It is not likely that a dwarf galaxy brings a supermassive black hole to the table. But the Andromeda doesn't look like the result of a larg-ish merger. It is not elliptical, has not whispy hang-ons or stuff in ex-centric orbits.
Supermassive black holes in merger galaxies snack on one star every year, according to a paper published on Thursday. The Andromeda galaxy, also known as Messier 31 or M31, sits next door to the Milky Way only about 2.5 million light years away. It’s a giant spiral galaxy teeming with stars and astroboffins have spotted a pair …
> It is not likely that a dwarf galaxy brings a supermassive black hole to the table.
They are beginning to think that it's normal for even Dwarf Galaxies to have SMBH's.
The supermassive black hole is about five times more massive than the one at the center of the Milky Way, but the dwarf galaxy in which it was found--known to astronomers as M60-UCD1--is about 500 times smaller than our own galaxy,...
The discovery suggests that supermassive black holes may be twice as numerous in the nearby universe as previously thought, ...
The discovery suggests that there are many other small galaxies containing supermassive black holes....
Feel free to correct me if I am wrong about this. I think that the conditions, basically the climate, on a planet is not solely dependent on the sun it orbits, but also on radiation from nearby and faraway sources in space. I thus imagine that being thrown through centre of a galaxy on a regular basis will tend to make the planet inhabitable. Not to mention what the gravitational forces nearby stars can do the orbit. So any life on these rocks will be long gone before they get eaten by a black hole. So unless they are truly advanced and can vacate the premises, and move to a mostly harmless planet orbiting a star situated far out in the uncharted backwaters of the unfashionable end of the Western Spiral Arm of the Galaxy, they are goners.
As for the odds, I'll recommend starting with Drake's equation and narrow it down to the set of stars involved.
" but also on radiation from nearby and faraway sources in space."
Correct to a point, that's why a nearby supernova would make for a bad day on earth.
Even without that risk, our own star will make the surface uninhabitable in less than 500 million years (it's getting hotter as it gets older), and this tendency of stars makes the window for evolution of intelligent life that can get itself space-faring before extinction in any given system even smaller than we might think.
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