“The Ashen Light of the Moon”

Prof. Denis Bastieri
University of Padova

DATE: 01 September 2018
TIME: 9:00 – 10:00 am
LOCATION: Rigoni Stern Institute, Asiago


The Ashen Light of the Moon is the dark, but still observable to the naked eye, gibbous area which complements the crescent Moon.  The first explanation was given by Leonardo in his collections of scientific notes known as the “Codex Leicester”, which was acquired by Bill Gates for more than 30M$ and that topped the list of the most expensive books for many years.
The term “Ashen Light” comes from another Italian scientist, the Jesuit G.B. Riccioli, who observed a bewildering glow in the night hemisphere of Venus and had been used ever since to describe those two faint emissions.
The phenomenon, in the case of the Moon, is due to the light from the Sun reflected by the Earth toward the Moon and, more generally, is nowadays known as “planetshine”.
In this lecture, we will follow the lead of Leonardo and delve into the motion of the Moon around the Earth and the Sun, learning what an astronomer from the Renaissance should have known and understand why the “Ashen Light” happens.  Then, we will leverage “planetshine” as a long-term monitor of Earth’s own climate and as a tool to discover habitable planets outside the Solar System.

will be provided during the lecture