanding what’s going on in the jet could be understanding how different wavelength bands [for example, differences between the X-ray data and the radio data] trace different parts of the environment.
Bogensberger explained:
The jet in X-rays is different from the jet in radio waves. The X-ray data traces a unique picture that you can’t see in any other wavelength.
Bogensberger and an international team of colleagues published their findings on October 18, 2024, in The Astrophysical Journal.
appearance of superluminal speed due to its motion relative to Chandra’s vantage point near Earth. The distance between the knot and Chandra shrinks almost as fast as light can travel.
Still, the knot is moving fast! The team determined its actual speed is at least 94% the speed of light. A knot in a similar location had previously had its speed measured using radio observations. That result clocked the knot with a slightly slower speed, about 80% of the speed of light. Bogensberger said:
What this means is that [knots in the jet visible at radio wavelengths, and knots visible at X-ray wavelengths] move differently.
That’s a big clue as to what these knots might be, and how they behave. And that finding wasn’t the only one that stood out from the data.
For example, radio observations of knots suggested the structures closest to the black hole move the fastest. In the new study, however, Bogensberger and his colleagues found the fastest X-ray knot in a sort of middle region. It wasn’t the farthest from the black hole, but it wasn’t the nearest to it either. Bogensberger said:
There’s a lot we still don’t really know about how jets work in the X-ray band. This highlights the need for further research. We’ve shown a new approach to studying jets, and I think there’s a lot of interesting work to be done.
The jet in Centaurus A is special to us because it’s the closest supermassive black hole jet we know, at about 12 million light-years away. This relative proximity makes it a good first option for testing and validating new methodology.
But, for his part, Bogensberger will be stepping further out from here, using the team’s approach to examine other supermassive black hole jets, in other, more distant galaxies. Features like knots become more challenging to resolve in jets that are farther away. Bogensberger said:
But there are other galaxies where this analysis can be done. And that’s what I plan to do next.
Bottom line: There’s new knotty science to discover around black holes. A new study looked at the high-energy jet of particles being blasted across space by the supermassive black hole at the center of the galaxy Centaurus A.
Source: Superluminal Proper Motion in the X-Ray Jet of Centaurus A