Diagram showing the variation of a Cepheid variable over time with strict periodicity. Cepheids are pulsating variable stars, whose spectral type and
Diagram showing the variation of a Cepheid variable over time with strict periodicity. Cepheids are pulsating variable stars, whose spectral type and luminosity class (and therefore their brightness and size) vary over a few days to months. The prototype is Delta Cephei. As they grow larger, they cool down and get redder, while their brightness drops. The green curve shows the variation in radius; the red, the change in brightness. The orange dashes indicate the period. They fall into two main classes. Type I Cepheids are bright yellow giants and supergiants, thousands of times more luminous than the Sun and several times more massive. They vary their radius by as much as 25 per cent. Type II Cepheids are much less massive, around half that of the Sun. The variations of many Cepheids, such as the prototype, can easily be seen with the naked eye ever a period of days or weeks.
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Photo credit: © MARK GARLICK/SCIENCE PHOTO LIBRARY / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: art, artwork, astronomical, astronomy, astrophysical, astrophysics, brightness, cephei, cepheid, change, class, delta, diagram, giant, illustration, luminosity, pulsation, schematic, spectral, star, stellar, supergiant, variability, variable, variation
