Supermoon
Tonight’s full moon is a “supermoon,” which comes because the moon is at its closest point in its orbit to the Earth.
This is because the moon’s orbit is not a perfect circle, but more of an oval. So, at the closest point of the orbit the moon is a little over 40,000 km closer to the Earth than at its farthest point.
NASA said that this will make tonight’s moon a little larger and brighter in the sky.
Unfortunately, NASA said, you may not be able to notice a big size difference, since it looks about 14% larger in the sky, about the size difference between a quarter and a nickel.
Blue moon
Tonight’s full moon is also a “blue” moon because it is the second full moon this month, a phenomenon that happens every two to three years.
The reason it happens so infrequently, NASA said, is because the moon’s phases take 29.5 days, so the first full moon needs to take place on the first or second of a month to have enough time for a second full moon at the end.
The next one
If you wanted to see the super blue moon but missed it, it will be a little bit before the next one comes around.
NASA said that intervals between super blue moons are very irregular, and could take as much as 20 years. However, the next super blue moons will actually both come as a pair, in January and March of 2037.
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