When the black hole has a companion star orbiting it, matter from the companion can form a disk of material close to the black hole. These disks often radiate brightly from the heat of friction. Clumps of material from the companion star, if they fall onto the disk, can result in the occasional ejection of powerful jets of charged particles, sometimes at speeds approaching that of light.
Swirling around the black hole like water circling the drain in a bathtub, the matter compresses and the resulting friction turns it into plasma heated to a billion degrees or more causing it to glow and radiate energy.
By imaging the glow of matter swirling around the black hole before it goes over the edge of the point of no return and plunges into the abyss of spacetime, scientists can only see the outline of the black hole, called shadow. Because the laws of physics cannot describe what happens beyond that point of no return from which not even light can escape, that boundary is called the Event Horizon. General Relativity predicts that the bright outline defining the black hole's shadow must be a perfect circle.
The Planck length is the building block of space. The only way that we can pass beyond this size is, if we exit the objective world and imagine singularity. Our objectivity based scientific laws do not govern in this arena. Any attempt to carry over these laws is doom to assumptions, uncertainty and confusion.
Photons that have the highest amount of energy also have wavelengths that are near to the Planck length. This makes them more apt to intermingle with those "blocks" which slows them down. The amount of slowdown is obviously very tiny, but as the photons travel so far for so long, the effect is amplified.
In other words, Planck time is the building block of time and, as such, it is the absolute unit of time. With the same token, Planck length is the building block for space and as such is the absolute unit of space. Out of this boundaries, the meaning of space and time breaks down. If distance less than Planck length and time less than Planck time has no meaning, can we assume that Inside Planck unit limits is out of our space-time universe, because it does not contain meaningful space or time?