Mira

MiraCC

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Mira light curve

Mira the star

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Mira in UV and Visible Light

Mira 1997

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Chi Cygni pulsations

Mira (Bayer designation: ο Ceti, Omicron Ceti) is a binary star system in the constellation of Cetus. It consists of a red giant called Mira A, which is a pulsating variable star of the Mira variable type, and a white dwarf companion, Mira B. Mira A is notable for being one of the first non-nova variable stars to be discovered in the galaxy, with records of its variability dating back to the 14th century. The system is approximately 300 light-years from Earth.

Discovery and Observation

The variability of Mira was first recorded by the astronomer David Fabricius in 1596. Observations over many years have shown that Mira A's brightness varies over approximately 332 days, ranging from magnitude 2 to 10. This variability is due to pulsations in the star's outer layers, causing it to expand and contract. Mira's changes in brightness were so significant that it was initially thought to be a nova.

Characteristics

Mira A is a red giant undergoing the final stages of its life, shedding its outer layers to form a planetary nebula. It is one of the most notable examples of a Mira variable, a class of stars characterized by their long-period variability. Mira A's surface temperature varies as it pulsates, and it is losing mass at a high rate, which contributes to the surrounding material that forms a nebula around the system.

Mira B, the white dwarf companion, orbits Mira A at a distance that varies due to the highly elliptical orbit. The interaction between the two stars, particularly the accretion of material from Mira A onto Mira B, is a subject of ongoing research. This process is believed to cause occasional flares and other phenomena observed in the system.

Significance in Astronomy

Mira has been a subject of interest not only because of its variability but also because it is one of the closest examples of a star in the late stages of stellar evolution. It provides astronomers with a valuable opportunity to study the processes involved in the life cycle of stars, including mass loss, pulsation, and binary star interactions. The system has been observed across the electromagnetic spectrum, from radio to X-ray wavelengths, providing a wealth of data on its properties and behavior.

Cultural Impact

The visibility of Mira to the naked eye and its dramatic changes in brightness have made it a point of interest since ancient times. Its name, which means "wonderful" or "astonishing" in Latin, reflects the surprise of early observers at its variability. Mira's behavior challenged the Aristotelian idea of the unchangeability of the heavens, contributing to the shift in understanding of the universe that took place during the Renaissance.

See Also

• Variable star
• Red giant
• White dwarf
• Binary star
• Stellar evolution