A near-total lunar eclipse will be visible across large areas of North and South America on Thursday night, offering millions of people the chance to observe a striking celestial event. At the eclipse's peak approximately 96% of the Moon's surface will lie within Earth's shadow, producing a dramatic dimming of the lunar disk.
What is a lunar eclipse?
Lunar eclipses occur when Earth moves between the Sun and the Moon and casts its shadow onto the lunar surface. Because the Moon must pass through Earth's shadow for an eclipse to occur, the effect is visible from any location where the Moon is above the horizon at the time of the event.
Near-total, not quite total
This particular event is described as near-total because a small portion of the Moon will remain illuminated even at maximum eclipse. That residual brightness means the Moon will not be completely obscured as it would be during a full totality.
Why the Moon can look reddish
The darkened portion of the Moon may take on a reddish tint — a phenomenon often called a "blood moon" in popular accounts — because of the way sunlight is scattered by Earth's atmosphere. As sunlight passes through the atmosphere, shorter blue wavelengths are scattered out and longer red wavelengths are refracted into the shadow, imparting a coppery or red hue to the lunar surface.
Millions expected to see the event
Large populations across both continents are in positions to view the eclipse, and organizers and observers have said millions could witness the spectacle. The event provides astronomers and skywatchers alike a clear example of the orbital mechanics and atmospheric effects that combine to produce lunar eclipses.