Consumption of a galaxy by its central black hole

[Televisionary]

I was thinking about the supermassive black hole that is theorized to be at the center of our galaxy, and indeed, at the center of most galaxies. If that black hole is continuously consuming the stars, planets and gas around it, given enough time, will it not consume the entire galaxy that orbits it? Or is there a size limit for black holes? Do they just keep adding mass as long as there is matter and energy to consume? Does this include dark matter and dark energy? Are they affected by black holes like ordinary matter?

I have more, but the next questions depend on the answers to these. Thanks for any help.

 

[mrcotton]

It was my own very limited understanding that the mass in a galaxy will eventually fall into the black hole in the centre. Just over an incredibly large timescale. THen these black hole will eventually evaporate due to Hawking radiation, leaving a universe full of leptons.

 

[Drakkith]

Supermassive black holes do not continuously suck up material. For example, the SMBH in the center of our galaxy currently has nothing to suck up. Orbital interactions between the nearby stars may swing one near enough to be torn apart, but this doesn't happen that often. (Depending on what time scale you're talking about)

Put simply, black holes, of any type, are not like vacuum cleaners. If the Sun were suddenly replaced by an equal mass black hole, nothing would happen to the Earth or any of the other planets. (Other than suddenly losing all of our light, obviously) Our orbits would remain exactly the same.

Or is there a size limit for black holes? Do they just keep adding mass as long as there is matter and energy to consume? Does this include dark matter and dark energy? Are they affected by black holes like ordinary matter?

There is no size limit. They grow to any size. It would include dark matter, but not dark energy. Dark energy is not "energy" in the usual sense, and does not add to mass or gravity.

 

[Televisionary]

Ah...well, that answers that. I think the piece I was missing is that the presence of a black hole in any system doesn't necessarily destabilize that system. Thank you all for helping me understand this better. I think I get it now.