William Parsons, 3rd Earl of Rosse
William Parsons, 3rd Earl of Rosse (1800-1867)
(public domain image)
An Irish astronomer and Chancellor of Trinity College, Dublin between 1862 and 1867. He was also a member of parliament and president of the Royal Society (1848–1854).
He built the world's largest telescope of the day and used it to investigate the nature of nebulae, discovering the spiral structure of many galaxies and attempting to prove that all nebulae were many dim, unresolved stars.