IAU designated constellations

[1] Each constellation is a region of the sky bordered by arcs of right ascension and declination, together covering the entire celestial sphere.

[2] The ancient Mesopotamians and later the Greeks established most of the northern constellations in international use today, listed by the Roman-Egyptian astronomer Ptolemy.

In 1922, the International Astronomical Union adopted three-letter abbreviations for 89 constellations, the modern list of 88 plus Argo.

Some constellations are no longer recognized by the IAU, but may appear in older star charts and other references.

In the 1750s the French astronomer Nicolas Louis de Lacaille divided this into three separate constellations: Carina, Puppis, and Vela.

Some ancient asterisms, for example Coma Berenices, Serpens, and portions of Argo Navis, are now officially constellations.