Nebula in M17, Hubble Space Telescope (HST) image. This is a closeup of a region 3 light years wide in the Omega Nebula (M17). M17 is also called the Swan Nebula. A cloud (nebula) of hydrogen gas and dust covers the lower right half of the image. It is heated by nearby young, massive stars (not seen). Hot gases (blue) spread out from the warm surface (orange). The colours correspond to light emitted by hydrogen (green), sulphur (red) and oxygen (blue). The Omega Nebula, about 5500 light years away, is in the constellation Sagittarius. Image acquired from 2930 May 1999, using the HSTs Wide Field Planetary Camera 2 (WFPC2).