Eclipse Diagram

What's a solar eclipse?

The August 21, 2017 total solar eclipse was the first to cross a large portion of the United States since 1918. Solar eclipses occur when the Moon comes between the Sun and the Earth, blocking the light of the Sun and casting a shadow on the Earth. The Moon looks almost exactly the same size as the Sun in the sky. This similarity is coincidental! The Sun is 400 times wider than the Moon but it is also 400 times further away, so the two cover the same sized area from our point of view on Earth. For a visual interpretation, see these NASA animations. For more detailed information about the 2017 total solar eclipse, visit our Resources page.

Dynamic Sun Diagram

Our Dynamic Sun

Stars, including our Sun, are complicated wonders of the universe. At the center of the Sun is its hot, dense core, where energy is produced by the process of nuclear fusion (the same source of energy as a hydrogen bomb). The Sun has many other layers, as shown in our diagram. For example, the one labeled “photosphere” is where the light we see from the Sun emerges. Solar scientists are still trying to understand many of the details of the Sun’s structure and overall behavior. Click here to learn more about the new data the Megamovie team aims to discover with your help!