Ursa Major is a constellation visible throughout the year in the northern hemisphere. Its name means Great Bear in Latin, and is associated with the legend of Callisto.
Its seven brightest stars form a famous asterism known in the United Kingdom as the Plough, and was formerly called by the old name Charles's Wain ("wain" meaning "wagon") as it still is in Scandinavia, Karlavagnen. This common Germanic name originally meant the men's wagon (the churls' wagon) in contrast to the women's wagon (Ursa Minor). There is also a theory that it was named after Charlemagne. In North America it is commonly known as the Big Dipper, because the major stars can be seen to follow the rough outline of a large ladle, or dipper; this is recognized as a grouping of stars in many cultures throughout the eras. In Hindu astronomy , it is referred to as Sapta Rishi meaning "The Seven Sages".
It is also known as the Vrihat Saptarishi.
Notable features
From the bowl to the handle, the stars in the Big Dipper are called Dubhe, Merak, Phecda (or Phad), Megrez , Alioth, Mizar, and Alkaid (or Benetnash), and are given Bayer designations of Alpha to Eta Ursae Majoris, in that order. Mizar has a companion star called Alcor, just visible to the naked eye, that served as a traditional test of sight. Both stars are actually multiple in and of themselves, including the first telescopic and spectroscopic binaries.
The star Polaris, the Pole Star, can be found by measuring a line five times the angular distance between the two pointer stars Dubhe and Merak forming the end of the dipper cup, through those stars and up and away from the dipper. The dipper also points the way to other stars, for instance by sweeping down from the handle one reaches Arcturus (α Boötis) and Spica (α Virginis). A mnemonic for this is "Follow the arc to Arcturus, and speed on to Spica.".
In 1869, Richard A. Proctor noticed that, except for Dubhe and Alkaid, the stars of the Big Dipper all have proper motions heading towards a common point in Sagittarius. This group, of which a few other members have been identified (notably Alphecca in Corona Borealis), formed an open cluster at some distant point in the past. Since then the sparse group has been scattered over a region about 30 by 18 light-years, centered some 75 light-years away, making it the closest cluster-like object. About 100 other stars, including Sirius, form a stream sharing approximately the same proper motion as the ex-cluster, but the exact relationship is unclear. Our Solar System is in the outskirts of this stream, but is not a member, being about 40 times older.
In addition to the Big Dipper, another asterism comes from Arab culture – the "leaps of the gazelle", 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, the bear's toes.
W Ursae Majoris is the prototype of a class of contact binary variable stars, and ranges in magnitude between 7.75m and 8.48m.
47 Ursae Majoris has a planetary system with three confirmed planets, 2.54 times and 0.76 times the mass of Jupiter. it is also known as the Vrihat Saptarishi.
Several galaxies are found in Ursa Major, including the pair M81 (one of the brightest galaxies in the sky) and M82 above the bear's head, and M101, a beautiful spiral northwest of η Ursae Majoris. The constellation contains about 50 galaxies, most of which are below 10th magnitude.
History
It was one of the 48 constellations listed by Ptolemy.
This is one of the most widely-known constellations, having been mentioned by such poets as Homer, Spenser, Shakespeare, and Tennyson. The Finnish epic Kalevala mentions them, and Vincent Van Gogh painted them.
When slavery was still allowed in the southern part of the United States of America, slaves wishing to escape to the Yankee North were advised to "follow the drinking gourd," or the circumpolar constellation of Ursa Major, towards freedom.
Mythology
The constellation of Ursa Major, has been seen by many distinct civilizations have seen this figure as a bear. In consequence, together with the nearby Ursa Minor, it formed the basis of the myth of Callisto.
In earlier times, in Greek mythology, Ursa Major was not considered as a bear, and instead its 3 bright stars (situated in the tail) were considered to be apples growing on a tree (sometimes represented by the fainter stars in the remainder of the constellation). The stars were associated with the Hesperides (considered at the same period to be the stars of Ursa Minor). Together with the other constellations in the zodiac sign of Libra (i.e. Boötes, and Draco) these may have formed the origin of the myth of the apples of the Hesperides, which forms part of The Twelve Labours of Hercules
See Also
