Today the Vela supernova remnant marks the position of a relatively close and recent explosion in our Galaxy . A roughly spherical, expanding shock wave is visible in X-rays . In the above optical photograph, the upper left corner of the spherical blast wave is shown in detail. As gas flies away from the detonated star , it reacts with the interstellar medium , knocking away closely held electrons from even heavy elements . When the electrons recombine with these atoms , light in many different colors and energy bands is produced.
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