Constellations, the name given by astronomers to the conventional divisions of the stars. Some of these are very ancient, and would seem to have been based on actual resemblances between certain star groups and the objects with which they were originally associated. But probably the real extent of the ancient constellation figures differed very much from that at present assigned to them. Many of the 48 constellations enumerated by Ptolemy must be regarded as comparatively modern. They are as follows: 12 zodiacal constellations, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricornus, Aquarius, and Pisces; 20 constellations north of the zodiac, Ursa Major, Ursa Minor, Draco, Cepheus, Bootes, Corona Borealis, Hercules, Lyra, Cygnus, Cassiopeia, Perseus, Auriga, Ophiu-chus, Serpens, Sagitta, Delphinus, Equulus, Pegasus, Andromeda, Triangulum Boreale; and 16 constellations south of the zodiac, Antinous, Cetus, Orion, Eridanus, Lepus, Canis Major, Canis Minor, Argo, Hydra, Crater, Corvus, Centaurus, Lupus, Ara, Corona Australia, and Piscis Australis. To this list Tycho Brahe added one, Coma Berenices; Hevelius added 13 constellations, Bayer 12, Lacaille 14, Royer 5, and Bode, Lemonnier, Poczobut, and others, some score more.

Only 36 of these new constellations are, however, admitted into the British association catalogue of stars. The leading stars in the constellations are named by Greek letters, numbers, and so on.