Black hole
LMC X-1
The first extragalactic black hole, in the Large Magellanic Cloud
A persistently bright X-ray binary in the Large Magellanic Cloud discovered in 1969; one of the first black holes outside the Milky Way to have its mass measured. Its disc, fed by the wind of a giant O star, stays almost always in the "soft" (thermal) state.
| Mass | 10.9 solar masses |
|---|---|
| Event horizon radius | 32 km: the size of a city |
| Time for light to circle the event horizon once | 6.7 × 10⁻⁴ seconds |
| Mass | 10,9 M☉ |
| Companion | O7 III, ~32 M☉ |
| Orbital period | 3.91 days |
| Distance | 48 kpc (LMC) |
| Rotation | a* ≈ 0,92 |
| Discovery | 1969 (Uhuru öncesi roket uçuşları) |
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).