puhdistusvaiheeseen

Puhdistusvaiheeseen refers to a stage in the life cycle of a star, specifically a main-sequence star like our Sun. This phase occurs after the star has exhausted the hydrogen fuel in its core and begins to fuse hydrogen into helium in a shell surrounding the core. The core, now composed primarily of helium, contracts and heats up, causing the outer layers of the star to expand significantly. This expansion leads to an increase in the star's luminosity and radius, transforming it into a red giant.

During the red giant phase, the star's outer layers become cooler and more diffuse, while the core continues to fuse helium into carbon and oxygen. This process is much slower than the initial hydrogen fusion, leading to a longer duration in the red giant stage. Eventually, the star will shed its outer layers, forming a planetary nebula, and the remaining core will cool down to become a white dwarf.

The duration of the red giant phase depends on the star's initial mass. For stars like the Sun, this phase lasts for about a billion years. The exact details of the red giant phase, including the structure and evolution of the star, are subjects of ongoing research in astrophysics.