Universe

Black hole toroid. Active Universe

Black hole toroid. Active Universe

Why are the surroundings of some black holes brighter than others? In the center of active galaxies, supermassive black holes predominate at least thousands of times the mass of the Sun. Many of them, called Seyfert Type I, are very bright in the spectrum of visible light. Others, Seyfert Type II are quite weak.

The difference could be caused because the accretion of some black holes drags much more matter than others. It could also be because the black holes that occupy the center of the Seyfert Type II galaxies were obscured by a toroid around them.

To help us decide between the two hypotheses, the nearby galaxy NGC 4388, of the Seyfert II type, has been observed in X-rays. It has been found that the flow of X-rays in some colors (X-ray) varies rapidly, while in others it is quite stable.

The constant flow and apparent absorption of some very specific X-ray colors by cold iron offer us evidence that we are observing the central black hole of NGC 4388 through a very dense toroid composed of molecular gas and dust.

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