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HISTORY OF SCIENCE AND TECHNOLOGY
ASAPH HALL (1829-1907)
Asaph Hall was born in Goshen, Connecticut. His family was poor and Hall attended local schools and was partly educated by his father. When his parents died in 1845, the sixteen year-old Hall became an apprentice carpenter. He seems to have enrolled in College in 1853 to study geometry and algebra, but is it unclear whether he completed his degree. He taught in a Wisconsin school for several years before entering Michigan University, where he only completed one trimester. After a brief teaching post in Ohio, Hall became a student at Harvard.
Hall married Angeline Stickney in 1656 and, one year later he took up the post of an assistant astronomer at Harvard College Observatory in Cambridge, Massachusetts. Hall made a name for himself as an expert in working out orbits. In 1862 he made the move to the US Naval Observatory at Foggy Bottom, on the banks of the Potomac River, near Washington D.C. Although he started as an assistant astronomer he was made a full professor within twelve months. He was awarded the rank of captain and taught mathematics at the Naval College.
Hall led many astronomical expeditions over the next twelve years. He was based in the Bering Sea (1869) and in Sicily (1870) for the solar eclipses. He observed the transits of Venus from Vladivostok (1874) and San Antonio, Texas (1882). Back at the Naval Observatory, he was in charge of the largest refracting telescope in the World at the time. He noticed a “spot” on Saturn that allowed him to work out the planet’s rotation time. He also studied the orbit of Saturn’s moon, Hyperion, and recognised that it was a retrograde orbit.
In 1877, Hall had been looking for satellites orbiting Mars for some time and he was ready to give up his quest. It was his wife who convinced him to keep looking. The very same night he saw what could have been taken to be a faint star near Mars. Hall realised that this was, in fact, a moon. One week later he discovered a second moon, closer to Mars but brighter than the other moon. At the suggestion of Henry Madan, the science master at Eton College in England, Hall named these moons Phobos and Demos. These names were used for the attendants of Mars, the God of War, in Homer’s Iliad.
Hall is credited with a few other “firsts”. He worked out the mass of Mars and made some important observations on double stars. He was awarded the Gold Medal of the Royal Astronomical Society of Great Britain in 1879.