Work Friedrich Bessel

königsberg observatory 1830

while observatory still in construction bessel elaborated fundamenta astronomiae based on bradley s observations. preliminary result produced tables of atmospheric refraction won him lalande prize french academy of sciences in 1811. königsberg observatory began operation in 1813.

starting in 1819, bessel determined position of on 50,000 stars using meridian circle reichenbach, assisted of qualified students. prominent of them friedrich wilhelm argelander.

with work done, bessel able achieve feat best remembered today: credited being first use parallax in calculating distance star. astronomers had believed time parallax provide first accurate measurement of interstellar distances—in fact, in 1830s there fierce competition between astronomers first measure stellar parallax accurately. in 1838 bessel won race, announcing 61 cygni had parallax of 0.314 arcseconds; which, given diameter of earth s orbit, indicated star 10.3 ly away. given current measurement of 11.4 ly, bessel s figure had error of 9.6%. @ same time friedrich georg wilhelm struve , thomas henderson measured parallaxes of vega , alpha centauri.

as helping determine parallax of 61 cygni, bessel s precise measurements using new meridian circle adolf repsold allowed him notice deviations in motions of sirius , procyon, deduced must caused gravitational attraction of unseen companions. announcement of sirius s dark companion in 1844 first correct claim of unobserved companion positional measurement, , led discovery of sirius b.

bessel first scientist realized effect later called personal equation, several simultaneously observing persons determine different values, recording transition time of stars.

in 1824, bessel developed new method calculation circumstances of eclipses using so-called besselian elements. method simplified calculation such extent, without sacrificing accuracy, still in use today.

bessel s work in 1840 contributed discovery of neptune in 1846 @ berlin observatory, several months after bessel s death. on bessel s proposal (1825) prussian academy of sciences started edition of berliner akademische sternkarten (berlin academic star charts) international project. 1 unpublished new chart enabled johann gottfried galle find neptune near position calculated leverrier in 1846.

in second decade of 19th century while studying dynamics of many-body gravitational systems, bessel developed known bessel functions. critical solution of differential equations, these functions used throughout both classical , quantum physics.

bessel responsible correction formula sample variance estimator named in honour. use of factor n − 1 in denominator of formula, rather n. occurs when sample mean rather population mean used centre data , since sample mean linear combination of data residual sample mean overcounts number of degrees of freedom number of constraint equations — in case one. (also see bessel s correction).

an additional field of work geodesy. bessel published method solving main geodesic problem. responsible survey of east prussia joined prussian , russian triangulation networks , obtained estimate of increased accuracy figure of earth, nowadays referred bessel ellipsoid.

despite lacking university education, bessel major figure in astronomy during lifetime. elected member of prussian academy of sciences in 1812, french academy of sciences in 1816, foreign member of royal swedish academy of sciences in 1823, , fellow of royal society in 1825. in 1832, elected foreign honorary member of american academy of arts , sciences. in 1827 bessel became member of royal institute of netherlands, predecessor of royal netherlands academy of arts , sciences.

bessel won gold medal of royal astronomical society twice in 1829 , 1841.

the largest crater in moon s mare serenitatis , main-belt asteroid 1552 bessel named in honour.