Mira Variables are the class of pulsating stars which are in very late stage of stellar evolution and lie on the Asymptotic Giant Branch of the Hertzsprung-Russel diagram. They are named after the protostar Mira, the first one to be discovered of its class. Mira Variables have pulsation period of more than 100 days, infrared magnitude of more than 1 and visual magnitude of more than 2.5. Mira variables will soon expel their outer layers as planetary nebula and become white dwarfs within a few million years.
Mira Variables are the red giants that have already undergone helium fusion in their core. They can be thousand times more luminous than the sun due to their distended envelopes. They are pulsating stars. The pulsating depends on the mass and radius of the star which has direct impact on the luminosity and temperature of the stars.They are pulsating because the entire star is expanding and contracting. These stars are not spherically symmetric as thought earlier.
Mira Variables are carbon or oxygen rich stars. These stars are popular targets of the Amateur Astronomers interested in variable star observation as they change their brightness dramatically.