Astronomy Picture of the Day

The Tail of a Wonderful Star

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The Tail of a Wonderful Star


To seventeenth century
astronomers, Omicron Ceti or
Mira was
as a
wonderful star, a star whose brightness could change dramatically in
the course of about 11 months.

Mira is
now seen as the archetype of an entire class of long-period
variable stars.

Surprisingly, modern astronomers have only recently discovered
another striking characteristic of Mira -- an enormous
comet-like tail nearly 13 light-years long.

The discovery
was made using ultraviolet image data from the
Galaxy Evolution Explorer
(GALEX) satellite.

Billions of years ago Mira was likely similar to our Sun, but has
now become a swollen
red giant star, its outer layers of material
blowing off into interstellar space.

Fluorescing in ultraviolet light,
the cast off material trails behind the
star as it
plows through the surrounding interstellar medium at
130 kilometers per second.

The amount of material in Mira's tail is estimated to be equivalent
to 3,000 times the mass of planet Earth.

About 400 light-years away toward the constellation Cetus, Mira is
presently too faint to be seen by the unaided eye, but
will become visible again in mid-November.

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