Average size of the biggest G-bound structures in the Universe

[tzimie]

After Dark Energy will tear our Universe apart, every Hubble sphere would contain only 1 or 0 gravitationally bound structures. What is an average size of such structures? (As I understand, galaxy clusters are the "seeds" of such remnants?)

 

[mfb]

Over very long timescales: single solid objects or single black holes. All orbits are unstable over sufficiently long timescales, so objects tend to either merge or get ejected from gravitationally bound systems.

Over not that long timescales: somewhere at the scale of superclusters, what exactly will stay bound is still subject of discussion.