A NASA spacecraft designed to study some of the earliest stars has found that the bright, hot light from those first celestial bodies wasn’t able to clear a path through the surrounding gas and dust as effectively as scientists had thought. The result, according to research published Thursday in the journal Science, was a murkier early universe where stars couldn’t shine as brightly as anticipated. The finding is based on observations from NASA’s Cosmic Origins Spectrograph, or COS, a device aboard the Hubble Space Telescope that studies the chemical composition of objects in space by examining the wavelengths of light they emit or absorb. COS was used to study a pair of quasars, the brilliant, active centers of distant galaxies powered by supermassive black holes. By measuring the absorption of light from the quasars as it passed through intervening clouds of gas, scientists were able to calculate the opacity of those clouds and determine how murky they were. The results showed that the gas clouds were about twice as opaque as expected. This means that the ultraviolet light from the early stars was not able to penetrate the gas as deeply as scientists had thought, and as a result, the early universe was not as clear and transparent as previously believed. .