NASA's Galaxy Evolution Explorer discovered an exceptionally long
comet-like tail of material trailing behind Mira -- a star that has been
studied thoroughly for about 400 years. So, why had this tail gone
unnoticed for so long? The answer is that nobody had scanned the extended
region around Mira in ultraviolet light until now.
As this composite demonstrates, the tail is only visible in ultraviolet
light (top), and does not show up in visible light (bottom). Incidentally,
Mira is much brighter in visible than ultraviolet light due to its low
surface temperature of about 3,000 kelvin (about 5,000 degrees
Fahrenheit).
The Galaxy Evolution Explorer, one of NASA's Small Explorer class
missions, is the first all-sky survey in ultraviolet light. It found
Mira's tail by chance during a routine scan. Since the mission's launch
more than four years ago, it has surveyed millions of galaxies and stars.
Such vast collections of data often bring welcome surprises, such as
Mira's unusual tail.
The visible-light image is from the United Kingdom Schmidt Telescope in
Australia, via the Digitized Sky Survey, a program affiliated with the Space
Telescope Science Institute, Baltimore, Md.
