Swan Nebula (M17), infrared image. This cloud of gas and dust is dominated by a central group of massive stars. These central stars give off large outflows of expanding gases that meet stellar winds from the region's other massive stars, creating bow shocks within the nebula. The colours indicate the composition of the nebula: dust is red, hot gas is green, and mixtures of gas and dust are white. M17 is located in the constellation of Sagittarius and is around 6000 light years from Earth. The nebula is some 15 light years across. This image, published in 2008, was obtained using the Infrared Array Camera (IRAC) of the Spitzer Space Telescope (SST).