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- This article is about the asterism; for other uses, see Big Dipper (disambiguation).
The seven brightest stars of the constellation Ursa Major, the Great Bear, form a well-known asterism that has been recognized as a distinct grouping in many cultures from time immemorial.
Names and lore
In the United Kingdom this pattern is known as the Plough. It was formerly called by the old name Charles' Wain ("wain" meaning "wagon," and derived from the still older Carlswæn) as it still is in Scandinavia, Karlavagnen', or Karlsvognen. 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 Romania, it is known as Carul Mare ("Great Wagon"), as opposed to Carul Mic ("Small Wagon"), Ursa Minor. In German it is sometimes called Großer Wagen (Great Cart).
In North America it is universally known as the Big Dipper because the major stars can be seen to follow the rough outline of a large ladle or dipper. This figuration appears to be derived originally from Africa, where it was sometimes seen as a drinking gourd. In the 19th century, runaway slaves would follow the Drinking Gourd to the north and freedom.
These seven stars ("Septentrio") are the origin of the Latin word septentrion meaning "north" and now found as the adjective septentrional (northern) in French and Spanish, to go with adjectives for the other three directions that refer to the position of the sun.
The Casserole (saucepan) is a name for the grouping in southern France.
In Hindu astronomy, it is referred to as (Vrihat) Sapta Rishi meaning "The Seven (Great) Sages".
The Japanese name is .
A widespread American Indian figuration had the bowl as a bear. Some groups considered the handle to be three cubs following their mother, while others pictured three hunters tracking the bear.
The Bible refers to it as "the seven stars" (Amos 5:8), though some translations have "Big Dipper" explicitly, and some translations of that verse refer to the Pleiades, which also has seven stars, instead.
In Tolkien's Middle-earth mythos, it is called the Sickle of the Valar, the sign of Hope signifying doom for Evil while in T.A. Barron's Great Tree of Avalon series, it is called the Wizard's Staff, symbolizing Merlin's staff.
Stars
Within Ursa Major the stars of the Big Dipper have Bayer designations in consecutive Greek alphabetical order from the bowl to the handle.
| Proper Name | Bayer Designation | Apparent Magnitude | Distance (L Yrs) |
|---|---|---|---|
| Dubhe | α UMa | 1.8 | 124 |
| Merak | β UMa | 2.4 | 79 |
| Phecda | γ UMa | 2.4 | 84 |
| Megrez | δ UMa | 3.3 | 81 |
| Alioth | ε UMa | 1.8 | 81 |
| Mizar | ζ UMa | 2.1 | 78 |
| Alkaid | η UMa | 1.9 | 101 |
Mizar has a companion star called Alcor that served as a traditional test of sight. At magnitude 4.1, Alcor would normally be relatively easy to see with the unaided eye, but its proximity to Mizar renders it more difficult to resolve. Both stars are actually multiple in and of themselves, including the first telescopic and spectroscopic binaries.
Five of the stars of the Big Dipper are at the core of the Ursa Major Moving Group. The two at the ends, Dubhe and Alkaid, are not part of the swarm, and are moving in the opposite direction. Relative to the central five, they are moving down and to the right in the map. This will slowly change the Dipper's shape, with the bowl opening up and the handle becoming more bent. In 50,000 years the Dipper will no longer exist as we know it, but be re-formed into a new Dipper facing the opposite way. The stars Alkaid to Phecda will then constitute the bowl, while Phecda, Merak, and Dubhe will be the handle.
Guidepost
Not only are the stars in the Big Dipper easily found themselves, but they may also be used as guides to yet other stars.
- Polaris, the North Star, is found by imagining a line from Merak to Dubhe and then extending it for five times the distance between the two Pointers.
- Extending a line from Megrez to Phecda, on the inside of the bowl, leads to Regulus (α Leonis).
- Crossing the top of the bowl from Megrez to Dubhe takes one in the direction of Capella (α Aurigae).
- Castor and Pollux (α and β Geminorum) can be located by crossing the bottom of the bowl from Phecda to Merak and continuing onward.
- By following the curve of the handle from Alioth to Mizar to Alkaid, one reaches Arcturus (α Boötis) and Spica (α Virginis). A mnemonic for this is "Arc to Arcturus then speed to Spica."
See also
Ursa Major constellation | Astronomical asterisms
Karlsvognen | 북두칠성 | 北斗七星 | Karlsvognen | 北斗
"Big Dipper"