The three largest constellations are gracing the evening skies. Hydra, the sea serpent; Virgo, the maiden; and Ursa Major, the big bear are visible in the night sky right now. The largest constellation by area is Hydra which is 3.16% of the sky. The smallest is Crux which only takes up 0.17 percent of the sky. Small patterns of stars within a constellation are called asterisms. The word "constellation" comes from a Latin term meaning "set with stars." The International Astronomical Union divided the celestial sphere into 88 constellations in 1922, with the help of Henry Norris Russell, an American astronomer. 48 of the 88 constellations officially recognized by the International Astronomical Union were recorded in 150 AD by Ptolemy, a Greek astronomer. He recorded the constellations in his book Almagest.
