Abstract
A variable star is one which varies in brightness (or some other physical property). A graph of the brightness of a variable star vs. time is called a light curve – the basic tool of variable star astronomy. Variable stars provide astronomers with essential information on stellar properties, processes, and evolution. There are two broad classes of variable stars: geometrical variable stars in which the variability is caused by the mutual eclipse of stars in orbit around each other, or by the rotation of a spotted star; and intrinsic or physical variable stars, in which the variability is caused by pulsation, or some form of eruption. The eruptions may be minor, as in a flare star, or catastrophic, as in a supernova. Variable stars are numerous: there are over 50 000 catalogued variable stars, and new variable stars are being discovered by the tens of thousands each year.
Variable stars are central to many aspects of modern astronomical research. They can also play a special role in astronomical education at all levels, and in astronomical development – because much useful research on variable stars can be done with small astronomical telescopes. There are small telescopes in over a hundred countries, in government or university departments, in public or private observatories. These telescopes can play an important role in astronomical education, research, and development. This paper will emphasize these aspects of the topic. For a more complete discussion of variable stars, see the monographs by Hoffmeister et al. (1985), Percy et al. (1992), Petit (1987), Sterken and de Groot
(1994), and Sterken and Jaschek (1996).
