An asterism is a recognizable pattern of stars that is smaller than a constellation. While a constellation is a larger, officially recognized region of the sky containing many stars, an asterism is simply a smaller, more easily identifiable group of stars within that constellation.

Here are some famous examples:

* The Big Dipper: This familiar asterism is part of the constellation Ursa Major (the Great Bear).

* The Little Dipper: This is a smaller asterism within the constellation Ursa Minor (the Little Bear).

* Orion's Belt: This asterism of three stars is a prominent feature of the constellation Orion.

Let me know if you have any other astronomy questions!