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galaxy – n. any one of the very large groups of stars that make up the universe
stellar – adj. of or relating to the stars
x-ray – n. powerful invisible rays that can pass through various objects and that make it possible to see inside things, such as the human body
spiral – n. a circular curving line that goes around a central point while getting closer to or farther away from it
layer – n. an amount of something that is spread over an area
