Editing Variable star (section)

=====Mira variables=====
[[File:Chi Cygni light curve.png|thumb|[[Light curve]] of [[Mira variable]] [[χ Cygni]]]]
{{Main|Mira variable}}

Mira variables are [[Asymptotic giant branch]] (AGB) red giants. Over periods of many months they fade and brighten by between 2.5 and 11 [[apparent magnitude|magnitude]]s, a 6 fold to 30,000 fold change in luminosity. [[Mira]] itself, also known as Omicron Ceti (ο Cet), varies in brightness from almost 2nd magnitude to as faint as 10th magnitude with a period of roughly 332 days. The very large visual amplitudes are mainly due to the shifting of energy output between visual and infra-red as the temperature of the star changes. In a few cases, Mira variables show dramatic period changes over a period of decades, thought to be related to the thermal pulsing cycle of the most advanced AGB stars.