22 July 1784|
Minden, Minden-Ravensberg (present-day Germany)
|Died||17 March 1846
Königsberg, Prussia (present-day Kaliningrad, Russia)
|Fields||Astronomy and Mathematics|
|Institutions||University of Königsberg|
|Doctoral students||Friedrich Wilhelm Argelander|
|Known for||Bessel functions
|Notable awards||Gold Medal of the Royal Astronomical Society (1829 & 1841)|
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German mathematician, astronomer, and systematizer of the Bessel functions (which were discovered by Daniel Bernoulli). He was a contemporary of Carl Gauss, also a mathematician and physicist. The asteroid 1552 Bessel was named in his honour.
Life and work
Bessel was born in Minden, administrative center of Minden-Ravensberg, as son of a civil servant. At the age of 14 Bessel was apprenticed to the import-export concern Kulenkamp at Bremen. The business's 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.
Bessel 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 in 1804. Within two years Bessel had left Kulenkamp and become an assistant at Lilienthal Observatory near Bremen. There he worked on James Bradley's stellar observations to produce precise positions for some 3,222 stars.
This work attracted considerable attention, and in January 1810, at the age of 25, Bessel was appointed director of the new founded Königsberg Observatory by King 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 French Academy of Sciences in 1811. Bessel 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, in the 1830s there was a fierce competition between astronomers to be the first to measure a stellar parallax accurately. 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 is 10.3 ly away. Given the current measurement of 11.4 ly, Bessel's figure had an error of 9.6%. 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's "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.
An additional responsibility of Bessel at Königsberg was geodesy. Bessel published a method for solving the geodesic problem; he was responsible for the survey of East Prussian which joined the Prussian and Russian trianguation networks; and he obtained an accuracy estimate for the figure of the earth, nowadays referred to as the Bessel ellipsoid.
Despite lacking a university education, Bessel was a major figure in astronomy during his lifetime. He was elected a fellow of the Royal Society, a foreign member of the Royal Swedish Academy of Sciences in 1823, and the largest crater in the Moon's Mare Serenitatis is named Bessel after him. Bessel's work in 1840 contributed in some degree to the discovery of Neptune. In 1832, he was elected a Foreign Honorary Member of the American Academy of Arts and Sciences. Bessel won the Gold Medal of the Royal Astronomical Society in 1829 and 1841.
In the second decade of the 19th century while studying the dynamics of 'many-body' gravitational systems, Bessel developed what are now known as Bessel functions. Critical for the solution of certain differential equations, these functions are used throughout both classical and quantum physics. Even in the absence of any work in astronomy, Bessel's role in developing the functions which now bear his name would have, by itself, placed him among the most significant and influential mathematicians of the 19th century.
Bessel is responsible for the correction to the formula for the sample variance estimator named in his honour. This is the use of the factor n-1 in the denominator of the formula, rather than just n. This occurs when the sample mean rather than the population mean is used to centre the data and since the sample mean is a linear combination of the data the residual to the sample mean overcounts the number of degrees of freedom by the number of constraint equations — in this case one.
He died in the spring of 1846 in Königsberg from retroperitoneal fibrosis. This was several months short of the discovery of Neptune in the fall of that year, by his colleagues at Berlin Observatory.
- Fundamenta Astronomiæ (1818)
- Tabulæ Regiomontanæ (1830)
- Bessel, F. W. (1838). "Bestimmung der Entfernung des 61sten Sterns des Schwans" [Determination of the distance to 61 Cygni]. Astronomische Nachrichten (in German) 16 (365–366): 65–96. Bibcode:1838AN.....16...65B. doi:10.1002/asna.18390160502.
- Bessel, F. W. (1838b). "On the parallax of 61 Cygni". Monthly Notices of the Royal Astronomical Society 4: 152–161. Bibcode:1838MNRAS...4..152B.
- "A brief history of light years". National Geographic. Retrieved 14 August 2013.
