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Ursa Major
Ursa Major (also known as the Great Bear and Charles' Wain) is a constellation in the northern celestial hemisphere. One of the 48 constellations listed by Ptolemy (second century AD), it remains one of the 88 modern constellations. It can be visible throughout the year in most of the northern hemisphere. Its name, Latin for "the greater (or larger) she-bear", stands as a reference to and in direct contrast with Ursa Minor, "the smaller she-bear", with which it is frequently associated in mythology and amateur astronomy. The constellation's most recognizable asterism, a group of seven relatively bright stars commonly known as the "Big Dipper", "the Wagon" or "the Plough" (among others), both mimicks the shape of the lesser bear (the "Little Dipper") and is commonly used as a navigational pointer towards the current northern pole star, Polaris in Ursa Minor. The Big Dipper and the constellation as a whole have mythological significance in numerous world cultures, usually as a symbol of the north.
The third largest constellation in the sky, Ursa Major is home to many deep-sky objects including seven Messier objects, four other NGC objects and I Zwicky 18, the youngest known galaxy in the visible universe.
==Characteristics==
Ursa Major occupies a large area in the northern celestial hemisphere. The third largest constellation in the night sky (after Hydra and Virgo), its 1279.66 square degrees of surface area being equivalent to 3.10% of the total sky. The official constellation boundaries, set by Eugène Delporte in 1930, form a 28-sided irregular polygon which, according to the equatorial coordinate system, stretches between the right ascension coordinates of and and the declination coordinates of 28.30° and 73.14°. It is bordered by eight other constellations: Draco to the north and northeast, Boötes to the east, Canes Venatici to the east and southeast, Coma Berenices to the southeast, Leo and Leo Minor to the south, Lynx to the southwest and Camelopardalis to the northwest. It's also the namesake of its constellation family, which includes all the constellations it borders except for Leo (a member of the Zodiac), and also Ursa Minor and Corona Borealis. The three-letter abbreviation for the constellation, as adopted by the International Astronomical Union in 1922, is 'UMa'.
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