Question

what is ment by galaxy

Answer 1

galaxy is a cluster of stars, planets, meteors, astroids, Nebula, some black holes, and at the center of each galaxies there is a massive black hole. and there are millions of galaxies, our one is just one of those millions.
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Answer 2

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A galaxy is a huge collection of gas, dust, and billions of stars and their solar systems. A galaxy is held together by gravity.