- The Cepheid found in Andromeda by Hubble had been discovered earlier by Milton Humason. But when he showed the marked image to Harlow Shapley - who had argued that the Milky Way *is* the entire universe - Shapley erased the marks.
- VAR! In the early morning hours #OTD in 1923, Edwin Hubble took a photo plate of M31 that showed a Cepheid variable star. Using Henrietta Swan Leavitt’s distance-luminosity relationship, Hubble concluded that M31 is another galaxy outside the Milky Way. 🧪 🔭 ⚛️ Image: Carnegie Observatories
