Full Idea
The centre of mass of the solar system seems to lack causal powers, and so is an abstract object, even though it has a location and movement.
Gist of Idea
The centre of mass of the solar system is a non-causal abstract object, despite having a location
Source
E.J. Lowe (A Survey of Metaphysics [2002], p.368)
Book Reference
Lowe,E.J.: 'A Survey of Metaphysics' [OUP 2002], p.368
A Reaction
Nice example, with rich ramifications. Abstraction is deeply tied into our understanding of the physical world, and our concept of identity.