Mira

Mira , [Lat.,=marvelous], variable star in the constellation Cetus; Bayer designation Omicron Ceti; 1992 position R.A. 2 ^h 19.0 ^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.

Mira The star Omicron Ceti, the prototype Mira star or long-period variable. It was first observed by D.Fabricius in 1596, and was originally believed to be a nova. It was found to be periodic by the Dutch astronomer Jan Fokkens (Latinized as Johannes Phocylides) Holwarda (1618–51) in 1638, and was named Mira (Latin for ‘Wonderful’) by J.Hevelius. Mira has a period of 331.96 days, a range of 2.0–10.1 mag., and is a red giant of spectral type M5e–M9e. Its diameter is 400–500 times that of the Sun. It forms a binary with VZ Ceti, a white dwarf that is accreting material from the giant's stellar wind. Mira is 420 l.y. away.

Mira star A type of red giant or supergiant pulsating variable; abbr. M. Mira stars have highly characteristic late-type spectra (Me, Ce, or Se) with molecular bands, and there is extensive mass loss. Their light-curves may be approximately sinusoidal, but most show a steep rise to maximum and slower decline; amplitudes range from 2.5 to as much as 11 magnitudes, with periods from 80 to 1000 days. Because of their relatively high luminosities, large amplitudes, and well-defined features, Mira stars are readily detectable. More of them are known than any other type of variable star.