An asterism is a recognizable group of stars that is not accepted as a constellation by the International Astronomical Union. The Big Dipper is the perfect example: it is part of Ursa Major. The Dipper, the Wagon, or the Plough was recognized as a distinct image by various peoples in what is today “Great Britain.” To ancient people in modern Finland, it was a net. To some native Americans (Ojibiway or “Chippewa”) the bowl of the Dipper was a Bear, and the three (or four) stars of the Handle were cubs trailing, or else hunters in pursuit. Mizar was supposed to be one of the hunters, and Alcor was the pot in which the Bear was to be cooked, something of a challenge to be sure - hunters are optimists.
Australian Astronomical Observatory.
Essay by Pleiade Architects of Bristol UK.
The Belt of Orion, the Sword of Orion, the Spout of the Tea Kettle, the Pleiades the Northern Cross, … we find them useful.
In that utility, asterisms remain important to the societal institution that we call astronomy. Certainly, the physics of astronomy also must remain important. We are not merely gaping open-mouthed at the splendor of the night skies like slack-jawed anthropoids. However, the sociology of the science of astronomy is a different pursuit entirely. Papers published in peer-reviewed academic journals may or may not illuminate the thrills and wonders of the night sky. The distinction between an asterism and a constellation must remain a modern nicety. After all, nothing about these is actually written in the stars. We decide what images to see when we connect the dots.
It is true that some of them do look similar to things we know. The first three recorded constellations were the Bull, the Lion, and the Scorpion. They marked the year in old Sumeria. But the head of the Lion is also the Sickle... and the poor Scorpion lost his powerful claws when the Romans invented the constellation of Libra: 12 constellations, for 12 months, for 12 gods, 12 ounces to the pound, and a dozen more that made them feel that the universe is an orderly place. And, indeed, it is. Just look at the night sky.
List of asterisms from Farmers' Almanac.
List of 88 official constellations from The International Astronomical Union.
ALSO ON NECESSARY FACTS