What are protostar?

A protostar is an early stage in the formation of a star, occurring after a cloud of gas and dust collapses under its own gravity. During this phase, the material accumulates in a dense core, and the temperature and pressure increase, eventually leading to nuclear fusion. Protostars are typically surrounded by a rotating disk of material, which can contribute to the formation of planets. This phase can last from thousands to millions of years before the protostar becomes a main-sequence star.