This is a term which Andrew Pickering uses on pg 10 of the Cybernetic Brain to describe the conference series and dining club around which cybernetics coalesced, as organisationally loose and somewhat self-selecting gatherings substituted for the secure institutional base which the majority of participants lacked.
Scholarly centres of gravity are what bring people together outside of institutional concerns, with the intellectual and relational goods which can be found there drawing people back to them. In the process of course, this contributes to the reproduction of those goods as common projects, commitments and understandings emerge from what people do in these assemblies. If they stop coming back, or if the meetings cease to resonate for those concerned, these goods will rapidly erode.
This is the perils of scholarly centres of gravity outside of institutional settings. They can provide a richer lived experience of why we do what we do. But the resources of an institution can help buttress projects and initiatives during fallow times when things don’t quite work. In their absence, a shared project can rapidly unwind with nothing beyond the commitment of those involved to hold it in its place.