Cosmologists study the Universe by making a vast range of observations using a variety of modern techniques. Each observation can reveal different details about the Universe’s composition over a certain period of its history. An astronomical survey—a map of a region of the sky—is a powerful way to scan a large swath of the Universe and the objects it contains. For example, a weak-lensing survey does that by obtaining sharp images of galaxies, which can then be used to map the distribution of the Universe’s matter throughout history. The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is one such weak-lensing survey, and it has the highest resolution and the deepest depth of all current weak-lensing surveys. Over the past six years, the HSC-SSP survey team has spent 330 nights scanning 3% of the entire spherical sky, capturing the light emitted by galaxies up to 10 billion years ago. The team has now analyzed 40% of its data [1–5], finding results that are inconsistent with the predictions of cosmological models derived from Planck-satellite data of the early Universe, such as measurements of the Universe’s first light. This inconsistency has repeatedly turned up in weak-lensing surveys, suggesting there exists a fundamental defect in the standard cosmological model, known as ΛCDM.
To read more, click here.