Astronomy - Active sun: Many sunspots are visible
The number of dark sunspots is currently as high as it has been in 20 years. "We are currently at the maximum of a relatively strong solar cycle," explains solar physicist Achim Gandorfer from the Max Planck Institute for Solar System Research in Göttingen. The number of spots is dependent on solar activity, which changes within an eleven-year cycle. "Whether we are already at the end of the cycle or if there will be another increase, cannot be said at the moment."
The spots are caused by temperature differences on the surface, as Gandorfer explains. "The sun is a stratified gas ball. Energy is generated in the interior, and the hot gas rises." At the surface, the energy is radiated, and the temperature of the matter drops suddenly. "The gas then sinks back in a cooler and denser form." This cycle is also known as convection.
However, it can happen that locally strengthened magnetic fields prevent the cooler gas from sinking. As a result, the cooler matter remains on the surface for a longer period. Therefore, the spots are about 4,000 degrees cooler than the surrounding surface, which is about 6,000 degrees. "The spots are still very, very hot, but they appear darker in contrast because the surroundings are even hotter and brighter."
While there may be no spots for months at a time, there can be hundreds during peak periods, says the expert. He speaks of the so-called sunspot relative number, which is calculated from the sum of individual spots plus the number of spot groups, each weighted by a factor of ten. "The weighting makes the number higher, we actually see fewer spots," adds Gandorfer. Furthermore, a part of the spots is always on the side of the sun facing away from the Earth.
In this cycle, the so-called sunspot relative number reached a maximum of 160 to 170, while in the previous cycle, the number was 130.
Those who wish to observe the sunspots should do so only with appropriate protective equipment such as certified glasses or telescopes with protective filters. Otherwise, severe eye damage could occur.
The Max Planck Institute for Solar System Research in Göttingen is where solar physicist Achim Gandorfer works. During a strong solar cycle, Gandorfer explains that the number of dark sunspots can reach high levels, as seen currently.
