Asaph Hall’s Achievements in Astronomy

Asaph Hall

Asaph Hall

On October 15, 1829, American astronomer Asaph Hall III was born, who is most famous for having discovered the moons of Mars, Deimos and Phobos, in 1877. He determined the orbits of satellites of other planets and of double stars, the rotation of Saturn, and the mass of Mars.

Asaph Hall was born in Goshen, Connecticut and due to the early death of his father, Hall had to leave school at the age of 16 to become an apprentice to a carpenter. Later on, Asaph Hall enrolled at the Central College in McGrawville, New York, studying mathematics. There, Hall took classes from an instructor of geometry and German, Angeline Stickney.

In 1856, Hall took a job at the Harvard College Observatory in Cambridge, Massachusetts, and turned out to be an expert computer of orbits. Hall became assistant astronomer at the US Naval Observatory in Washington DC in 1862, and within a year of his arrival he was made professor.Asaph Hall was given the responsibility for the USNO 66cm telescope, the largest refracting telescope in the world at the time. Hall managed to discover Phobos and Deimos in 1877 with that telescope and he also noticed a white spot on Saturn which he used as a marker to ascertain the planet’s rotational period.

Further, Asaph Hall demonstrated that the position of the elliptical orbit of Saturn’s moon, Hyperion, was retrograding by about 20° per year. Hall also investigated stellar parallaxes and the positions of the stars in the Pleiades star cluster.He submitted an article entitled “On an Experimental Determination of Pi” to the journal Messenger of Mathematics in 1872. In it, the scientist reported the results of an experiment in random sampling that Hall had persuaded his friend, Captain O.C. Fox, to perform when Fox was recuperating from a wound received at the Second Battle of Bull Run. The experiment involved repetitively throwing at random a fine steel wire onto a plane wooden surface ruled with equidistant parallel lines. This paper, an experiment on the Buffon’s needle problem, is a very early documented use of random sampling in scientific inquiry.

Asaph Hall retired from the Navy in 1891 and became lecturer celestial mechanics at Harvard University in 1896.

Hall retired from the Navy in 1891. He became a lecturer in celestial mechanics at Harvard University in 1896, and continued to teach there until 1901.

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