Black hole
M81*
The low-luminosity nucleus of Bode's Galaxy
The 70-million-solar-mass black hole at the centre of M81; one of the nearest and best-studied low-luminosity active nuclei, a bridge between Sgr A* and bright quasars.
| Mass | 70 million solar masses |
|---|---|
| Event horizon radius | 1.38 AU: 0.046 times Neptune's orbit |
| Time for light to circle the event horizon once | 72 minutes |
| Mass | 7 × 10⁷ M☉ |
| Distance | 3.6 Mpc |
| Status | Low-luminosity AGN |
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).