constellation (in astronomy)
constellation, in common usage, group of stars that appear to form a configuration in the sky; properly speaking, a constellation is a definite region of the sky in which the configuration of stars is contained. Identifiable groupings of bright stars have been recognized and named since ancient times, the names corresponding to mythological figures (e.g., Perseus, Andromeda, Hercules, Orion), animals (e.g., Leo the Lion, Cygnus the Swan, Draco the Dragon), or objects (e.g., Libra the Balance, Corona the Crown). Ptolemy listed 48 constellations in his Almagest (2d cent. AD).
As systematic observations were extended to the entire southern sky from the 17th cent. on, more constellations were added to the list by J. Bayer, N. L. de Lacaille, and others. For example, Ptolemy's 48th constellation, Argo Navis, representing a ship, was divided into four smaller constellations corresponding to different parts of the ship. The final list consists of 88 constellations, each associated with a definite region of the sky. Thus, the entire celestial sphere is divided according to a plan prepared by Eugene Delporte, with the boundaries fixed by international agreement in 1930, along lines of right ascension and declination (see equatorial coordinate system). The 12 constellations located along or near the ecliptic, the apparent path of the sun through the heavens, are known as the constellations of the zodiac; the remaining constellations are officially classified as northern (28 constellations) or southern (48 constellations).
The table entitled Constellations lists the constellations according to their official Latin names, with the English equivalents and the approximate positions given. In some cases, the English name for a constellation is not an exact translation of the Latin; e.g., the English name for Pictor reflects the fact that the figure in the constellation is not the painter himself but his easel. Certain familiar star groups, or asterisms, are not listed as constellations because they form only part of a larger constellation; the Big Dipper and Little Dipper are parts of the constellations Ursa Major and Ursa Minor, and the Northern Cross is part of Cygnus.
Bright stars within a constellation are designated according to a system originated by Bayer in 1603: the brightest star is designated by the Greek letter alpha followed by the genitive form of the Latin name for the constellation, the second brightest star by beta, and so on, with Roman letters and pairs of Roman letters being used after the Greek letters have all been assigned. For example, the brightest star in Taurus, Aldebaran, is designated Alpha Tauri, the second brightest, Elnath, is designated Beta Tauri, and so on. The alphabetical order does not always indicate the stars' relative brightness: in a few cases, e.g., Ursa Major, the assignment of a Bayer name is according to position rather than brightness.
Constellation (kŏnstĬlā´shən), U.S. frigate, launched in 1797. It was named by President Washington for the constellation of 15 stars in the U.S. flag of that time. The frigate was built to serve against the pirates of the Barbary States, but after the outbreak (1798) of hostilities between the United States and France, it was stationed in Caribbean waters. After the Constellation, commanded by Thomas Truxtun, encountered and captured (Feb., 1799) the vessel Insurgente, it won (Feb., 1800) a hard-fought victory over another French frigate, the Vengeance. The Constellation was blockaded at Norfolk, Va. during the War of 1812, but further victories followed in the Mediterranean in 1815. Rebuilt in 1853–55, the Constellation was used against Confederate commerce cruisers in the Civil War and later served (1873–93) as a training ship at Annapolis, Norfolk, and Philadelphia. It became the ship with the longest period of service in the navy when it saw duty as flagship of the U.S. Atlantic fleet during World War II. It is preserved at Baltimore.
See study by H. I. Chapelle and L. D. Polland (1970).