More than Half Galaxies have collided
A new study published in the recent issue of the Astronomical Journal has found that more than half of the largest galaxies in the nearby universe have collided and merged with another galaxy in the past two billion years.
The idea of large galaxies being assembled primarily by mergers rather than evolving by themselves in isolation has grown to dominate cosmological thinking. However, a troubling
inconsistency within this general theory has been that the most massive galaxies appear to be the oldest, leaving minimal time since the Big Bang for the mergers to have occurred.