Friedrich Bessel
Friedrich Wilhelm Bessel was a
German mathematician,
astronomer, and systematizer of the
Bessel functions . He was born in
Minden, Westphalia and died of
cancer in Knigsberg . Bessel was a contemporary of
Carl Gauss, also a mathematician and astronomer.
Bessel was the son of a civil servant, and at the age of 14 he was apprenticed to the import-export concern Kulenkamp. He shortly became an accountant for them, and the business' reliance on cargo ships led him to turn his mathematical skills to problems in navigation. This in turn led to an interest in astronomy as a way of determining longitude.
Encyclopedia
Friedrich Wilhelm Bessel was a
German mathematician,
astronomer, and systematizer of the
Bessel functions . He was born in
Minden, Westphalia and died of
cancer in Königsberg . Bessel was a contemporary of
Carl Gauss, also a mathematician and astronomer.
Bessel was the son of a civil servant, and at the age of 14 he was apprenticed to the import-export concern Kulenkamp. He shortly became an accountant for them, and the business' reliance on cargo ships led him to turn his mathematical skills to problems in navigation. This in turn led to an interest in astronomy as a way of determining longitude.
He came to the attention of a major figure of German astronomy at the time,
Heinrich Wilhelm Olbers, by producing a refinement on the orbital calculations for
Halley's Comet. Within two years he had left Kulenkamp and become an assistant at Lilienthal Observatory near Bremen, Germany. There he worked on
James Bradley's stellar observations to produce precise positions for some 3222 stars.
This work attracted considerable attention, and at the age of 26 he was appointed director of the
Königsberg Observatory by
Frederick William III of Prussia. There he published tables of atmospheric refraction based on Bradley's observations, which won him the Lalande Prize from the
Institut de France. On this base, he was able to pin down the position of over 50,000 stars during his time at Königsberg.
With this work under his belt, Bessel was able to achieve the feat for which he is best remembered today: he is credited with being the first to use
parallax in calculating the
distance to a
star. Astronomers had believed for some time that parallax would provide the first accurate measurement of interstellar distances -- in fact, the 1830s housed a fierce competition between astronomers to be the first to accurately measure a stellar parallax. In 1838 Bessel won the "race", announcing that 61 Cygni had a parallax of 0.314 arcseconds; which, given the diameter of the
Earth's orbit, indicated that the star was ~3
parsecs away.
Hipparcos experiment has now calculated the parallax at 0.28547 arcseconds. He narrowly beat
Friedrich Georg Wilhelm Struve and Thomas Henderson, who measured the parallaxes of
Vega and
Alpha Centauri in the same year.
As well as helping determine the parallax of 61 Cygni, Bessel's precise measurements allowed him to notice deviations in the motions of
Sirius and
Procyon, which he deduced must be caused by the gravitational attraction of unseen companions. His announcement of Sirius' "dark companion" in 1844 was the first correct claim of a previously unobserved companion by positional measurement, and eventually led to the discovery of
Sirius B.
Despite lacking a university education, Bessel was a major figure in astronomy during his lifetime. He was elected a fellow of the
Royal Society, and the largest
crater in the moon's
Mare Serenitatis was named after him.
He won the
Gold Medal of the Royal Astronomical Society in 1841. The asteroid 1552 Bessel was named in his honour.
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