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Bes·sel(bĕs′əl), Friedrich Wilhelm 1784-1846.
Prussian astronomer who recalculated the orbit of Halley's comet (1804), used parallax to measure the distance from Earth to the twin star 61 Cygni (1838), and developed a class of mathematical functions based on his study of planetary perturbation.
(Biography) Friedrich Wilhelm (ˈfriːdrɪç ˈvɪlhɛlm). 1784–1846, German astronomer and mathematician. He made the first authenticated measurement of a star's distance (1841) and systematized a series of mathematical functions used in physics