Do Solo Black Holes Roam the Universe?

sciencehabit writes "Two mysterious bright spots in a disheveled, distant galaxy suggest that astronomers have found the best evidence yet for a supermassive black hole being shoved out of its home. If confirmed, the finding would verify Einstein's theory of general relativity in a region of intense gravity not previously tested. The results would also suggest that some giant black holes roam the universe as invisible free floaters, flung from the galaxies in which they coalesced. Although loner black holes may be an entity that has to be reckoned with, they would still be rare."

Fantastic

[dreamchaser]

I find it fascinating that theories developed in the first half of the last century continue to stand up to observation. This fits the predictions of general relativity, and that is almost as exciting as if they discovered something that totally blew away the predictions. The latter would mean we go back to the cutting board, but this is, as I said, almost as exciting. It makes me wonder how much of the 'missing mass' that we lump into the dark matter bucket is actually contained in bodies like this; bodies so massive that we can barely fathom their 'size'.

Black holes are hard to see

[MetricT]

If you were to take the 3 million solar mass black hole in the center of the Milky Way, and plop it into the solar system where the sun is, the Schwartzchild radius would be well within the orbit of Mercury. We wouldn't lose a single planet, though an earth "year" would shrink to roughly 2 hours. Hold your fist at arm's length. That's how big it would appear in the sky.

Now imagine trying to see something like that, from 4 billion light years away, moving faster than galactic escape velocity. The only reason you can see it at *all* is that it's still siphoning galactic gas into its accretion disk. Once it hits intergalactic space, you'll never see it again.

Three million solar masses sounds huge, but is a microscopic fraction of the Milky Way's total mass (1-4 trillion solar masses). Given the quantity of matter orbiting near the center of a galaxy, I'd believe it likely that even if the central black hole were ejected, a new one would form in short (cosmologically speaking) time. So core ejection may not be a one-off, but a common event during galaxy collisions. In which case, there might be enough of them to partly explain dark matter (though certainly not enough to explain it all).

We also know there is a relationship between the mass of the central black hole, and the "tightness" of the arms in a spiral galaxy. But how would core ejection affect this? Given the speed of light, the outer regions of a galaxy would be tightly wound, while the inner region would be loosely wound (after core ejection). Wouldn't that look an awful lot like a barred spiral?

So many interesting questions, so few answers...

Re:YES! And I can prove it...

[Eponymous Hero]

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