Home Page | Overview | Site Map | Index | Appendix | Illustration | About | Contact | Update | FAQ |
![]() | ---------- (15c) |
![]() |
![]() ![]() |
Figure 09m Bending of Light [view large image] |
object, the path will be bent so much that it runs around in a circle. For non-rotating black hole such special trajectory occurs at r = 3rs/2 = 3GM/c2. The sphere with such a radius is called the photon sphere. However, the orbit is unstable; it can be |
![]() |
This is called static limit. It can be intuitively characterized as the region where the rotation of the space-time is dragged along with the velocity of light. Within this region, space-time is warped in such a way that no observer can maintain him/herself in a non-rotating orbit, but is forced to become co-rotating (Figure 09n). The surface of this region is elliptical with its major axis at ![]() ![]() |
Figure 09n Frame Dragging |
rotating Schwarzschild's radius). The minor axis is in the directions of ![]() ![]() |
![]() |
r+ = [GM + (G2M2 - a2c2)1/2] / c2 ---------- (15j) The inner horizon (sometimes called the Cauchy horizon) is located at r- = [GM - (G2M2 - a2c2)1/2] / c2 ---------- (15k) |
Figure 09o Kerr's Solution [view large image] |
The Ergosphere is the region between the static limit and the outer event horizon. Since this region is outside the event horizon, particles falling within the ergosphere may escape the black hole extracting its spin energy in the process. |
![]() |
The mere thought of such possibility makes a lot of physicists very uncomfortable. Nevertheless, the Penrose's conjecture on cosmic censorship, which forbids the occurrence of naked singularity, may not hold up any longer in view of the Kerr's solution and more recently the revelation of computer simulations (with one such results shown in Figure 09oa). Other stellar configurations that can develop into naked singularity; include inhomogeneous density (such as onionlike structure), shearing of material near a singularity, and very rapid collapsing rate. Each of such |
Figure 09oa Naked Singularity [view large image] |
case has a threshold separating the formation of black hole or naked singularity. |
![]() |
Talking about black hole spinning rate, by measuring the line broadening of the Fe-line emission in the X-ray region it is reported in 2013 that the central black hole in NGC 1365 spins rapidly near to the naked black hole limit (Figure 09ob), which can be expressed in the form : 1 > Jc/GM2 = A, where J is the black hole's angular momentum and A ![]() ![]() |
Figure 09ob BH Spin in NGC 1365 [view large image] |
![]() |
|
Figure 09p Penrose Diagram |
![]() |
|
Figure 09ra Disk and Jets |
![]() |
disk's innermost edge. One of the techniques is to observe the line profile of the Fe K![]() |
Figure 09rc Black Hole Spin [view large image] |
to the location of the disk's inner edge. Table 02 lists the spin for a few of the black holes. The spin s in the table is relative to the tangential velocity v = c (the speed of light), i.e., s / sc = v / c (at the event horizon). |
Black Hole | Spin | Astronomical Characteristics |
---|---|---|
GRS 1915 | 0.98 ![]() |
Micro-quasar (a 33 Msun black hole acting like a quasar) |
Cygnus X-1 | 0.05 ![]() |
X-ray Binary (stellar black hole + O star) |
MCG-6-30-15 | > 0.98 | Bright core of spiral galaxy |
NGC 7469 | 0.69 ![]() |
Interacting galaxy |
Markarian 335 | 0.70 ![]() |
Seyfert galaxy |