Massive 12-billion-year-old galactic collision helped form the Milky Way

Our home galaxy the Milky Way has grown in size by crashing into its neighbours for billions of years.

One of the biggest crashes we know of, just over 10 billion years ago, was with a galaxy with the enigmatic name of “Gaia-Sausage-Enceladus”.

Now, evidence is mounting that another, similarly…