What is a Cepheid variable? (Intermediate)

What is a Cepheid variable? I came across the term in a general interest news magazine and it piqued my curiosity.

Cepheid variables are a subgroup of a class of stars called variable stars. Other classes include RR Lyrae variables, Mira variables, W. Virginis stars etc. Variable stars are those stars whose brightness oscillates with a definite periodicity. The variation is caused because of the star puffing out and contracting back again. Cepheid variable stars have masses between five and twenty times the mass of the sun.

The period of oscillation has a relation to its luminosity (thus there is a period-luminosity relation for these stars), which is why they are so useful. If you have a method of determining the luminosity of stars, then you can calculate the distance to these stars easily. It was the observations of Cepheid variable stars which enabled astronomer Hubble (after whom the Hubble Space Telescope is named) to determine that spiral nebulae like the one in Andromeda were galaxies separate from the Milky Way.


This page updated on June 27, 2015

About the Author

Jagadheep D. Pandian

Jagadheep D. Pandian

Jagadheep built a new receiver for the Arecibo radio telescope that works between 6 and 8 GHz. He studies 6.7 GHz methanol masers in our Galaxy. These masers occur at sites where massive stars are being born. He got his Ph.D from Cornell in January 2007 and was a postdoctoral fellow at the Max Planck Insitute for Radio Astronomy in Germany. After that, he worked atĀ the Institute for Astronomy at the University of Hawaii as the Submillimeter Postdoctoral Fellow. Jagadheep is currently at the IndianĀ Institute of Space Scence and Technology.