Moving stars using light pressure. The mass of the statite reflector attracts the star like a gravity tug, causing the star and statite to slowly move
A satellite can remain stationary (non-orbiting) with respect to a star by using a solar sail to cancel out the star's gravitational attraction. This results in an asymmetry in the light emission of the system, yielding acceleration of the star and stationary satellite (statite). By considering gravitational redshift, it can be shown that this system is self-stabilising. This is not a reactionless drive; the exhaust is photons.
Equations and Definitions of symbols
Images from Andrew Broeker
I'd like to apologise for using this term; it's the best short description of the concept I can think of. The long version is 'total energy of all the light passing through the area over a period of time'. You can't do it by photon because the higher energy ones count for more.