1 article for "Halley, Edmund"

(1656-1742) English astronomer. Born at Haggerston (near London); died in Greenwich (near London).

At age 19, he published a work on Kepler's Laws. With the urging of Flamsteed, he left England for the island of St. Helena in the South Atlantic to establish the first astronomical abservatory in the southern hemisphere. There he discovered Omega Centauri (actually, a huge globular cluster of stars), and returned with a published catalogue of only 341 southern stars (due to the poor climate at St. Helena). This contribution was, nevertheless, sufficient to establish his reputation, and he was elected to the Royal Society. He became the close friend of Newton, and financed the publication of the latter's Principia. His character was blotted by his unauthorized publication of the observations of Flamsteed. He attempted to apply Newton's Theory of Gravitation to the motion of comets, noting that a comet which he had observed in 1682 might be identified with others observed in 1456, 1531, and 1607 (with intervals of 65 or 66 years). He predicted its return in the year 1758, aware that gravitational effects of planets might alter the orbit and, thus, affect the date of its return. (Clairaut worked out the perturbations, obtaining the dat of 1759 APR 13 for perihelion; it was spotted on 1758 DEC 25). The comet has returned in 1835, 1910, and 1986, and is known today as Halley's Comet. Noting that the stars Sirius, Procyon, and Arcturus had altered their positions since Greek times, he was first to realize that stars had Proper Motions, which could be detected only over long periods of time. He also prepared the first mortality tables, which has influenced modern insurance companies.

See also:
♦ Newton, Sir Isaac ♦ Flamsteed, John ♦ Clairaut, Alexis Claude