To see any distance in space, you need some kind of telescope. We’ve got some pretty powerful ones here on Earth, but nature has us beat with gravitational lenses. This is a phenomenon when a relatively nearby object passes directly between us and a more distant object. The gravity from the nearby object acts as like a telescope lens to bend light and magnify the more distant object.
Until now, these gravitational lens have been single stars or distant galaxies, but now a new class of lens is being called into service: entire groups of galaxies. The research is being done as part of the Canada-France-Hawaii Legacy Survey. which will devote 500 nights of telescope time over the next 5 years. They intend to view approximately 1% of the visible sky from their perch in Hawaii.
The survey is about 25% right now, but the team has already turned up several gravitational lensing arcs around galaxy groups. These arcs are highly magnified distant galaxies, which allow scientists to study their light. This survey will allow astronomers to make direct observations, and chart the formation of these structures in the early Universe. They also hope to understand the role of dark matter in their evolution.