Where are the hot stars in M81, one of the closest major spiral galaxies?  To help find out, astronomers took a deep image in  
ultraviolet light  of the sprawling spiral with the Earth-orbiting  
Galex telescope.    Hot stars emit more ultraviolet than cool stars, and are frequently associated with young  open clusters of stars and energetic  star forming regions.    Magnificent  
spiral galaxy M81, slightly smaller in size to our own  
Milky Way Galaxy,  shows off its young stars in its winding spiral arms in the  
above image.   Less than 100 million years old, the young stars are blue in the  
above false-color Galex image and seen to be well separated from the  older yellowish stars of the galactic core.  Visible above  M81 is a satellite galaxy dubbed  
Holmberg IX.     Studying the unexpectedly bright ultraviolet glow of this small  
irregular galaxy  may help astronomers understand how the  
many satellites  of our own Milky Way Galaxy developed.    
M81,  visible through a small telescope, spans about 70,000  
light years  and lies about 12 million light years away toward the  
constellation of the Great Bear  (
Ursa Major).