Granulation (astronomy)
In astronomy, granulation is the grainy structure of star surfaces , especially the sun , as it is the only star so close that its surface can be observed in detail. The granulation is shown by the fact that the surface appears to be divided into many small "grains" with dark borders. These are called granules . The individual granules are up to 1000 km in diameter and exist for a few minutes.
The granulation is caused by convection in one of the visible "surface", the photosphere , underlying layer. In the process, hot and therefore brightly shining material rises from the interior of the star to the surface, where it cools and sinks back as darker material at the edge of such a current. The temperature difference is 500 K . In contrast to magnetic sunspots, granulation is a purely thermal phenomenon.
Web links
- Bright spots on the calm sun APOD April 16, 2010
- Photospheric Features Solar Physics @ Marshall Space Flight Center
- Granulation in time-lapse, virtual cork crumbs collect where matter sinks ( MPG ; 6.1 MB) Solar Physics @ Marshall Space Flight Center