This three-colour image of the W3 giant molecular cloud combines Herschel bands at 70 μm (blue), 160 μm (green) and 250 μm (red). The image spans about 2 x 2 degrees. North is up and east is to the left.
W3 is an enormous stellar nursery about 6200 light-years away in the Perseus Arm, one of the Milky Way galaxy’s main spiral arms, that hosts both low- and high-mass star formation. In this image, the low-mass protostars are seen as tiny yellow dots embedded in cool red filaments, while the highest-mass stars – with greater than eight times the mass of our Sun – emit intense radiation, heating up the gas and dust around them and appearing here in blue. W3 Main and W3 (OH) contain the most recent high-mass star formation.