If the predator black hole was powerful enough to strip the galaxy surrounding the orphan black hole, intuition suggests that it would also attract the orphan black hole itself, no?
But what do I know? I'm just a brain surgeon... :-)
Boffins analysing old Chandra x-ray telescope data have spotted a rarity indeed: an X-ray source that seems to be a black hole, but without a galaxy to surround it. At an estimated 100,000 times the mass of the sun, the black hole in question – at the edge of lenticular galaxy SDSS J141711.07+522540.8, about 4.5 billion light …
No, the surrunding galaxy would have been stripped by a larger galaxy nearby.
This would eventually result in a more noisy galaxy (looking a lot more elliptical than spiral) and the massive black hole continuing to follow its path more or less hyperbolically around the center of the larger galaxy.
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"It is impossible for a black hole to swallow a whole galaxy"
Can you please expand on that? Genuine question, I haven't the faintest idea. Surely a black hole sucks in everything and just continues to increase its mass? Or is there some sort of limit, in which case what happens when the limit is reached?
Well, consider that a black hole in a galactic center just hoovers up mass nearby, i.e. gas and passing stars (which go into intersecting orbits when they come too near). The hole grows fast (indeed, it's radius is linearly related to its mass, unlike for normal objects, which then more to radius being third-root of mass) but not that fast, so for the stars outside the central bulge, it will always look like a tiny kernel of multimillion solar-mass far away and they will happily continue to whirl around the galactic center which has not changed in its gravitational nature (although it has changed in structure).
If black holes were able to hoover up large amounts of dark matter like open drains, they might be growing seriously large indeed. This seems to not be happening, so I suppose dark matter has its own internal dynamics which keep it from the event horizon.
The smaller black hole may have been catapulted out of its galaxy by a gravitational slingshot effect, perhaps. There are hints of double super-massive black holes in certain blazars (OJ-287 being one, the most distant object I have been able to see in my humble 8" scope, at 3.5 billion ly). The heavier one might catapult the lighter right out of the galaxy, possibly during a merger of galaxies
Cool stuff, anyway (actually, rather hot)
...and now need a dose of mind bleach.
Back on topic, why the need for an exotic explanation re stolen galaxies? If it's inside a lenticular galaxy, perhaps it formed there - there are comfortably 100k's worth of solar masses in any segment of such a galaxy and it only needs to be seeded by a large star- and since this is 4.5 billion years ago, it's almost certainly moved to the middle since.
/Just a thought
//not fully informed, but not totally ignorant
///Arrrgh! Extended goth strips!
Okay, so this is where it was 4.5 billion years ago: WHERE THE EFF IS IT NOW?!?!? It's my running argument with science writers, they forget (probably on purpose), that "light years" mean "years ago" in terms of time, not just distance. So, if Chandra is just picking up the signal now, that "wandering supermassive blackhole" can be anywhere by now.
Were there any clues as to vector or velocity? I mean, these are important facts. In 4.5 billion years, it's like somewhere else by now - it may may even be heading heading for us!!!!!! It may sound picky, but things like where a supermassive blackhole wandering around the universe might be of some concern. In terms of the age of the universe, that's a fairly short time ago (about 1/3rd the age of the universe give or take).
When science writers "assume" even a technically savvy bunch of geeks, like most of El Reg's readers are, don't really know that distance (in light years) = time (in relation to the number of orbits our planet has made around its local star). When you look up at the night sky with your naked eyes (unless you need corrective lenses hanging off your nose) you can only see things that are, at most, a few thousand light years from where are (and they've been moving to, in relation to us). All you're seeing (even with the Hubble) are things as they were, that have already happened, you can't see the "now" of the universe. Betel Guese may have already blown up, that Wolf whatever number it is, has collapsed into a black hole and there's a huge a** gamma pulse headed for us (we won't see it coming, by the way, and if it does hit us, 90+% of everything on Earth goes bye-bye).
We are insignificant little, oversized barely microbes in this universe, and yet we think ourselves gods that can make big changes in nature. Get over yourselves. If a tiny hurricane can destroy Florida (another reason why I'm glad I didn't live there that long, one Hurricane Andrew was enough for me). Just remember species H. Sapiens has only been around about 200,000 years (+\- 10% fudge factor). Plus, we almost didn't survive the "bottle-neck" 70,000 years ago when there were only about 1,000 mating pairs of our species left, for God only knows what reason. The universe is 13.85 billion years old, and we barely understand more than .000000000000000001% of what makes it work (sorry, didn't count the Zero's so I can be off by one or two). Yes, it's fun and interesting looking at all that stuff that happened in the past, but it's in the PAST. It took us 400 years to figure out that tobacco was bad for us. That doesn't speak too well of our supposed intelligence.