From GALEX: Speeding-Bullet Star Leaves Enormous Streak Across Sky
It looks like a comet.
[Compared to other red giants, Mira is traveling unusually fast, possibly due to gravitational boosts from other passing stars over time. It now plows along at 130 kilometers per second, or 291,000 miles per hour. Racing along with Mira is a small, distant companion thought to be a white dwarf. The pair, also known as Mira A (the red giant) and Mira B, orbit slowly around each other as they travel together in the constellation Cetus 350 light-years from Earth.]
Too much to quote, it's all interesting.
More from: http://www.nasa.gov/mission_pages/galex/galex-20070815.html