The galaxy Messier 101 (M101, also known as NGC 5457 and also nicknamed the Pinwheel Galaxy) lies in the northern circumpolar constellation, Ursa Major (The Great Bear), at a distance of about 21 million light-years from Earth. 
This is one of the largest and most detailed photos of a spiral galaxy that has been released from Hubble. The galaxy's portrait is actually composed of 51 individual Hubble exposures, in addition to elements from images from ground-based photos. A high-res version with 15852 x 12392 pixels in jpg and tiff format is also available, see below for url.
<p><b>Credit:</b>
</p><p>Image: European Space Agency &amp; NASA
</p><p>Acknowledgements:
</p><p>Project Investigators for the original Hubble data: K.D. Kuntz (GSFC), F. Bresolin (University of Hawaii), J. Trauger (JPL), J. Mould (NOAO), and Y.-H. Chu (University of Illinois, Urbana)
</p><p>Image processing: Davide De Martin (ESA/Hubble)
</p><p>CFHT image: Canada-France-Hawaii Telescope/J.-C. Cuillandre/Coelum
</p>
NOAO image: George Jacoby, Bruce Bohannan, Mark Hanna/NOAO/AURA/NSF
CC BY 4.0
<a rel="nofollow" class="external free" href="http://www.spacetelescope.org/news/html/heic0602.html">http://www.spacetelescope.org/news/html/heic0602.html</a> (<a rel="nofollow" class="external text" href="https://cdn.spacetelescope.org/archives/images/screen/heic0602a.jpg">direct link</a>)
<ul><li><b>See also:</b> <a rel="nofollow" class="external free" href="http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/10/image/a">http://hubblesite.org/newscenter/newsdesk/archive/releases/2006/10/image/a</a></li></ul>