Edgeworth, Kenneth Essex (1880–1972), soldier, engineer, economist, and astronomer, was born 26 February 1880 at Daramona House, Streete, Co. Westmeath, eldest child among two sons and a daughter of Thomas Newcomen Edgeworth (1850–1931) and Elizabeth Dupré (née Wilson; d. 1929), eldest daughter of John Wilson of Daramona. Thomas belonged to the junior branch of the Edgeworth family of Kilshrewly, Co. Longford, and shared with Richard Lovell Edgeworth (qv) a common ancestor in Sir John Edgeworth (1638–1701).
Kenneth Edgeworth was educated at home by governesses and at boarding schools in Cheshire and north Wales. At the age of 14 he won a scholarship to Marlborough College, where he excelled in mathematics. At Kilshrewly he enjoyed making steam engines in his father's workshop. As a teenager, he sometimes stayed with his uncle and aunt at Daramona House. His uncle, William Edward Wilson (qv), FRS, had a well equipped observatory and workshop, and they often discussed astronomical problems, including the search for a planet beyond Neptune.
At 17 Edgeworth joined the Royal Military Academy at Woolwich. In 1898 he obtained a commission in the Royal Engineers and joined the School of Military Engineering at Chatham, transferring to South Africa for the Boer war two years later. From 1902 he was stationed at Aldershot before serving in Somaliland, Egypt, the Sudan, Chatham, and Dublin. During the first world war he was in charge of a signals unit in France. He was awarded the DSO and MC and was three times mentioned in dispatches.
In 1920 he joined the Signals Training Centre at Maresfield, Sussex, and took command of a battalion at nearby Crowborough. He retired from the army in 1926 with the rank of lieutenant-colonel. During this period he attended meetings of the Institution of Electrical Engineers and he published several papers on wireless telegraphy. In 1931 Edgeworth became chief engineer in the Sudanese department of posts and telegraphs at Khartoum. After five years in this post, he resigned and returned to Ireland to live at Cherbury, Booterstown, Co. Dublin, his parents’ former home.
In retirement, Edgeworth turned his attention to economics and theoretical astronomy. He published four books on economics, and the ideas that he put forward have since been judged very progressive. However, it was theoretical astronomy that interested him most and over a twenty-three-year period he published a score of papers and letters, culminating in his book The Earth, the planets and the stars: their birth and evolution (1961). Edgeworth's astronomical work was concerned mainly with star formation and the origin and development of the solar system. In 1943 he published a paper, ‘The evolution of our planetary system’, in the Journal of the British Astronomical Association, where he suggested the existence of a vast reservoir of cometary material beyond the orbit of Neptune. This was seven years before Jan Oort made a similar suggestion and eight years before Gerard Kuiper presented his ideas on this topic. This reservoir of cometary material is generally known as the Kuiper Belt and the first object belonging to it was discovered in 1992 by D. C. Jewitt and J. X. Luu. Many more members of the Belt have since been detected and it is estimated that there are at least 70,000 trans-Neptunian objects with diameters greater than 100 km in the radial zone extending from 30AU to 50AU. These objects are confined to a thick band around the plane of the solar system.
Edgeworth died in Dublin 10 October 1972 at the age of 92. Although he was elected to membership of the RIA in 1948, the full significance of his astronomical research was not recognised till 1995. He was elected a fellow of the Royal Astronomical Society in 1903 and a member of the British Astronomical Association in 1943, and he also belonged to the Institution of Electrical Engineers.
He married (1917) Isabel Mary, widow of Arthur F. Eves and daughter of John Trench Pigott. Collections of his papers and other material are in the National Archives and the National Photographic Archive, Dublin.