Free Astronomy Magazine March-April 2016

GALACTIC EVOLUTION MARCH-APRIL 2016 25 age of disks fact that more and more fre- quently are discovered galaxies of considerable size in eras sub- sequent to the Big Bang by only 700-800 million years; namely, structures which according to the most reliable models on the evolution of galaxies should not have yet even existed at that time. Another unclear point is the difficulty of proving that the larger and most massive gal- axies of our contemporary uni- verse are really the ones that have undergone a greater number of merg- ers, as we would expect if that was the main, if not the only, mechanism of galaxy growth. Proving the existence of that re- lationship would support the most up to date models, but it is not an easy challenge as of each galaxy we only have a ‘still im- A bove, video showing a computer simula- tion of the appearance of two merging spiral galaxies as they would look through the telescope, taking also into account the light absorption due to the interstellar dust. The col- ours are approximately those perceived by the human eye. [Patrik Jonsson, Greg Novak & Joel Primack, University of California, Santa Cruz]