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 by a perseistent astrophotographer is constructed from 22 years of lunar eclipses. 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.