Field guide · Reading the sky
ConstellationConstellation
Officially, one of 88 regions that divide the whole sky with no gaps, like countries on a map. The stick figures are the old pictures the regions are named after.
- Official number
- 88, since 1922
- Biggest
- Hydra
- Smallest
- Crux, the Southern Cross
- Borders drawn
- 1930, by Eugène Delporte
Every culture has joined the stars into pictures. The ones used internationally today come mostly from ancient Greece by way of Ptolemy’s 48 constellations, filled out in the 1500s–1700s by Dutch navigators and astronomers mapping the southern sky Europeans had never seen.
By 1900 there were rival maps with overlapping, ill-defined figures. In 1922 the International Astronomical Union settled on 88, and in 1930 Eugène Delporte drew their borders along lines of right ascension and declination. Since then a constellation is an area, not a shape: every star, galaxy and asteroid belongs to exactly one.
The stars in a constellation are usually not related at all. They lie at wildly different distances and only look close from where we stand. Switch on the boundaries layer to see the regions; tap one to see what lives in it.
See it in the sky
Each one opens the sky map pointed at it, for tonight, from where you are.