Asaph Hall

American astronomer (1829–1907)

Born at Goshen in Connecticut, Hall had to leave school at the age of 13 and support his family as a carpenter, following the death of his father. He educated himself, and his interest in astronomy was strong enough for George Bond to employ him as his assistant at Harvard in 1857. In 1863 Hall became professor of mathematics at the Naval Observatory in Washington. He returned to Harvard as professor of astronomy in 1895.

In 1877 Mars was in opposition to the Sun at a distance of about 30 million miles from the Earth. Hall decided to search for Martian satellites using the 26-inch (66-cm) refractor that the Clark firm had provided for the Naval Observatory. On 11 August he discovered a tiny satellite (the smaller moon) but was then compelled to wait a further six nights for the persistent cloud to clear before he could confirm his sighting and discover a further satellite. Both were very small, having diameters of 17 miles (27 km) and 9 miles (15 km) only. He named the larger ‘Phobos’ and the smaller ‘Deimos’ (Fear and Terror), after the sons of Mars. One curious feature of the two satellites was that Jonathan Swift had spoken of Martian satellites in Gulliver's Travels (1726). Not only did Swift get their number correct but also spoke accurately of their size and orbital period.

In 1876, by noticing a white spot on the surface of Saturn, Hall was able to work out correctly the rotation period as 10.75 hours, which compares well with today's figure of 10 hours 14 minutes (for its equatorial region).

The American astronomer Asaph Hall (1829-1907) discovered the two satellites of the planet Mars and was an important figure in government scientific circles during the period following the Civil War.

Asaph Hall was born in Goshen, Conn. He attended the district schools until he was 13. At 16 he was apprenticed to a carpenter, and he worked at that trade sporadically. His education in astronomy was spotty at best. He attended the Norfolk Academy to study mathematics one winter, spent a year and a half at Central College at McGrawville, N.Y., and received special instruction in astronomy from F. F. E. Brünnow during 3 months at the University of Michigan.

After a period as a schoolmaster in Ohio and some months working as a carpenter, in 1857 Hall finally secured a position at the Harvard Observatory. This gave him the opportunity to attend lectures and informally complete his education. He immediately proved to be a brilliant observer, and in 1859 he began to send papers, chiefly on the orbits of comets and asteroids, to scientific journals. In 1862 he went to Washington as an aide in the Naval Observatory and the following year was appointed professor of mathematics there. In 1872 Hall was made chief of the Naval Observatory. Five years later Hall, using the observatory's new 26-inch telescope, discovered the satellites of Mars.

Hall achieved a reputation as an extremely careful observer and an accurate mathematician and computer. In his lifetime he was the recipient of numerous scientific awards in the United States and abroad. His nearly 500 published papers include investigations of the orbits of the various satellites, the mass of Mars, the perturbations of the planets, the advance of Mercury's perihelion, the parallax of the sun, stellar parallax, the distances of Alpha Lyrae and 61 Cygni, the mass of Saturn's rings, and the orbits of double stars, along with the solution of many mathematical problems suggested by these investigations. Disdainful of textbooks and popularizations, Hall refused to publish a book.

Following his retirement from the Naval Observatory in 1891, Hall taught at Harvard and continued to work in astronomy. His first wife died in 1892; in 1901 he married again. In 1902 he was elected president of the American Association for the Advancement of Science. He published his final paper in September 1906 and died on Nov. 22, 1907.

Further Reading

There is no book-length study of Hall. One source is David B. Hall's genealogical and biographical study, The Halls of New England (1883).

The noun has one meaning:

Meaning #1: United States astronomer who discovered Phobos and Deimos (the two satellites of Mars) (1829-1907)
  Synonym: Hall

Asaph Hall III
Asaph Hall at the USNO
Born	October 15, 1829(1829-10-15) Goshen, Connecticut
Died	November 22, 1907 (aged 78) United States
Residence	United States
Nationality	American
Fields	Astronomer
Alma mater	New-York Central College, McGrawville
Known for	Discovery of 2 Martian moons

Asaph Hall III (October 15, 1829 – November 22, 1907) was an American astronomer who is most famous for having discovered the moons of Mars (namely 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.

Hall was born in Goshen, Connecticut, the son of Asaph Hall II, a clockmaker, and Hannah Palmer. His father died when he was 13, leaving the family in financial difficulty, so Asaph left school at 16 to become an apprentice to a carpenter. He later enrolled at the Central College in McGrawville, New York, where he studied mathematics. There he took classes from an instructor of geometry and German, Angeline Stickney. In 1856 they married.

In 1856, he 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.

In 1875 Hall was given responsibility for the USNO 26-inch (66-cm) telescope, the largest refractor in the world at the time. It was with this telescope that he discovered Phobos and Deimos in August 1877. He also noticed a white spot on Saturn which he used as a marker to ascertain the planet's rotational period. In 1884, he showed 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 cluster.

Hall was responsible for apprenticing Henry S. Pritchett at the Naval Observatory in 1875.

On June 5, 1872 Hall submitted an article entitled "On an Experimental Determination of Pi" to the journal Messenger of Mathematics. The article appeared in the 1873 edition of the journal, volume 2, pages 113-114. In this article Hall 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. Pi was computed as 2ml/an where m is the number of trials, l is the length of the steel wire, a is the distance between parallel lines, and n was the number of intersections. This paper is a very early documented use of random sampling (which Nicholas Metropolis would name the Monte Carlo method during the Manhattan Project of World War II) in scientific inquiry.

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.

Asaph and Angeline had four children. All graduated from Harvard University. His son Asaph Hall Jr also became an astronomer, Samuel Stickney Hall died at thirty after beginning a career in insurance, Angelo Hall became a Unitarian Minister and professor of mathematics at the US Naval Academy, and Percival Hall became the second president of Gallaudet University. Angeline Hall died in 1892. Asaph Hall married Mary Gauthier after he fully retired to Goshen, Connecticut in 1901.

Asaph Hall died in November, 1907 while visiting his son, Angelo, in Annapolis, Maryland.

Contents 1 Awards and honors 2 Bibliography 3 References 4 External links

Awards and honors

He won the Lalande Prize of the French Academy of Sciences in 1878, the Gold Medal of the Royal Astronomical Society in 1879, the Arago Medal in 1893, and was made a Chevalier in the Ordre national de la Légion d'honneur (French Legion of Honor).^[1] Hall crater on the Moon as well as Hall crater on the Martian moon Phobos^[2] are named in his honor. Asteroid 3299 Hall is also named in his honor.

Bibliography

• Angelo Hall. An Astronomer's Wife: The Biography of Angeline Hall. Baltimore: Nunn & Company, 1908. [1] This book has been reprinted by BiblioLife (December 9, 2008). (includes a biographical chapter on Asaph Hall.)

• Percival Hall. Asaph Hall, Astronomer. Self published, nd. (booklet, 46 pp.)

• George William Hill. A Biographical Memoir of Asaph Hall, 1829-1907. Judd and Detwiler: Washington, DC, 1908.

References

1. ^ Asaph Hall obituary by W.S. Eichelberger, published in Astronomische Nachrichten, 1908
2. ^ Hall crater on Phobos

External links

Wikisource has original text related to this article: a contemporary account of Hall's calculation of Saturn's rate of rotation.

• The History of the Detroit Observatory at www.umich.edu
• US Naval Observatory Library search for photos
• Hall Memorabilia at the US Naval Observatory
• photograph archive of Emilio Segrè at American Institute of Physics
• Washington anecdotes
• Mrs. Hall's bio

Wikimedia Commons has media related to: Asaph Hall

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