Edmond Halley
Edmond Halley, b. Nov. 8 (Oct. 29, O.S.), 1656, d. Jan. 14, 1742,
was an English astronomer who discovered the proper motion of
stars and the periodicity of comets. His activities also ranged
from studying archaeology to serving as deputy comptroller of the
mint at Chester. He was an integral part of the English
scientific community at the height of its creativity. A graduate
of Oxford, he became a member of the Royal Society at the age of
22. From the island of Saint Helena, he catalogued (1676-78) the
positions of about 350 Southern Hemisphere stars and observed a
transit of Mercury; he urged that the latter phenomenon and
future transits of Venus be used to determine the distance of the
Sun. He worked out a theory of cometary orbits, concluded that
the comet of 1682 (which still bears his name) was periodic, and
correctly predicted that it would return in 76 years. In 1710,
comparing current star positions with those listed in Ptolemy's
catalog, he deduced that the stars must have a slight motion of
their own, and he detected this proper motion in three stars.
Halley was appointed Savilian professor of geometry at Oxford in
1704, and in 1720 he succeeded John Flamsteed as astronomer
royal. At the Greenwich Observatory he used the first transit
instrument and devised a method for determining longitude at sea
by means of lunar observations.
Halley played an active role in the events and controversies of
his time. He both morally and financially supported Isaac Newton,
pacified the astronomer Johannes Hevelius regarding the disputed
accuracy of methods for measuring stellar positions, and
infuriated Flamsteed by scheming with Newton to publish
Flamsteed's observations long before they were complete.