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The Milky Way’s Most Recent Meal was a Galaxy it Gobbled up 8-10 Billion Years ago

12 Jan 2022, 17:30 UTC
The Milky Way’s Most Recent Meal was a Galaxy it Gobbled up 8-10 Billion Years ago
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A central aspect of galactic evolution is that they must eat or be eaten. Dark energy strives to push galaxies apart, but gravity tries to pull them together. As a result, galaxies tend to form into local groups. As these superclusters of galaxies become more isolated due to cosmic expansion, they gravitationally turn on each other, and in time the largest galaxies of the group will consume the smaller ones. The Milky Way is one of the larger galaxies in our local group, and so it has consumed smaller galaxies in the past. But piecing together the history of these galactic meals is a real challenge.

But thanks to the Gaia spacecraft we’re learning quite a bit, as a recent study shows. The results were published in the Astrophysical Journal and reconstructs when the last major galactic merger with the Milky Way occurred.

The globular cluster NGC 2808 is possibly GSE’s remnant core. Credit: NASA, ESA, A. Sarajedini, and G. Piotto

Based on earlier observations, we know that many of the remnant stars from galactic collisions end up in the halo of the Milky Way. This is a roughly spherical collection of stars that surrounds our galaxy. The most recent ...

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