How many constellations are there?
There are 88 official constellations, recognized by the International Astronomical Union since 1922. Together, they cover the entire sky with no gaps.
The IAU adopted the list of 88 constellations in 1922, and in 1930 Belgian astronomer Eugène Delporte drew their official boundaries. Every star and point in the sky now belongs to exactly one constellation. This system helps astronomers describe where objects are located.
Of the 88, 48 come from the ancient list compiled by Ptolemy. Others were added from the 1500s to the 1700s, especially after European explorers traveled south and saw stars invisible from Europe. French astronomer Nicolas-Louis de Lacaille named 14 southern constellations, many after scientific instruments, such as Telescopium and Microscopium.
Largest and smallest
Hydra, the water snake, is the largest constellation, stretching across more than a quarter of the sky's width. Crux, the Southern Cross, is the smallest, but it is one of the best known in the Southern Hemisphere and appears on the flags of Australia, New Zealand, Brazil, Papua New Guinea and Samoa.
Did You Know?
From any one place on Earth, you can see only part of the 88 constellations over the course of a year.