ScienceDaily (Oct. 14, 2010) — Astronomers using the South Pole Telescope report that they have discovered the most massive galaxy cluster yet seen at a distance of 7 billion light-years. The cluster (designated SPT-CL J0546-5345) weighs in at around 800 trillion Suns, and holds hundreds of galaxies.
"This galaxy cluster wins the heavyweight title. It's among the most massive clusters ever found at this distance," said Mark Brodwin, a Smithsonian astronomer at the Harvard-Smithsonian Center for Astrophysics. Brodwin is first author on the paper announcing the discovery, which appeared in the Astrophysical Journal.....
http://www.sciencedaily.com/releases...1013122559.htm
I thought this part interesting as well as the main discovery:
They're hunting for giant galaxy clusters using the Sunyaev-Zel'dovich effect -- a small distortion of the cosmic microwave background (a pervasive all-sky glow left over from the Big Bang). Such distortions are created as background radiation passes through a large galaxy cluster.