# Friedrich Bessel

BesselFriedrich Wilhelm BesselBesselgymnasiumF.W. BesselBessel, Friedrich WilhelmFrederik Wilhelm BesselBessel, Friedrich
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist and geodesist.wikipedia
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### Bessel function

spherical Bessel functionBesselmodified Bessel function
A special type of mathematical functions were named Bessel functions after Bessel's death, though they had originally been discovered by Daniel Bernoulli and then generalised by Bessel.
Bessel functions, first defined by the mathematician Daniel Bernoulli and then generalized by Friedrich Bessel, are the canonical solutions

### Parallax

solar parallaxmotion parallaxtrigonometric parallax
He was the first astronomer who determined reliable values for the distance from the sun to another star by the method of parallax.
The first successful measurements of stellar parallax were made by Friedrich Bessel in 1838 for the star 61 Cygni using a heliometer.

### Astronomy

astronomicalastronomerastronomers
This in turn led to an interest in astronomy as a way of determining longitude.
The distance to a star was announced in 1838 when the parallax of 61 Cygni was measured by Friedrich Bessel.

One of their sons was the renowned Egyptologist Adolf Erman.
Born in Berlin, he was the son of Georg Adolf Erman and grandson of Paul Erman and Friedrich Bessel.

### Stellar parallax

parallax shiftparallaxparallax method
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.
It was first observed in 1806 by Giuseppe Calandrelli who reported parallax in α-Lyrae in his work "Osservazione e riflessione sulla parallasse annua dall’alfa della Lira". Then in 1838 Friedrich Bessel made the first successful parallax measurement ever, for the star 61 Cygni, using a Fraunhofer heliometer at Königsberg Observatory.

### 61 Cygni

61 Cygni A61 Cyg61 Cyg B
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.
In 1838, Friedrich Bessel measured its distance from Earth at about 10.4 light-years, very close to the actual value of about 11.4 light-years; this was the first distance estimate for any star other than the Sun, and first star to have its stellar parallax measured.

### Carl Friedrich Gauss

GaussGauss, Carl FriedrichC.F. Gauss
On the recommendation of fellow mathematician and physicist Carl Friedrich Gauss (with whom he regularly corresponded) he was awarded an honorary doctor degree from the University of Göttingen in March 1811.
On Gauss's recommendation, Friedrich Bessel was awarded an honorary doctor degree from Göttingen in March 1811.

### Friedrich Wilhelm Argelander

ArgelanderFriedrich W. ArgelanderFriedrich Argelander
The most prominent of them was Friedrich Wilhelm Argelander.
He studied with Friedrich Bessel, and obtained his Ph.D. in 1822 at University of Königsberg.

### Vega

2828constellation of VegaWhānui
Nearly at the same time Friedrich Georg Wilhelm Struve and Thomas Henderson measured the parallaxes of Vega and Alpha Centauri.
Friedrich Bessel was skeptical about Struve's data, and, when Bessel published a parallax of 0.314″ for the star system 61 Cygni, Struve revised his value for Vega's parallax to nearly double the original estimate.

### Bessel ellipsoid

Bessel 18411841 Bessel ellipsoidBessel 1830
nowadays referred to as the Bessel ellipsoid.
The Bessel ellipsoid was derived in 1841 by Friedrich Wilhelm Bessel, based on several meridian arcs and other data of continental geodetic networks of Europe, Russia and the British Survey of India.

### Gotthilf Hagen

G. H. L. Hagen
Bessel married Johanna, the daughter of the chemist and pharmacist Karl Gottfried Hagen who was the uncle of the physician and biologist Hermann August Hagen and the hydraulic engineer Gotthilf Hagen, the latter also Bessel's student and assistant from 1816 to 1818.
In 1816 Hagen began studying mathematics and astronomy with Friedrich Wilhelm Bessel, but in 1818 he switched to study civil engineering as he was more attracted to applied than theoretical science.

### Gold Medal of the Royal Astronomical Society

Gold MedalGold Medal of the RASGold Medal for Astrophysics
Bessel won the Gold Medal of the Royal Astronomical Society twice in 1829 and 1841.

