andlt;strongandgt;Spiral galaxy M101,andlt;/strongandgt; Hubble Space Telescopeimage. M101 is also known as the Pinwheel Galaxy.It lies around 25 million light years from Earthin the constellation Ursa Major. The disc of thegalaxy is some 170,000 light years across, nearlytwice as wide as our own Milky Way. The spiralarms appear blue as they contain hot young stars.The central nucleus is yellow as the stars thereare older, and much of the light is obscured bydust. Released in 2006, this is the most detailedimage of a galaxy ever taken by the HST. It iscomposed of 51 separate HST exposures takenbetween 1994 and 2003, which were superimposed onground-based images. The full 562Mb image isavailable on request.