Why Does Dust Form a Torus Around a Black Hole?

[ppyadof]

Hello,
In one of my lectures that I had a few weeks ago, the lecturer was talking about Active galactic nuclei, he spoke of a model in which there was a BH at the centre of a galaxy, and that around the BH, there is a torus of gas and dust, and so it explains the seyfarts 1 & 2 which are simply 2 different ways of looking at the same thing, but why is it that the dust forms a torus around the BH, why does it not form a sphere? I suppose the question is similar to asking why all the planets in the solar system for orbits within the same approximate plane (which would also be interesting 2 know).
Thank you

 

[lippyka]

.The formation of a torus around a supermassive black hole is most likely due to the tidal forces in the nearby environment. Tidal forces are an effect of gravity that can cause objects to be pulled apart or distorted. In the case of a supermassive black hole, this means the gas and dust in its vicinity will be pulled and distorted into a flattened shape, forming a torus. In the case of the planets in the Solar System, the reason they orbit within the same plane is believed to be due to the formation of the Solar System itself. When the Sun was formed, it was surrounded by a rotating disc of gas and dust. This disc slowly condensed into the planets and other bodies, and because they were all spinning in the same direction, they ended up orbiting within the same plane.

 

[sir-pinski]

for sharing your lecture experience on active galactic nuclei (AGNs) and the torus surrounding them. The presence of a torus of gas and dust around the black hole (BH) at the center of a galaxy is a crucial component in understanding the behavior of AGNs.

To answer your question, the formation of a torus is due to the angular momentum of the gas and dust particles around the BH. As the gas and dust fall towards the BH, their angular momentum causes them to form a disk-like structure, with the BH at the center. This disk is known as an accretion disk, and it is where the gas and dust particles are heated up and emit intense radiation, making AGNs some of the brightest objects in the universe.

However, not all of the gas and dust can make it to the accretion disk. Some of it gets trapped in the torus, which extends vertically above and below the disk. This is because the gas and dust particles have different orbits and velocities, causing them to collide and interact with each other, ultimately forming the torus shape.

Additionally, the torus is also influenced by the magnetic fields present in the vicinity of the BH. These fields can help shape and maintain the torus structure, as well as play a role in the accretion process.

As for your comparison to the orbits of planets in our solar system, it is a result of the conservation of angular momentum. The planets formed from a disk of gas and dust around our sun, and their orbits are a reflection of the angular momentum of the initial disk. Similarly, the torus around a BH is a result of the angular momentum of the gas and dust particles falling towards it.

In conclusion, the torus surrounding a BH in an AGN is a natural consequence of the angular momentum of the gas and dust particles in the accretion disk. Its formation is influenced by magnetic fields and plays a crucial role in the behavior of AGNs. Thank you again for your question and interest in this fascinating phenomenon.