William Jacob

William Stephen Jacob (1813–1862) was an English immigrant astronomer in India, who acted as the director of the Madras Observatory from 1848 to 1859. His early claim of 1855 to have detected an exoplanet, in orbit around 70 Ophiuchi, is now thought to have been mistaken.

Life The seventh child of Stephen Long Jacob (1764–1851), vicar of Woolavington, Somerset, he was born at his father's vicarage on 19 November 1813; John Jacob (1812–1858) was his brother, and Sir George le Grand Jacob a cousin. He entered Addiscombe College as an East India Company cadet in 1828, passed for the engineers, and completed his military education at Royal Engineer Establishment, Chatham.

After Jacob's arrival at Bombay in 1831, he spent some years with the Great trigonometrical survey in the North-West Provinces, and established a private observatory at Pune in 1842. In 1843 he went back to England on furlough, married in 1844, and returned in 1845 to India, but left the company's service on attaining the rank of captain in the Bombay engineers. His project of erecting a mountain observatory at Pune was funded by parliament in 1862. He engaged to work there for three years with a 9-inch equatorial, his own purchase from Noël Paymal Lerebours, and landed at Bombay on 8 August, but died on reaching Pune on 16 August 1862, aged 48. He was elected a fellow of the Royal Astronomical Society in 1849. While these anomalies are now thought to have other causes, this was the first serious claim by an astronomer to have detected an exoplanet using scientific methods: 100 years before the first exoplanet was conclusively detected and well before the science of exoplanets was even in its infancy. Professor David Kipping states that the ‘“claim is so remarkable because Jacob was making tiny measurements (80 milliarc seconds or 22 millionths of a degree) with the naked eye, at a time when he wasn’t even sure whether Newton’s law of gravity held sway in distant parts of the galaxy. While Jacob... was ultimately proved wrong, he had the audacity to try.”

Family Jacob married in 1844, Elizabeth, fourth daughter of Mathew Coates of Gainsborough, who survived him. They had six sons and two daughters.