Scientists at NASA's Goddard Space Flight Center have made a surprising (to them) discovery about the evolution of galaxies.
For the longest time, it was believed that the organized galaxies we see around us, like our own Milky way, settled into their current layout and motion 8 billion years ago and then remained relatively static, in that the stars in them followed a predictable circular motion around the center of the galaxy.
At the same time, young galaxies, further away, are full of chaotic motion with stars going round in all directions, interacting with each other in sometimes violent ways.
But it was thought that this happened only early in a galaxy's lifetime and the chaos died soon enough.
A new study, in which researchers looked at several hundred galaxies from two billion to eight billion light years away, so two to eight billion years younger, and found that the transition from chaos to order took a lot more than previously thought.
Our own Milky Way was still seeing chaotic movements around the time the Sun and the Earth were forming, four to five billion years ago.