Samuel Heinrich Schwabe

1789-1875

German Pharmacist and Astronomer

Samuel Schwabe, a pharmacist by training and profession, is best known for his discovery of the 11-year cycles of solar activity and sunspot abundance. As an amateur astronomer, Schwabe's observations helped found the modern era of solar observations and sunspot research.

Schwabe was born in Dessau, Germany, in 1789, the son of a local councilor who was the personal physician to the duke. The oldest of 11 children, Schwabe studied pharmacology in Berlin and, when possible, attended additional lectures in astronomy and botany. Upon his grandfather's death in 1812, Schwabe returned to Dessau to assume responsibility for his pharmacy. There he plied his formal profession until selling the pharmacy in 1829 for enough money to allow him to pursue his scientific interests full-time.

Schwabe was one of the first astronomers to spend extensive time studying the sun. In 1610 Galileo (1564-1642), while observing the sun directly, risked blindness from the extreme brightness. His discovery of sunspots, contested by two others, came as a surprise because the face of the sun had been thought to be perfect in all respects. Another co-discoverer, the priest Christoph Scheiner (1573-1650), developed a safer way to observe the sun by projecting its image onto a screen. This technique is still in use today by amateur and professional astronomers alike. After early activity directed toward the confirmation of sunspots, however, the field languished until Schwabe's work.

Schwabe's interest in astronomy changed from theoretical to observational in 1825 when he won a telescope in a lottery. Later that year he ordered a larger refracting telescope and erected a small observatory from which he began making observations. A larger instrument was added shortly afterwards, with a focal length of six feet. Using these instruments, Schwabe made observations of Saturn (discovering eccentricity in the rings) and began searching for planets inside the orbit of Mercury. He never found new planets, but kept detailed notes of the locations and numbers of sunspots he observed, noticing over time that their numbers changed in a regular fashion. In 1843, based on his notes from 1825 through 1843, Schwabe announced his discovery of a 10-year sunspot cycle, but received little serious consideration. Only later, after independent observations by professional astronomers confirmed his claims, was Schwabe taken seriously. Further studies showed that the sunspot cycle, now known to be 11 years in length, was related to cyclic variations in the earth's magnetic field, adding to Schwabe's support.

Today, the 11-year sunspot cycle is accepted by all solar astronomers and is linked to periodic changes in solar activity. Because of its proximity and strength, these solar changes affect the Earth. Solar magnetic storms have caused widespread power outages, disrupted satellite communications, interfered with spacecraft (in fact, solar heating of the atmosphere led to Skylab's early demise), and have been correlated with weather patterns, rabbit populations, and more. While some of these associations are undoubtedly appropriate, others are still under study. Nonetheless, it is apparent and well accepted that the cycle first noticed by Schwabe is both real and important.

In addition to his astronomical discoveries, Schwabe served as founder and long-time president of a local Society for Natural History, sharing his interests in mineralogy and botany with his fellow members. He also published a two-volume book on local plants in which he described over 2400 specimens in some detail. Because of his contributions to astronomy and his wide-ranging interests, Schwabe was elected a Fellow of the Royal Society in 1868, having already received its Gold Medal in Astronomy in 1857.

Schwabe died in his hometown of Dessau in 1875, 20 years after his wife passed away. He left his scientific papers to the Society for Natural History and the local college.

P. ANDREW KARARN