- Thomas James Henderson
Thomas James Henderson (
28 December 1798 –23 November 1844 ) was a Scottish astronomer noted for being the first person to measure the distance toAlpha Centauri , the major component of the nearest stellar system toEarth , and for being the firstAstronomer Royal for Scotland .Early life
Born in
Dundee ,Scotland , he was educated at theHigh School of Dundee , after which he trained as a lawyer, working his way up through the profession as an assistant to a variety of nobles. However, his major hobbies were astronomy and mathematics, and after coming up with a new method for using lunaroccultation to measurelongitude he came to the attention of Thomas Young, superintendent of theRoyal Navy 's "Nautical Almanac". Young helped Henderson enter the larger world of astronomical science, and on his death a posthumous letter recommended to the Admiralty that Henderson take his place.Career
Africa
Henderson was passed over for that position, but the recommendation was enough to get him a position as the British observatory at the
Cape of Good Hope inSouth Africa . There he made a considerable number of stellar observations between April 1832 and May 1833, including those for which he is remembered today. It was pointed out to him that the bright southern star Alpha Centauri had a largeproper motion , and Henderson concluded that it might be a close star.The 1830s version of the "space race" was to be the first person to measure the distance to a star using
parallax , a task which is easier the closer the star. Henderson was thus in a good position to be this person. After retiring back to the United Kingdom due to bad health, he began analysing his measurements and eventually came to the conclusion that Alpha Centauri was just slightly less that oneparsec away, 3.25light year s. This figure is reasonably accurate, being 33.7% too small.Doubts about the accuracy of his instruments kept him from publishing, however (there had been previous, discredited attempts to claim a measurement of stellar parallax), and eventually he was beaten to the punch by
Friedrich Wilhelm Bessel , who published a parallax of 10.4 light years (9.6% too small) for61 Cygni in 1838. Henderson published his results in 1839, but was relegated to second place because of his lack of confidence.cotland
In the meantime, his measurement work at the Cape had led him to be appointed the first
Astronomer Royal for Scotland in 1834. The vacant chair of astronomy at theUniversity of Edinburgh was given to him on the advice of Prime MinisterLord Melbourne .From 1834 he worked at the
City Observatory, Edinburgh until his death. He is buried inGreyfriars Kirkyard . He also claimed a right to different types of astronomy.References
# [http://www.astronomyedinburgh.org/publications/journals/38/hend.html Astronomical Society of Edinburgh - journal 38]
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