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It's not clear how the gap between solar-mass scale black holes and supermassive black holes was traversed; was it a build up from small black holes, or did the
by graerg 6y ago
It's not clear how the gap between solar-mass scale black holes and supermassive black holes was traversed; was it a build up from small black holes, or did they start out as seeds of a few million solar masses in the early universe? What about the dearth of intermediate sized black holes (tens of thousands of solar masses)? Is this just because they are just hard to see to begin with, or is there really a gap? This is intimately related to the Salpeter time, which is how long it takes to grow black holes if they accrete at the Eddington limit, and can also be inferred from the quasar luminosity function. IIRC this favors the massive seed scenario, but there's no shortage of clever explanations around it.
- a1369209993 6y agoBlack holes get less dense as they gain mass - assuming I didn't drop a factor of 2 or τ, a 1 solar mass black hole has a density of 147 quadrillion tons per cubic meter. A black hole of 100 million solar masses had density of only 14.7 tons per cubic meter (for reference, lead is 11.3 Tn/m3 and osmium is 22.6 Tn/m3). So a sphere of 100M (actually >81M) solar masses of osmium would collapse into a black hole without even having to compress under it's own gravity first. You'd need 384 million solar masses for something with the density of water.