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Figure 11-1 RIVUXG The Orion Nebula (a) The middle “star” of the three that make up Orion’s sword is actually an interstellar cloud called the Orion Nebula. (b) A mosaic of HST and ground-based images reveal a bright central region of stars known as the Trapezium. (c) Bow shocks created by young stars emitting streams of material that collide with and heat nearby gas can be seen, as can a “bright bar” emanating from the Trapezium. More outflows of material can be seen to the left and top of the image. About 1500 ly from Earth, the nebula contains thousands of young stars that cause the nebula to glow.