Nancy Grace Roman

Ezzy Pearson celebrates a scientist whose legacy can be felt across all astronomy

- Ezzy Pearson

Nancy Grace Roman (16 May 1925 -25 December 2018) not only laid the groundwork for our understanding of how galaxies grow but also founded NASA's space astronomy programme, becoming 'the mother of Hubble'.

Roman's love of the stars was evident from an early age, and she set up an astronomy club for her friends when she was just 10. However, when she told her guidance counsellor she wanted to be a professional astronomer, she was asked, "What lady would take mathematics instead of Latin?".

Ignoring this discouragement, she went on to attain her degree from Swarthmore University before moving to the University of Chicago's Yerkes Observatory for her PhD. Here she studied the motions of stars which formed in the same cluster as the Plough, but which had drifted apart over time.

Later, Roman expanded this research to all Sun-like stars visible to the naked eye and soon noticed that where stars orbited in the Milky Way was connected to their metallicity. Metals (meaning anything heavier than helium in astronomy) are only formed inside stars, so if a star contains a lot of metal it must have been born after several generations of previous stars had already produced them. Younger, metal-rich stars tended to move in circular orbits near our Galaxy's centre, while older, metal-poor stars were further out.

This connection was the first clue towards understanding how the Milky Way grows over time, providing the foundation for modern studies of galactic evolution. Her work also developed a method of gauging stellar metallicities by comparing their brightness at blue and ultraviolet wavelengths, which is still used today.