What if the modern universe still speaks in an alphabet written by a woman history almost sidelined? Before black holes trended in headlines and telescopes orbited Earth, astronomy faced a crisis of excess. Spectral lines multiplied. Photographic plates piled up. The stars were catalogued—but not understood. Into this disorder stepped Annie Jump Cannon , a deaf astronomer working at Harvard College Observatory , who imposed coherence on chaos. Between 1901 and 1924, Cannon classified over 350,000 stars and reordered the stellar alphabet into the now-universal sequence O, B, A, F, G, K, M. It was not clerical labor. It was architectural. Her system constrained how stellar temperature, luminosity, and composition would be theorized for generations. This book argues something sharper than celebration: classification is power. By deciding which differences mattered, Cannon shaped astrophysics itself. Inside, you’ll encounter: The intellectual battles behind the Henry Draper Catalogue - The methodological tensions between Williamina Fleming, Antonia Maury, and Cannon - How Cecilia Payne-Gaposchkin made Cannon’s sequence physically legible - The infrastructural dominance that made Harvard’s system global - Why machine-learning surveys like Gaia still rely on her grammar Cannon did not theorize ionization equilibria. She did something more foundational: she stabilized the language in which theory could speak. If you care about the architecture beneath scientific revolutions—about who fixes the syntax of knowledge—this book belongs on your shelf.