Black hole
A0620-00
A quiet X-ray nova in Monoceros (V616 Mon)
An X-ray nova discovered through the outburst caught by the Ariel 5 satellite in 1975; its fading afterwards allowed the companion's orbit to be measured and, in 1986, the mass function confirmed it as a black hole. For a long time it was the nearest known black hole.
| Mass | 6.6 solar masses |
|---|---|
| Event horizon radius | 19 km: the size of a city |
| Time for light to circle the event horizon once | 4.1 × 10⁻⁴ seconds |
| Mass | 6,6 M☉ |
| Distance | 1,060 pc (3,460 light-years) |
| Orbital period | 7.75 hours |
| Status | Quiet (faint disc) |
| Discovery | 1975 (Ariel 5) · 1986 (kütle ölçümü, McClintock & Remillard) |
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).