~13 billion years agoReputable sourceWell documented
The Birth of the Milky Way
On the timeline · around ~13 billion years ago · The Age of Galaxies
What happened
Our own galaxy began taking shape very early. Measurements from the European Space Agency's Gaia mission show that the Milky Way's thick disc started forming about 13 billion years ago — only around 0.8 billion years after the Big Bang. Over the following billions of years the galaxy grew by pulling in and merging with smaller galaxies, including one called Gaia-Sausage-Enceladus about 10 billion years ago.
Why it matters
The Milky Way is our cosmic home, and mapping how it assembled from ancient stars and galactic collisions tells us where the Sun, the Earth, and we ourselves come from.