nine questionsWhat kind of black hole are you?
Nine kinds, from the 1916 solution that nobody has found to the mountain-mass one finishing its evaporation somewhere right now. Whatever you turn out to be, the result comes with its numbers.
He who fights with monsters should be careful lest he thereby become a monster. And if thou gaze long into an abyss, the abyss will also gaze into thee.Wer mit Ungeheuern kämpft, mag zusehn, dass er nicht dabei zum Ungeheuer wird. Und wenn du lange in einen Abgrund blickst, blickt der Abgrund auch in dich hinein.
The nine, for reference
| Kind | Defined by | Found? |
|---|---|---|
| Schwarzschild | mass only; no spin, no charge (1916) | as an idealisation; everything real turns |
| Kerr | mass and spin (1963) | yes — most of them |
| Reissner–Nordström | mass and charge (1916–18) | no; charge neutralises in moments |
| Stellar-mass | 3 to ~100 M☉, from a collapsed star | yes — dozens weighed, hundreds heard |
| Intermediate-mass | 10² to 10⁵ M☉ | yes since 2019 — GW190521's 142 M☉ remnant |
| Supermassive | 10⁶ to 10¹⁰ M☉, one per galaxy centre | yes — two photographed |
| Merging binary | two, spiralling in | yes — about 300 heard |
| Primordial | from density ripples in the first second | no; still allowed at asteroid masses |
| Evaporating | hotter than the sky, so shrinking | no; a primordial one of 5 × 10¹¹ kg would be finishing now |