Jones, Harold Spencer (1890–1960)

British astronomer. He worked at the Royal Observatory, Greenwich, 1913–23, and the Cape of Good Hope 1923–33, and was the tenth Astronomer Royal 1933–55. Knighted 1943.

He was responsible for organizing the successful international campaign to redetermine the astronomical unit (the mean distance of the Sun) by observing the asteroid Eros during its near approach 1931. As Astronomer Royal he was responsible for moving the observatory from Greenwich to Herstmonceux Castle in Sussex, and for greatly enlarging its scope and equipment in timekeeping.

He was born in London and educated in London and Cambridge. He made an extensive spectroscopic study of Nova Pictoris, and initiated two major programmes, one for determining the distances of stars by measuring their trigonometrical parallax, the other for determining a large number of proper motions by reobserving the position of stars photographically. His study of the deviations in the motions of the Sun, Moon, and planets, published 1939, was the first convincing demonstration of the irregularities in the Earth's rate of rotation. He published many technical papers and several books, and received many honours, among them Fellow of the Royal Society 1931, and the presidency of the International Astronomical Union 1945–48.