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Ursa Major
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Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. 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.
se stars are found along the southwest border of the constellation.
pt for Dubhe and Alkaid, the stars of the Big Dipper all have proper motions heading towards a common point in Sagittarius.
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Ursa Major is a constellation visible throughout the year in most of the northern hemisphere. Its name means the Great Bear in Latin. 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 well-known 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:
- ? and ? Ursae Majoris, Alula Borealis and Australis, the "first leap";
- ? and µ Ursae Majoris, Tania Borealis and Australis, the "second leap";
- ? and ? 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, the stars of the Big Dipper all have proper motions heading towards 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 (ß Ursae Majoris) and Dubhe (a 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 has a planetary system with two confirmed planets, 2.54 times and 0.76 times the mass of Jupiter.
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 beautiful spiral northwest of ? Ursae Majoris. The other notable spiral galaxies Messier 108 and Messier 109 may also be found in this other constellation. Altogether, the constellation contains about 50 galaxies observable through amateur telescope. The bright planetary nebula Owl Nebula (M97), named for its appearance, can be found along the bottom of the bowl of the Big Dipper. Of note as a curiosity more than an interesting deep sky object is Messier 40, a double star that Messier nonetheless included in his catalogue.
The Hubble Deep Field is located to the northeast of d Ursae Majoris.
History
Ursa Major was one of the 48 constellations listed by the 1st century astronomer Ptolemy. It is mentioned by such poets as Homer, Spenser, Shakespeare, Tennyson and Bertrand Cantat. The Finnish epic Kalevala mentions it, and Vincent Van Gogh painted it.
Mythology
The constellation of Ursa Major has been seen as a bear by many distinct civilizations.
In Greek mythology, Zeus lusts after a young woman named Kallisto, a nymph of Artemis. Hera, Zeus's wife, turns Kallisto into a bear because of her jealousy. Kallisto, while in bear form later encounters her son Arcas. Arcas almost shoots the bear, but to avert the tragedy, Zeus sweeps them both into the sky, forming Ursa Major. In another tale, Ursa Major was associated with the Hesperides. With Ursa Minor, Boötes, Draco, and Hercules it may have inspired the myth of the Apples of the Hesperides, one of The Twelve Labours of Hercules.
One of the few star groups mentioned in the Bible (Job 9:9; 38:32; Amos 5:8 — Orion and the Pleiades being others), Ursa Major was also pictured as a bear by the Jewish peoples. ("The Bear" was mistranslated as "Arcturus" in the Vulgate and the error persisted in the KJV. Later translations have corrected this.)
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 Burmese, Pucwan Tara (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 prawn, shrimp, crab, lobster, etc.
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, and 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.
See also
External links
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