Abetti, Giorgio (1882–1982)
Adams, John Couch (1819–1892)
Adams, Walter Sydney (1876–1956)
Airy, George Biddell (1801–1892)
Aitken, Robert Grant (1864–1951)
Al‐Battani, abu‐Abdullah Muhammad ibn‐Jabir (c. 850–c. 929)
Aldrin, Buzz (1930– )
al‐Farghānī, abu‐al‐Abbās Ahmad (lived 9th century AD)
Alpher, Ralph Asher (1921–2007)
al‐Sufi (903–986)