Black holes have captured our imagination and fascination since they were first hinted to exist in the universe. People love to ask about black holes, how they work, how we know they are there.
My favorite black holes are the monsters that live in the centers of most galaxies where they have the potential to make themselves known through powerful processes that can be seen across the universe.
Active galactic nuclei, or AGNs, are the bright, sometimes chaotic, always powerful regions around a supermassive black hole that is eating up the surrounding material. How massive? Try millions, even billions of times the mass of our sun, which is something like 300,000 times the mass of our whole planet. So yeah, “behemoth” doesn’t even begin to describe it.
So far, we know that when material gets pulled into a black hole, it is gone from the observable universe for good. So, how can we see so much activity in an AGN? Well, not all of the material makes it in, and the stuff that does sure can make its presence known beforehand.
Astronomers have been plugging away at describing the details of these regions for decades, figuring out all the complex balances of radiation pressure and gas pressure and turbulent velocities and rotational velocities and so much more. Yet, the complex puzzle has yet to be solved.
No wonder it’s taken a team of 26 astronomers on four continents to get the latest, finest probe of the AGN of a galaxy called Markarian 509.
This “test case” went under extreme scrutiny by 5 different space telescopes in order to probe the finer effects of the supermassive black hole on its surroundings. The AGN was monitored in visible, x-ray, and gamma-ray wavelengths with the European Space Agency’s XMM-Newton and INTEGRAL satellites.
Astronomers go to such high frequencies when studying AGN because these show where some of the most energetic processes are happening. After monitoring in this way for six weeks, they acquired deep observations with two of the best imaging telescopes in space, the Hubble Space Telescope and Chandra X-Ray Observatory. To top it off, the satellite Swift monitored the galaxy at several wavelength through the whole campaign.
After so much effort, what did they find? They saw a hot cloud of gas around the black hole which gave off x-rays. This gas is probably heated by the ultraviolet light coming from the disk of material surrounding the black hole. Suspended within the hot gas were colder, denser gas “bullets” that are speeding away from the black hole at a million miles an hour, not towards it as you might think. I don’t ever want to get close to a black hole that’s capable of that kind of power!
In this era of survey science, where large telescopes monitor huge swaths of sky in order to do statistical analyses of thousands of objects, it is nice to see a cosmic monster really go under the microscope. Individual observations like this compliment large surveys when they show the details that might otherwise be missed.
Image credit: NASA, ESA, G. Kriss (STScI), and J. de Plaa (SRON Netherlands Institute for Space Research)