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POPSStar Factory Shows Off Three Kinds of Nebulae The Trifid’s third kind of nebula can be seen in the dark stripes that criss-cross the rest of the image. Called dark nebulae because of their light-obscuring properties, these clouds of gas and dust contain the remnants of previous star births. As higher pressure and temperatures build up inside the streaks of gas, nuclear fusion will lead to the formation of yet more stars