Ursa Major

Ursa Major (Latin: "Larger Bear"), also known as the Great Bear, is a constellation visible throughout the year in most of the northern hemisphere. It can best be seen in April. It is dominated by the widely recognized asterism known as the Big Dipper or Plough, which is a useful pointer toward north, and which has mythological significance in numerous world cultures.
==Asterisms==
The seven brightest stars of Ursa Major form the asterism known as the Big Dipper in the United States and Canada, or the Plough in the United Kingdom and Ireland.
Another asterism is recognized in Arab culture, a series of three pairs of stars:
* ν and ξ Ursae Majoris, Alula Borealis and Australis, the "first leap";
* λ and μ Ursae Majoris, Tania Borealis and Australis, the "second leap";
* ι and κ Ursae Majoris, Talitha Borealis and Australis, the "third leap".
These stars are found along the southwest border of the constellation.
==Notable features==
===Stars===
Except for Dubhe and Alkaid (Eta Ursae Majoris), the stars of the Big Dipper all have proper motions heading toward a common point in Sagittarius. A few other such stars have been identified, and together they are called the Ursa Major Moving Group.
Mizar, a star in the Big Dipper, forms the famous optical double star with Alcor.
The stars Merak (β Ursae Majoris) and Dubhe (α Ursae Majoris) are known as the "pointer stars" because they are helpful for finding Polaris, also known as the North Star. By visually tracing a line from Merak through Dubhe and continuing, one's eye will land on Polaris, accurately indicating true north.
W Ursae Majoris is the prototype of a class of contact binary variable stars, and ranges between 7.75m and 8.48m.
47 Ursae Majoris is a Sun-like star with a three-planet system. 47 Ursae Majoris b, discovered in 1996, orbits every 1078 days and is 2.53 times the mass of Jupiter. 47 Ursae Majoris c, discovered in 2001, orbits every 2391 days and is 0.54 times the mass of Jupiter. 47 Ursae Majoris d, discovered in 2010, has an uncertain period, lying between 8907 and 19097 days; it is 1.64 times the mass of Jupiter. The star is of magnitude 5.0 and is approximately 42 light-years from Earth.
===Deep-sky objects===
Several bright galaxies are found in Ursa Major, including the pair Messier 81 (one of the brightest galaxies in the sky) and Messier 82 above the bear's head, and Pinwheel Galaxy (M101), a spiral northeast of η Ursae Majoris. The spiral galaxies Messier 108 and Messier 109 are also be found in this constellation. The bright planetary nebula Owl Nebula (M97) can be found along the bottom of the bowl of the Big Dipper. 
M81 is a nearly face-on spiral galaxy 11.8 million light-years from Earth. Like most spiral galaxies, it has a core made up of old stars, with arms filled with young stars and nebulae. Along with M82, it is a part of the galaxy cluster closest to the Local Group. M82 is a galaxy that is interacting gravitationally with M81. It is the brightest infrared galaxy in the sky.
M97, also called the Owl Nebula, is a planetary nebula 1,630 light-years from Earth; it has a magnitude of approximately 10. It was discovered in 1781 by Pierre Méchain.
M101, also called the Pinwheel Galaxy, is a face-on spiral galaxy located 25 million light-years from Earth. It was discovered by Pierre Méchain in 1781. Its spiral arms have regions with extensive star formation and have strong ultraviolet emissions. It has an integrated magnitude of 7.5, making it visible in both binoculars and telescopes, but not to the naked eye.
NGC 2787 is a lenticular galaxy at a distance of 24 million light-years. Unlike most lenticular galaxies, NGC 2787 has a bar at its center. It also has a halo of globular clusters, indicating its age and relative stability.
NGC 3079 is a starburst spiral galaxy located 52 million light-years from Earth. It has a horseshoe-shaped structure at its center that indicates the presence of a supermassive black holes. The structure itself is formed by superwinds from the black hole.
NGC 3310 is another starburst spiral galaxy located 50 million light-years from Earth. Its bright white color is caused by its higher than usual rate of star formation, which began 100 million years ago after a merger. Studies of this and other starburst galaxies have shown that their starburst phase can last for hundreds of millions of years, far longer than was previously assumed.
NGC 4013 is an edge-on spiral galaxy located 55 million light-years from Earth. It has a prominent dust lane and has several visible star forming regions.
I Zwicky 18 is a young dwarf galaxy at a distance of 45 million light-years. The youngest known galaxy in the visible universe, I Zwicky 18 is about 4 million years old, about one-thousandth the age of the Solar System. It is filled with star forming regions which are creating many hot, young, blue stars at a very high rate.
The Hubble Deep Field is located to the northeast of δ Ursae Majoris.
===Meteor showers===
The Kappa Ursae Majorids are a newly-discovered meteor shower, peaking between November 1 and November 10.
==History==
Ursa Major was one of the 48 constellations listed by the 2nd century AD astronomer Ptolemy. It is mentioned by such poets as Homer, Spenser, Shakespeare, Tennyson and Bertrand Cantat. The Finnish epic Kalevala mentions it, Vincent van Gogh painted it and Federico Garcia Lorca mentions in his poem "Song for the Moon" written August 1920. In 2009, the American rock band Third Eye Blind named their fourth album, Ursa Major, after the constellation.
