Observatory · the dark instrument
The horizon
A black hole is not a thing you can photograph from here, but it is a thing you can calculate. Everything on this page is worked out in your browser from Schwarzschild's 1916 solution: the lens traces a photon for every pixel of what you see. Two more instruments stand in the rooms beside this one: the clock at the horizon and the redshift.
The lens
Drag to look around it. Scroll to come closer.
What you are seeing. The dark circle is not the horizon itself but its shadow, about 2.6 times wider: light that passes closer than that falls in. The thin bright ring hugging it is the photon ring, light that has gone round the hole once or more before reaching you. The disk looks wrong on purpose: the far side appears to rise over the top of the hole and curl under it, because its light is bent around on its way to you. One side of the disk is brighter and bluer because that side is coming towards you at a good fraction of the speed of light (Doppler beaming); the other side is dimmer and redder. The whole thing is a little redder than it should be because the light climbs out of a gravity well to reach you.
Units: distances are in Schwarzschild radii, rs = 2GM/c². The disk starts at 3 rs, the innermost stable circular orbit. The colours are a thin-disk temperature gradient, not a spectrum, but the brightening, dimming and shifts are the real factors to the real powers.