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What’s a Blood Moon? And Other Lunar Eclipse Questions.

Tonight, Australians, Africans, Europeans, Asians and South Americans will have the opportunity to see the longest lunar eclipse of the century. Sorry North America. 

Lunar eclipses occur about 2-4 times per year, when the Moon passes into the Earth’s shadow. In order to see a lunar eclipse, you must be on the night side of the Earth, facing the Moon, when the Earth passes in between the Moon and the Sun. Need help visualizing this? Here you go:

What’s the difference between a solar eclipse and a lunar eclipse?

An easy way to remember the difference between a solar eclipse and a lunar eclipse is that the word ‘eclipse’ refers to the object that is being obscured. During a solar eclipse, the Moon blocks the Sun from view. During a lunar eclipse, the Earth’s shadow obscures the Moon.

Why does the Moon turn red?  

You may have heard the term ‘Blood Moon’ for a lunar eclipse. When the Moon passes into the Earth’s shadow, it turns red. This happens for the exact same reason that our sunrises and sunsets here on Earth are brilliant shades of pinks and oranges. During a lunar eclipse, the only light reaching the Moon passes through the Earth’s atmosphere. The bluer, shorter wavelength light scatters and the longer wavelength red light passes through and makes it to the Moon.

What science can we learn from a lunar eclipse?

"During a lunar eclipse, the temperature swing is so dramatic that it’s as if the surface of the Moon goes from being in an oven to being in a freezer in just a few hours,” said Noah Petro, project scientist for our Lunar Reconnaissance Orbiter, or LRO, at our Goddard Space Flight Center in Greenbelt, Maryland.

The Diviner team from LRO measures temperature changes on the Moon through their instrument on the spacecraft as well as through a thermal camera on Earth. How quickly or slowly the lunar surface loses heat helps scientists determine characteristics of lunar material, including its composition and physical properties.

When is the next lunar eclipse?

North Americans, don’t worry. If skies are clear, you can see the next lunar eclipse on January 21, 2019. The eclipse will be visible to North Americans, South Americans, and most of Africa and Europe.

To keep an eye on the Moon with us check out nasa.gov/moon or follow us on Twitter and Facebook.

Make sure to follow us on Tumblr for your regular dose of space: http://nasa.tumblr.com.