Thomas Henderson

FRSE Fellowship of the Royal Society of Edinburgh (FRSE) is an award granted to individuals that the Royal Society of Edinburgh, Scotland's national academy of science and Literature, letters, judged to be "eminently distinguished in their subject". ...

FRS FRAS (28 December 1798 – 23 November 1844) was a Scottish astronomer and mathematician noted for being the first person to measure the distance to

Alpha Centauri Alpha Centauri (, α Cen, or Alpha Cen) is a star system in the southern constellation of Centaurus (constellation), Centaurus. It consists of three stars: Rigil Kentaurus (), Toliman (), and Proxima Centauri (). Proxima Centauri ...

, the major component of the nearest stellar system to Earth, the first to determine the

parallax Parallax is a displacement or difference in the apparent position of an object viewed along two different sightline, lines of sight and is measured by the angle or half-angle of inclination between those two lines. Due to perspective (graphica ...

of a fixed star, and for being the first Astronomer Royal for Scotland.

Early life

Born in

Dundee Dundee (; ; or , ) is the List of towns and cities in Scotland by population, fourth-largest city in Scotland. The mid-year population estimate for the locality was . It lies within the eastern central Lowlands on the north bank of the Firt ...

, he was educated at the

High School of Dundee The High School of Dundee is a private, co-educational, day school in Dundee, Scotland, which provides nursery, primary and secondary education to just over one thousand pupils. Its foundation has been dated to 1239, and it is the only private sc ...

, 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 lunar

occultation An occultation is an event that occurs when one object is hidden from the observer by another object that passes between them. The term is often used in astronomy, but can also refer to any situation in which an object in the foreground blocks f ...

to measure

longitude Longitude (, ) is a geographic coordinate that specifies the east- west position of a point on the surface of the Earth, or another celestial body. It is an angular measurement, usually expressed in degrees and denoted by the Greek lett ...

he came to the attention of Thomas Young, superintendent of the

Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

's "Nautical Almanac". Young helped the young 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 at the Royal Observatory at the

Cape of Good Hope The Cape of Good Hope ( ) is a rocky headland on the Atlantic Ocean, Atlantic coast of the Cape Peninsula in South Africa. A List of common misconceptions#Geography, common misconception is that the Cape of Good Hope is the southern tip of Afri ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

. 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 by Manuel John Johnson of the East India Company's observatory on

Saint Helena Saint Helena (, ) is one of the three constituent parts of Saint Helena, Ascension and Tristan da Cunha, a remote British overseas territory. Saint Helena is a volcanic and tropical island, located in the South Atlantic Ocean, some 1,874 km ...

that the bright southern star

had a large

proper motion Proper motion is the astrometric measure of changes in the apparent places of stars or other celestial objects as they move relative to the center of mass of the Solar System. It is measured relative to the distant stars or a stable referenc ...

, and Henderson concluded that it might be relatively close. The 1830s version of the "space race" was to be the first person to measure the distance to a star using

, 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 The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

due to bad health, he began analysing his measurements and eventually came to the conclusion that Alpha Centauri was just slightly less than one

parsec The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to or (AU), i.e. . The parsec unit is obtained by the use of parallax and trigonometry, and ...

away, 3.25

light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...

s. This figure is reasonably accurate, being 25.6% too small. Henderson did not immediately publish his results, 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 Friedrich Wilhelm Bessel (; 22 July 1784 – 17 March 1846) was a German astronomer, mathematician, physicist, and geodesist. He was the first astronomer who determined reliable values for the distance from the Sun to another star by the method ...

, who published a parallax of 10.3 light years (9.6% too small) for

61 Cygni 61 Cygni is a binary star system in the constellation Cygnus (constellation), Cygnus, consisting of a pair of K-type main-sequence star, K-type dwarf stars that orbit each other in a period of about 659 years. Of apparent magnitu ...

in 1838. Henderson published his results in 1839, but was relegated to second place because of his lack of confidence. He later published confirming observations by

Thomas Maclear Thomas Maclear (17 March 1794 – 14 July 1879) was an Ireland, Irish-born Cape Colony astronomer who became Her Majesty's astronomer at the Cape of Good Hope. Early life Born on 17 March 1794, in Newtownstewart, the eldest son of Rev. James ...

