If I recall my physics correctly, the force of gravity falls off as the square of the distance from its source. You could actually be fairly close, in cosmic terms, to even a monstrously huge black hole without feeling any unusual gravitational pull; that's why large numbers of stars can exist in the galactic core without getting swallowed up. And in a galactic merger, while theory says that the central black holes should usually eventually merge, multi-body interactions at very close range could also cause momentum to be transferred to one body (the "migrant" black hole), sending it shooting out of the galaxy in the company only of the material in its accretion disk.

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Thanks. Yes, it's the square of the distance.

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There's no more (and no less) reason for a black hole to "drag stars along with it" than there would be for an ordinary star of the same mass to do so -- except at very close ranges (where things can't get that close to a normal star because they'd actually be inside it), the two act the same way as far as gravity goes.

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My assumption was that it was a center-of-the-galaxy black hole of unusual size, but mrgoodwraith has covered that.

Too late, too late, but I wish it were possible to see a black hole dragging its galaxy behind it as painted by Kelly Freas.

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The article does call it a "supermassive" black hole, which would be much more massive than a star. But another factor could be that it's moving fast enough that few stars are within its close gravitational influence for long.

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Such a thing, if it could happen, might look kind of like Arp 148.

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