Is there an application of graph theory (or group theory) in astronomy. If there is, refer me some references.
It happens that there is one publication using GAP in the category "Mechanics of particles and systems". Secondary MSC codes and the list of citations point that it is relevant to celestial mechanics:
Ferrario, D. L. and Terracini, S., On the existence of collisionless equivariant minimizers for the classical $n$-body problem, Invent. Math., 155 (2) (2004), 305--362.
See also the preprint http://arxiv.org/abs/math-ph/0302022v3