(b. Goshen, Connecticut, 15 October 1829; d. Goshen, 22 November 1907)
Hall belonged to an old and once prosperous New England family. His father, also called Asaph Hall, a manufacturer of wooden clocks, died in 1842 on a clock-selling trip in Georgia, leaving the family in difficult circumstances. His mother, Hannah Palmer, attempted unsuccessfully for three years to pay the mortage on a family farm by operating a cheese factory. At age sixteen, Asaph became a carpenter’s apprentice. Three years later, a strong, athletic lad, standing over six feet, he went to work as a journeyman carpenter, and in the six years that followed, employed skills that must have proved useful later in his career when he supervised the construction of observing shelters on several astronomical expeditions.
As a boy, Hall read the histories of Gibbon and Hume, which were in his father’s varied library. He went at first to the district school, but later his formal education was less regular. During one winter of his apprenticeship he studied algebra and geometry at the Norfolk Academy, eight miles from his home, but soon found he was a better mathematician than his teacher. By 1854 he became impatient to continue his education and, hoping to become an architect, enrolled in Central College in McGrawville, New York. There, according to the New York Tribune, students could meet part of their expenses by manual labor. In McGrawville he found a motley crowd of adventurers and idealists who cared little for a classical education. Among the students, however, he met Chloe Angeline Stickney, a frail but determined suffragist, who taught mathematics while completing her senior year. Hall was among her pupils, and she soon became his fiancée. After their marriage in March 1856, they went to Ann Arbor, where for three months Hall studied under Franz Brünnow, director of the University of Michigan Observatory. Lacking money to continue his schooling, the couple took teaching posts for a year at the Shalersville Institute in Ohio.
Firmly determined to become an astronomer, Hall proceeded to Cambridge, Massachusetts, where, in spite of George Bond’s admonition that he would starve, he took a low-paid job at the Harvard College Observatory. He quickly became both an observer and an expert computer of orbits. Having been taught German by his wife, he read Brünnow’s Astronomie and by 1858 he was studying Gauss’s Theoria motus. At this time he published the first of his numerous mathematical and astronomical articles in scientific journals. He supplemented his meager salary by computing almanacs and by observing moon culminations at a dollar per observation.
In 1862, enticed by an adequate income, Hall became an assistant astronomer at the U.S. Naval Observatory. But his first years in Washington were troubled by the Civil War; exhausted by the unwholesome climate as well as by exertions on behalf of wounded friends, Hall was so weakened by jaundice that it was two years before he fully recovered. A year after his arrival, a professorship in mathematics opened at the Naval Observatory. Hall, believing the office should seek the man, simply waited, but unknown to him, his wife proposed his name by letter to the superintendent of the observatory, and Hall was given the position.
From 1862 to 1866 he was assistant observer with the nine-and-one-half-inch equatorial, then considered a large instrument. For a year he took charge of the meridian circle and from 1868 to 1875 was again in charge of the nine-and-one-half-inch equatorial. His observations were primarily of asteroids and comets. In 1869 Hall traveled to the eastern coast of Siberia to observe a total solar eclipse, and the following year he went to Sicily for another eclipse. In 1874 he led a party to Vladivostok to observe the transit of Venus. Inclement weather and the lack of adequate photographic apparatus prevented these expeditions from fulfilling their expectations. Hall was more successful as the leader of expeditions to Colorado to observe the eclipse of 1878 and to Texas to observe the transit of Venus in 1882.
In 1875 Hall was placed in charge of the twenty-six-inch Clark equatorial at the Naval Observatory, then the largest refractor in the world. His first discovery with this telescope, in December 1876, was a white spot on the planet Saturn, which he measured through more than sixty rotations, thus finding the first reliable period of Saturn’s rotation since Herschel’s determination in 1794.
At the time of the unusually close approach of Mars in August 1877, Hall undertook a systematic search for possible satellites. In this search he was fortunately guided by theoretical considerations, which showed that any Martian satellite must revolve very close to the planet; otherwise the solar gravity would over-power the attraction of Mars. “The chance of finding a satellite appeared to be very slight,” Hall wrote, “so that I might have abandoned the search had it not been for the encouragement of my wife.” Angeline Hall was an enthusiast, and Angelo, the third of the four Hall sons, claimed that she “insisted upon her husband’s discovering the satellites of Mars.”
Hall first glimpsed the object that was eventually named Deimos on 11 August, and, after a few days of bad weather, by 17 August he convinced himself that it was indeed a satellite. He also found the second satellite, Phobos, on 17 August. He then disclosed his observations to Simon Newcomb, the scientific head of the observatory. Newcomb erroneously believed that Hall, in his modest conservatism, was reluctant to recognize the “Mars stars” as satellites, and hence took for himself an undeserved credit for this recognition in the wide press coverage that followed. For many years Hall quietly harbored a grudge against Newcomb, who eventually offered his apologies.
