Here's why:

* Constellations are patterns of stars that have been given names by different cultures throughout history. These patterns are not physically connected, but they appear close together in the sky from our perspective on Earth.

* The Big Dipper is actually part of a larger constellation called Ursa Major (the Great Bear). The Big Dipper itself is an asterism, which is a recognizable pattern of stars within a constellation.

So, while the Big Dipper is a recognizable group of stars, its official designation is an asterism within the constellation Ursa Major.