The PRESS Pad

On the night of October 5–6, 1923, American astronomer Edwin Hubble, working with the 100-inch Hooker Telescope at Mount Wilson Observatory, photographed what was then called the Andromeda Nebula. One apparently ordinary point of light on that photographic plate would transform astronomy. The object, subsequently designated M31-V1 or V1, was a Cepheid variable star. By measuring its changing brightness, Hubble showed that Andromeda was far beyond the known dimensions of the M