Astronomer. Famous for being the first Astronomer Royal for Scotland, but more importantly, the first person to measure the distance to Alfa Centauri, a major component of the nearest stellar system to Earth, and the first to determine the parallax of a fixed star. Although he trained as a lawyer, his hobbies were astronomy and mathematics, which led him to come up with a new method of using lunar occultation to measure longitude. This brought him to the attention of Thomas Young, superintendent of the Royal Navy's "Nautical Almanac," who helped him enter the larger world of astronomical science. Upon Young's death, he was recommended to the Admiralty as the replacement, but was passed over. This recommendation, though, was enough to get him a position at the Royal Observatory at the Cape of Good Hope in South Africa, where he made a considerable number of stellar observations between April 1832 and May 1833. His measurement work at the Cape led him to be appointed the first Astronomer Royal for Scotland in 1834 and the vacant chair of astronomy at the University of Edinburgh was given to him on the advice of Prime Minister Lord Melbourne. From 1834 he worked at the City Observatory (then called the Calton Hill Observatory) in Edinburgh. Once back to the UK he began analyzing his measurements and eventually came to the conclusion that Alpha Centauri was just slightly less than one parsec away, 3.25 light years. He did not publish his results immediately, but at the end of the decade did so and was given full recognition. Alpha Centauri remained the nearest known star until the discovery of Proxima Centauri in 1915. A large memorial naming him is incorporated in the external wall of the City Observatory and a blue plaque is installed on his house in Edinburgh. Additionally, Asteroid 3077 Henderson is named in his honour.