Transit of the Moon

There are two spacecraft following Earth's orbit, STEREO-A and STEREO-B. STEREO-B is following 1 million miles behind the Earth, and STEREO-A is leading 1 million miles ahead of the Earth. Both of them are looking at the Sun and can combine their data into a 3-dimensional image of the Sun.

Recently, the moon passed between STEREO-B and the Sun. When that happens on Earth, it's an eclipse. By coincidence, the size of the Moon and Sun are almost equal when seen from earth, so the moon fully blocks out the sun. From STEREO-B's position, though, the Moon looks much smaller than the Sun, just a small black circle.

Here's a picture. If you click through the link, they have a movie of the Moon passing in front of the Sun.


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