premainsequencefasen

The pre-main sequence phase, also known as the pre-main sequence (PMS) phase, is a critical stage in the life of a star, occurring before it begins nuclear fusion in its core. This phase is particularly relevant to low-mass stars, including our Sun, and is characterized by the star's contraction and heating as it accumulates mass from its surrounding protostellar envelope.

During the PMS phase, a star is primarily supported by gravitational energy rather than nuclear fusion. As the star contracts, its temperature and density increase. This contraction is accompanied by the formation of a circumstellar disk, which can lead to the formation of planets and other celestial bodies. The PMS phase can last for millions of years, depending on the mass of the star.

As the star continues to contract, its core temperature eventually reaches the point where nuclear fusion can begin. This marks the transition from the PMS phase to the main sequence phase, where the star spends the majority of its life. The PMS phase is a crucial stage in stellar evolution, as it sets the initial conditions for the star's future life and the formation of its planetary system.