M31, the Andromeda galaxy The Cepheid Distance Scale: A History

A critical review of the Cepheid distance scale, from its inception to the Hipparcos mission and beyond.

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Section 1: The Early Years of the Cepheid Distance Scale: Leavitt and Hertzsprung

1.1: Henrietta Leavitt’s Cepheid Variable Observations

1.2: Hertzsprung’s First Cepheid Distance Scale Calibration

Section 2: The Great debate and the Great mistake: Shapley, Hubble, Baade

2.1: A new Cepheid calibration by Shapley

2.2: Extragalactic distances obtained with Cepheid Variables

2.3: The Great Mistake: Two Cepheid populations

Section 3: Cepheid Period-Luminosity-Colour Relations: 1952-1980s

3.1: Semi-theoretical Approaches

3.2: PLC versus PL relations for Cepheids

3.3: Reddening and colour terms

3.4: A few notes on metallicity in Cepheids

3.5: Two Further Cepheid Calibrations

Section 4: The Modern Era

4.1: A New Emphasis in Cepheid Calibration

4.2: Demise of the PLC relation for Cepheids?

4.3: Multiwavelength Observations: CCD and near IR Coverage of Cepheids and other Variable Stars

4.4: Metallicity of Variable Stars

4.5: Hipparcos and the Cepheid zero-point calibration

Concluding Remarks on the Cepheid Distance Scale


Appendix:  A computer model of the PL relation for Cepheids


About this site

The Cepheid Distance Scale: A history is based upon a dissertation presented towards the award of MSc (astrophysics) at Queen Mary College, University of London. The original text contained extensive footnotes which have been removed for the sake of simplicity. They nevertheless clarified, and in many cases justified, certain points made in the text. If you have any questions or disagreements please e-mail me. I might be able to resolve these by coding some of the original footnotes back in.


Thanks to the American Association of Variable Star Observers for providing copies of the original Leavitt papers, and the library of the Royal Astronomical Society London for obtaining Hertzsprung’s early work. Extensive use has also been made of NASA's Astrophysics Data System Bibliographic Services.

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The Cepheid Distance Scale: A History ã Nick Allen AGSM BA BEd MSc FRAS MInstPI 2001 

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Last Updated: May 2009