We’ve found an answer to the puzzle of how the largest galaxies formed

Two galaxies — also known as NGC 4038 and NGC 4039 — colliding to eventually form an elliptical galaxy. Nasa

It is as humbling as it is motivating to think about how much we still have to learn about the universe. My collaborators and I have just tackled one of astrophysics’ enduring mysteries: how massive elliptical galaxies can form.

Now, for the first time, we have solid observational evidence that provides an answer. Our results have recently been published in Nature.