James Harold writes "Today NASA unveiled a new infrared mosaic of our galaxy. The result of over 800,000 individual images collected by the Spitzer Space Telescope, it is the largest, highest-resolution, and most sensitive infrared picture ever taken of the Milky Way (and will likely remain so for the foreseeable future). Because Spitzer sees in infrared, it penetrates much farther into the galaxy, revealing previously hidden star clusters, star-forming regions, shocked gases, glowing 'bubbles' and more. The complete mosaic is about 400,000 by 13,000 pixels, and a 180' printed version is being shown at the American Astronomical Society meeting in St. Louis. A zoomable, annotated version of two different variants on the image (as well as some additional information on the science) is available at Alien Earths, a NASA- and NSF-supported education site." The Spitzer survey is already causing a stir potentially bigger than that raised when Pluto was deemed not a planet: two minor spiral arms of the Milky Way may be demoted.