How to spot the 'Da Vinci Glow' crescent moon
Stargazers may be able to catch a glimpse of a ghostly crescent moon this week, aptly named after the genius scientist who first discovered the phenomenon: Leonardo da Vinci.
Starting May 16, the crescent moon will have a shadowy full-moon outline until the new moon sets in on May 19.
This cool lunar occurrence has been marveled at by humans for thousands of years, but it wasn't until the 16th century that Leonardo was able to figure out the "ancient astronomical riddle" that caused the eerie moon shadow, according to NASA.
What is the 'Da Vinci Glow'?
The "ashen glow" of this week's moon, NASA explains, is caused by a phenomenon known as "earthshine," which was first discovered by Leonardo.
A new moon, or when the moon is not visible in the sky, occurs when all of the sun's light is reflected away from the Earth. However, for the next few nights, the usually darkened moon will catch the Earth's reflected glow and return its light -- giving the appearance of a ghostly full moon, according to NASA.
Earthshine typically tends to be the brightest between April and June due to the position of its orbit around the sun.
Although Leonardo was the first to theorize earthshine, he wrongly predicted the source of the Earth's light. The 16th-century astronomer believed that Earth's oceans were the primary source of Earth's light reflection. Only centuries later were Apollo astronauts able to discover that Earth's shine is actually reflected mostly by clouds, according to NASA.