==Mythology==
The constellation of Ursa Major has been seen as a bear by many distinct civilizations. This may stem from a common oral tradition stretching back more than 13,000 years.Bradley E Schaefer, The Origin of the Greek Constellations: Was the Great Bear constellation named before hunter nomads first reached the Americas more than 13,000 years ago?, Scientific American, November 2006, reviewed at The Origin of the Greek Constellations 
In Greek mythology, Zeus (the king of the gods) lusts after a young woman named Callisto, a nymph of Artemis. Hera, Zeus' jealous wife, transforms the beautiful Callisto into a bear. Callisto, while in bear form, later encounters her son Arcas. Arcas almost shoots the bear, but to avert the tragedy, Zeus turns them into bears and puts them in the sky, forming Ursa Major and Ursa Minor. Callisto is Ursa Major and her son, Arcas is Ursa Minor. In ancient times the name of the constellation was Helike, ("turning"), because it turns around the Pole. In Book Two of Lucan it is called Parrhasian Helice, since Callisto came from Parrhasia in Arcadia, where the story is set.Hamilton, Edith Mythology New American Library, New York, 1942, chapter 21 (Callisto). The Odyssey notes that it is the sole constellation that never sinks below the horizon and "bathes in the Ocean's waves". It is also referred to as the "Wain".
One of the few star groups mentioned in the Bible (Job 9:9; 38:32; — Orion and the Pleiades being others), Ursa Major was also pictured as a bear by the Jewish peoples. ("The Bear" was translated as "Arcturus" in the Vulgate and it persisted in the KJV.)
The Iroquois Native Americans interpreted Alioth, Mizar, and Alkaid as three hunters pursuing the Great Bear. According to one version of their myth, the first hunter (Alioth) is carrying a bow and arrow to strike down the bear. The second hunter (Mizar) carries a large pot — the star Alcor — on his shoulder in which to cook the bear while the third hunter (Alkaid) hauls a pile of firewood to light a fire beneath the pot.
In Hinduism, Ursa Major is known as Saptarshi, each of the stars representing one of the Saptarshis or Seven Sages viz. Bhrigu, Atri, Angirasa, Vasishta, Pulastya, Pulalaha and Kratu. The fact that the two front stars of the constellations point to the pole star 
is explained as the boon given to the boy sage Dhruva by Lord Vishnu.
In Finnish language, the asterism is sometimes called with its old Finnish name, Otava. The meaning of the name has been almost forgotten in Modern Finnish; it means a salmon weir.
In Burmese, Pucwan Tārā (pronounced "bazun taja") is the name of a constellation comprising stars from the head and forelegs of Ursa Major; pucwan is a general term for a crustacean, such as prawn, shrimp, crab, lobster, etc.
In theosophy, it is believed the Seven Stars of the Pleiades focus the spiritual energy of the Seven Rays from the Galactic Logos to the Seven Stars of the Great Bear, then to Sirius, then to the Sun, then to the god of Earth (Sanat Kumara), and finally through the seven Masters of the Seven Rays to the human race.Baker, Dr. Douglas The Seven Rays:Key to the Mysteries 1952
In South Korea, the constellation is referred to as "the seven stars of the north". In the related myth, a widow with seven sons found comfort with a widower, but to get to his house required crossing a stream. The seven sons, sympathetic to their mother, placed stepping stones in the river. Their mother, not knowing who put the stones in place, blessed them and, when they died, they became the constellation.
In Javanese, as known as "Bintang Kartika". This name comes from Sanskrit which refers "krttikã" the same star cluster. In ancient Java, this star clusters so popular because its emergence into the start time marker for planting.
In Shinto, the 7 largest stars of Ursa Major belong to Amenominakanushi, the oldest and most powerful of all kami.
==Graphic visualisation==
In European star charts, the constellation was visualized with the 'square' of the Big Dipper forming the bear's body and the chain of stars as a long tail. However, bears do not have long tails, and Jewish astronomers considered Alioth, Mizar, and Alkaid instead to be either three cubs following their mother, and the Native Americans as three hunters.
Noted children's book author H. A. Rey, in his 1952 book The Stars: A New Way to See Them, (ISBN 0-395-24830-2) instead had the "bear" image of the constellation, much as Johannes Hevelius had done (as far as the figure of the bear facing "left"), oriented with Alkaid as the tip of the bear's nose, and the "handle" of the Big Dipper part of the constellation forming the outline of the top of the bear's head and neck, rearwards to the shoulder. Because of Rey's book, many amateur astronomers have come to accept Rey's star chart interpretation of Ursa Major, dropping the idea of the Big Dipper's "handle" as being the hind end of the bear, with a non-natural "tail" extending rearwards.
File:Ursa Major2.jpg|Ursa Major as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.
File:Ursa Major constellation Hevelius.jpg|Johannes Hevelius drew Ursa Major as if being viewed from outside the celestial sphere.
File:Starry Night Over the Rhone.jpg|Starry Night Over the Rhone by Vincent van Gogh
==See also==
* Ursa Minor
==References==
;Citations
;Bibliography
* 
==Further reading==
* Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0-00-725120-9. Princeton University Press, Princeton. ISBN 978-0-691-13556-4.
==External links==
* The Deep Photographic Guide to the Constellations: Ursa Major
* AAVSO: The Myths of Ursa Major
* The Origin of the Greek Constellations
* Star Tales – Ursa Major
* Ursa Major - Constellation Guide
 
Category:Constellations
Category:Northern constellations
Category:Constellations listed by Ptolemy