Schwabe carefully observed the Sun and recorded the number and position of every sunspot he saw.
He didn’t find any new planets, but what he did find was an even more important result.
Schwabe found that the number of sunspots changed over the years in a very regular way. He found that every 11 years the number of sunspots grows from small to large and then goes back to small again. This is now known as the solar cycle.
You can see the solar cycle in this graph, which shows the number of sunspots visible from about 1900 onward.
Samuel Schwabe (1789-1875), courtesy of
Museum für Stadtgeschichte