Convection zone
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A convection zone, convective zone or convective region of a
Stellar convection consists of mass movement of plasma within the star which usually forms a circular convection current with the heated plasma ascending and the cooled plasma descending.
The Schwarzschild criterion expresses the conditions under which a region of a star is unstable to convection. A parcel of gas that rises slightly will find itself in an environment of lower pressure than the one it came from. As a result, the parcel will expand and cool. If the rising parcel cools to a lower temperature than its new surroundings, so that it has a higher density than the surrounding gas, then its lack of buoyancy will cause it to sink back to where it came from. However, if the temperature gradient is steep enough (i.e. the temperature changes rapidly with distance from the center of the star), or if the gas has a very high heat capacity (i.e. its temperature changes relatively slowly as it expands) then the rising parcel of gas will remain warmer and less dense than its new surroundings even after expanding and cooling. Its buoyancy will then cause it to continue to rise. The region of the star in which this happens is the convection zone.
Main sequence stars
In
In main sequence stars of less than about 1.3 solar masses, the outer envelope of the star contains a region where partial
In main sequence stars similar to the Sun, which have a radiative core and convective envelope, the transition region between the convection zone and the radiation zone is called the tachocline.
Red giants
In
References
Further reading
- Hansen, C. J.; Kawaler, S. D. & Trimble, V. (2004). Stellar Interiors. Springer. ISBN 0-387-20089-4.
- Zeilik, M.; Gregory, S. A. (1998). Introductory Astronomy and Astrophysics. Brooks Cole. ISBN 978-0-03-006228-5.
External links
- Animated explanation of the Convection zone Archived 2015-11-16 at the Wayback Machine (University of South Wales).
- Animated explanation of the temperature and density of the Convection zone Archived 2015-11-16 at the Wayback Machine (University of South Wales).
