Asaph Hall

Asaph Hall

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Asaph Hall III was an American astronomer
Astronomy is a natural science that deals with the study of celestial objects and phenomena that originate outside the atmosphere of Earth...

 who is most famous for having discovered the moons of Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

 (namely Deimos
Deimos (moon)
Deimos is the smaller and outer of Mars's two moons . It is named after Deimos, a figure representing dread in Greek Mythology. Its systematic designation is '.-Discovery:Deimos was discovered by Asaph Hall, Sr...

 and Phobos
Phobos (moon)
Phobos is the larger and closer of the two natural satellites of Mars. Both moons were discovered in 1877. With a mean radius of , Phobos is 7.24 times as massive as Deimos...

) in 1877. He determined the orbits of satellite
In the context of spaceflight, a satellite is an object which has been placed into orbit by human endeavour. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as the Moon....

s of other planets and of double star
Double star
In observational astronomy, a double star is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope. This can happen either because the pair forms a binary star, i.e...

s, the rotation of Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...

, and the mass of Mars.


Hall was born in Goshen, Connecticut
Goshen, Connecticut
Goshen is a town in Litchfield County, Connecticut, United States. The population was 2,697 at the 2000 census.Each July, the Connecticut Agricultural Fair is held in town. It is also home to the Goshen players.-Geography:...

, the son of Asaph Hall II (1800-42), a clockmaker, and Hannah Palmer (1804-80). His grandfather Asaph Hall I was a Revolutionary War officer and Connecticut state legislator. 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
New-York Central College, McGrawville
New-York Central College, McGrawville was an institution of higher learning founded by Cyrus Pitt Grosvenor and other anti-slavery Baptists in 1849 in McGraw, New York...

 in McGrawville, New York
New Hudson, New York
New Hudson is a town in Allegany County, New York, United States. The population was 736 at the 2000 census.The Town of New Hudson is on the west border of the county, northeast of Olean, New York.- History :The town was first settled around 1820....

, where he studied mathematics. There he took classes from an instructor of geometry and German, Angeline Stickney
Angeline Stickney
Chloe Angeline Stickney Hall , suffragist, abolitionist, and mathematician, was the wife of astronomer Asaph Hall...

. In 1856 they married.

In 1856, he took a job at the Harvard College Observatory
Harvard College Observatory
The Harvard College Observatory is an institution managing a complex of buildings and multiple instruments used for astronomical research by the Harvard University Department of Astronomy. It is located in Cambridge, Massachusetts, USA, and was founded in 1839...

 in Cambridge, Massachusetts
Cambridge, Massachusetts
Cambridge is a city in Middlesex County, Massachusetts, United States, in the Greater Boston area. It was named in honor of the University of Cambridge in England, an important center of the Puritan theology embraced by the town's founders. Cambridge is home to two of the world's most prominent...

, 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
Hyperion (moon)
Hyperion , also known as Saturn VII, is a moon of Saturn discovered by William Cranch Bond, George Phillips Bond and William Lassell in 1848. It is distinguished by its irregular shape, its chaotic rotation, and its unexplained sponge-like appearance...

, was retrograding
Retrograde motion
Retrograde motion is motion in the direction opposite to the movement of something else, and is the contrary of direct or prograde motion. This motion can be the orbit of one body about another body or about some other point, or the rotation of a single body about its axis, or other phenomena such...

 by about 20° per year. Hall also investigated stellar parallax
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek παράλλαξις , meaning "alteration"...

es and the positions of the stars in the Pleiades
Pleiades (star cluster)
In astronomy, the Pleiades, or Seven Sisters , is an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky...

Open cluster
An open cluster is a group of up to a few thousand stars that were formed from the same giant molecular cloud and have roughly the same age. More than 1,100 open clusters have been discovered within the Milky Way Galaxy, and many more are thought to exist...


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
Messenger of Mathematics
The Messenger of Mathematics is a defunct mathematics journal.The editor-in-chief was William Allen Whitworth with Charles Taylor and volumes 1–58 were published between 1872 and 1929...

. 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
Second Battle of Bull Run
The Second Battle of Bull Run or Second Manassas was fought August 28–30, 1862, as part of the American Civil War. It was the culmination of an offensive campaign waged by Confederate Gen. Robert E. Lee's Army of Northern Virginia against Union Maj. Gen...

. 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
Nicholas Metropolis
Nicholas Constantine Metropolis was a Greek American physicist.-Work:Metropolis received his B.Sc. and Ph.D. degrees in physics at the University of Chicago...

 would name the Monte Carlo method
Monte Carlo method
Monte Carlo methods are a class of computational algorithms that rely on repeated random sampling to compute their results. Monte Carlo methods are often used in computer simulations of physical and mathematical systems...

 during the Manhattan Project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...

 of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

) 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. Asaph Hall, Jr. (1859-1930) became an astronomer, Samuel Stickney Hall (1864-1936) worked for Mutual Life Insurance Company, Angelo Hall (1868-1922) became a Unitarian
Unitarian Universalism
Unitarian Universalism is a religion characterized by support for a "free and responsible search for truth and meaning". Unitarian Universalists do not share a creed; rather, they are unified by their shared search for spiritual growth and by the understanding that an individual's theology is a...

 minister and professor of mathematics at the US Naval Academy, and Percival Hall
Percival Hall
Percival Hall, was the second president of Gallaudet University . He was a strong advocate of the use of sign language in the education of the deaf, and also an advocate for deaf rights to vote, work, participate in sports, marry, and drive automobiles.The son of astronomer Asaph Hall, III and...

 (1872-1953) became president of Gallaudet University
Gallaudet University
Gallaudet University is a federally-chartered university for the education of the deaf and hard of hearing, located in the District of Columbia, U.S...

. Angeline Hall died in 1892. Asaph Hall married Mary Gauthier after he fully retired to Goshen, Connecticut
Goshen, Connecticut
Goshen is a town in Litchfield County, Connecticut, United States. The population was 2,697 at the 2000 census.Each July, the Connecticut Agricultural Fair is held in town. It is also home to the Goshen players.-Geography:...

 in 1901.

Asaph Hall died in November 1907 while visiting his son Angelo in Annapolis, Maryland
Annapolis, Maryland
Annapolis is the capital of the U.S. state of Maryland, as well as the county seat of Anne Arundel County. It had a population of 38,394 at the 2010 census and is situated on the Chesapeake Bay at the mouth of the Severn River, south of Baltimore and about east of Washington, D.C. Annapolis is...


Awards and honors

He won the Lalande Prize
Lalande Prize
The Lalande Prize was an award for scientific advances in astronomy, given from 1802 through 1970 by the French Academy of Sciences.The prize was named for, and endowed by, astronomer Jérôme Lalande in 1801...

 of the French Academy of Sciences
French Academy of Sciences
The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...

 in 1878, the Gold Medal of the Royal Astronomical Society
Gold Medal of the Royal Astronomical Society
-History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should jointly be made to John Couch Adams and Urbain Le Verrier...

 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) in 1896. Hall crater
Hall (lunar crater)
Hall is a lunar crater named in honor of American astronomer Asaph Hall that is located in the southeast part of the Lacus Somniorum, a lunar mare in the northeast part of the Moon. This feature can be found to the west of the prominent walled plain Posidonius. Just to the south, and nearly...

 on the Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

 as well as Hall crater on the Martian moon Phobos are named in his honor. Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...

 3299 Hall
3299 Hall
3299 Hall is a main-belt asteroid discovered on October 10, 1980 by Shoemaker, C. at Palomar.- External links :*...

 is also named in his honor.

External links