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| The Omega Nebula (which is also known as M 17 and the Swan Nebula) is a glowing cloud of gas and dust located some 5500 light years away toward the constellation Sagittarius. The Omega Nebula is illuminated by ultraviolet radiation from several young, massive stars, which are located just beyond the upper right corner of the image. Ultraviolet radiation from the stars causes the gas to glow through a process known as fluorescence. The ultraviolet radiation from the stars also eats away at the dense cloud of cold gas from which the stars were formed. The walls of the cloud shine primarily in the blue, green, and red light emitted by excited atoms of hydrogen, nitrogen, oxygen, and sulfur. The nebula stretches several light years across. |
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