The environment around a supermassive black hole is quite complex.
Sitting in the centers of galaxies, that’s not so surprising. It’s crowded there, like being in the center of a big city during rush hour. But in this case, it’s worse, because in a city you do not have more amounts of material swirling around the city center at almost the speed of light, heated to millions of degrees and blasting out large amounts of energy, making them the most powerful. radiation sources in the universe.
While supermassive black holes many times do. The disk is called an accretion disk, and the conditions in it are difficult to understand. To make matters worse, sometimes these black holes and disks somehow focus this energy and matter in double rays, like a double light saber screaming out at almost the speed of light up and down from the disk.
These rays, which astronomers call rays, contain energy across the electromagnetic spectrum from radio waves to X-rays. If this ray points towards the Earth, we can see all this radiation, and we call these types of objects quasars (or if super high energy light is even seen, blazarer). They are phenomenally bright, and we can see them from billions of light-years away, aware of the observable universe.
These jets have a major impact on the galaxy around the black hole. They can push away gas in the galaxy, suppressing star formation. They can also drive shock waves into gas further out and encourage the clouds to collapse and form stars. The growth in the black hole itself may also depend on this, as it grows by feeding on that particular gas.
So astronomers are trying to understand them, which can be difficult since they are so far away. But a new study looking at a staggering 729 quasars found a link between quasars with jets and those without them, and it contradicts the common model astronomers have been using for decades.
The astronomers looked at high-energy X-ray emission from the black holes. It is well known that quasars without nozzles emit a certain amount of ultraviolet light (which comes from the inner disk) and that X-ray emissions depend on it. If there is more UV from a quasar, we also see more X-rays and vice versa.
The reason for this is thought to come from black hole corona. This is extremely high energy gas that surrounds the access disk like a halo. UV photons from the disk hit the electrons in this corona gas and get boosted in energy, just like how a rear end of a truck can push a car forward. The result is that the UV light is amplified to X-ray energies. The more UV that is emitted, the more X-rays you get.
Now quasars with rays also emit X-rays, and also tend to be brighter (gives more X-rays). It has been thought that the X-rays come from the bottom of the beam, where magnetic fields are wound up in a vortex of all the swirling matter. This can focus the energy moving along the magnetic field lines. So they focus the rays, and the large energies exerted on the jet base are the cause of the X-rays.
BUT. What the new study found is a similar relationship between x-rays and ultraviolet light as with quasars without rays. It involves a similar process, which means that the X-rays do not necessarily come from the jet base, but from black hole coronas! And these coronas have strong magnetic field lines that penetrate them, which helps increase the emitted energies, which is why quasars with rays emit more X-rays than those without.
This is a big deal. The physics of the corona are different than at the jet base, so this changes how we think the jets will be launched. Remember, these jets can stretch for millions of light years, far larger than the host galaxy for the black hole! They are huge structures, so it is crucial to understand how they get started.
As it happens, all quasars seem to need a fast-spinning black hole in their hearts. The spin actually pulls the substance in space-time around them, affecting the disk. It has been thought that the jets are dependent on the spin of the black hole, but what the new study shows is that if the corona of the black hole is weak, you will not get jets even if the black hole spins wildly.
Again, this is a big deal. It changes the way astronomers think of jets.
So the next question is, are these researchers right? Well, the trends they found seem real and compelling, if not compelling. And they looked at a whole lot of quasars. I expect theorists who study the connection between black holes, their coronas, the magnetic fields, the disk and the rays (phew!) Will eagerly blow up on this idea and try to see if they can figure out all the connections and if they make sense . It will be interesting to see that there are also some exceptions to this rule. It can really help, because sometimes quasars can have a strange property that separates them, making the rules easier to understand instead (the idea of the exception proving the rule*).
We know that the properties of entire galaxies depend on the properties of the black hole in their nuclei, even though the galaxy may have a million times the mass of the black hole. Clearly, black holes are small but mighty and how they operate these jets is a big player in this game. Our own galaxy was once very likely a quasar, so in many ways we even exist because of that fact. I think understanding how these work is an important piece of understanding how the universe makes people. And I’m human, so I take that quite personally, too.
And personally, I think all of this is incredibly cool.
*In this link you will find different meanings of this sentence, and in this case I mean it in the sense of an exception testing the rule under different circumstances, which may help to support the general rule.