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There’s two main formation pathways for black holes: ongoing stellar collapse and galaxy collapse in the early universe. The former makes stellar-mass black hol
by kobeya 9y ago
There’s two main formation pathways for black holes: ongoing stellar collapse and galaxy collapse in the early universe. The former makes stellar-mass black holes. The latter makes enormous million-stellar mass black holes or larger. That’s 5-6 orders of magnitude difference.
What’s interesting is that we can measure/infer the mass of a black hole from these gravitational waves and we are finding a lot of ~1000x stellar mass black holes. Too big to be stellar collapse, too small to be galaxy centers. Where do these come from?
The number for how many there should be is very close to zero. Presumably you’d only get one from a stellar black hole gobbling up enough mass to get that big, but 10 doublings is too much to have happened except by freak accident, and these are regularly occurring.
The current best theory is that they formed in the early universe before or during galaxy formation by some process that we don’t yet understand.
- stromgo 9y agoWhere did you get this 1000x stellar mass figure from? According to https://en.wikipedia.org/wiki/List_of_gravitational_wave_observations https://en.wikipedia.org/wiki/List_of_gravitational_wave_obs... so far the observed merger components were between 7.5 and 35.4 solar masses. The sample of stars in the night sky is biased by luminosity and longevity. I'd be curious to see a distribution of stellar masses that compensates for these two biases. On such a chart, extrapolating the trend in the high-mass range just before the error bars become too large would tell us whether 30-solar-mass stellar remnants are expected or unexpected by observation data.
- kobeya 9y agoThose are solar mass. https://en.m.wikipedia.org/wiki/Intermediate-mass_black_hole https://en.m.wikipedia.org/wiki/Intermediate-mass_black_hole
- stromgo 9y agoI mean, where did you get this 1000x figure as what "we're finding a lot of"?
- kobeya 9y agoThere's examples in the article I linked to. (FWIW finding any at all, let alone the half dozen or so found in the last few years is "a lot" given the minuscule priors involved.)
- stromgo 9y agoI'm sorry I still don't see it. Your linked article says at the very top "There is as yet no unambiguous detection of an IMBH". Concerning gravitational waves, reference [7] says "We show that space based detectors such as the Laser Interferometer Space Antenna are likely to detect several of these sources". Reference [8] says "gravitational-wave observations could be used to accurately measure masses of black holes in merging binaries and probe the existence of intermediate-mass black holes". So no discovery yet, just theoretical work on what the signal would look like.