Rudolf Wolf

The Sun has been exceptionally quiet for most of this year, with few sunspots marking its surface. In fact, the number of sunspots peaked more than two years ago. It’ll probably bottom out in about three more years — completing another cycle of magnetic activity.
The man who was the first to precisely plot the solar cycle was born 200 years ago today. Rudolf Wolf was born in Switzerland, and became one of Europe’s leading astronomers.
In the 1840s, Wolf became fascinated with the findings of another astronomer, who’d spent years counting sunspots. He found that the number of spots seemed to vary over a period of about a decade.
Wolf began counting sunspots himself — something he did for almost half a century. He also tracked down records of sunspots as far back as 1610. From that, he found that, on average, the number of sunspots peaked every 11 years. And later, Wolf was one of several astronomers to notice a link between spots on the Sun and auroras and other magnetic events on Earth