A small group of stars that forms a pattern within a constellation is called an asterism.

Here's the difference between a constellation and an asterism:

* Constellation: A larger, recognized area of the sky that contains many stars. It's often named after a mythical figure, animal, or object.

* Asterism: A smaller, recognizable pattern of stars within a constellation. It's not formally recognized like a constellation, but is easily identifiable.

Some famous examples of asterisms include:

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

* The Little Dipper: Part of the constellation Ursa Minor (the Little Bear).

* The Summer Triangle: This asterism is formed by the stars Vega, Deneb, and Altair, located in the constellations Lyra, Cygnus, and Aquila, respectively.

Let me know if you have any other questions!