Astronomers Debate the Mysterious Glow on Venus's Dark Side
Astronomers have been puzzled for centuries by a faint glow observed on the dark side of Venus, known as 'ashen light.' This phenomenon was first noted by Italian astronomer Giovanni Battista Riccioli in 1643. Despite numerous theories over the years, including solar ultraviolet light, aurorae, and lightning, the exact cause remains elusive. Recent data from NASA's Parker Solar Probe suggests that the glow might be due to 'nightglow,' where the upper atmosphere of Venus lights up after a coronal mass ejection from the sun. This emission, primarily at 557.7 nm, is similar to the green tint seen in some of Earth's auroras. However, the glow is difficult to detect with the naked eye, leading to speculation that those who claim to have seen it may have unusually red-sensitive vision or are experiencing an optical illusion. 
