Star or comet ?

New observations of the star Mira with GALEX show a spectacular comet-like tail. Known for 400 years, the star has revealed its turbulent wake only now because the tail glows only in UV light and a very wide field of view is needed, both conditions met by GALEX.

The tail lies in the trail of the fast moving star and must be formed by matter ejected by AGB winds. Mira’s mass loss history can thus be traced back to 30’000 years ago.

In front of the star, the astronomers have discovered a bow shock, which probably explains the UV fluorescence, though the physics involved is not yet clear