This wide, detailed Spitzer Space Telescope view features infrared light from dust (red) and old stars (blue) in Andromeda, a massive spiral galaxy a mere 2.5 million light-years away.
Andromeda's population of bright young stars define its sweeping spiral arms in visible light images, but here the infrared view clearly follows the lumpy dust lanes heated by the young stars as they wind even closer to the galaxy's core.
Constructed to href="http://nedwww.ipac.caltech.edu/level5/ANDROMEDA_Atlas/Hodge_contents.html">explore Andromeda's infrared brightness and stellar populations, the full mosaic image is composed of about 3,000 individual frames.
Two smaller companion galaxies, NGC 205 (below) and M32 (above) are also included in the combined fields.
The data confirm that Andromeda (aka M31) houses around 1 trillion stars, compared to 4 hundred billion for the Milky Way.
