It was only a few months ago, that we discussed observing double stars. This month, I would like to take a look at variable stars.
Many stars vary in brightness over periods ranging from less than a day to several years.
These variations can be followed by amateurs using small instruments, or even with the naked eye. There are so many variable stars that professional astronomers cannot monitor them all, and amateur observations provide valuable information that helps in the understanding of stars. Among the most interesting variables are the red giant and supergiants, which include some of the brightest naked-eye stars. Such stars have swollen up inside its at the end underlie and have as a result become unstable, changing erratically in size and brightness. Most abundant of all types of known variables are the long-period variables, also known as Mira stars after their prototype, Mira, which was the first variable star to be noticed.