An asterism is a recognizable pattern of stars, but unlike a constellation, it's not officially defined by the International Astronomical Union (IAU).

Here are some examples of well-known asterisms:

* The Big Dipper: Part of Ursa Major (the Great Bear), this is a very recognizable pattern in the Northern Hemisphere.

* The Summer Triangle: Made up of the bright stars Vega (Lyra), Deneb (Cygnus), and Altair (Aquila), this asterism dominates the summer sky.

* Orion's Belt: Three stars in a row in the constellation Orion, easily spotted in the winter sky.

While not official constellations, asterisms are still valuable for amateur astronomers. They serve as helpful landmarks to navigate the night sky and often lead to the discovery of other, less obvious constellations.