There are many types of intrinsic variables, but among the most common are long period variables. These stars have left the main sequence and become unstable. The variability is caused by pulsation in the size and temperature of the star. Cepheid variables are also giants but their periods are in the range of days to weeks. The period of variability is relate to their luminosity which makes them very important as distance indicators.
Many variable have periods which are semi-regular, irregular or have no period at all.
An famous example is SS Cygni shown below. These types of variables are poorly understood and are the subject of much research by professional astronomers. Procedure Observing Take one image of each of the nine selected stars. Display the historical light curves of each star in SkyPro . Use a spreadsheet program to import the historical light curve data for each star.