These brightness changes can range from a few hundredths to as much as twenty magnitudes over periods of a fraction of a second to years, depending on the type of variable star.
Stars change in brightness when they are very young, or when they are very old or dying.
The Information Bulletin on Variable Stars is a bulletin of the Commissions IAUC27 and IAUC42 of the International Astronomical Union , published by Konkoly Observatory , Budapest, Hungary. In the footsteps of John Goodricke - The sky is full of variable stars and many of them are regularly observed by professional and amateur astronomers. For many amateur astronomers variable stars provide the perfect field of study to develop highter level observing skills. Variable Star Network - Data distribution, alert on the discovery of supernovae, novae, rare outbursts, discovery of new variable star, dramatic change of known variable stars, general information, complied data, preprints, and distributing finding charts. Copyright 2001 - Samuel J. Wormley, Iowa State University.