Reference Work Entry

Biographical Encyclopedia of Astronomers

pp 2241-2243

Date:

von Auwers, Arthur Julius Georg Friedrich

Alternate Name

Auwers, Arthur Julius Georg Friedrich von

Born Göttingen, (Germany), 12 September 1838

Died Berlin-Lichterfelde, Germany, 24 January 1915

Arthur von Auwers’s primary interest for most of his life was in preparing extremely accurate catalogs of the positions of stars.

Auwers’s father was Gottfried Daniel Auwers, master of the horses at the University in Göttingen, while his mother was Emma Christiane Sophie (née Borkenstein). He lost both parents while still a child and was sent to finish schooling at the gymnasia at Schulpforta at the age of about 12.

Auwers’s interest in astronomy originated in his early school years; in 1862, he published a work on William Herschel ’s catalog of nebulae and clusters that was based on observations Auwers made, starting in about 1854. Auwers studied astronomy in Göttingen and Königsberg and was appointed assistant at the observatory in Königsberg in 1859. During this period he made observations of comets, asteroids, and variable stars in addition to nebulae. In 1862, Auwers received a doctoral degree from Königsberg for a thesis in which he computed the orbits of Sirius and Procyon assuming an invisible companion in each case. Friedrich Bessel had speculated, as early as 1842, that minor variations in the proper motion of these stars were due to invisible companions. The discovery of the companion of Sirius by Alvan Graham Clark confirmed Bessel’s hypothesis in 1862. However, the companion of Procyon was not observed until John Schaeberle found it in 1896.

In November 1862 Auwers married Marie Henriette Jacobi (1837–1915) and departed for Gotha where he worked with theoretician Peter Hansen at the private observatory of the Duke of Mecklenburg. During his 4 years with Hansen, Auwers determined parallaxes for a number of stars. In 1866, Auwers received an appointment as astronomer at the Berlin Academy, and it was there that his most important work was completed.

The opportunity that Auwers seized, on his arrival at Berlin, deserves some explanation. Both before and after becoming Astronomer Royal, the British astronomer James Bradley had concentrated his observing activity on measuring the positions of stars. His observations are the earliest trustworthy position measurements now available. But Bradley never reduced his observations, so that at the time of his death in 1762, the manuscript of his observations was not directly usable. Nevertheless, two friends of Bradley arranged to have the manuscripts set in type and published in book form at Oxford University; the second and final volume appeared in 1798, 36 years after Bradley’s death. Heinrich Olbers acquired copies of these books and provided them to Bessel in Königsberg. Bessel realized the value of a long homogeneous series of observations made with the same instruments at the same location, and undertook the reduction of Bradley’s observations. The resulting catalog, titled Fundamenta Astronomæ pro anno 1755, was published in 1819 and revolutionized positional astronomy.

In the 50 years between the appearance of Fundamenta Astronomæ and Auwers’ arrival at Berlin, enormous progress was made in positional astronomy, both on observational work and on techniques of reducing those observations. Furthermore, systematic differences had become apparent in comparisons of the work of various astronomers, and it was no longer clear that Fundamenta Astronomæ could be relied upon. There were, for example, serious discrepancies between the right ascensions of Fundamenta Astronomæ and those determined by Urbain Le Verrier . Thus, in 1868, Auwers undertook a completely fresh reduction of Bradley’s observations. He worked from Bradley’s original manuscripts, rather than the published volumes, used all of Bradley’s observations, and discovered many of Bradley’s errors that Bessel had overlooked in addition to errors in Bessel’s own work. Where there were questions that could be resolved by further observations, Auwers undertook those observations personally. He extended the work to include observations made by Bradley from locations other than Greenwich, and eventually included some observations by Stephen Groombridge and Giuseppi Piazzi to fill in gaps in Bradley’s observational records. Using all these resources Auwers eventually republished Bradley’s catalog of 3,268 stellar positions for the epoch 1755.0. Auwers then extended these positions by rigorous mathematical calculations to form a new catalog for the epoch 1865.0. A similar catalog of fresher observations carried out at Greenwich, and in Berlin, between 1854 and 1867 was reduced rigorously to the epoch 1865.0. Comparison of these two catalogs at epoch 1865.0 provided precise proper motions for the 3,268 stars. The revised Bradley catalog was published in three volumes between 1882 and 1903.

With the revised Bradley data available, Auwers then reanalyzed all available observations, spanning a period of several hundred years, for 36 bright stars that became the fundamental framework to which all subsequent measures of other stars could be referred. His work formed the basis for the fundamental catalog of the Astronomische Gesellschaft known as the AGK1. In his 1888 presidential address at the time the Royal Astronomical Society’s Gold Medal was presented to Auwers, James Whitbread Glaisher reviewed in considerable detail both the steps in this lengthy and detail-laden process of data reduction and the advances achieved by Auwers through this work

Auwers’ work in Berlin was interrupted by three scientific expeditions. In 1874 he traveled to Luxor, Egypt, to observe the transit of Venus. He traveled to Punta Arenas, Chile, in 1882 to observe the second transit of Venus of the nineteenth century, obtaining data on both expeditions for an exact determination of the Sun’s parallax. The results of these two expeditions filled six volumes. Another expedition took Auwers to the Cape of Good Hope in 1889 to observe an opposition of the minor planet (12) Victoria with David Gill, again for the purpose of making an accurate determination of the solar parallax.

In 1881, Auwers was honored by his election as president of the Astronomischen Gesellschaft. In addition to the Royal Astronomical Society Gold Medal, which he received in 1888, Auwers’ British colleagues presented him a portrait of James Bradley in 1912, the same year that Auwers was elevated to hereditary nobility.

Auwers had three sons, including the noted chemist Karl Friedrich von Auwers. A crater on the Moon is named to honor Arthur von Auwers.

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