Kiepenheuer Institute for Solar Physics

The Kiepenheuer Institute for Solar Physics (KIS) conducts experimental and theoretical investigations of physical processes on and within the Sun. Its headquarter is in Freiburg, Germany. The KIS operates the german solar telescopes at Teide Observatory on Tenerife (Spain) where most of the scientific observations are performed. KIS offers lectures on astronomy and astrophysics at Freiburg university and trains young scientists.

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As early as in 1611, shortly after the discovery of the telescope, sunspots were observed and scientifically analysed. Johann Fabricus (1587 - 1616) described the movement of sunspots and deduced therefrom the rotation of the sun. In 1630, Christoph Scheiner determined that the orbital period is 27 days. Today we know that the sun rotates differentially, so that spots near the equator rotate faster than those in higher latitudes.

Since 2010, the position of sunspots can be measured with unprecedented accuracy using the data obtained with the HMI on the American SDO satellite. In a study carried out at KIS, the movement of 163 stable sunspots was measured between 2010 and 2015. The chart shows the angular velocity of the spots depending on the observed latitude ϑ on the sun. The unit used was degree/day. A rotation velocity of 14.4 degrees/day is equivalent to a rotation period of 25 days. The dependency on the latitude follows the square sine function: 14.421 (+/- 0.026) - 3.116 (+/- 0.179) sin...

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