HANSEN, PETER ANDREAS (1795-1874)

This article appears in Volume V12, Page 931 of the Encyclopedia Britannica.

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HANSEN, PETER ANDREAS (1795-1874) , Danish astronomer, was born on the 8th of December 1795, at Tondern, in the duchy of Schleswig. The son of a goldsmith, he learned the trade of a watchmaker at Flensburg, and exercised it at Berlin and Tondern, 1818-182o. He had, however, long been a student of science; and Dr Dircks, a physician practising at Tondern, prevailed with his father to send him in 1820 to Copenhagen, where he won the patronage of H. C. Schumacher, and attracted the personal notice of King Frederick VI. The Danish survey was then in progress, and he acted as Schumacher's assistant in

work

WORK

connected with it, chiefly at the new

observatory

OBSERVATORY

of Altona, 1821-1825. Thence he passed on to Gotha as director of the Seeberg

observatory

OBSERVATORY

; nor could he be tempted to relinquish the post by successive invitations to replace F. G. W. Struve at Dorpat in 1829, and F. W. Bessel at Konigsberg in 1847. The problems of gravitational astronomy engaged the

chief

CHIEF (from Fr. chef, head, Lat. caput)

part of Hansen's attention. A research into the mutual perturbations of Jupiter and Saturn secured for him the prize of the Berlin

Academy

ACADEMY, GREEK
ACADEMY, ROYAL

in 183o, and a memoir on cometary disturbances was crowned by the Paris

Academy

ACADEMY, GREEK
ACADEMY, ROYAL

in 185o. In 1838 he published a revision of the lunar theory, entitled Fundamenta nova investigationis, &c., and the improved Tables of the Moon based upon it were printed in 1857, at the expense of the British government, their merit being further recognized by a grant of 1000, and by their immediate adoption in the Nautical Almanac, and other Ephemerides. A theoretical discussion of the disturbances embodied in them (still familiarly known to lunar experts as the Darlegung) appeared in the Abhandlungen of the Saxon Academy of Sciences in 18621864. Hansen twice visited England and was twice (in 1842 and 186o) the recipient of the Royal Astronomical Society's gold

medal

MEDAL (Fr. medaille, from Lat. metallum)

. He communicated to that society in 1847 an able

paper

PAPER
PAPER (Fr. papier, from Lat. papyrus)

on a long-period lunar inequality (Memoirs Roy. Asir. Society, xvi. 465), and in 1854 one on the moon's figure, advocating the mistaken hypothesis of its deformation by a huge

elevation

ELEVATION

directed towards the earth (lb. xxiv. 29). He was awarded the Copley

medal

MEDAL (Fr. medaille, from Lat. metallum)

by the Royal Society in 185o, and his Solar Tables, compiled with the assistance of Christian Olufsen, appeared in 1854. Hansen gave in 1854 the first intimation that the accepted distance of the sun was too

great

GREAT

by some millions of miles (Month. Notices Roy. Asir. Soc. xv. 9), the error of J. F. Encke's result having been rendered evident through his investigation of a lunar inequality. He died on the 28th of

March

1874, at the new observatory in the town of Gotha, erected under his care in 1857.
See Vierteljahrsschrift astr. Gesellschaft, x. 133; Month. Notices Roy. Asir. Society,

xxxv

XXXV

. 168; Proc. Roy. Society, xxv. p. v.; R. Wolf, Geschichte der Astronomic, p. 526; Wochenschrift fur Astra' nomie, xvii. 207 (account of early years by E. Heis) ; Allgemeine deutsche Biographie (C. Bruhns). (A. M. C.)

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