Allan R. Sandage, 18 June 1926 - 13 November 2010

TL;DR

Allan Sandage was a pioneering observational astronomer who significantly revised the cosmic distance scale, clarified the universe's expansion, and contributed to stellar evolution and galactic formation studies through extensive observations and analysis.

Contribution

The paper details Sandage's groundbreaking work in refining the universe's distance measurements, correcting Hubble's analysis, and establishing key insights into stellar and galactic evolution.

Findings

Revised the cosmic distance scale and confirmed universe expansion.

Discovered the error in Hubble's original interpretation of redshifts.

Contributed to understanding stellar evolution and galaxy formation.

Abstract

Allan Sandage was an observational astronomer who was happiest at a telescope. On Hubble's sudden death Allan Sandage inherited the programmes using the world's largest optical telescope at Palomar to determine the distances and number counts of galaxies. Over many years he greatly revised the distance scale and, on re-working Hubble's analysis, discovered the error that had led Hubble to doubt the interpretation of the galaxies' redshifts as an expansion of the universe. Sandage showed that there was a consistent age of Creation for the stars, the elements, and the Cosmos. Through work with Baade and Schwarzschild he discovered the key to the interpretation of the colour-magnitude diagrams of star clusters in terms of stellar evolution. With others he founded Galactic Archaeology, interpreting the motions and elemental abundances of the oldest stars in terms of a model for the Galaxy's formation. He published several fine atlasses and catalogues of galaxies and a definitive history of the Mount Wilson Observatory.