NASA Moon Data Provides More Accurate 2017 Eclipse Path

Using LRO elevation maps, NASA visualizer Ernie Wright at Goddard Space Flight Center in Greenbelt, Maryland, created a continuously varying lunar limb profile as the moon’s shadow passes over the United States as it will during the upcoming eclipse. The mountains and valleys along the edge of the moon’s disk affect the timing and duration of totality by several seconds. Wright also used several NASA data sets to provide an elevation map of Earth so that eclipse observer locations were depicted at their true altitude.

The resulting visualizations show something never seen before: the true, time-varying shape of the moon’s shadow, with the effects of both an accurate lunar limb and the Earth’s terrain.

“We couldn’t have done visualizations like this even 10 years ago,” Wright said. “This is a confluence of increasing computing power and new datasets from remote sensing platforms like LRO and the Shuttle Radar Topography Mission.”

The lunar umbra is the part of the moon’s shadow where the entire sun is blocked by the moon. On an eclipse map, this tells you where to stand in order to experience totality. For centuries, eclipse maps have depicted the shape of the moon’s umbra, or darkest part of its shadow, as a smooth ellipse.

As evidenced in the new visualizations, the umbral shape is dramatically altered by both the rugged lunar terrain and the elevations of observers on Earth.

“We’ve known for a while now about the effects of the lunar limb and the elevation of observers on the Earth, but this is the first time we’ve really seen it in this way,” Wright said. “I think it’ll change how people think about mapping eclipses.”