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About 11,000 years ago, a star in the constellation Vela exploded, creating a flash of light briefly visible to humans living near the beginning of our recorded history. The outer layers of the star collided into interstellar gas and dust, driving a shock wave still visible today, as you can see in the photo above. The resulting dramatic nebula spans almost 100 light years and appears 20 times the diameter of the full Moon from our POV. As gas rockets away from the exploded star, it decays and reacts with the interstellar stuff around it, producing light in many colors and energy bands. At the center of the Vela Supernova Remnant glows a pulsar, a star as dense as matter can get, which rotates more than ten times per second.