The Ashen Light of Venus
For almost four centuries, astronomers have reported a faint glow on the dark side of Venus, where there should be nothing to see.
What was reported
In 1643, the Jesuit astronomer Giovanni Riccioli, in Bologna, reported that when Venus showed as a thin crescent, the dark part of the planet seemed to glow faintly, like the dim light on the Moon's dark side. Since then, many observers, including famous astronomers, have reported the same 'ashen light'.
Others, using the same telescopes, have never seen it. Unlike the Moon, Venus has no bright world nearby to light up its night side.
Explanations offered
The ashen light has never been clearly recorded by a spacecraft, and many astronomers think it's an illusion: the eye fills in the rest of a disc beside a bright crescent. Others have suggested lightning in Venus's clouds or a glow from its upper atmosphere. In 2001, a faint glow from oxygen was detected on the night side, but it's probably too dim to see.
- When
- First reported in 1643
- Where
- Bologna, Emilia-Romagna, Italy
- Witnesses
- Giovanni Riccioli and many astronomers since
- Status
- Unconfirmed
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.
More from Italy