August 30: Johann Hieronymus Schröter

Johann Hieronymus Schröter

August 30, 1745 – August 29, 1816

Johann Hieronymus Schröter was a German astronomer. Schröter was born in Erfurt, and studied law at Göttingen University from 1762 until 1767, after which he started a ten-year-long legal practice.

In 1777 he was appointed Secretary of the Royal Chamber of George III in Hanover, where he made the acquaintance of two of William Herschel's brothers. In 1779 he acquired a three-foot-long (91 cm, almost one metre) achromatic refractor with 2.25-inch (57 mm) lens (50 mm) to observe the Sun, Moon and Venus. Herschel's discovery of Uranus in 1781 inspired Schröter to pursue astronomy more seriously, and he resigned his post and became chief magistrate and district governor of Lilienthal.

He made extensive drawings of the features of Mars, yet curiously he was always erroneously convinced that what he was seeing was mere cloud formations rather than geographical features. In 1791 he published an important early study on the topography of the Moon entitled Selenotopographische Fragmente zur genauern Kenntniss der Mondfläche. In 1793 he was the first to notice the phase anomaly of Venus, now known as the Schröter effect, where the phase appears more concave than geometry predicts.

In 1813, he suffered the disruptions of the Napoleonic Wars: his work was ruined by the French under Vandamme, who destroyed his books, writings and observatory. He never recovered from the catastrophe.

His drawings of Mars were not rediscovered until 1873 (by François J. Terby) and were not published until 1881 (by H. G. van de Sande Bakhuyzen), well after his death.

He was elected a member of the Royal Swedish Academy of Sciences in 1794.

The lunar crater Schröter, Vallis Schröteri (Schröter's Valley) and the Martian crater Schroeter are named in his honor.