Passage: Henrietta Swan Leavitt (; July 4, 1868 – December 12, 1921) was an American astronomer.  A graduate of Radcliffe College, she worked at the Harvard College Observatory as a "computer", tasked with examining photographic plates in order to measure and catalog the brightness of stars. This work led her to discover the relation between the luminosity and the period of Cepheid variables.  Leavitt's discovery provided astronomers with the first "standard candle" with which to measure the distance to faraway galaxies.  After her death, Edwin Hubble used Leavitt's luminosity–period relation, together with the galactic spectral shifts first measured by Vesto Slipher at Lowell Observatory, in order to establish that the universe is expanding (see Hubble's law).

Question: What was his job?
astronomer