. Alpha Centauri remained the nearest known star until the discovery of

Proxima Centauri Proxima Centauri is the nearest star to Earth after the Sun, located 4.25 light-years away in the southern constellation of Centaurus. This object was discovered in 1915 by Robert T. A. Innes, Robert Innes. It is a small, low-mass st ...

in 1915 by

Robert T. A. Innes Robert Thorburn Ayton Innes FRSE FRAS (10 November 1861 – 13 March 1933) was a British-born South African astronomer best known for discovering Proxima Centauri in 1915, and numerous binary stars. He was also the first astronomer to have see ...

Scotland

Thomas Henderson memorial on Calton Hill

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 the

University of Edinburgh The University of Edinburgh (, ; abbreviated as ''Edin.'' in Post-nominal letters, post-nominals) is a Public university, public research university based in Edinburgh, Scotland. Founded by the City of Edinburgh Council, town council under th ...

was given to him on the advice of Prime Minister

Lord Melbourne Henry William Lamb, 2nd Viscount Melbourne (15 March 177924 November 1848) was a British Whig politician who served as the Home Secretary and twice as the Prime Minister of the United Kingdom. His first premiership ended when he was dismissed ...

. From 1834 he worked at the City Observatory (then called the Calton Hill Observatory) in Edinburgh until his death.Encyclopædia Britannica online
Retrieved 20 March 2013. In April, 1840 he was elected a

Fellow of the Royal Society Fellowship of the Royal Society (FRS, ForMemRS and HonFRS) is an award granted by the Fellows of the Royal Society of London to individuals who have made a "substantial contribution to the improvement of natural science, natural knowledge, incl ...

. Henderson became a member or fellow of several distinguished societies, including the

Royal Astronomical Society The Royal Astronomical Society (RAS) is a learned society and charitable organisation, charity that encourages and promotes the study of astronomy, planetary science, solar-system science, geophysics and closely related branches of science. Its ...

(1832) and the

Royal Society of Edinburgh The Royal Society of Edinburgh (RSE) is Scotland's national academy of science and letters. It is a registered charity that operates on a wholly independent and non-partisan basis and provides public benefit throughout Scotland. It was establis ...

(1834).

Personal life and death

He married

Alexander Adie Alexander James Adie FRSE MWS (7 November 1775, Edinburgh – 4 December 1858, Edinburgh) was a Scottish maker of medical instruments, optician and meteorologist. He was the inventor of the sympiesometer, patented in 1818. Life He was born t ...

's daughter Janet Mary Adie (1808–1842) in 1836 and had one daughter, Janet Mary Jane Henderson (1842–1893) who is buried in the

Grange Cemetery The Grange (originally St Giles' Grange) is an affluent suburb of Edinburgh, just south of the city centre, with Morningside and Greenhill to the west, Newington to the east, The Meadows park and Marchmont to the north, and Blackford Hi ...

. He died at home 1 Hillside Crescent in Edinburgh on 23 November 1844 and is buried in

Greyfriars Kirkyard Greyfriars Kirkyard is the graveyard surrounding Greyfriars Kirk in Edinburgh, Scotland. It is located at the southern edge of the Old Town, Edinburgh, Old Town, adjacent to George Heriot's School. Burials have been taking place since the late 1 ...

. The grave may be either in the grave of

or in a grave marked by the stone "to his memory". His name is not recorded on the Adie grave; Adie himself died 14 years after Henderson.

Recognition

A blue plaque is installed on his house at 1 Hillside Crescent. It refers to him as "Thomas J. A. Henderson", similar to middle names wrongly added to Wikipedia around 2007. A larger memorial (naming him "Thomas Henderson") is incorporated in the external wall of the City Observatory.

Asteroid An asteroid is a minor planet—an object larger than a meteoroid that is neither a planet nor an identified comet—that orbits within the Solar System#Inner Solar System, inner Solar System or is co-orbital with Jupiter (Trojan asteroids). As ...

3077 Henderson is named in his honour.

Publications

* *

References

External links

Astronomical Society of Edinburgh - journal 38
* {{DEFAULTSORT:Henderson, Thomas 1798 births 1844 deaths 19th-century Scottish scientists 19th-century British astronomers Scientists from Dundee People educated at the High School of Dundee Academics of the University of Edinburgh

Thomas Thomas may refer to: People * List of people with given name Thomas * Thomas (name) * Thomas (surname) * Saint Thomas (disambiguation) * Thomas Aquinas (1225–1274) Italian Dominican friar, philosopher, and Doctor of the Church * Thomas the A ...

Fellows of the Royal Society of Edinburgh Fellows of the Royal Society Fellows of the Royal Astronomical Society Scottish astronomers 19th-century Scottish lawyers 19th-century Scottish mathematicians Burials at Greyfriars Kirkyard South African astronomers