South Pole Telescope Maps Matter With the Clearest CMB Lensing Yet
SPT-3G mapped the matter between us and the Big Bang's afterglow by measuring how gravity bends that light, the most sensitive such map to date.
The South Pole Telescope has produced the clearest map yet of the matter spread through the distant universe, built from the way that matter bends the cosmic microwave background (CMB), the afterglow of the Big Bang. It is the most sensitive measurement of CMB lensing to date. The paper, led by Yuuki Omori of the University of Chicago with scientists from 30 institutions, was posted to arXiv on September 1, 2026, and UChicago reported the result on September 3.
The CMB has been traveling toward us since the universe was about 400,000 years old, and it was first detected in 1965 by Penzias and Wilson. On its way, the gravity of everything in between, ordinary and dark matter alike, bends its path slightly. By measuring that distortion with the SPT-3G camera at the Amundsen-Scott South Pole Station, the team reconstructed all the intervening matter, visible or not.
The results agree very well with the Planck satellite and the Atacama Cosmology Telescope. Combined with the Dark Energy Survey, they give the best constraints yet on how structure grew. That matters because measuring how “clumpy” the universe is in its middle years tests whether the standard cosmological model holds between the CMB era and today. The paper is a preprint, not yet peer reviewed. For background, see our cosmology guide and our dark matter guide.
What to watch next: the team’s longer-term goals are to weigh neutrinos and to look for primordial gravitational waves from cosmic inflation.
Primary source
This summary is based on University of Chicago News and the peer-reviewed paper. Read the original for full details, data and caveats.
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