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The differential rotation of the Sun and its Chromosphere


In this laboratory students will calculate the Sun's differential rotation tracking sunspots at different latitudes in time-spaced images. By the end of this Science Case students will understand how the Sun moves and will be able to calculate velocities by tracking targets in images.


The Sun is not a solid body, its gaseous composition allows different rotation speeds on its surface, that is, different angular velocities. This is what we call "differential rotation" and it also occur in other gaseous planets such as Jupiter or Saturn. We can use an h-alpha telescope to observe this phenomena and also learn about one of the thinnest and hottest layers of the Sun: the Chromosphere. Sunspots cannot only be used to measure the activity of the Sun but also its rotation. Since the 17th century the moving of sunspots across the solar disc was observed by astronomers and used to measure the equatorial rotation of the sun. These observations also led to the discovery that the Sun rotation was slower at higher latitudes than on the solar equator (differential rotation of the Sun). With the CESAR solar telescope, taking pictures every week, we can determine the solar differential rotation.

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