|
No edit summary
|
No edit summary
|
||
| Line 1: | Line 1: | ||
==Starspots== |
|||
Starspots are equivalent to [[sunspots]] but located on other stars. Spots the size of sunspots are very hard to detect since they are too small to cause fluctuations in brightness. Observed starspots are in general much larger than those on the Sun, up to about 30 % of the surface may be covered, corresponding to a size 100 times greater than the ones on the Sun. |
Starspots are equivalent to [[sunspots]] but located on other stars. Spots the size of sunspots are very hard to detect since they are too small to cause fluctuations in brightness. Observed starspots are in general much larger than those on the Sun, up to about 30 % of the surface may be covered, corresponding to a size 100 times greater than the ones on the Sun. |
||
|
==Detection and Measurements== |
||
To detect and measure the extent of starspots one uses several types of methods. |
To detect and measure the extent of starspots one uses several types of methods. |
||
● For rapidly rotating stars - Doppler imaging and Zeeman-Doppler imaging. |
● For rapidly rotating stars - Doppler imaging and Zeeman-Doppler imaging. |
||
Starspots are equivalent to sunspots but located on other stars. Spots the size of sunspots are very hard to detect since they are too small to cause fluctuations in brightness. Observed starspots are in general much larger than those on the Sun, up to about 30 % of the surface may be covered, corresponding to a size 100 times greater than the ones on the Sun.
To detect and measure the extent of starspots one uses several types of methods. ● For rapidly rotating stars - Doppler imaging and Zeeman-Doppler imaging. With the Zeeman-Doppler imaging technique the direction of the magnetic field of stars can be determined since light from the spots is be split according to the Zeeman effect, revealing the direction of the field. The magnetic field magnitude is determined from the Zeeman splitting in spectral lines. ● For slowly rotating stars - Light Depth Ratio (LDR). Here one measures two different spectral lines, one sensitive to temperature and one which is not. Since starspots have a lower temperature then their surroundings the temperature-sensitive line changes in depth. From the difference between these two lines the temperature and size of the spot can be calculated, the temperature to an accuracy of 10K.
