AIthough it may not be obvious at first sight, many stars vary in brightness overtime. Some of these variable stars change magnitude on predictable timescales, others are less regular. Recording the variations is a rewarding and straightforward form of observing which ultimately helps decode how certain stars work. In this article we'll look at different types of variable, howto observe them and howto interpret the results. We'll also give you some examples to get you started.
A star's brightness is quantified by its magnitude. Some stars remain at constant magnitude, some vary a little and some vary a lot. Indeed, some stars become bright enough to change the visual appearance of their host constellation, such as Betelgeuse (Alpha (α) Orionis) and Mira (Omicron (ο) Ceti) (see ‘Six variable stars to get you started’ on page 66). Variability can
