What does "Extra Mixing" mean?
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Extra mixing is a process that happens in stars, especially as they grow older. It refers to a way that materials inside the star move around and mix together more than usual. This mixing can change the amounts of certain elements, like carbon and lithium, that we find on the star's surface.
Importance of Extra Mixing
In some stars, particularly those nearing the end of their life cycle, extra mixing can lead to the creation of new elements. For example, in red giants, extra mixing affects the levels of lithium and other elements. It can start when the star reaches a specific brightness level and can continue as the star evolves.
How Extra Mixing Works
Extra mixing can be driven by different processes within the star. Some of these include:
- Rotation-driven circulation: When a star spins, it can create currents that help mix materials.
- Thermohaline convection: This process happens when different temperatures in the star cause materials to rise and fall, mixing them together.
- Magnetic effects: Magnetic fields within the star can also help move materials around.
These processes can work together to increase the amount of mixing, particularly in stars that are changing rapidly, such as those near the tip of the red giant branch.
Impact on Stars
The effects of extra mixing can lead to significant changes in the star's surface composition. Stars that undergo this process can show higher levels of certain elements, which can help scientists understand the star's history and evolution better.
Overall, studying extra mixing gives insight into how stars develop and what happens to them over time.