After these discoveries Hall gradually became known as the caretaker of the satellites not only of Mars, but of Saturn, Uranus, and Neptune. In 1884 he showed that the position of the elliptical orbit of Saturn’s satellite Hyperion was retrograding by about twenty degrees per year. The celestial mechanician George William Hill called Hall’s memoir on Iapetus (the outer satellite of Saturn) one of “the most admirable pieces of asronomical literature” and compared its clarity and precision to the work of Bessel.
Hall’s principal papers on the satellites are listed in the bibliography. In addition to his work on planetary satellites, Hall was also an assiduous observer of double stars, with numerous investigations of binary star orbits. In 1892 he showed that the two components of 61 Cygni were physically related. He worked on determinations of stellar parallax and on the positions of faint stars in the Pleiades cluster.
For his discoveries Hall won the Gold Medal of the Royal Astronomical Society (1879), the Lalande Prize (1877) and Arago Medal (1893) of the French Academy of Sciences, and became a chevalier of the French Legion of Honor in 1896. Elected to the National Academy of Sciences in 1875, he served as its home secretary for twelve years and as vice-president for six. In 1902 he served as president of the American Association for the Advancement of Science. Beginning in 1888, he acted as a consulting astronomer to the Washburn Observatory in Madison, Wisconsin, and from 1897 to 1907 he was associate editor of the Astronomical Journal.
Following his mandatory retirement at age sixty-two from the Naval Observatory in 1891, Hall continued to work as a voluntary observer on the twenty-six-inch telescope. His wife died in 1892, and in 1894 Hall left Washington for Connecticut. Four years later he went to Harvard to teach celestial mechanics, becoming professor of mathematics. After five years of teaching, he married a longtime protégé of his brother’s family, Mary Gauthier, and retired to his rural home in Connecticut, where he lived until his death.
I. Original Works. An extensive bibliography by William D. Horigan of 486 publications appears in the Biographical Memoirs. National Academy of Sciences, 6 (1908), 276–301. Hall’s principal memoirs were published as separate appendices to the Washington Observations (more fully Astronomical and Meteorological Observations Made During the Years... at the United States Naval Observatory); these include “Catalogue of 151 Stars in Praesepe,” appendix IV, 1867 (1870); “Observations and Orbits of the Satellites of Mars,” in the vol. for 1875 (1878); “Observations of Double Stars,” appendix VI, 1877 (1881); “The Orbits of Oberon and Titania,” appendix I, 1881 (1885); “Orbits of the Satellite of Neptune,” appendix II, 1881 (1885); “The Orbit of lapetus,” appendix I, 1882 (1885); “The Six Inner Satellites of Saturn,” appendix I, 1883 (1886); “Observations for Stellar Parallax,” appendix II, 1883 (1886); “Saturn and Its Ring. 1875–1889,” appendix II, 1885 (1889); and “Observations of Double Stars,” appendix I, 1888 (1892).
Other papers of note include “On the Determination of the Mass of Mars,” in Astronomische Nachrichten, 86 (1875), cols. 327–334; “On the Rotation of Saturn,” ibid., 90 (1877), cols. 145–150; “The Motion of Hyperion,” in Monthly Notices of the Royal Astronomical Society, 44 (1884), 361–365; “The Orbit of Iapetus,” in Astronomical Journal, 11 (1891–1892), 97–102; and “Science of Astronomy,” in Proceedings of the American Association for the Advancement of Science, 52 (1902–1903), 313–323, Hall’s widely reprinted and translated address as retiring president of the Association.
II. Secondary Literature. For works about Hall, see Percival Hall, Asaph Hall, Astronomer (n.p., 1945), written and printed for private distribution by Hall’s fourth son; George William Hill,”Biographical Memoir of Asaph Hall,” in Biographical Memoirs. National Academy of Sciences, 6 (1908), 240–275; and H.S.Pritchett, “Asaph Hall,” in Science, n.s. 26 (13 Dec. 1907), 805, repr. in Popular Astronomy, 16 (1908), 67–70. See also Owen Gingerich, “The Satellites of Mars: Prediction and Discovery,” Journal for the History of Astronomy, 1 (1970), 109–115; Angelo Hall, An Astronomer’s Wife (Baltimore, 1908), a biography of his mother.
An extensive evaluation of Hall’s scientific work up to 1879 is given in the Royal Astronomical Society’s presidential address by Lord Lindsay at the presentation of the Gold Medal, in Monthly Notices of the Royal Astronomical Society, 39 (1879), 306–318.
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.
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). □