Questions regarding the motions of celestial objects.
Celestial mechanics is a field regarding the motion and trajectory of certain objects in space. This field includes many sub-fields such as the launching and orbits artificial satellites, and lunar theory. Celestial mechanics currently consists of five main fields:
Astrodynamics and stellar dynamics.
Stellar dynamics and galactic dynamics.
All of the above fields obviously overlap, but mostly are treated as separate, especially the study of the motion of stars within galaxies and interactions between whole galaxies, which both tend to rely heavily on fluid mechanics.