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Mira was the first variable star to be discovered (discovery 1596, variability 1639). Mira or Omicron Ceti is a red giant, which irregularly pulsates very strong.
It is orbited by a white dwarf, which by itself changes its luminosity. Probably this is due to influences of the main star, because single white dwarfs are rather stable.

In August 2007 a comet-like tail was discovered at Mira, which extends nearly 13 light-years into space. It is the first star knwon to have such a tail.

Constellation: Cetus
Distance: 418 light-years
Space between Mira A and B: 70 AU
Orbit period of Mira A and B: 1800 years

Mira A

Spectral class: M6 - M9
Visual magnitude: 2.0 - 10.1
Luminosity: 20 - 15 000 * Sun
Mass: circa 5 * Sun
Diameter: circa 100 - 700 * Sun
Pulsation period: circa 331 days

Mira B (VZ Ceti)

Visual magnitude: 9.5 - 12

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One of only a few stars where the diameter can be seen with a telescope.
Photo: Nasa, Hubble Telescope

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