What is the structure of black holes?

Answer 1

Black holes that aren't spinning (Schwarzchild) are all remarkably similar in structure (some texts will tell you that by their nature and definition they are almost identical, see the "no-hair theorem"). To the best of our scientific understanding, they are spherical with the boundary of the black hole being defined by the event horizon whose diamater is proportional to the black hole's mass - the event horizon being a boundary at which escape velocity is the speed of light. Hence, inside the black hole, within this sphere, no light nor matter can escape. At the center of the black hole is a singularity, a point where matter is crushed by gravitational force to infinite density or infinite space-time curvature, where laws of physics would seem to break down and notions of time and space may no longer apply. Because of their mass you would likely observe other structures outside the black hole such as an accretion disk of accumulated matter in orbit, or jets of particles or radiation cause by infalling matter and electromagnetic effects, and perhaps other effects but strictly speaking these would not be part of the black hole itself. For a spinning black hole, there are some other considerations; a notional oblate spheroid (the ergosphere) would surround the spherical horizon and touch at the poles on the axis of spin; it would also possess a ring-shaped singularity (see Kerr black holes).

Answer 2

Black holes have a central point of infinite density, or singularity, and a spherical event horizon centered upon it where the escape velocity reaches the speed of light, and from within which sphere no light can thus escape. The model of a spinning black hole includes an additional oblate spheroid (ergosphere) touching the event horizon at the poles and a ring-shaped singularity. Although not part of the black hole proper, black holes near the presence of infalling matter would be surrounded by a highly energetic rotating accretion disk which radiates in the x-ray portion of the electromagnetic spectrum; the disk also gives rise to the presence of energetic jets at the poles perpendicular to the plane of the disk, the creation mechanism for which is not well understood.

Answer 3

Black holes have no internal structure, they are completely empty (unless they are rotating, in which case the singularity is a ring instead of just one point).