Astro*Dictionary
by Michael Erlewine

1 article for
"Bessel, Friedrich Wilhelm"

(1784-1846) German astronomer. Born at Minden, Prussia; died at Konigsberg, Prussia.

At age 20 he calculated the orbit of Halley's comet and sent his results to Olbers. Appointed by King Frederick William III of Prussia to superintend the construction of the observatory of Konigsberg, he became its director, remaining in that position for the remainder of his life. His star catalogue, published in 1818, contains 50,000 stars. He introduced many numerical techniques for astronomical calculations, including Bessel Functions, which have been used in the solution of problems arising in numerous branches of science. He was the first to determine the parallax of a star (61 Cygni), which supplied visible evidence of the Earth's motion about the Sun, supporting the Copernican theory. Using an instrument of his own design, the heliometer, his measurements of the stars Sirius and Procyon revealed small oscillations in their proper motions. He suggested that this phenomena was caused by nearby companions of these stars which, though unseen, interacted gravitationally with them. His investigation of the residuals in the observed motion of Uranus suggested the possibility of another planet. He recomputed the masses of Jupiter and Saturn, and showed that the residuals for Uranus could not be explained by the perturbations of these two bodies.

See also:
♦ Annual Parallax ♦ Binary Star ♦ Neptune