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Constellation families also known as a constellation groups or groups of constellations, are gatherings of constellations within the same region of the celestial sphere. Some constellation families are named after their most important constellation within the group. Some others are named after the zodiac or themed on mythological regions; "Heavenly Waters" is a more recent grouping. Astronomers Nicolas Louis de Lacaille and Johann Bayer, who invented the constellations in the southern sky, contributed as well. There are eight modern constellation families: Ursa Major, the Zodiac, Perseus, Hercules, Orion, Heavenly Waters, Bayer, and La Caille. All are based on ancient collections of constellations. The Ancient Egyptians had a particular area of the sky with several separately identified constellations collectively known, celestially speaking (not just the underworld), as the Duat.
The Ursa Major Family is a group of 10 constellations composed of Ursa Major, Ursa Minor, Draco, Canes Venatici, Boötes, Coma Berenices, Corona Borealis, Camelopardalis, Lynx, and Leo Minor. This family can be found around the north celestial pole. The prototypical constellation Ursa Major contains the famous Big Dipper.
The Zodiac is a group of 12 constellations composed of Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, Pisces, Aries, Taurus, Gemini, and Cancer. These constellations have zodiac signs. The ecliptic and the sun apparently pass through these constellation throughout the year. However, the sun and the ecliptic also pass through the constellation Ophiuchus, which doesn't have a zodiac sign. The northern zodiacal constellations are in the eastern celestial hemisphere and the southern are in the west.
The Perseus Family or Perseus Group is a group of 9 constellations composed of Cassiopeia, Cepheus, Andromeda, Perseus, Pegasus, Cetus, Auriga, Lacerta, and Triangulum. It spans from near the north celestial pole down to –30°. Six of the constellations are named for figures in the Perseus myth – Perseus, his winged horse Pegasus, Andromeda, her parents Cepheus and Cassiopeia, and the sea monster Cetus.
The Hercules Family is a group of 19 constellations composed of Hercules, Sagitta, Aquila, Lyra, Cygnus, Vulpecula, Hydra, Sextans, Crater, Corvus, Ophiuchus, Serpens, Scutum, Centaurus, Lupus, Corona Australis, Ara, Triangulum Australe, and Crux. Several of the constellations, including Hercules and Centaurus, are named for figures in the Heracles myth, while Lyra is the lyre of Orpheus. It is the largest constellation family, spanning from +60° down to –70°, mostly in the western hemisphere.
The Orion Family is a group of 5 constellations composed of Orion, Canis Major, Canis Minor, Monoceros, and Lepus. This group of constellations represent the hunter (Orion) and his two dogs (Canis Major and Canis Minor) chasing the hare (Lepus). The unicorn (Monoceros) was a later addition.
The Heavenly Waters, also known as the Cosmic Waters, is a group of nine constellations composed of Delphinus, Equuleus, Eridanus, Piscis Austrinus, Carina, Puppis, Vela, Pyxis, and Columba. These constellations are associated with lake, river, sea creatures, and ship, in reference to the former constellation Argo Navis, which included what is now Carina, Puppis, and Vela.
The Bayer Family, also known commonly as the Bayer Group, is a group of 11 constellations composed of Hydrus, Dorado, Volans, Apus, Pavo, Grus, Phoenix, Tucana, Indus, Chamaeleon, and Musca. These constellations were introduced to the public by Johann Bayer (hence the name) in 1603. All are named after animals, mostly water animals like the water snake (Hydrus) and the goldfish (Dorado). Because these constellations are located in the far southern sky, they were not visible for the ancient Greeks and Romans. Bayer acquired them from Petrus Plancius who had directed others that the southern skies be charted.
The La Caille Family is a group of 13 constellations composed of Norma, Circinus, Telescopium, Microscopium, Sculptor, Fornax, Caelum, Horologium, Octans, Mensa, Reticulum, Pictor, and Antlia. These constellations were introduced by Nicolas Louis de Lacaille (hence the name) in 1756. Mensa (the table; originally "Mons Mensa" for table mountain) was named after Table Mountain in South Africa where his observatory was located; the remaining dozen were named after scientific instruments and apparatuses like the telescope, microscope, and reticle. Because these constellation are located in the far southern sky, they were not visible for the ancient Greeks and Romans.