Assertion: andromeda galaxy's structure | /r/HasProperty | behind counter-rotating disk of gas
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text: There have been interactions with satellite galaxies like M32, M110, or others that have already disappeared absorbed by M31 that have formed structures like Andromeda's Giant Stellar Stream and a merger roughly 100 million years ago that is behind a counter-rotating disk of gas found in the center of M31 as well as the presence there of a relatively young (100 million years) stellar population.