Cosmic Breakthrough: How CLASS Telescopes Crack the Universe’s Oldest Code

ATACAMA DESERT, Chile, June 12, 2025— The CLASS telescopes in Chile’s Atacama Desert just captured 13-billion-year-old light from the Cosmic Dawn, using groundbreaking tech to outsmart Earth’s noise. Is the discovery the dawn of a new era in astronomy?

Pioneering Polarization Tech

The Cosmology Large Angular Scale Surveyor (CLASS) array, situated at 5,200 meters, uses Variable-delay Polarization Modulators (VPMs) to detect polarized microwave light, which is a million times fainter than regular cosmic microwaves. The transition-edge-sensor bolometers, operating at 40, 90, 150, and 220 GHz, achieve an optical efficiency of 68%.

“No other ground-based experiment can do what CLASS is doing,” says Nigel Sharp of the NSF. This tech filters out galactic and atmospheric noise, revealing the first stars’ fingerprints.

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Outsmarting Earth’s Interference

Detecting Cosmic Dawn’s faint signals from Earth was once deemed impossible due to radio waves, radar, and weather distortions. CLASS’s VPMs modulate polarized light at 10 Hz, separating it from unpolarized atmospheric signals. The 90 GHz telescope’s shift to a rotating half-wave plate boosts linear polarization detection.

By comparing data with Planck and WMAP space missions, researchers like Yunyang Li pinpointed the CMB’s polarized glare, akin to filtering car hood glare with sunglasses. The result is a clear view of the universe’s infancy.

Redefining Ground-Based Astronomy

CLASS’s feat, published in The Astrophysical Journal, surveys 70% of the sky, matching space telescope precision at a fraction of the cost. Its constant-elevation scans trace vast celestial circles, capturing the CMB’s B-mode power spectrum. “Overcoming these obstacles is a significant achievement,” says project leader Tobias Marriage.

CLASS, in collaboration with collaborators from Johns Hopkins, NASA Goddard, and the University of Chicago, demonstrates the capability of ground-based telescopes to compete with satellites, thereby providing deeper insights into the universe.

Did you know?
CLASS’s bolometers, cooled to near absolute zero, are so sensitive they could detect the heat of a single candle from 250 miles away.

A New Cosmic Frontier

CLASS’s success sets the stage for future ground-based observatories like the Simons Observatory, probing dark matter, neutrinos, and cosmic inflation. Its COSMOCal calibration, aiming for 0.1-degree precision, will unify global telescope data.

As the Atacama Desert becomes astronomy’s epicenter, CLASS’s tech-driven triumph challenges space mission dominance, promising cheaper, adaptable cosmic discoveries. Can these telescopes unlock the universe’s deepest secrets?