Mira A is part of a binary star system called Mira, also called Omicron Ceti, within the constellation Cetus. Mira A is an oscillating variable star that pulsates over a period of about 330 days. At its brightest, it is visible to the naked eye on the Earth.

Mira B is its companion star, a smaller star about the size of the Sun. The two stars are about 90 astronomical units (AU) apart, where one AU is equal to the distance between the Earth and the Sun. In addition, one light-year is the distance that light travels in vacuum in one year, about 6 trillion miles (6,000,000,000,000 miles).

The research group used NASA’s Galaxy Evolution Explorer (Galex) space telescope, which performs an ultraviolet survey of the sky while in orbit about 425 miles above the Earth, to discover the star’s tail. The scientists contend that the tail was formed about 30,000 years ago, and that it formed because of Mira’s extremely fast traveling speed (about 80 miles [130 kilometers] per second) that forces compressed plasma and gas to be ejected from its outer envelope.

Their findings (“A turbulent wake as a tracer of 30,000 years of Mira's mass loss history”) are written up in the August 16, 2007 issue of the journal Nature (448, 780-783).
 
The authors of the article are: D. Christopher Martin, James D. Neill, Karl Forster, Tom A. Barlow, and Patrick Morrissey (all from California Institute of Technology), Mark Seibert and Barry F. Madore (from Observatories of the Carnegie Institution of Washington), David Schiminovich (Columbia University), Jonathan M. Wheatley and R. Michael Rich (University of California at Los Angeles), and Barry Y. Welsh (University of California at Berkeley).

According to the abstract of their paper, “This wind wake is a tracer of the past 30,000 years of Mira's mass-loss history and provides an excellent laboratory for studying turbulent stellar wind–ISM [interstellar medium] interactions.”

Mira A’s tail, which is tens of thousands of times the length of the solar system, gives astronomers the ability to track its movements over its history, providing them with valuable information on the possible future of the Sun (which will begin to turn into a red-giant star in about five million years) and the beginnings of new stars and planets created from old stars.
 

The researchers found that the older material from Mira A is located in the outer tail of the star, while the more recently ejected material is closer to the star. Such information will help scientists unravel the mystery contained within "the star with a tail."

In the end, Mira A will eject all of its gas into space and it will turn into a burnt out star called a white dwarf. The Earth’s Sun will also end up this way.

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