- Bessel, F. W. (1844a). "Ueber Veränderlichkeit der eigenen Bewegungen der Fixsterne" [Variations of the proper motions of the fixed stars]. Astronomische Nachrichten (in German) 22 (514): 145–160. Bibcode:1844AN.....22..145B. doi:10.1002/asna.18450221002.
- Bessel, F. W. (1844b). "Ueber Veränderlichkeit der eigenen Bewegungen der Fixsterne (Fortsetzung)" [Variations of the proper motions of the fixed stars (continued)]. Astronomische Nachrichten (in German) 22 (515): 169–184. Bibcode:1844AN.....22..169B. doi:10.1002/asna.18450221202.
- Bessel, F. W. (1844c). "On the variations of the proper motions of Procyon and Sirius". Monthly Notices of the Royal Astronomical Society 6: 136–141. Bibcode:1844MNRAS...6R.136B.
- Viik, T. (2006). "F.W. Bessel and Geodesy". Struve Geodetic Arc 2006 International Conference: The Struve Arc and Extensions in Space and Time. August 13–15, 2006. Haparanda and Pajala, Sweden: Lantmäteriet, Gävle, Sweden, 2006. pp. 53–63.
- Bessel, F. W. (2010) . "The calculation of longitude and latitude from geodesic measurements". . Translated by C. F. F. Karney & R. E. Deakin. Astronomische Nachrichten 331 (8): 852–861. arXiv:0908.1824. doi:10.1002/asna.201011352. English translation of Astron. Nachr. 4, 241–254 (1825). Errata.
- Bessel, F. W.; Baeyer, J. J. (1838). Gradmessung in Ostpreussen und ihre Verbindung mit Preussischen und Russischen Dreiecksketten [The East Prussian Survey and its connection with the Prussian and Russian networks] (in German). Berlin: Dümmler.
- Bessel, F. W. (1837). "Bestimmung der Axen des elliptischen Rotationssphäroids, welches den vorhandenen Messungen von Meridianbögen der Erde am meisten entspricht" [Estimation of the axes of the ellipsoid through measurements of the meridian arc]. Astronomische Nachrichten (in German) 14 (333): 333–346. Bibcode:1837AN.....14..333B. doi:10.1002/asna.18370142301.
- Bessel, F. W. (1841). "Ueber einen Fehler in der Berechnung der französischen Gradmessung und seinen Einfluß auf die Bestimmung der Figur der Erde" [Concerning an error in the calculation of the French survey and its influence on the determination of the figure of the Earth]. Astronomische Nachrichten (in German) 19 (438): 97–116. Bibcode:1841AN.....19...97B. doi:10.1002/asna.18420190702.
- "Book of Members, 1780–2010: Chapter B". American Academy of Arts and Sciences. Retrieved 24 June 2011.
- "Bessel's Tod" [Bessel's death]. Astronomische Nachrichten (in German) 24 (556): 49–52. 1846. Bibcode:1846AN.....24...49B. doi:10.1002/asna.18460240402.
- John Frederick William Herschel, A brief notice of the life, researches, and discoveries of Friedrich Wilhelm Bessel, London: Barclay, 1847 (on-line)
- Karl Christian Bruhns (1875), "Bessel, Friedrich Wilhelm", Allgemeine Deutsche Biographie (ADB) (in German) 2, Leipzig: Duncker & Humblot, pp. 558–567
- "Bessel, Friedrich Wilhelm". New International Encyclopedia. 1905.
- Fricke, Walter (1970–80). "Bessel, Friedrich Wilhelm". Dictionary of Scientific Biography 2. New York: Charles Scribner's Sons. pp. 97–102. ISBN 0684101149.
- O'Connor, John J.; Robertson, Edmund F., "Friedrich Bessel", MacTutor History of Mathematics archive, University of St Andrews.
- Friedrich Bessel at the Mathematics Genealogy Project
- "Bessel, Friedrich Wilhelm". The Nuttall Encyclopædia. 1907.