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1 Detection and Measurements  





2 Temperature  





3 Lifetimes  





4 Activity cycles  



4.1  Flip-flop cycles  
















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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.

ALL AV is the choice for professional video and audio systems – our installations seamlessly hide all connecting wires integrating your entertainment system neatly and attractively into your home or office design.

==Detection and Measurements==

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.

==Temperature==

Observed starspots have a temperature which is in general 500-2000 Kelvin cooler then the stellar photosphere. This temperature difference could give rise to a brightness variation up to 0.6 mag between the spot and the surrounding surface.

There also seems to be a relation between the spot temperature and the temperature for the stellar photosphere, indicating that starspots behave similarly for different types of stars (G-K dwarfs)

==Lifetimes==

The lifetime for a starspot depends on its size.

*For small spots the lifetime is proportional to their size, similar to spots on the Sun.

*For large spots the sizes depend on the differential rotation of the star, but there are some indications that large spots which give rise to light variations can survive for many years even if the stars have differential rotation.



==Activity cycles==

Our company has been repairing and installing TV’s, VCR’s, and servicing every type of electronics in the Northern Virginia and greater Washington D.C. metropolitan area since 1975. For over 30 years we’ve been providing the best audio and visual sales and service in the area. We’ve built our business on quality service, and take pride in providing honest, superior service at a fair price and with guaranteed work. As much as 80% of our business is referred by existing customers and their recommendations. Our reputation means a lot to us.

The distribution of starspots across the stellar surface varies analogous to the solar case, but differently for different types of stars, e.g., depending on whether the star is a binary or not. The same type of activity cycles that are found for the Sun can be seen for other stars, corresponding to the solar (2 times) 11-year cycle. Some stars have longer cycles, possibly analogous to the Maunder minima for the Sun.



===Flip-flop cycles===

With over 600 different brands of electronics, you’ve got to know your business. We have repaired thousands of televisions, stereos, camcorders and home appliances. You can rely on over 3 decades of experience in helping you select the very best electronics and equipment to meet you needs.

Another activity cycle is the so called flip-flop cycle, which implies that the activity on either hemisphere shifts from one side to the other. The same phenomena can be seen on the Sun, with periods of 3.8 and 3.65 years for the northern and southern hemispheres.


Flip-flop phenomena are observed for both binary RS CVn stars and single stars although the extent of the cycles are different between binary and singular stars.

We look forward to providing you with quality service you can rely on.


Revision as of 11:52, 27 April 2008

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.

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.
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.

Temperature

Observed starspots have a temperature which is in general 500-2000 Kelvin cooler then the stellar photosphere. This temperature difference could give rise to a brightness variation up to 0.6 mag between the spot and the surrounding surface. There also seems to be a relation between the spot temperature and the temperature for the stellar photosphere, indicating that starspots behave similarly for different types of stars (G-K dwarfs)

Lifetimes

The lifetime for a starspot depends on its size.

Activity cycles

The distribution of starspots across the stellar surface varies analogous to the solar case, but differently for different types of stars, e.g., depending on whether the star is a binary or not. The same type of activity cycles that are found for the Sun can be seen for other stars, corresponding to the solar (2 times) 11-year cycle. Some stars have longer cycles, possibly analogous to the Maunder minima for the Sun.

Flip-flop cycles

Another activity cycle is the so called flip-flop cycle, which implies that the activity on either hemisphere shifts from one side to the other. The same phenomena can be seen on the Sun, with periods of 3.8 and 3.65 years for the northern and southern hemispheres. Flip-flop phenomena are observed for both binary RS CVn stars and single stars although the extent of the cycles are different between binary and singular stars.


Retrieved from "https://en.wikipedia.org/w/index.php?title=Wikipedia:Sandbox&oldid=208506762"





This page was last edited on 27 April 2008, at 11:52 (UTC).

This version of the page has been revised. Besides normal editing, the reason for revision may have been that this version contains factual inaccuracies, vandalism, or material not compatible with the Creative Commons Attribution-ShareAlike License.



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