Friedrich Wilhelm Bessel

Friedrich Wilhelm Bessel was born in Minden on July 22, 1784. At the age of 14, he went to Bremen to work in an import-export business for the Andreas Kuhlenkamp company. During his 7-year apprenticeship at the company, Bessel prepared himself for naval overseas voyages with geography, Spanish, English, navigation, astronomy, and mathematics.
In 1804, Bessel wrote a paper on comet Halley with the observations made by Harriot in 1607. With Olbers’s advice, Bessel elaborated his work and got it published. Then in 1806, Bessel started observational work at the Lilienthal Observatory near Bremen. His work revolved around comets, asteroids, planets, occultations, eclipses, atmospheric effects, and instrumental studies. In 1809, Bessel became the director of King Frederick William III of Prussia’s new Konigsberg Observatory and a professor of astronomy at Albertus University. But before that, he was awarded a doctorate by the University of Gottingen. In 1812, he was elected to the Berlin Academy of Sciences. In the same year, he also married Johanna Hagen and had 4 children later.
Bessel contributed significantly to mainly astronomy and related fields. His first contribution to astronomy was on Halley’s 1607 aparation. His continued interest in comets led to numerous observations and calculations of the orbits which improved the methods for orbit calculation. In 1831, he started working together with J.J. Baeyer to undertake a geodetical survey of East Prussia which was later published in 1938. Using the differences between geodetical and astronomical coordinates, Bessel derived with the Bessel Normal Ellipsoid which stated that the figure of Earth is an oblated spheroid with ellipticity 1/299. In 1836, Bessel published the Physical Theory of Comets which stated that comets are mainly made of volatile matter. In addition, he was able to accurately determine the masses of Jupiter and Saturn after observing their satellites. His most prominent contribution is his success in being the first to successfully determining a stellar parallax and distance of a star, specifically the double star 61 Cygni. Then his physical studies in 1939 led up to the new Prussian measurement system. In 1824, Bessel invented the Bessel functions to the mathematics. He also developed the potential theory and second pendulum for physics.
On March 17, 1846, Bessel died from a long mysterious disease that is believed to be intestine cancer. During his lifetime, he was honored by numerous academy memberships, including honor from Fellow of Royal Society and a gold medal from the Royal Astronomical Society. He was honored more after his death when the astronomical community named a moon crater and an asteroid after him.