protostarvorming

Protostar formation is the initial stage in the birth of a star. It begins within large, cold, and dense clouds of interstellar gas and dust, known as molecular clouds. These clouds are primarily composed of hydrogen and helium, with trace amounts of heavier elements. Gravitational instabilities within these clouds can cause localized regions to become denser. As these denser regions accumulate more material, their self-gravity increases, leading to further contraction.

This process of gravitational collapse causes the core of the collapsing cloud fragment to heat up. As the protostar contracts, its temperature and pressure rise. The infalling material forms a rotating disk around the central protostar, from which additional material continues to accrete onto the protostar. This accretion process is crucial for the protostar to gain mass. During this phase, strong stellar winds and bipolar jets are often ejected from the poles of the protostar, carrying away some of the excess angular momentum and mass.

The protostar stage is characterized by its luminosity, which is generated by the gravitational energy released during its contraction, rather than nuclear fusion. As the protostar continues to contract and heat up, its core eventually reaches a critical temperature and density where nuclear fusion of hydrogen into helium can begin. This marks the transition from a protostar to a main-sequence star. The duration of the protostar phase varies depending on the mass of the star being formed, with more massive stars evolving through this stage much faster than less massive ones.