Astronomy Picture of the Day

Explanation: What’s creating this giant hole in space? This is not a black hole — it’s a shadow. It’s Earth’s shadow. Since at least the time of Aristotle, people have noted that Earth's dark shadow on the Moon during a partial lunar eclipse is circular -- although never a whole circle. Using modern digital technology, though, the images of multiple lunar eclipses can be combined to show Earth's complete shadow. The featured image compilation is constructed from 22 years of lunar eclipses by a persistent astrophotographer. The Moon is not eclipsed every month (moon-th) because the Moon's orbit is slightly tilted relative to Earth's orbit. Close inspection of some lunar eclipse images shows a faint blue band where Earth’s atmosphere filters out more red sunlight than blue. Later this week a new lunar eclipse will occur and will be best visible in parts of North and South America, Europe, and Africa.