A protostar is a gas giant planet which turns into a small star. The gas giant in question does have sufficient mass to sustain a fusion reaction and thereby act as a star, however it does not have enough mass to start the reaction by itself. The process of turning a gas giant into a protostar is called "helioforming" (as in terraforming). By helioforming the largest gas giants in the 34 Tauri (2020) star cluster, it was possible to sustain Earth-like life on many more moons than the primary stars themselves could support.