M101: Spitzer finds “No-organic” Zone

Spitzer Space Telescope was used to obtain this gorgeous false-color IR image of M101. Astronomers have found from these data that some special organic molecules, so-called polycyclic aromatic hydrocarbons, decrease in concentration toward the outer portion of the Pinwheel galaxy, and then quickly drop off and are no longer detected at its very outer rim.

Spitzer Press Release:
http://www.spitzer.caltech.edu/Media/releases/ssc2008-14/
Images:
http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2008-14a
http://gallery.spitzer.caltech.edu/Imagegallery/image.php?image_name=ssc2008-14b