Mira mī´rə [key], [Lat.,=marvelous], variable star in the constellation Cetus; Bayer designation Omicron Ceti; 1992 position R.A. 2 h19.0 m, Dec. −3°05′. The most famous long-period variable, Mira ranges in apparent magnitude from a maximum of about 2.0 to a minimum of about 10.1 with a period of a little less than a year (332 days). Thus, it is visible to the naked eye for about half a year and can be seen only through a telescope for the remainder of its period. Mira is of spectral class M6e III, the spectrum showing some emission lines. There is some variation in maximum brightness that is thought to be due to clouds of hydrogen gas surrounding the star. Mira's distance from the earth is about 100 light-years.
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