### List of things named after Friedrich Bessel

full list here
This is a (partial) list of things named for Friedrich Wilhelm Bessel, a 19th-century German scholar who worked in astronomy, geodesy and mathematical sciences:

### Sirius

As well as helping determine the parallax of 61 Cygni, Bessel's precise measurements using a new meridian circle from Adolf Repsold 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.
There were several unsuccessful attempts to measure the parallax of Sirius: by Jacques Cassini (6 seconds); by some astronomers (including Nevil Maskelyne) using Lacaille's observations made at the Cape of Good Hope (4 seconds); by Piazzi (the same amount); using Lacaille's observations made at Paris, more numerous and certain than those made at the Cape (no sensible parallax); by Bessel (no sensible parallax).

### 1552 Bessel

The largest crater in the Moon's Mare Serenitatis and the main-belt asteroid 1552 Bessel were named in his honour.
It was discovered on 24 February 1938, by Finnish astronomer Yrjö Väisälä at Turku Observatory in Southwest Finland, and named after German astronomer Friedrich Bessel.

### Geodesy

geodeticgeodesistgeodesic
Friedrich Wilhelm Bessel (22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist and geodesist.
Friedrich Wilhelm Bessel 1784–1846, Königsberg (Germany)

### Berlin Observatory

Berlin-Babelsberg ObservatoryBerlina new observatory
Bessel's work in 1840 contributed to the discovery of Neptune in 1846 at Berlin Observatory, several months after Bessel's death.
When the time came to seek a successor by virtue of Bode's retirement, both Carl Friedrich Gauß and Friedrich Wilhelm Bessel turned the post down.

### Minden

Minden-on-the-Wesertown in the North Rhine–WestphaliaMinden (in Westfalen)
Bessel was born in Minden, Westphalia, administrative center of Minden-Ravensberg, as second son of a civil servant.
The town keeps three schools of higher secondary education: the Herdergymnasium, Besselgymnasium and Ratsgymnasium; three other secondary schools, the Freiherr-von-Vincke-Realschule, Käthe-Kollwitz-Realschule and the main school (Hauptschule Todtenhausen); a comprehensive school, the Kurt-Tucholsky-Gesamtschule and various elementary schools, special schools and occupational training schools.

### Heinrich Wilhelm Matthias Olbers

OlbersH. W. OlbersHeinrich Olbers
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, using old observation data taken from Thomas Harriot and Nathaniel Torporley in 1607.
In July 1804 the young Friedrich Wilhelm Bessel contacted Olbers to get his opinion of Bessel's treatise on orbit calculation of Halley's comet.

### Bessel's correction

Bessel-corrected
(Also see Bessel's correction).
This technique is named after Friedrich Bessel.

### Franz Ernst Neumann

NeumannFranz NeumannF. Neumann
The physicist Franz Ernst Neumann, Bessel's close companion and colleague, was married to Johanna Hagen's sister Florentine.
In his section on mathematical physics Neumann taught mathematical methods and as well as the techniques of an exact experimental physics grounded in the type of precision measurement perfected by his astronomer colleague Friedrich Wilhelm Bessel.

### Johann Hieronymus Schröter

SchröterJohann H. SchröterJohann Hieronymus Schroeter
Two years later Bessel left Kulenkamp and became Johann Hieronymus Schröter's assistant at Lilienthal Observatory near Bremen.
His two famous assistant astronomers were Karl Ludwig Harding (1796–1804) and Friedrich Wilhelm Bessel (1806–1810).

### Halley's Comet

1P/HalleyHalleycomet
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, using old observation data taken from Thomas Harriot and Nathaniel Torporley in 1607.
Streams of vapour observed during the comet's 1835 apparition prompted astronomer Friedrich Wilhelm Bessel to propose that the jet forces of evaporating material could be great enough to significantly alter a comet's orbit.

### Atmospheric refraction

refractionrefractedastronomical refraction
As a preliminary result he produced tables of atmospheric refraction that won him the Lalande Prize from the French Academy of Sciences in 1811.
As early as 1830, Friedrich Bessel had found that even after applying all corrections for temperature and pressure (but not for the temperature gradient) at the observer, highly precise measurements of refraction varied by ±0.19′ at two degrees above the horizon and by ±0.50′ at a half degree above the horizon.

### Alpha Centauri

α CentauriAlphaα Centauri A
Nearly at the same time Friedrich Georg Wilhelm Struve and Thomas Henderson measured the parallaxes of Vega and Alpha Centauri.
He withheld his results, however, because he suspected they were too large to be true, but eventually published them in 1839 after Friedrich Wilhelm Bessel released his own accurately determined parallax for 61 Cygni in 1838.