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A significant number of stars are intrinsically variable; that is their total energy output fluctuates over time. Of these the pulsational variables are stars in which light and colour vary as a result of pulsations in the star. Their periods may vary from a few days to nearly a year. Such variability is a characteristic of any star whose evolution carries it to a certain size and luminosity.
Metaphor
It can be useful to interpret the energy output of any social group in terms of such variability. Many groups, particularly those with activities limited to large periodic conferences, are distinctly variable if only as evidenced by funds flow, paper output and media coverage.
[Features]The detailed investigations of pulsation theory have established important qualitative and quantitative relationships between the cyclic phenomena. In the case of periodic variables such as the Cepheids, the period of variation tends to be proportional to their luminosity so that they are of great importance in the measurement of interstellar and intergalactic distances.
[Contrast]This metaphor is used in its non-periodic form in connection with the (nova-like) explosion into visibility of some new media 'star'. It is not used in its periodic form.
[Keys]Other types of variable star.