Who they are
Harlow Shapley supplied the luminosity calibration Hubble used to turn Cepheid periods into estimates of distance. This built on the relation established by Henrietta Leavitt. His contribution in the linked milestone is the calibration connecting observed stellar behavior to the scale used for locating spiral nebulae.
He shows how Hubble’s distance argument depended on earlier astronomical work.
Selected contributions
- Provided the period–luminosity calibration used in Hubble’s Cepheid analysis.Source ↗
Primary records
Academic paper · 1925
Cepheids in Spiral Nebulae
Hubble uses Cepheid variables and an existing luminosity calibration to place spiral nebulae beyond the Milky Way. The paper records the distance argument, which is distinct from his later velocity–distance study.
Reading scope & citation
Reuses documented prior inspection: Selected original pages visually read as screenshots; the complete plate-measurement reduction was not reconstructed.
In the timeline
Biography sources & portrait credit
- Cepheids in Spiral Nebulae ↗The Observatory 48, 139–142; SAO/NASA Astrophysics Data System scan
Portrait credit
Unknown photographer. Public domain (U.S. federal government work). Via Wikimedia Commons.
Photograph. Cropped to 4:5, resized to 320 × 400 and converted to WebP.
Image source & identification ↗ · Public domain (U.S. federal government work) ↗
