Constellations and asterisms: the map of the sky
The 88 official constellations, the familiar shapes inside them and a simple route through the seasonal sky.
A constellation is an official area of sky; there are 88, with borders fixed by the IAU in 1930. An asterism is a recognisable pattern that is not one of them: the Big Dipper is part of Ursa Major, and the Summer Triangle spans three constellations.
Learn the sky with signposts
Start from a few bright patterns and hop outward:
- All year (north): the Big Dipper → Polaris → Cassiopeia. They never set from northern Europe or Canada.
- Winter: Orion’s belt points down to Sirius and up to Aldebaran and the Pleiades.
- Spring: follow the arc of the Dipper’s handle to Arcturus, then “spike” on to Spica.
- Summer: Vega, Deneb and Altair make the Summer Triangle, with the Milky Way running through it.
- Autumn: the Great Square of Pegasus leads to the Andromeda Galaxy, the farthest thing you can see with the naked eye (2.5 million light years).
Shapes depend on culture
The figures are inherited mostly from Greek astronomy, but every culture drew its own: the Big Dipper is a plough in Britain, a wagon in Scandinavia and Germany, and an elk in Sámi and Finnish tradition. Browse all 88 constellations and the brightest stars.