What could be the largest structure yet seen in the observable universe has emerged from data taken during a 12-year survey of the night sky.
The discovery is an apparent cluster of quasars some 4 billion light-years across. If it holds up to further scrutiny, it could challenge a long-held assumption that at the cosmos's largest scales, the physical processes at work and the distribution of matter and energy are the same, regardless of an observer's location.
That's the view of the team formally reporting the results Friday in the journal Monthly Notices of the Royal Astronomical Society.
Quasars are the hyperactive centers of large galaxies and are among the brightest, most energetic objects in the sky. Some recent theoretical work suggests that the upper limit to the largest gatherings of galaxies is about 1.2 billion to 1.5 billion light-years across. The structure that the team reports is nearly four times larger than this theoretical limit.