The Birthday of Annie Jump Cannon (1863) – Mathematics of Stellar Classification

Cannon classified over 350,000 stars (Harvard Classification, OBAFGKM). She used algebra and statistics to order stars by temperature. The sequence is a one‑dimensional parameter (effective temperature) – a mapping from spectrum to number. She also discovered 300 variable stars. Her work turned astronomy from description to a quantitative science. The number 346 = 2 × 173, both primes. Cannon’s work shows that classification (putting things in order) is mathematics at its most fundamental.