Annie Jump Cannon was an American astronomer whose work as a computer and star identifier was instrumental in the development of contemporary stellar classification. Her system of ranking stars as O, B, A, F, G, K or M, with "O" being the hottest stars and "M" the coolest is still used today.

References
Payne Gaposchkin, Cecilia. “Annie Jump Cannon.” Science, 1941, 93:2419, 444
Mack, Pamela Etter. “Women in Astronomy in the United States 1875-1920” (1977). Publications. 7, 21
Welther, Barbara L. “Highlights of an Exhibit to Honor Annie Jump Cannon.” 87
Greenstein, George. “The Ladies of Observatory Hill: Annie Jump Cannon and Cecilia Payne-Gaposchkin.” The American Scholar, 1993, 62:3, 444
Bowler, Sue. “Annie Jump Cannon, Stellar Astronomer.” Astronomy & Geophysics. 2016, 57:3. 3.14