A supermoon is broadly defined as a full moon that is closer to the Earth than normal. That makes it appear slightly brighter and bigger in the sky.

According to the Old Farmer’s Almanac, the August full moon is traditionally known as the “sturgeon moon” because of the abundance of that fish in the Great Lakes in August hundreds of years ago.

Tuesday’s supermoon will be followed by another on the night of August 30. Because it will be the second full moon in the same month, it will be what is called a “blue moon”.

The last time two full supermoons were seen in the same month was in 2018. They are not expected to happen again until 2037.

This year’s first supermoon was in July. The fourth and last will be in September. The two in August will be closer than either of those.