Ursa Major

This article is about the constellation. For other uses, see Ursa Major (disambiguation).

Ursa Major

Constellation
List of stars in Ursa Major
Abbreviation	UMa
Genitive	Ursae Majoris
Pronunciation	/ˈɜrsə ˈmeɪdʒər/, genitive /ˌɜrsiː məˈdʒɒrɨs/
Right ascension	10.67
Declination	+55.38
Area	1280 sq. deg. (3rd)
Main stars	7, 20
Bayer/Flamsteed stars	93
Stars with planets	9
Stars brighter than 3.00m	6
Stars within 10.00 pc (32.62 ly)	12
Brightest star	ε UMa (Alioth) (1.7124m)
Messier objects	7
Meteor showers	Alpha Ursa Majorids Leonids-Ursids
Bordering constellations	Draco Camelopardalis Lynx Leo Minor Leo Coma Berenices Canes Venatici Boötes
Visible at latitudes between +90° and −30°. Best visible at 21:00 (9 p.m.) during the month of April. The Big Dipper or Plough.

Ursa Majortony stank 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

Main article: Big Dipper

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, 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 (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 7.75^m and 8.48^m.

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 η 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 δ 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.

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 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.

Ursa Major is known as Saptarshi Mandal in India, 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 known as Dhruva in India is explained as the boon given to the boy sage Dhruva by Lord Vishnu.

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 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 Rayss to the human race.

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.

• Ursa Major as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.
  Ursa Major as depicted in Urania's Mirror, a set of constellation cards published in London c.1825.
• 
  Johannes Hevelius drew Ursa Major as if being viewed from outside the celestial sphere.
• 
  Starry Night Over the Rhone by Vincent van Gogh

See also

• Ursa Minor

References

• Ian Ridpath and Wil Tirion (2007). Stars and Planets Guide, Collins, London. ISBN 978-0007251209. Princeton University Press, Princeton. ISBN 978-0691135564.

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