The trouble with an answer is that there are very many different types of variavle stars, and each usually has a different mechanism going on which causes the variability. One type is Cepheids, which you can read about in the thread below.varsha said:i don't get it. really large stars are unstable and there are frequent outbursts. so they are called variable stars. but when they burst they create a nebula and remain as a star right? how is that? shouldn't they turn into a black hole or a nutron star or just a nebula?
or do they just vary in brightness?
Variable stars are stars that exhibit changes in their brightness over time. These changes can occur over periods of hours, days, or even years.
There are several factors that can cause the brightness of variable stars to vary. These include changes in the star's internal structure, pulsations, eclipses by companion stars, and changes in the amount of material being ejected from the star.
Scientists use a unit called magnitude to measure the brightness of variable stars. The lower the magnitude, the brighter the star appears. However, some variable stars can have magnitudes that change by several orders of magnitude, making them incredibly difficult to measure accurately.
There are several types of variable stars, including Cepheid variables, RR Lyrae variables, and eclipsing binaries. Each type has its own unique characteristics and can be used for different purposes in astronomical research.
Studying variable stars can provide valuable information about stellar evolution, the structure and composition of stars, and the properties of the universe. They can also serve as important tools for measuring distances in space and detecting exoplanets.