Mira (pronounced my-rah, after the Latin word for "wonderful"), has been closely studied as a variable star (a star whose brightness varies) for over 400 years. Over the course of approximately 331 days, Mira goes from a very dim magnitude 9 (invisible to the naked eye), all the way to a brilliant magnitude 2 (making it one of the brightest stars in the sky), and back again. And in August, 2007, when NASA turned one of its ultraviolet telescopes in the star's direction, they discovered something previously unknown. The star has a tail, similar to a comet, except of course very much larger and longer. Mira's tail extends 13 light years across space, a distance many thousands of times greater than our entire solar system.

Mira is an unusual star in more ways than one. Instead of following the rest of the stars in our galaxy in a long, slow circle around the galaxy's centre, Mira is speeding along at right angles to the disk of the galaxy at a breakneck speed of 291,000 miles per hour. Below is NASA's ultraviolet image of Mira (moving left to right) and its spectacular tail.

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