A team of astronomers has discovered the most distant cluster of
red galaxies ever observed using FourStar, a new and powerful
near-infrared camera on the 6.5-metre Magellan Baade Telescope.
The galaxy cluster is located 10.5 billion light-years away in
the direction of the constellation Leo. It is made up of 30
galaxies packed closely together, forming the earliest known
“galaxy city” in the universe. The findings will be published in
the Astrophysical Journal Letters.  Remarkably, the cluster was
completely missed by previous surveys, which searched this
region of the sky for thousands of hours and were conducted by
all the major ground- and space-based observing facilities,
including the Hubble Space Telescope. Despite these intense
observations, accurate distances for such faint and distant
galaxies were missing until the advent of FourStar.  Eric
Persson of the Carnegie Observatories led the development of the
new camera that enabled these observations.  Persson and his
team equipped FourStar with five