The Milky Way begins to form
Our galaxy takes shape near the dawn of time
Quick facts
- Milky Way's thick disc
- Began forming about 13 billion years ago
- After the Big Bang
- Only about 0.8 billion years
- Surprise
- Roughly 2 billion years earlier than expected
- Measured by
- ESA's Gaia mission, from millions of stars
What happened
Our own galaxy started coming together remarkably early. Using data from its Gaia mission, which measured the positions, motions, and ages of millions of individual stars, the European Space Agency showed that a major part of the Milky Way known as the thick disc began forming about 13 billion years ago. That is only around 0.8 billion years after the Big Bang, and roughly 2 billion years earlier than astronomers had expected the galaxy's structure to appear.
Why it matters
The Milky Way is the galaxy the Sun, the Earth, and you belong to. Learning that its backbone assembled this close to the beginning places our entire local story near the dawn of cosmic history rather than late in it, and it shows how quickly the raw universe organized itself into the kind of galaxy that could one day hold planets and people.
How we know
The finding comes from ESA's Gaia spacecraft, a mission built to chart the Milky Way in three dimensions. By dating the galaxy's oldest stars from their light and tracking how they move, researchers pushed the age of the thick disc back to about 13 billion years, a result ESA describes as surprising precisely because it is so early.
Sources
- European Space Agency. Gaia finds parts of the Milky Way much older than expected (European Space Agency) (2022) · Reputable sourceesa.int · The domain "esa.int" is on our Reputable source registry. · Link is live and its text matches the event's key terms (Jul 2026)
- A time-resolved picture of our Milky Way's early formation history (Nature, 2022, via PubMed Central) (2022) · Peer-reviewed (author-declared)pmc.ncbi.nlm.nih.gov · Cited as a "journal" source (no stronger domain match). · Link is live and its text matches the event's key terms (Jul 2026)
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