Peering into the infant universe via 0.1 kelvin microwave detectors

Space · Published 25 October 2026 Swipe more like this →

In short: To understand how the cosmos began, scientists must look at light emitted just 380,000 years after the Big Bang. The Simons Observatory uses a high-altitude array in Chile to capture this faint microwave haze, seeking clues about cosmic inflation and the mysterious nature of dark energy.

The Simons Observatory (SO) is designed to measure the Cosmic Microwave Background (CMB), the oldest light in the universe. To avoid atmospheric water vapor interfering with microwaves, researchers situated the site on Cerro Toco mountain within Chile's Atacama Desert at 17,000 ft. The observatory utilizes four telescopes—three small-aperture 0.5-m units and one large-aperture 6-m telescope—equipped with 60,000 detectors cooled to a frigid 0.1 kelvin to achieve unprecedented sensitivity.

Scientists aim to describe early perturbations from cosmic inflation, which is a proposed rapid period of exponential growth during the universe's infancy. By measuring temperature and polarization anisotropy across six frequency bands (27, 39, 93, 145, 225, and 280 GHz), researchers hope to distinguish between different inflationary models and potentially discover exotic particles. The project also aims to measure the mass of neutrinos—particles whose mass creation remains unexplained by current physics—by observing gravitational lensing and energy changes in CMB photons as they pass through galaxy clusters.

Beyond the early universe, SO serves as a tool for 'backlight' astronomy. By observing how CMB photons are affected by matter, it will map tens of thousands of galaxy clusters to study galaxy evolution and the process of reionization, when the first stars ionized ordinary hydrogen. It also seeks to resolve discrepancies in the Hubble constant (H0), the current expansion rate of the universe. If these measurements confirm a deviation from the standard model, it could force a fundamental revision of our cosmological understanding.

The project is a $120 million initiative funded mostly by the Simons Foundation. It began its survey following the cancellation of the larger CMB-S4 experiment by the National Science Foundation and Department of Energy. While less sensitive than the original CMB-S4 plans, SO covers all the same science goals and provides a unique opportunity to study our own Milky Way's interstellar medium, including its dust, gas, and magnetic fields.

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