Mira

Mira is a binary star system with a white dwarf (Mira B, also known as VZ Ceti) star and a red giant (Mira A). Scientists think Mira is 200-400 light years away in the constellation Cetus. Mira A is a variable star, changing its size and brightness. Other red giant stars that do the same are called Mira variables. 
Size.
Mira has a diameter 332 to 541 times that of our sun.
If Mira did not change size, its diameter would be only 240 times larger than the Sun.