Black hole
M106 kara deliği
The black-hole mass measured most precisely, using water masers
Clouds of water masers orbit the black hole at the centre of M106 (NGC 4258) in perfect agreement with Kepler's laws. This disc yields both the black hole's mass (40 million M☉) and the galaxy's distance geometrically; it is an anchor of the cosmic distance ladder.
| Mass | 40 million solar masses |
|---|---|
| Event horizon radius | 0.79 AU: 0.026 times Neptune's orbit |
| Time for light to circle the event horizon once | 41 minutes |
| Mass | 4,0 × 10⁷ M☉ |
| Distance | 7.2 Mpc (maser geometry) |
| Status | Seyfert 2 / LINER |
| Discovery | 1995 (Miyoshi ve ark., VLBA maser diski) |
The event horizon is the boundary where the escape velocity equals the speed of light: nothing inside, not even light, can get out. Its radius grows in direct proportion to the mass (the Schwarzschild radius, for a non-rotating black hole).