Filaments in M51. This is M51, the Whirlpool Galaxy. The pictures from which we built this package, are a part of a release at the NASA's Spitzer Space Telescope. A new program called "Legacy" is aiming at providing the astronomers community with enhanced, more friendly, products, instead of raw materials. Pictures taken by the Spitzer Space Telescope are processed and enhanced with complementary information from other telescopes. The Galactic Legacy Infrared Mid-Plane Survey Extraordinaire (GLIMPSE), Great Observatories Origins Deep Survey (GOODS), Spitzer Infrared Nearby Galaxies Survey (SINGS), Spitzer Wide-area Infrared Extragalactic Survey (SWIRE), Formation and Evolution of Planetary Systems: Placing Our Solar System in Context (FEPS), and From Molecular Cores to Planet-Forming Disks (C2D) projects, are part of the Legacy program. M51 maybe is a good example of a collision between two galaxies as the companion galaxy (NGC 5195) might be actually colliding with the main spiral. M51 is seen in visible light (left) and is a text-book image of a spiral galaxy with its arms spiraling away from a central core. Dark interstellar clouds are seen, providing raw materials for star formation. The central bulge is rather old, yellow stars, as the galaxy's center is harbouring a huge black hole. The infrared view by NASA's Spitzer Space Telescope (center) is showing curious filaments of dust (inset, right) which are linking the arms. The view is showing too that the satellite companion is young stars-poor and devoided of any intersteller dust. As part of its work objectives, the Spitzer Space Telescope will dedicate 500 hours of observation to 75 nearby galaxies, leading to a better understanding of star formation, hence to data, tools, and inputs for studies about how galaxies evolve since the early Universe. picture © site 'Amateur Astronomy' based on pictures NASA/JPL-Caltech/R. Kennicutt (Univ. of Arizona) (left) and DSS (center and inset)