Adoption of Annie Jump Cannon's stellar classification system
On May 9th, 1922, the International Astronomical Union passed a resolution to adopt Annie Jump Cannon's stellar classification system.
Cannon was born in Delaware in 1863. As a child, she used to stargaze with her mom, who pushed her to study physics and astronomy. She achieved remarkable feats as one of the first women in astronomy, another field which was traditionally male-dominated. She was a suffragist and member of the National Women's Party.
The stellar spectral classification system she devised with Edward C. Pickering was a compromise among her colleagues' proposals. Still in use today, the system classifies stars based on their temperature and spectral type. It is believed Cannon classified around 350,000 stars!