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Collision of Galaxies May Have Spurred Our Solar System’s Formation

The galaxies first crashed more than 6 billion years ago. Since then, Sagittarius — a “dwarf” galaxy 10,000 times less massive than the Milky Way — has twice passed through our galaxy’s immense disk containing most of its roughly 100 billion stars. All three galactic interactions were associated with a burst of Milky Way star formation. Data from the European Space Agency’s Gaia space observatory revealed a prolonged star-formation episode from 6.2 billion to 4.2 billion years ago associated with the initial crash. Two other star-formation surges linked to the galactic collision peaked 1.9 billion years ago and 1 billion years ago, each lasting a few hundred million years.

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