Samuel Heinrich Schwabe (25 October 1789 – 11 April 1875) a German astronomer remembered for his work on sunspots.
Schwabe was born at Dessau. At first an apothecary, he turned his attention to astronomy, and in 1826 commenced his observations on sunspots. Schwabe was trying to discover a new planet inside the orbit of Mercury which was tentatively called Vulcan. Because of the proximity to the Sun, it would have been very difficult to observe Vulcan, and Schwabe believed one possibility to detect the planet might be to see it as a dark spot when passing in front of the Sun. For 17 years, from 1826 to 1843, on every clear day, Schwabe would scan the sun and record its spots trying to detect Vulcan among them. He did not find the planet but noticed the regular variation in the number of sunspots and published his findings in a short article entitled "Solar Observations during 1843". In it he made the suggestion of a probable ten-year period (i.e. that at every tenth year the number of spots reached a maximum). This paper at first attracted little attention, but Rudolf Wolf who was at that time the director of Bern observatory, was impressed so he began regular observations of sunspots. Schwabe's observations were afterwards utilized in 1851 by Alexander von Humboldt in the third volume of his Kosmos. The periodicity of sunspots is now fully recognized; and to Schwabe is thus due the credit of one of the most important discoveries in astronomy.