SETI Institute#PPOD: What may look like a strangely nearby galaxy is actually a normal rocket's exhaust plume -- but unusually backlit. Like noctilucent clouds, the plume's brightness is caused by the Twilight Effect, where an object is high enough to be illuminated by the twilight Sun, even when the observer on the ground experiences the darkness of night. The spiral shape is caused by the Falcon rocket reorienting to release satellites in different directions. Credit: Seung Hye Yang
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