The full moon next Tuesday evening, September 17, is called the harvest moon because it is the full moon closest to the equinox. This year it is also a "supermoon," because it will be closer to earth than it normally is, and will appear slightly bigger. That's not rare this year, as we have four supermoons in a row, but September's is the closest. If those aren't enough reasons to go out and look at the moon Tuesday, there will also be a partial eclipse visible from all of North America.
A lunar eclipse happens when the moon passes through earth's shadow. The large area of visibility compared to a solar eclipse is because the moon is a lot closer to us than the sun is. The moon won't darken, except for a spot where we will see a "bite" taken out of it. This is a great time to gaze at the sky with anyone you know who insists the earth is flat, because the bite will be curved, showing us that the earth is indeed round. Smithsonian has tips for watching the lunar eclipse and the explanation behind it.
(Image credit: Catalin CACIULEANU)