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New data from the Sloan Digital Sky Survey and Europe's Gaia spacecraft suggest that a brush with another galaxy caused the strange, potato chip-like "warp" in our Milky Way galaxy.

We know little about our own galaxy's warp because of the difficulty of studying the galaxy from within it, but scientists have observed similar distortions in roughly 50% to 70% of spiral galaxies like our own. (Technically speaking, the Milky Way is a particular subset of the group, called a barred spiral galaxy.)

The new results suggest that our galaxy's twist came from a "recent" interaction with another galaxy — recent, that is, compared to the 13.7-billion-year-old age of the universe. Roughly three billion years ago, the scientists suggest, a satellite galaxy came close enough to our own to create a ripple effect still visible in the Milky Way's stars today.

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"Our usual picture of a spiral galaxy is as a flat disk, thinner than a pancake, peacefully rotating around its center," lead author Xinlun Cheng, an astronomy graduate student at the University of Virginia, said in a statement from Sloan. "But the reality is more complicated."

It's difficult for scientists to map out our galaxy's warp because Earth is embedded deep in the Milky Way. Even our spacecraft have only ventured a little ways from our planet, in cosmic terms, as most remain within the bubble our star forms around the planets.

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https://www.space.com/galaxy-encounter-warped-milky-way