Daniel Kirkwood (1814-1895), US astronomer and mathematician. Kirkwood started his career as a school teacher before moving into university eduction. From 1856 to 1886, he was mathematics professor at Indiana University, where the observatory is named after him. Kirkwood is best known for his work in astronomy, especially his study of asteroids. He discovered patterns in the orbits of the main-belt asteroids, and identified gaps in the asteroid belt now known as Kirkwood gaps in his honour. He became a lecturer in astronomy at Stanford University in 1891 at the age of 77. This image is from volume 1 (1893) of the US magazine Popular Astronomy.